Agdex#171/4

CROPSIRETA Publication No. 3/89

TARO BREEDING

AUTHOR: Jill E. Wilson, Root Crop Breeder

Illustrations: Shirley Tjendana.

Trade names mentioned do not constitute IRETA approval to the exclusion ofsuitable alternative products.

All or part of this publication may be reproduced for educational purposes.When doing so, please credit the University of the South Pacific forResearch, Extension and Training in Agriculture (IRETA).

Produced with financial assistance from the UNDP/FAO RootCrops Development Systems Project (RAS/86/034).

Published 1990, by the Institute forResearch, Extension and Training inAgriculture.

IRETA PublicationsUSP Alafua CampusP.O. Private BagApia, WESTERN SAMOA

Printing: Communications Support CentreLayout–Richard W. Tenney

ISBN 982-175-002-8 59/891M

TABLE OF CONTENTS

Taro Breeding .............................................................................................................................. 1Steps in a Taro Breeding Programme .......................................................................................... 4Step 1 – Plant Crossing Block to Provide Improved Population of Seeds .................................. 7

The Crossing Block ......................................................................................................... 8Promoting Flowering ....................................................................................................... 9Floral Biology ................................................................................................................ 11Controlled hand-pollination ........................................................................................... 14Harvesting Seeds ........................................................................................................... 20Seed Storage .................................................................................................................. 21Record Keeping ............................................................................................................. 22

Step 2 – Plant Seeds and Rear Seedlings ................................................................................... 23Step 3 – Transplant Seedlings to the Field ................................................................................ 24Step 4 through 7 – Evaluate and Select Clones ......................................................................... 24

Conducting Trials .......................................................................................................... 25Step 8 – Name and Release the Best Clones ............................................................................. 36Step 9 – Distribute New Cultivars to Farmers ........................................................................... 36

Multiplication ................................................................................................................ 37Recurrent Selection........................................................................................................ 39Genetics ......................................................................................................................... 41

Evaluating Specific Characters .................................................................................................. 42Plant Characters ............................................................................................................. 42Plant Vigour ................................................................................................................... 42Sucker Number and Attachment .................................................................................... 43Disease, Insect, and Nematode Resistance .................................................................... 44Time from Planting to Harvest ...................................................................................... 45Yield .............................................................................................................................. 45Corm Characters ............................................................................................................ 46Field Selection ............................................................................................................... 46Eating Quality ................................................................................................................ 47Nutritional Value ........................................................................................................... 50

Supplies ..................................................................................................................................... 51

1

TARO BREEDING

date, these programmes have developed andreleased only 2 improved cultivars of taro.Both of these were developed here in thePacific: Samoa Hybrid released by theMinistry of Primary Industries, Fiji, in 1984and Alafua Sunrise released by the Universityof the South Pacific (USP) Institute forResearch, Extension and Training inAgriculture (IRETA), Western Samoa, in1988.

The procedures and techniques presentedhere are important to the success of yourbreeding programme. Equally important isyour knowledge of taro production in yourcountry, particularly your knowledge ofyield-reducing factors such as environmentalstresses and disease, insect and nematodepests. You must also be familiar with theother problems farmers face and with the taroquality characters favoured by farmers andconsumers.

Thorough knowledge of these factors isnecessary to determine the goals of yourbreeding programme. To set your short-termgoals, you must answer the question, “Whattype(s) of taro do the farmers need now?”And to set your long-term goals, you mustanswer the question, “What type(s) of tarowill the farmers need in 10 years?”Remember that it often takes 10 years ormore from the time you make a pollinationuntil your new, improved cultivar finallyreaches a large number of farmers.

This manual is for researchers in the Pacificregion who are starting taro breedingprogrammes but lack training and experiencein genetics and plant breeding. It is also forresearchers and extension workers who areevaluating local and newly introduced tarogermplasm. It may also be useful to teachersand students, of crop improvement courses atthe diploma, degree, and post-graduate levels.

The objective of this manual is to provideyou with the procedures and techniquesneeded to carry out a Colocasia taro breedingprogramme. Parts of the text have been,copied from the IRETA Agro-Fact, ‘SweetPotato Breeding’, since breeding of these twocrops is similar in many ways. Practicalaspects of breeding are emphasized, ratherthan theory. Use of technical terminology isminimized. To keep the manual concise,detailed explanations are avoided whenpossible, and many concepts are simplified.After learning the material presented here,you may want to read other texts to gainmore complete understanding of plantbreeding.

The taro breeding procedures andtechniques included in this manual are beingsuccessfully used in IRETA’s breedingprogramme. However, taro breeding is a newscience, and we still have much to learnabout it. World-wide there are only 6programmes that are breeding taro orstudying its floral habits and genetics. To

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Figure 1. Steps in a taro breeding programme

Step 1plant CROSSING BLOCK (CB)

to provide improved population of seeds

Step 2plant seeds and rear seedlings

in SEEDLING NURSERY (SN)

Step 3transplant SEEDLINGS toHILL TRIAL (HT) in field,

evaluate, and select best clones

Step 4evaluate clones in

PRELIMINARY TRIAL (PT)and select best clones

IntrogressNEW

GERMPLASMas available

3

Step 5evaluate clones in

INTERMEDIATE TRIALand select best clones

Step 6evaluate clones in

ADVANCED TRIAL (AT)and select best clones

Step 7evaluate clones in

ON-FARM TRIALS in several seasonsand several locations and select best clones

Step 8NAME best clone(s)

and RELEASE

Step 9DISTRIBUTE to farmers

MULTIPLYplanting material

4

There are 3 methods to obtain improvedcultivars (agricultural varieties) of taro fordistribution to farmers in your country:

• Collecting, evaluating, and selecting fromthe local germplasm.

• Importing cultivars that have been bred inother parts of the world and evaluatingthem under your conditions.

• Breeding cultivars in your ownprogramme.

During the On-Farm Trials (Step 7), youwill identify one or more clones that both youand the farmers like. You are now ready toofficially name and release these clones inStep 8 and distribute them to farmers in Step9.

Figure 1 shows clearly that multiplicationis a continuous activity that begins after youharvest the seedlings in the Hill Trial (Step3), but the largest multiplication takes placebetween Steps 8 and 9 to produce enoughplanting material for distribution to farmers.

This manual will concentrate on the lastof these methods, that of breeding. However,much of the discussion under Steps 4 through9, concerning conducting trials and reducingexperimental error, will be useful if you areevaluating local germplasm or importedcultivars.

STEPS IN A TARO BREEDING PROGRAMMEA proposed breeding procedure is outlined inFigure 1. In Steps 1, 2, and 3, sexualpropagation is used to produce seeds andseedlings. In Step 3, each seedling is clonedby propagating it vegetatively, and in all thefollowing steps, vegetative propagation isused.

The purpose of using sexual propagationin Steps 1, 2, and 3 is to create geneticvariability. Each seedling produced duringsexual propagation is genetically differentfrom all others and is potentially a new,improved cultivar.

During Steps 4 and 5, youevaluate clones derived from the seedlingsproduced in Steps 1, 2, and 3 to determinewhich ones you will advance to additionaltrials for further testing in Steps 6 and 7,which ones you will use as parents in the nextCrossing Block (Step 1), and which ones youwill discard.

A clone consists of all thedescendants of a vegetativelypropagated individual.

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Why do you go through theprocess of completing Steps 1 to 5 and thenreturn some clones to Step 1? This is done toincrease your chances of finding seedlingsthat have all the characters you need in animproved cultivar. This process is calledpopulation improvement. During eachbreeding cycle, parent clones are selected andcross-pollinated in such a way that theresulting seedling population is improved.That is, it contains more good seedlings thanprevious seedling populations. The method ofpopulation improvement that we use isRECURRENT SELECTION. Recurrentselection, especially the step of choosing theparent clones that you plant in Step1, determines the direction andsuccess of your breeding programme; it is soimportant that a separate section is devoted toit later in this manual.

Your programme can include all 9 stepsoutlined above, or it can beginat Step 2 or Step 4 if you are collaboratingwith other breeding programmes. Forexample, if you receive seeds from anotherbreeding programme, then you would start atStep 2. If you receive tissue culturesof improved clones from another breedingprogramme or you are evaluating your localgermplasm, then you would start at Step 4.

Although Figure 1 may look complex, itdoes in fact oversimplify a recurrent selectionbreeding programme, since it presents onlyone cycle. Recurrent selection is a long-term,continuous process with a new cycle ofbreeding (a new Crossing Block) startedevery year and with the chance for new andbetter clones ready for release every year.

Figure 2 tries to capture the morecomplex picture. It is important that abreeding programme be continued for longenough to benefit from the investments madein the early years.

After a clone has been named andreleased, we generally call it a cultivar.

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Figure 2. Breeding is a long-term, continuous process with a new Crossing Block started everyyear. In this flow chart, On-Farm Trials are grown for only one year. It is better togrow On-Farm Trials for several years in several locations.

Year 1 Year 2 Year 3 Year 4 Year 5 Year 6

CB SN&HT PT IT AT O-F

CB SN&HT PT IT AT

CB SN&HT PT IT

CB SN&HT PT

CB SN&HT

CB

Year 12 Year 11 Year 10 Year 9 Year 8 Year 7

N, R&D

N, R & D O-F

N, R&D O-F AT

N, R&D O-F AT IT

N, R&D O-F AT IT PT

N, R&D O-F AT IT PT SN&HT

CB = Crossing Block IT = Intermediate TrialsSN = Seedling Nursery AT = Advanced TrialHT = Hill Trial O-F = On-Farm TrialPT = Preliminary Trial N, R & D = Name, Release & Distribute

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Step 1–Plant Crossing Block To Provide Improved Population Of Seeds

If there are naturally, occurring insectsthat pollinate taro in your country, you couldplant parent clones in a Crossing Blockisolated from other flowering taro plants andallow them to be open-pollinated by theseinsects. However, this will permit asignificant amount of self-pollinationbetween inflorescences of the same clone,and this self-pollination is usuallyundesirable. Therefore, you should useopen-pollination only if you do not haveenough time and labour for hand-pollination.

Locate your Crossing Block in a field wherethe soil is high in fertility and organic matter,and where you can water the plants wheneverrainfall is not adequate for maximum growth.

Generally you will want to plant yourCrossing Block conveniently nearby andmake controlled hand-pollinations to insurethat specific cross-combinations are,represented in the seeds you produce.

Taro seeds are tiny.

With open-pollination, you know the femaleparents of seeds, but not the male parents.With controlled hand-pollination, you knowboth the female and male parents of theseeds.

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The Crossing BlockTaro flowers best during the rainy season.Therefore, summer is the best time forproducing seeds in the Southern Hemisphere.Also, the high relative humidity typical ofthis season promotes abundant pollenproduction.

In Western Samoa, we like toplant the Crossing Block during the firstweek in November, but some years we mustdelay planting when the rainy season is latecoming. About 2 months after planting, weapply gibberellic acid (GA) to promoteflowering. Flowering begins about 2 monthsafter GA application and continues for 3months. This means that we are pollinatingmostly during March, April, and May andharvesting seeds during April, May, andJune.

In the Crossing Block, plant large,healthy headsetts or suckers of the parentclones. Use a spacing wide enough toencourage vigourous growth and to permityou to walk around the plants whilepollinating. We use 1.0 x 1.0 m or 1.5 x 1.5m. The latter is better, if you have enoughland. Usually, 5 to 10 plants of each clone areenough, although you may need more plantsof sparse-flowering clones, clones that arepoor pollen and/or seed producers, and clonesthat you plan to use in a large number ofcrosses.

Vigourous plant growth in the CrossingBlock is essential. Why? Because rapidlygrowing taro plants which have not sufferedwater or nutrient stress produce moreinflorescences, stronger inflorescences, andabundant, viable pollen. Therefore youShould do everything necessary to growlarge, fast growing plants in your CrossingBlock. For example, mulch plants with grass,palm leaves, or old jute sacks (copra bags)and water plants whenever rainfall is notadequate. Fertilise the Crossing Block withN-P-K if soil fertility is not adequate formaximum growth.

Insects and diseases can reduce floweringand seed set. Therefore, you should regularlycontrol them in your Crossing Block,especially armyworm (Spodoptera), tarohornworm (Hippotion), taro beetle(Papuana), and taro planthopper(Tarophagus) if it is particularly severe inyour location. In Papua New Guinea,Solomon Islands, Hawaii, and some islandsof Micronesia, you may need to control(Phytophthora), and in Papua New Guineaand Solomon Islands, you must control thedevastating virus disease called alomae andbobone.

If you plant your Crossing Block before November,flowering will occur during December, January, andFebruary, and you will find it very difficult topollinate because of the heavy rains during thesemonths.

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Promoting FloweringMany clones of taro do not flower naturally.In other clones, natural flowering is sporadicand not predictable enough for breeding.However, you can promote abundant, earlyflowering by applying a solution ofgibberellic acid (GA) dissolved in water.

To make the solution, use eitherthe technical grade GA (75% to 90%) or thecommercial formulation, Pro-Gibb Plus (20%GA; trademark, Abbott Laboratories).Pro-Gibb Plus is much easier to handle andweigh because it is less hygroscopic and youare weighing larger quantities.

Since taro leaves are very waxy, asurfactant must be added to the GA solutionat a fairly high rate. We use Agral at 2.5 ml/litre or Citowett at 0.36 ml/litre.

CAUTION:CITOWETT WILL BURN TARO

LEAVES IF IT IS NOTMIXED VERY WELL

INTO THE SOLUTION.

The best concentration of GA variessomewhat with the clone. Clones that neveror rarely flower naturally usually require 500ppm GA, whereas clones that occasionally oroften flower naturally require only 250 ppm.We use 500 ppm, and this is a goodconcentration for you to try the first year. Infollowing years, you can adjust theconcentration according to how your clonesbehaved during the first year. If you did notget adequate flowering, then increase the GAconcentration. If the plants went ‘wild’ andproduced a large number of deformities andsmall weak inflorescences, then decrease theGA concentration.

Prepare the spray solution shortly beforeuse. The best times for spraying are earlymorning or late afternoon, when no rain isexpected. It is important to avoid rainbecause, to be effective, GA needs to stay onplants for several hours.

500 ppm GA = 0.56g/litre of90% GA or 2.5g/liter Pro-GibbPlus.CAUTION: WHEN WEIGHINGPRO-GIBB PLUS ALWAYS SHAKETHE CONTAINER VERY WELLBEFORE MEASURING TODISTRIBUTE GA EVENLY INTHE POWDER.

To determine the amount of GASolution you need to make, multiplythe number of plants you plan to sprayX 35 ml/plant, if you are using a smallhand-pumped sprayer or X 50 ml/plantif you are using a compressed-airsprayer.

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Apply the GA solution when plants havereached the 3 to 5 leaf stage. Apply GA onlyone time to each plant (unless it rainsimmediately after application; then it will benecessary to reapply the GA)

Apply the GA solution with ahand-pumped sprayer or compressed-airsprayer. Spray all the leaves lightly on bothsides and spray a little of the GA solutioninto the cup formed by the petiole bases.

The time from GA application to theappearance of the first inflorescences rangesfrom 60 to 90 days depending upon the cloneand the growing conditions. You can achievesimultaneous flowering of parent clones withdivergent flowering times by staggering datesof planting and/or dates of GA application.

Before a plant produces an inflorescence,it produces a floral bract or flag leaf. Bractproduction occurs in both natural floweringand GA- induced flowering and is a sign toyou that flowering will soon begin.

Some GA-induced deformities willappear before the normal inflorescences.These deformities include incompleteinflorescences that contain spathes but nospadices and patches of floral colour andtexture on the leaves.

Also GA usually stimulates plants toproduce more suckers than usual, as well asstolons, elongated petioles, and branchingcorms. Therefore, your GA-treated plants willlook funny and be difficult to weed.

GA-induced deformities

normal, completeinflorescence

incompleteinflorescence

patches of floral colourand texture

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Inflorescence with part ofthe spathe removed

Floral Biology

sterile tip

spathe

male flowers

sterile band

female flowers mixedwith sterile flowers

peduncle

spadix

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The small, sessile (without a stalk)flowers occur in inflorescences. Eachinflorescence consists of a spadix enclosed ina spathe. The male (staminate) and female(pistillate) flowers are in different locationson the spadix and are separated by aconstricted band of sterile flowers (see sketchbelow). There is a sterile tip at the very top ofthe spadix, and there are also sterile flowers,in varying numbers, scattered among thefertile female flowers. You can easilydistinguish the fertile and sterile femaleflowers. The fertile female flowers are greenwith distinctive stigmas, whereas the sterileflowers are ivory-coloured and usually tallerthan the fertile ones.

Depending on the location and clone,female flowers may be receptive (ready to bepollinated) one day before the male flowersin the same inflorescence shed their pollen(pollen shed), or the same day as pollen shed,or one day after pollen shed.

Here in the Pacific, female flowers areusually most receptive one day before pollenshed, and this is the best day to hand-pollinate. On this day the inflorescence has astrong aroma. Also, the base of the spathe iscracked open, and the constricted part of thespathe becomes loose around the band ofsterile flowers. In nature this allows insects toreach the female flowers by flying throughthe crack or by crawling down from the malepart of the spadix, past the band of sterileflowers. We call this the ‘crack’ stage. Thefollowing day (the day of pollen shed), thecrack closes, and the spathe becomes tightaround the band of sterile flowers.

The female flowers are located at thebottom of the spadix and are mixed with avarying number of sterile flowers. In thissketch the spadix on the left has no sterileflowers in the band of female flowers, but thespadix on the right has many sterile flowersscattered among the females. The spadix inthe centre is intermediate for number ofsterile flowers. Because of the greaternumbers of sterile flowers, the spadix on theright will produce the least seeds.

sterile flowers

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Pollinating insects occur in thosecountries where naturally-set seeds arecommon in farmers’ fields (for example,Solomon Islands). The most likely naturalpollinators are small flies, which are attractedto inflorescences by the distinctive aroma. Inother countries (for example, WesternSamoa), pollinating insects do not appear tobe active, and the small quantities ofnaturally-set seeds that occur there areprobably produced when rain washes pollendown onto the female flowers.

The fruit head is a cluster of denselypacked berries. Each berry generally contains1 to 10 seeds, but you may find as many as35 seeds.

Seeds are tiny, usually less than 2 mm.long. When mature, they are ovate in shape,hard, and conspicuously ridgedlongitudinally. They germinate in 7 to 14days with no apparent dormancy.

The fruit head is a cluster of berries

berry containing seeds

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Controlled Hand-pollinationTo carry out a controlled hand-pollination intaro, there are 6 steps:

1. preventing insect-pollination beforehand-pollination,

2. emasculating,

3. pollinating,

4. preventing insect pollinationafter hand-pollination,

5. labelling, and

6. removing pollinating bag and replacing itwith a fruit bag.

The purpose of Step 1 is to insure that theinflorescences that you plan to hand-pollinateare protected from Insect-pollination.Therefore, you should carry out Step 1 if youare working in a location where insectpollinators are present.

Why is it necessary to prevent insect-pollination? Because insects canself-pollinate by carrying pollen betweeninflorescences on the same plant and betweeninflorescence on different plants of the sameclone. And in taro breeding, self-pollinationis generally undesirable.

Even in countries where Step 1 is notnecessary to prevent insect-pollination,bagging the male parent can help preventlight rains from washing off pollen.Therefore, you may want to carry out thisstep if early morning rains are frequent inyour location.

Protect the inflorescences on both thefemale and male parent plants. To do this,select inflorescences that are large and full,but that still have their spathes closed aroundthe male portion of the spadix. Cover theseinflorescences with an insect-proof, cloth bag(pollinating bag) and close it at the bottom bytying it around the peduncle with a twist-tieor string.

Bagged inflorescences are easier to findat pollinating time if you mark plants withbrightly-coloured ribbons, which you removeafter pollinating.

Sew your own pollinating bags fromlight-weight, but stiff cloth or very, veryfine mesh. Remember that the insectpollinators are SMALL flies. The verybest material is the thrip-proof mesh thatis often used to construct quarantinehouses and insect rearing cages. Ask theentomologist in your research station forsome.

NOTE: If you are producing seeds for agenetic study, it is important that youeliminate ALL possibility of insect-pollination. Therefore, you should baginflorescences before and after hand-pollination, even if insect-pollinationappears to be rare in your location.

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Emasculate means to remove the malepart of the spadix before pollen is shed.Emasculating and pollinating, are carried outat the same time.

The best time to pollinate is in themorning between seven and noon, althoughon cool, cloudy, or rainy days, you may haveto start later in the morning because pollen isshed later.

On a male-parent plant, find a baggedinflorescence that has pollen. Taro pollen isextruded in clumps and is easy to see. Cut offthe entire inflorescence and carry it to thefemale-parent plant. Carry it carefully so thatyou do not shake off the pollen.

On a female-parent plant, choose aninflorescence that is at the ‘crack’ stage andgently remove the bag covering it. Thenemasculate this female inflorescence. To dothis, cut off the male portion of the spadix bycutting through the band of sterile flowersthat separates the male flowers from thefemale flowers. You can easily locate thisband of sterile flowers without removing thespathe, because it is under the constrictedarea where the green basal tube of the spathejoins the yellow top of the spathe.

Next, carefully cut away the spathesurrounding the female portion of the spadix.Be careful not to damage the peduncle.Remove the bag from the male-parentinflorescence and cut off the male portion ofthe spadix (in the same way that youemasculated the female inflorescence). Holdthe male portion by the sterile tip andcarefully remove it from the spathe. Thengently rub it over the female flowers. Sincesterile flowers are usually taller than fertilefemales, concentrate on applying pollen tothe fertile female flowers. Apply the pollenevenly to cover all the fertile female flowers,since a fruit with only a few berries will notdevelop. Check inside the spathe section thatyou removed from the male spadix. Often itcontains pollen that you can also dust overthe female flowers.

For emasculating and pollinating, youwill need a knife with a small, sharpblade.

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This inflorescence is at the ‘crack’ stage,which is the best time to hand-pollinate. Theeasiest way to identify this stage is to useyour nose! There is a distinct, STRONGaroma at the crack stage. Inflorescences atseveral other stages have MILD aromas, butmuch milder than at the ‘crack’ stage. Spendsome time sniffing a number ofinflorescences at various stages until you cansmell the difference between these milderaromas and the strong aroma that identifiesthe ‘crack’ stage.

crack

constricted part of spathe;cut here to emasculate

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After you have finished a pollination,carefully cover the female inflorescence withthe pollinating bag. This prevents insectpollination and helps keep light rain fromwashing off the pollen you have applied. Italso helps to maintain high humidity aroundthe female flowers, and this high humidityincreases the percentage of successfulpollinations. Therefore, you should carry outthis step whether or not you have insectpollinators.

Label each pollination with the date andthe names or numbers of the parents. Attachthe label to the peduncle of the inflorescencethat you pollinated. For labeling we useplastic Diamond-Lox labels because they areeasy to attach and are long-lasting in allweather (see Supplies).

To reduce contamination by undesiredpollen, wash your hands or clean them with adamp cloth each time you change to adifferent male parent.

pollinating bag

By convention, breeders write the femaleparent first when labelling a cross.Therefore, in this sketch 83002-1 is thefemale parent and 82025-4 isthe male parent.

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Three days after pollinating, the femaleflowers are no longer receptive, and you canremove the pollinating bag. You should notleave on the pollinating bag longer than 5days because it keeps the developing fruit toohot and damp.

In Western Samoa we have problemswith armyworms eating the developing fruits.Therefore, when we remove the pollinatingbag, we replace it with a fruit bag made fromplastic fly screen. This fruit bag keeps outmost (although not all) armyworms and stillallows enough air. And you can seeor feel through the fly screen to determinewhen the fruit is ready for harvest.

fruit bag

To make fruit bags from fly screen, ‘sew’seams by stapling; choose a brightlycoloured screen so you can easily findthe fruits under the leaves.

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Your success rate for hand-pollination isaffected by the weather, the health of theplants, the parents used, and your skill atpollinating. In the IRETA programme,usually more than 75% of the inflorescenceswe pollinate develop into fruit heads. Hereare some hints for improving your pollinatingsuccess, especially when conditions are notperfect:

1. When first learning to pollinate, writeon the pollinating label the initials of theperson pollinating, time of day, remarksabout the weather (very hot, rainy, etc.)and other comments that will help youimprove your pollinating skill.

2. Unless you want a particular maternally-inherited character, you can try using eachclone as both a male parent and a femaleparent. However, clones that are very poorpollen producers should be used as femaleparents only.

3. If you do not have enough inflorescences,you can use the same inflorescence as botha male and a female parent. When youcollect pollen, cut off only the maleportion of the spadix (rather than thewhole inflorescence), and use theremaining female portion of the spadix asa female parent for another pollination.The female flowers will stillhave some receptivity even though theyare one day older than the ‘crack’ stage.NOTE however, that some self-pollinationmay have occurred before you cut off themale portion.

4. When you emasculate inflorescences onfemale parents, you can save the maleportion of the spadix as a source of pollenfor the next day. Label the male portionof the spadix with the clone number, andkeep it inside its spathe covering bypulling the label tight around the spathe.Take these male spadices into the lab,wrap each one with a damp paper toweland place in a plastic bag to maintain high

relative humidity. Some, but not all, ofthem will shed pollen the next morning.

5. Some inflorescences produce very littlepollen or no pollen. Such poor pollenproduction also occurs sometimes innaturally produced inflorescences andtherefore is probably not related to GAapplication. Some poor pollen productionmay be genetic, but some is definitelyrelated to environmental stress, especiallydrought stress and low relative humidity.When relative humidity is low, manyclones do not shed pollen even when soilmoisture is adequate.We know that in some ornamental

aroids, maximum pollen germination andseed set is achieved when both pollen andfemale flowers are maintained at highrelative humidity before and after pollination.This is probably true for taro also. Duringperiods of low relative humidity, you can tryexposing pollen to high humidity byharvesting inflorescences from male parentsone or two days before pollen shed. Takethem into the lab and place the peduncles in acontainer of water. Wrap each inflorescencewith a damp paper towel and cover with aplastic bag. Similarly, you can increase therelative humidity around the female flowersafter pollinating by wrapping a damp papertowel around the female portion of thespadix before covering it with a pollinatingbag. NOTE that plastic bags would keep therelative humidity higher, but they get too hotinside when used in the field.

6. Fruit heads will not develop unless anumber of berries have been fertilised.Therefore, it is important that you haveenough pollen to cover each femaleflower. If inflorescences on your maleparent each have only a small amount ofpollen, use several of them to pollinate oneinflorescence on the female parent.

7. In contrast, if a male-parentinflorescence is covered with a largequantity of pollen, you can use it topollinate 2 female spadices.

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Harvesting SeedsA fruit head is ripe and ready to harvest whenthe berries become soft and the peduncleturns yellow and shrivels. This is usually 30to 45 days after pollination. The youngberries are usually dark green and change toa lighter green or yellow-green as they ripen.However, the berries on a few clones ripenorange.

In the lab, extract the seeds by washing inwater. We use the following method:Remove the berries from the core of the fruitand place them in a very fine screen orstrainer. Caution: The Screen Must Be SoFine That The Small Seeds Do Not WashThrough. We use a very fine tea strainermade with plastic mesh. Crush the berries byrubbing them GENTLY (do not crush theseeds!) against the sides and bottom of thescreen. Hold the screen under the cold-watertap and stir the crushed berries with yourfinger to wash out the fruit pulp. Dump theseeds and remaining fruit pulp into a smallglass container and add water. The heavy,viable seeds will sink to the bottom. Thelightweight seeds and most of the fruit pulpwill float to the top, and you can pour themoff and discard. In our experience mostof these lightweight seeds will not germinate.A few of the are viable, but it is usually notworth the time it takes to separate them fromthe fruit pulp unless you are very short ofseeds.

Repeat the steps of crushing and floatingseveral times until the seeds are clean. Thenpour the heavy seeds that sink to the bottominto the screen, tap gently to shake off asmuch water as possible, and place seeds onfilter paper in an uncovered petri dish. Leavethe petri dish in a well aerated location in thelab until seeds are dry. Remember to placethe pollinating label in the petri dish of seed.

Put the dry seeds into labeled envelopesand store. You can put seeds from differenthand-pollinated inflorescence into oneenvelope if they have the same female andmale parents, or, in the case of open-pollinated seeds, if they have the same femaleparent.

It is important that you check yourCrossing Block for ripe fruit heads every day,because a heavy rain can wash all the seedsfrom soft berries onto the ground. To avoidlosing seeds this way, we harvest fruit headswhen the berries are just beginning to softenand place them in the lab to finish ripening.We harvest each fruit head with a longpeduncle, which we place in water like abouquet.

Another danger is to let the ripe fruitheads dry up. It is very difficult to wash theseeds out of dry, hard berries.

Pick each hand-pollinated fruit head withits label. If you are using open-pollinatedfruit heads, label them with the same name ornumber of the female parent.

If the peduncle becomes soft and fallover in less than 2 weeks, then yourpollination was not successful.

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Seed StorageTaro seeds will store at least 2 years in adesiccator in the refrigerator. We make aninexpensive desiccator from a tin or glass jarwith a tight fitting lid. In the bottom of the tinor jar we place a layer of the desiccant, silicagel. The indicating type is best, since you cansee by the change in colour from blue to pinkthat it needs drying.

If you do not have silica gel, you can useuncooked rice that has been baked in a low-temperature oven until very dry and lightbrown. Try to find at least a small quantity ofindicating silica gel to mix with the bakedrice so you can see when the rice needsre-drying. Place a piece of screen over thedesiccant before adding the envelopes ofseeds.

You can make an inexpensivedesiccator for storing seeds

screen

silica gel or baked rice

ACeS/83004

envelopes of seed

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Record KeepingRecord keeping is an important part of yourbreeding programme. With some methods ofbreeding, for example pedigree breeding, it isessential that you be able to trace thepedigree of a clone back through manygenerations. This is generally not true whenusing recurrentselection to breed most crops. However, sincetaro breeding is a new science, we need tolearn as much about taro genetics as possible.Keeping records of pedigrees helps us to dothis, and that is why we keep individualcrosses separate and labelled.

Different breeders prefer differentmethods of recording pedigrees. Here is theone that we use:

When seeds are harvested fromthe Crossing Block, each individual cross isassigned a family number, for example,ACeS/86001. ACeS indicates seeds(S) ortaro (Ce=Colocasia esculenta) produced atAlafua (A), and 86001 is the family number(86 = 1986, the year the seeds wereharvested). When we harvest the seedlings inthe Hill Trial, we assigna clone number to each seedling thatis selected to go into the Preliminary Trail.This clone number consists of the familynumber followed by -1, -2, -3, etc., forexample, 86001-1. This clone number is aPERMANENT number, and does NOTchange from year to year.

Keep handwritten records in a boundrecord book – do NOT risk typing errors.

An example of a breeding record

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Step 2–Plant Seeds And Rear Seedlings

Taro seeds are very small, and youngseedlings are delicate and very slow growing.Careful attention to them is necessary forsuccess.

Sow seeds about 4 months before thebeginning of the rainy season. Petri dishes orsmall pots coveredwith glass can be used as containers forplanting seeds. We make inexpensive potsfrom aluminum beer tins. We cut off the topof each tin, then punch a drainage hole in thebottom, and cover with one half of a petridish.

Soak containers and lids in diluted Cloroxor other household bleach containing sodiumhypochlorite to sterilize them.

Fill containers to within 1 or 2 cm of thetop with STERILIZED, free-draining pottingmixture to which you have added fungicideto retard damp-off. For potting mixture, weuse a mixture of top soil, washed RIVER (notbeach) sand, and peat.

Dust seeds with fungicide. Scatter theseeds onto the soil surface (do not cover withsoil), gently water, and cover containers withlids. Lids are important because they keep theuncovered seeds from drying out. Place the

covered containers in a warm place with lightfor part of the day. Temperatures of 25-28°Cand 12 hours light give us good germination.Germination begins about 7 days aftersowing.

Seedlings are ready for transplantingwhen their roots are 1 to 1.5 cm long andcotyledons are fully expanded, generally 14to 21 days after sowing. Transplant them into“Jiffy-7” pellets or small pots filled withsterile soil. Place them in a warm, shadylocation, and water as necessary. Graduallyremove shade so that seedlings are adjustedto full sunlight before they are transplantedinto the field.

Aluminium beer tins make good containersfor germinating seeds

To help reduce damping-off ofseedlings, water with sterile water.Sterilize by boiling, then cool. Keepsoil damp, not wet.

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Step 3–Transplant Seedlings To The Field

Seedlings are ready for transplanting into thefield when they are 10 to 15 cm high andhave 3 to 5 leaves, which is about 4 monthsafter sowing seeds. You should removenets from “Jiffy-7” pellets as you transplantto prevent restricted corm development.

Transplant seedlings to the field at thespacing most commonly used by farmers inyour location.

Steps 4 through 7–Evaluate And Select Clones

In these steps, you evaluate the breedingclones in a series of 3 trials located on theresearch station, followed by trails infarmers’ fields.

At the end of each trial, you must makedecisions whether to select a clone for furthertrial, or to discard it, or to use it as a parent intheCrossing Block. Usually, you select10 to 50% of the clones for further trial.

In Preliminary Trials you have largenumbers of clones, but each clone isrepresented by only a few plants. InIntermediate and Advanced Trials you havefewer clones, but more plants in each clone.For instance, in a Preliminary Trial you mighthave 500 clones with 3 plants/clone,compared to an AdvancedTrial with 15 clones and 5 plants/clone/replication, 5 replications. With the smallnumber of plants/clone in Preliminary Trials,it is not possible to judge very accuratelysuch characteristics as yield. That is why weuse subjective ratings during these trials anddo not begin to actually count and weighyield until the Intermediate Trials.

Which characters should you evaluatewhen selecting clones? This will depend onthe goals of your breeding programme, but togive you some ideas, I have included in Table1 the characters that we evaluate ineach trial in the IRETA breeding programme.

NOTE that the number ofplants/clone given in Table I are minimumnumbers. It would be MUCH better to havelarger numbers of plants/clone in each trial,for example in the Advanced Trial, 10 plants/rep (planted in 2 adjacent rows of 5). But thisis possible only if you have labour andsupplemental water for extra manipulation.

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Conducting TrialsHere are some pointers for conducting thesetrials:

1. Trial Conditions. Ideally, trials should becarried out in as many sites as possible, butpractically we are often limited to one or twosites. Therefore, choose your trial sitescarefully to include as many as possible ofthe relevant biological and physicalconstraints faced by farmers. In other words,you should carry out your trials underconditions similar to those faced by farmers.

Do not make the common mistake ofconducting your trials under optimumconditions by adding fertiliser and water,controlling all pests and diseases, etc. If youdo, you will end up selecting breeding clonesthat perform well under optimum conditionsbut may perform poorly under the farmers’less-than-optimum conditions. For instance,if farmers do not irrigate their taro, youshould not irrigate your trials. If you predictthat in 5 or 10 years many farmers will beforced to grow their taro on low fertility soil,then you should grow your trials withoutadding fertilizer.

Obviously, there are many times whenyou must break this rule in order toaccomplish your breeding goals. Forexample, if you are selecting forPhytophthora resistance, you might need toapply small quantities of overhead irrigationto wet the leaves and maintain high relativehumidity, in order to encourage diseasespread.

2. Spacing. In your trials, youshould use the spacing most commonly usedby farmers in your location. For example,

most farmers in Western Samoa plant at 1 x 1m or 1.5 x 1.5 m, whereas some commercialfarmers in Fiji, plant at a closer spacing.

3. Wetland Conditions. Do not assume thatbreeding clones that perform well in upland/rainfed conditions will also perform well inwetland conditions. In locations, such as theCook Islands, where a significant amount ofthe taro is grown in wetland conditions, youshould plant trials in wetland as well asupland/rainfed conditions.

4. Disease and Pest Control. In your trials,you should normally NOT control thedisease, insects, or nematodes to which youare selecting resistance, even if farmers douse control measures. However, if you areNOT evaluating your breeding clones forcertain pests and diseases, you should controlthem in your trials if the damage they causewill obscure the characters you areevaluating. For example, we controlarmyworm and hornworms when populationsare high.

If you are evaluating for dasheen mosaicvirus resistance, do not spray your plots withany insecticides that will control Aphids,which are the insect vectors of this virus.Likewise, if you are evaluating for alomaeand bobone, do not control planthoppers(Tarophagus proserpina) or mealybugs(Planococcus citri).

NOTE that the rules for CrossingBlocks and trials are different. YouSHOULD protect plants in yourCrossing Blocks against all damagingdiseases and pests. But in trials,you should NOT control diseasesand pests to which you are selectingresistance.

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Table 1. Characters that we evaluate in each trial in the IRETA taro breeding programme.

TRIAL PLANTING PATTERN CHARACTERS

Seedling Nursery “Jiffy-7” pots in trays; plant vigour (do not transplant weak seedlings(SN) 1 plant/clone. into field); artificial inoculation to evaluate

seedlings for Phytophthora resistance is possiblein those countries where this disease occurs; itwould be very useful to develop a method ofartificial inoculation to evaluate seedlings forPythium resistance.

Hill Trial 1 x 1 m between plants; plant vigour, dasheen mosaic virus score (average(HT) 1 plant/clone. over season), golden virus score (average over

season), corm rot (at harvest), rose beetle score,sucker number (immediately before harvest),stolon production (absent or present), corm budcolour, basal ring colour, corm yield (high,medium, low), petiole colour of clones selected infield.

Preliminary Trial 1 x 1 m between plants; plant vigour, dasheen mosaic virus score (average(PT) 3 plants/clone over season), golden virus score (average over

season), corm rot (at harvest), rose beetle score,sucker number (immediately before harvest),stolon production (absent or present), petiolecolour, maturity (early, medium, late), corm budcolour, basal ring colour, corm yield (high,medium, low), corm smoothness, corm shape,specific gravity of clones selected in field.

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Intermediate 1 x 1 m between plants plant vigour, dasheen mosaic virus score (averageTrial (IT) 3 plants/rep; 3 reps. over season), golden virus score (average over

season), corm rot (at harvest), rose beetle score,sucker number (immediately before harvest),stolon production (absent or present), petiolecolour, maturity (early, medium, late), corm budcolour, basal ring colour, number edible ormarketable corms (count), weight edible ormarketable corms (weigh), corm smoothness,corm shape, field selection, specific gravity, tasteacridity, cooked flesh colour.

Advanced Trial 1 x 1 m between plants same as IT except substitute corm dry weight for(AT) 5 plants/rep; 5 reps specific gravity; if possible nutritional factors

should be measured at this stage.

On-Farm Trials spacing & planting pattern plant vigour, dasheen mosaic virus score,determined by farmer; number (immediately before harvest), golden virus scoreof plants and reps determined (immediately before harvest), corm rot (atby availability of planting harvest), sucker number (immediately beforematerial and land; best located harvest), maturity (early, medium, late), numberin the middle of farmer’s own edible or marketable corms (count), weight edibletaro production field. or marketable corms (weigh), with farmer

deciding which corms are edible or marketable,ease/difficulty of harvesting as decided by farmer,eating quality as judged by farmer and family,farmer’s overall opinion of breeding clones andfarmer’s choice of which ones he/she will growagain.

Table 1 continued

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5. Local Checks. You must always includein your trials one or more local checkcultivars. A local check is a cultivar that ispresently popular and grown by manyfarmers in your location, or a cultivar that ispresently recommended by the ExtensionDivision. In our IRETA trials we include 3local check cultivars, Niue, Paepae, andManua. Why is it necessary to include a localcheck? Because the purpose of your trials isto identify breeding clones that are as goodas, or better than, the cultivars that farmersare already growing. Local checks are treatedlike breeding clones in that they arerandomised and included in all replications.

6. Susceptible and ResistantChecks. If you are evaluating your breedingclones for disease, insect, or nematoderesistance, you should also include in yourtrials a susceptible check cultivar and aresistant check cultivar for each of theseconstraints.

A susceptible check is one that you knowis susceptible to the disease (or insect ornematode). It helps you to determine whetherthe disease (or insect or nematode) is presentin your trial and at what level. ForPhytophthora, for instance, if yoursusceptible check is severely infected withthe disease, then breeding clones in the sametrial that show mild or no infection are mostlikely resistant to this disease, and you canselect them for further trial. However, ifyour susceptible check does not becomeinfected with Phytophthora, then you cannotevaluate the breeding clones for resistance,because the disease is not present in yourtrial, or the environment is not favourable fordisease spread. If all rows of the susceptiblecheck in the different replications showsymptoms of the same intensity, then youknow that the disease is uniformly spread inthe trial.

A resistant check helps you to determinethe LEVEL of resistance of each breedingclone. Is it the same, higher than, or lowerthan the resistant check cultivar?

In Intermediate, Advanced, and On-FarmTrials, treat the susceptible and resistantchecks the same as the breeding clones byrandomising them in each replication. In Hilland Preliminary Trials containing largenumbers of breeding clones, repeat thesusceptible and resistant check (and localchecks) several times about once for every 10breeding clones.

7. Spreader Rows. When evaluating forresistance, it is important to have high levelsof the disease, insect, or nematode present inyour trials so that you can distinguishbetween resistant and susceptible breedingclones. Therefore, locate your trials at siteswhere the disease, insect, or nematode isnaturally epidemic.

You can also increase the amount ofdisease inoculum available to infect the trialby planting ‘spreader rows’ – rows ofinfected plants of a susceptible cultivar. But,be very careful to plant these rows so that allclones in the trial are an equal distance fromthe spreader rows. See Figures 4, 5, 6, and 7for examples. Similarly, you can increase thenumber of insect pests in your trial withspreader rows of infected plants or plantparts, but this is usually not necessary withtaro pests.

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When you transplant your seedlings tothe field, it is VERY important that you plantspreader rows for dasheen mosaic virus and‘golden virus’. Dasheen mosaic virus and‘golden virus’ are not carried in taro seeds,and all seedlings are free of virus until theyhave been infected by insect transmission.You can insure that there is plenty ofinoculum nearby for the insects to vector toyour seedlings by planting spreader rows ofsuckers and headsetts of local cultivars whichare infected with dasheen mosaic virus and‘golden virus’.

8. Guard Rows. In all field trials, guard rows(often called border rows) are essential. Alldata plants (plants that you will observe,measure, and collect data from) must besurrounded by 4 other plants in order toeliminate the ‘edge effect’. See Figures 4, 5,6, and 7 for examples. If you do not take theprecaution of planting guard rows, then dataplants on the edge of the plot will havemore space and will be more vigourous andhigher-yielding than plants in a typical fieldsituation.

Extra guard rows can also be planted to‘guard’ the trial from damage by tractors,trucks, and foot traffic. For guard rows, useplanting setts that are the same size as mostclones in that replication. For the Hill Trial,use SMALL planting setts of local cultivarsso that the guard rows will not be too muchmore vigourous than the seedlings.

9. Fill-ins. For the same reasons that youplant guard rows, you should ‘fill in’ allmissing plants that died soon after planting.For fill-ins, use a clone of Colocasia taro thatis so distinctive it cannot be confused withyour breeding clones or check cultivars. Oruse Xanthosoma. Do NOT replant thebreeding clone itself unless it died from‘unnatural’ causes, like pigs or hoe-damage.And, of course, do not take data on the ‘fill-in’ plant.

10. Labelling and Mapping. At plantingtime, one of the most important precautionsyou should take to avoid errors is to properlylabel all clones and to map the seedlings,trials, multiplication blocks, and crossingblocks IMMEDIATELY after planting. Labelstakes may be lost because a farm workerneeds wood to start a cooking fire or a staketo scrape mud off his shoes! Make apermanent map of the trial layout and keep itin a safe place, so that clones can beaccurately located even if every label ismoved or destroyed. For orientation, includecompass directions and permanent landmarkssuch as buildings or large trees.

In this permanent record, also writeplanting dates, harvest dates, dates ofimportant operations like fertiliser andpesticide applications, dates when data weretaken, spacing, number of plants per row, etc.

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Figure 4. Example of the layout of part of a Hill Trial. Note positions of guard rows and spreader rows.

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Figure 5. Example of the layout of a Preliminary Trial. Note positions of guard rows and spreader rows.Most of your Preliminary Trials will be larger than this one.

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Figure 6. Example of the layout of an Intermediate Trial. Note positions of guard rows and spreader rows.Most of your Intermediate Trials will be larger than this one.

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Figure 7. Example of the layout of an Advanced Trial. Note positions of guard rows and spreader rows.Most of your Advanced Trials will be larger than this one.

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11. Selection. To save land and labour, it isessential that you discard undesirable clonesas early in the trial sequence as you canaccurately identify them. However, in theHill and Preliminary Trials in which there areno replications and only one or a few plantsof each clone, you must be careful whenevaluating characters such as yield, which arestrongly influenced by the environment.Keeping this caution in mind, you should tryto identify clones that have poor yields anddiscard them, especially when your decisionis reinforced by other negative characterssuch as disease susceptibility or too manysuckers.

In these unreplicated trials, concentratemore on highly heritable characters such asbud colour, flesh colour, and broad categoriesof sucker number, such as too few, ok range,and too many.

Concentrate also on discarding thepoorest clones rather than selecting the best.For example, you may not be able toaccurately identify clones that are resistant toPythium, but you can discard any that showsymptoms of this disease. Clones withobviously poor corm shape, deep suckerscars, or otherwise unacceptable cormappearance can be discarded in these earlytrials.

12. Experimental Error. There are severalways you can reduce variability and thusexperimental error in your trials.

When planting trials, use uniformplanting material taken from plants that arethe same age and are growing in the samelocation. Ideally, you would also use allheadsetts or all suckers depending on whichare preferred by your farmers. This is usuallynot possible, however, because of the slowrate of multiplication. Sort planting materialinto piles according to vigour and size, withsize judged by the diameter at the base of thepetioles. Plant the ‘largest’ in replication 1,the ‘second largest’ in replication 2, the ‘thirdlargest’ in replication 3, etc.

From each trial, you usually select 10 to15% of the clones for planting in thenext trial. Therefore, you must startwith a large number of seedlings. Forexample:

2000 seedlings1500 clones in HT

150 clones in PT15 clones in IT7 clones in AT2 clones in On-Farm

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Throughout the growing season, apply alltreatments uniformly to all clones in areplication. This includes treatments such asplanting depth and style, fertiliser, pesticides,irrigating, and weeding.

Carry out operations like weeding byreplication, and if you can not complete theentire trial at one time, break after completinga replication, not in the middle of areplication.

Each field worker treats taro a littledifferently, in terms of cutting plantingmaterial, planting, weeding, applyingfertiliser, etc., and therefore, if more than oneworker is applying a treatment, assign oneworker to complete one replication. Forexample, when we plant our trials, oneworker plants all of replication 1, anotherworker plants all of replication 2, etc. Youmust also take the same precautions whencollecting data. If it begins to rain, forexample, finish the replication before youstop. If more than one worker is collectingdata, each worker must complete areplication; NEVER have different workersevaluate different clones within the samereplication.

small, medium, and large headsetts

Small, medium, and large suckers

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Step 8–Name And Release The Best Clones

After you have made your final selections inthe On-Farm trials, you are ready to nameand officially release the selected breedingclones as improved cultivars. To inform thepublic about this release you can use radio,newspaper, extension leaflets, displays atagriculture shows, and demonstration plotsplanted by the Extension Division.

Step 9–Distribute New Cultivars to Farmers

The breeder’s job is NOT completed until thenew cultivar has been distributed to farmers.This step requires large-scale multiplicationof high quality planting material andcollaboration with the Extension Division,farmer groups, schools, etc.

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MultiplicationDuring each season it is necessary to multiplyenough planting material for the nextseason’s trials. And after a cultivar has beenreleased, large amounts of planting materialneed to be multiplied for distribution tofarmers.

Often it is necessary to depend on suckersproduced in the trials for multiplication.Therefore, it is necessary to ‘store’ and‘grow’ suckers and headsetts in the soil fromthe time you harvest one trial until the timeyou plant the next trial. This varies from 2 to6 months. Unfortunately, this storage time isusually during the dry season, and suckersmay suffer from drought unless you canirrigate them.

When you harvest a trial, carefully pullthe central corm, so that you disturb thesuckers as little as possible. Resettle thesuckers by pressing them into the soil withyour feet, and then mound soil up aroundtheir bases. Obviously, the suckers willsurvive better and grow faster if you harvestwhen the soil is damp or when rain isexpected shortly after harvest. Remove theheadsett from each harvested corm and plantit near its mound of suckers.

Here are some ways you can increase therate of multiplication if you have thenecessary resources, mainly labour andirrigation. Note that these methods areexcellent for multiplying planting material todistribute to farmers, but some of them arenot very good for multiplying for trialsbecause the resulting planting material is notuniform in terms of age and location.

1. After harvesting corms and moundingsuckers, irrigate suckers whenevernecessary to promote vigourous growth.

2. After harvesting corms, pull all suckersand replant them and the headsetts in anursery where they can be regularlywatered.

3. If you have limited nursery space, pullonly the smallest suckers and replant themin the nursery, leaving the larger suckersand headsets in the field.

Note that there is one danger in usingirrigation and nurseries to assist withmultiplication. When you do so, thereis no opportunity for natural selectionto eliminate clones that do not haveenough drought tolerance for theirsuckers to survive and grow in the dryseason under farmers’ non-irrigatedconditions.

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4. You can produce suckers from corms leftafter determining dry weight and eatingquality and from corms that you used fordetermining specific gravity (just wash offthe salt before planting).

To plant corms, remove and plant anyheadsetts that were not removedin the field at harvest. Plant corms in nurserybeds, pots, or trays filled with vermiculite,Permalite, sand, light top soil, or other freedraining material. We prefer vermiculite andPermalite, because these light media make iteasy to remove the roots of the suckers. Planteach corm upright so that the cut surface leftafter removing the headsett is just abovethe growing medium and will dry out inbetween waterings. Cover all the rest of thecorm with the growing medium, so it will notdry out and rot. Water as necessary to keepthe planting medium damp but not wet.

The lateral buds on the corm will sproutand grow into small suckers. Once each weekharvest all of the suckers that have grown to10–15 cm tall, and plant them in a nurseryin the screen house or field (water must beavailable). When you are pulling off thesuckers, disturb the corm as little as possible,and it will continue to produce suckers formany weeks.

5. Once you have reached Step 9 and aremultiplying planting material to distributeto farmers, it will definitely be necessaryto grow multiplication plots in the fieldduring normal taro growing season. In themultiplication plots you are growing plantsjust for multiplication, not for evaluation,and therefore, you should alter thegrowing conditions to favour suckerproduction, not corm production. How?By using wide spacing, shallow planting,and high nitrogen, which all increase thenumber of suckers produced.

For rapid multiplication, corms can be planted intrays in the screen house.

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Seeds and PATHOGEN-TESTED (virus-indexed) plantlets growing as tissue culturesare safe ways to import materials if youfollow recommended quarantine procedures.The first step in the importation process is toobtain an Import Permit from yourQuarantine Division and then to cooperatefully with the requirements for phytosanitarycertificates, post-entry quarantine, etc.

Recurrent SelectionThere are 3 steps in a recurrent-selectionbreeding programme:

1. Create a base population by selectingparent clones and intercrossing them in asmany combinations as possible.

2. Grow, evaluate, and select the seedling-derived clones grown from seeds producedin the above step, and intercross selectedclones in as many combinations aspossible.

3. Include new germplasm in the CrossingBlock when available (this is calledintrogression).

In a recurrent-selection breedingprogramme, the first time you select andintercross parent clones you are creating whatis called the base population or the originalsource population. It is important to beginwith a wide genetic base. To do this, chooseat least 20 parent clones that are unrelatedand have a wide rangeof characters.

To widen the genetic base, or to obtainspecific characters not available in the localgermplasm, it is often necessary to importseeds or vegetative material from othercountries. However, this importation must bedone in such a way that there is not risk ofintroducing new diseases and pests.

How do you select seedling-derivedclones for each cycle of intercrossing? Youcan base your selection on the phenotype ofthe seedling itself. However, at the seedlingstage, you have only one plant of each clone,grown from a different kind of propagulethan farmers use (seed rather than headsett orsucker). Therefore, it is not possible to makeaccurate judgements on many characters atthe seedling stage. After cloning theseedlings and evaluating the seedling-derivedclones in the trial sequence, your judgementof their performance becomes increasinglyaccurate as you advance from Hill Trialthrough Preliminary Trial, Intermediate Trial,Advanced Trial, and finally On-Farm Trials.

For taro it takes about 4 years fromCrossing Block until harvest of theIntermediate Trial. Therefore, if youplant a Crossing Block once each year,you will in fact have 4 recurrent-selection populations running at thesame time.

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During the first 2 or 3 cycles of yourrecurrent-selection programme, apply onlylight selection pressure to allow maximumrecombination to occur. For example, in thefirst cycle you could select and intercross allthe seedling-derived clones that you selectfrom the Hill Trial for planting in thePreliminary Trial. In the second and thirdcycles, you could select and intercross all theseedling-derived clones that you select fromthe Preliminary Trial for planting in theIntermediate Trial.

After completing these earlyrecombination cycles, you should increasethe selection pressure. We do this byselecting and intercrossing all seedling-derived clones that we have selected from theIntermediate Trial for advancement to theAdvanced Trial (see Figure 1). We may alsoinclude in the Crossing Block a few clonesfrom earlier trials that have good charactersbut are not good enough overall to be

selected for further trial. For example, a clonethat has a very high level of Pythiumresistance but has poor corm shape, or aclone with exceptionally high yield andeating quality but too few suckers. In theselater recombination cycles, use 30 or moreparent clones.

Newly introduced germplasm can be usedin the base population for introgressed(crossed) at any later time.

With each cycle of recurrent selectionyour breeding population will improve. Thismeans that the frequency of desirable geneswill increase, and your chances of findingclones with all the characters you want willincrease.

If you have a clone with one or a fewgood characters but many undesirablecharacters, you can introgress it into yourimproved population without adding thegenes for the undesirable characters to yourimproved population. Plant the clone to beintrogressed in a border row of your CrossingBlock. Use it in crosses as a FEMALEPARENT ONLY. If you are collecting open-pollinated (insect-pollinated) seeds from yourCrossing Block, prevent its pollen fromcontaminating your improved population byemasculating all its inflorescences beforethey shed pollen. Evaluate the progenies fromthese crosses in the trial sequence and repeatthe procedure with the selections until theyare improved enough for most characters tobe included as normal parents in therecurrent-selection crossing block.

You can also base your selection on thebreeding value of a seedling-derivedclone, as judged by the performance ofits progeny (progeny testing). This isoften a better criterion thanthe phenotype of the seedling-derivedclone itself. However, progeny testingadds a number of lengthy steps to thebreeding programme, and for thisreason we are not using it in our tarobreeding programme.

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GeneticsSome taro clones are diploid (2n) and containa total of 28 chromosomes. Other clones aretriploid (3n) and contain a total of 42chromosomes. All the clones in our breedingprogramme have acted like diploids. Taro isalso heterozygous, and consequentlysegregation of characters always occurs in theoffspring (progeny). Taro has both qualitativeand quantitative characters. Qualitativecharacters are distinct and discontinuous andare easily distinguished from each other. Forexample, stolon production is a qualitativecharacter. Generally only 1 or 2 sets of genescontrol each qualitative character. In contrast,quantitative characters are indistinct andcontinuous and gradually grade into eachother, and usually many sets of genes areinvolved. For example, the shape and yield ofcorms are quantitative characters.

For some characters, improvementthrough selection is rapid, but for othercharacters it is slow. This is determined bythe heritability of the character. If a characterhas high heritability, the progeny willresemble the parents, and improvementthough selection will be rapid. For example,sucker number appears to have highheritability.

Other characters have lower heritabilitiessuch as yield, fibre content, corm shape, andeating quality.

If a character has low heritability,improvement through selection will often beslow. It is sometimes possible to increase lowheritabilities by increasing the number ofreplications in trials and using betterscreening techniques, such as artificialinoculation. Also, when heritabilities are low,it may be better to base your selection onprogeny testing rather than on the parents.

stolons

Stolon production on seedlings

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Evaluating Specific Characters

Even if we are not selecting for a certainpetiole colour, we always note the petiolecolour of each clone in our field evaluationbook. Having records of this character helpsus to sort out ‘mixtures’ or find a lost clonenumber. With care, ‘mixtures’ and lostnumbers are rare, but they do happen!

Plant VigourPlant vigour is related to yield as well aserosion and weed control. The best time toevaluate plant vigour is at the so-called‘grand growth stage’, when plants havereached their maximum height. We classifyvigour as LOW, MEDIUM, and HIGH.Clones with low vigour usually produce lowyields. Clones with medium vigour usuallyproduce medium yields. However, cloneswith high vigour can produce either highyields or low yields. How? Some clones putalmost all of their energy into very vigorousleaf growth and consequently have poor cormgrowth. Therefore, an ideal clone must haveboth high vigour and high corm yield.

Plant CharactersThere are 2 basic plant types in taro. Thedasheen type has a large central corm, withsuckers, stolons, or a few small cormels thatare generally not eaten. The eddoe type has asmaller central corm that is surrounded by alarge number of well-developed cormels.These cormels are the main harvestable yield.The dasheen type is classified as Colocasiaesculenta var. esculenta, and the eddoe typeis classified as Colocasia esculenta var.antiquorum. In the Pacific, most tarocultivars are the dasheen type, and yourbreeding programme should concentrate onthis type. However, eddoe-type cultivars dohave certain advantages: they are moredrought tolerant than dasheens and thecormels have longer storage life than dasheencorms. For these reasons, eddoes maydeserve some attention in your breedingprogramme.

Some cultivars of taro produce suckers.Others produce stolons. With very fewexceptions, stolon production is anundesirable character, and you should discardprogeny with stolons.

Petiole colour is very variable, but it isusually not important to farmers unless theyassociate certain petiole colours withdesirable or undesirable characters in thelocal cultivars that they grow. For exporttaro, the colour of the base of the petiole isoften important because consumers use thischaracter to identify the cultivars they preferto buy. For instance, many consumers in NewZealand prefer ‘Samoa Pink’ (which inWestern Samoa is the cultivar ‘Niue’) andthey look for the pink petiole bases and budswhen they are buying taro.

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Sucker Number and AttachmentSucker number varies from none to a few to30 or more. The ideal sucker number isdetermined by the farmers’ system ofplanting and marketing. A cultivar mustprovide enough planting material to permitfarmers to replant and expand their fields. Inthose locations where farmers use a mixtureof headsetts and suckers for plantingmaterial, 2 to 3 suckers/plant is adequate. Inother locations, farmers use only suckers,either because they prefer them to headsettsor because they market their taro with theheadsetts attached and thus have only suckersleft for planting. These farmers need 3 to 5suckers/plant. Therefore, we select clonesthat on the average produce 3 to 5 suckersthat are large enough for planting.

Clones that produce too many suckers areundesirable because they are too difficult toharvest. Also, corms from these clones areunsightly because they are covered withwounds where the suckers have broken off,and these wounds make corms moresusceptible to post-harvest rot anddesiccation.

We have found that the ease of harvestingand the size of wounds on corms is alsodetermined by the sucker attachment. Suckerswith wide bases where they are attached tothe corm are hard to break off, and they leavelarge, deep wounds on the corm. Suckerswith narrow bases are easier to break off, andthey leave smaller, shallower wounds on thecorms. Therefore, we select for narrow-basedsuckers.

Remember that sucker number is verymuch affected by plant spacing. Therefore, itis important that you select sucker numberwhen plants are gown at the spacing mostcommonly used by farmers. Also, we havefound that when we are evaluating the HillTrial, we can safely discard seedlings thathave 10 or more suckers. However, manyseedlings that have ‘too few’ suckers (none,1, or 2) will produce 5 or more suckers whenthey are cloned and grown from vegetativeplanting material.

In very few taro production systems,high sucker number is a desirablerather than undesirable character. Thisis the case when taro is grown inflooded conditions as a long durationcrop (12 or more months) and smallcorms are acceptable to farmers andconsumers. In such a system, suckercorms contribute significantly to themarketable yield. Hawaii paddy tarogrown for marking poi is an example.

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Trials (if inoculum and insect vectors arepresent in that field). We also know thatmany seedling-derived clones tend to losevigour and yield (that is they ‘run down’) asthey progress from Hill Trial to PreliminaryTrial to Intermediate Trial to Advanced Trialto On-Farm Trials. We assume that clonesthat lose vigour and yield fastest aresusceptible to virus and clones that are stillmore vigourous and higher yielding thanlocal checks in Advanced Trials are resistantto virus. However, it is possible that theimproved cultivars we release, may gradually‘run down’ as they are grown for a number ofyears by farmers. We hope that this does nothappen, but we will know for sure only afterreleased cultivars havebeen grown for many years.

For Pythium, we determine thepercentage of the corms of each cultivarrotted at harvest.

Most, if not all, local cultivars of taro arehighly resistant to rose beetle. However, wehave found that seedling populations containa low percentage of plants that aresusceptible. These susceptible plants areeasily identified during the Hill Trial andshould be discarded.

Disease, Insect, and Nematode ResistanceIt is important that you develop a reliablescoring system that can distinguish resistantfrom susceptible clones. Your scoring systemshould have at least 3 classes, but it must notbe so complex that it is difficult to use on alarge number of clones in the field.

For dasheen mosaic virus, we evaluateeach plant separately using a score of 0 to 3,with 0 meaning no leaves showing symptomsof the disease 1 meaning mild symptoms onone or a few leaves, 2 meaning severe,conspicuous symptoms covering most of oneor more leaves or mild symptoms on manyleaves, and 3 meaning some leaves distortedin shape by the virus. Since plants produceabout one new leaf/month, we score plants atone month intervals through out the growingseason.

We also evaluate each plant for what wecall ‘golden virus’ (veins near leaf edges areetched a golden yellow colour). It is possiblethat ‘golden virus’ is another symptom ofdasheen mosaic virus, but until the casualagent is confirmed by pathologists, weevaluate it separately. We use the samescoring system as for dasheen mosaic virus,but omit score 3, because ‘golden virus’ doesnot cause distortion of leaves.

Remember that seedlings are virus-freeuntil infected by insect vectors. We do notyet know how many years it takes forseedling-derived clones to accumulate amaximum load of virus. We do know thatseedlings show symptoms during the firstseason they are planted in the field in Hill

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YieldTOTAL YIELD of corms is made up ofEDIBLE YIELD plus REJECTS (nonedible,mostly rotten and very small corms). Edibleyield is made up of corms that are goodenough to be sold (MARKETABLE YIELD)and corms that cannot be marketed but can beeaten by farm families. Which yields shouldyou measure? If you are breeding newcultivars for subsistence farmers, then edibleyield is the most important. If you arebreeding for commercial farmers, thenmarketable yield is the most important tomeasure. However, we have found that fortaro edible yield and marketable yield areusually the same. Therefore, it is necessary tomeasure only one or the other. Total yield isusually not a very relevant measurement.

The yield of corms at the main (first)harvest is more important to farmers than theyield of sucker corms from the ratoon crop.But clones that produce high, reliable yieldsin the ratoon crop have another point in theirfavour.

Remember that you should calculate yieldbased on the land area occupied by thenumber of plants of each clone you planted,not the number that survived until harvest.Why? Because survival, especially the abilityto establish at planting, is a very importantcomponent of yield. For example: you plant 5headsetts of a clone at 1 x 1 m spacing, and 4plants survive until harvest producing 4corms weighing 1.2, 1.1, 0.9, and 1.5 kg. Themean yield for this clone is 4.7 kg/5 m = 0.9kg/m2, NOT 4.7kg/4m = 1.2 kg/m2. The onlyexception to this rule is when the missingplant(s) are missing because of unnaturalcauses such as shortage of planting material,theft, hoe or weeding damage, or pig damage.

Time from Planting to HarvestProduction of upland/rainfed taro is oftenseasonal because there is only one ‘best’ timefor planting taro (at the beginning of the rainyseason) and because most local cultivarsmature in about the same number of months.One way to provide a longer harvest season isto breed a series of different cultivars thathave a wide range of maturities. Farmerscould plant the different cultivars at the sametime but harvest at different times. Forexample, if farmers had 7 cultivars thatmature in 4, 6, 8, 10, 12, 14, and 16 months,they could plant them all in September andharvest every month of the year. We have notyet been able to find this wide range ofmaturities in our breeding material, butconscientious selection and recrossing ofearly X early and late X late should graduallycreate more variability for maturity inbreeding populations. As soon as you havemore variability for maturity, you will needto divide your Preliminary, Intermediate, andAdvanced Trials into different sets of trials,e.g. early maturing trials, medium maturingtrials, and late maturing trials and to harvesteach set at the appropriate time.

Another important character is the abilityto ‘hold in the field’, meaning that a cultivarcan be left in the soil for several months afterit is ready to harvest without rotting or losingits eating quality. For example, in WesternSamoa, farmers know that cultivar ‘Manua’holds better than ‘Niue’.

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Corm CharactersIs there a preference for a certain corm shapein your location? If there is, then you shouldselect breeding clones with that shape.Clones that produce more than one head on acorm are usually undesirable. We classifycorm shape as ROUND, ELONGATE-ROUND (oval), ELONGATE, and MORETHAN ONE HEAD.

Smoothness indicates how muchcleaning (removing roots and ‘mat’) a cormrequires for marketing, as well as the numberand appearance of sucker scars. Deep andragged sucker scars are unattractive. We usethe categories SMOOTH, MEDIUM, andROUGH.

Farmers and consumers may havea strong preference for certain colours of thebuds, basal rings, petiole bases, and flesh,or they may accept many different colours.Be certain that you understand the situationin your location before you begin yourbreeding programme.

Field SelectionPlant breeding is both a science and an art. Abreeder makes decisions about which clonesto keep or discard based on both data(science) and on a gut reaction to ‘the look’of a clone (art). Sometimes we just know thata clone is worth keeping, even though wecannot measure why.

In Hill and Preliminary Trials, itis easy to take into account our gut reactionto ‘the look’ of a clone because we make ourdecisions about which clones to keep ordiscard IN THE FIELD at the time ofharvest. (The only character evaluated afterharvest is specific gravity.) However, inIntermediate and Advanced Trials, we mustanalyze yield and quality data before makingdecisions. Therefore, it is necessary to recordour gut reaction to ‘the look’ of a clone at thetime of harvest so that this gut reaction canbe considered together with the data when wemake our decisions in the office. We call thisgut reaction ‘field selection’ and record YESor NO, with yes meaning that our gutreaction to this clone is a positive one.

Double or multiple heads are usually undesirable.

If farmers in your location marketcorms with petioles attached, you maywant to weigh your trial corms withpetioles attached (use the same lengthas the farmers do), but when reportingyour yields, always indicate that youhave included petiole weight.

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Eating QualityGenerally, Pacific Islanders prefer dry,firm-textured taro. Therefore, percent dryweight is one measure of eating quality. InWestern Samoa for example, cultivars havingdry weights higher than 30% are preferred tothose with dry weights lower than 30%.However, some clones with dry weightshigher than 40% may be considered pooreating quality because they are too dry(‘hard’, especially when cold).

We measure percent dry weight of allclones in Advanced Trials. To do this, weselect 3 to 5 sound corms of each cultivarfrom each replication. We treat each corm asa separate sample. We peel it in thetraditional way, cut off the petioles and cormbase as for cooking, cut out a centre,longitudinal slice 3 cm wide, and chop thisslice into cubes 1 cm square or smaller, andplace these cubes into a paper bag or smallaluminium foil baking pan. We then weigheach sample to determine its fresh weight,dry it in a laboratory oven at 100oC until ithas reached constant weight (that is, whenfurther drying does not lower the weight),and finally weigh it again to determine dryweight. We have found that merchandise tags(with strings removed) survive the dryingtemperature and thus work well for labellingsamples.

You calculate percent dry weight as:

Often there is not enough oven space andlabour to determine percent dry weight of thelarge number of breeding clones inPreliminary and Intermediate Trials. Whenthis occurs, specific gravity can be used toestimate dry weight and eating quality.

We estimate specific gravity bydetermining whether a corm sinks or floats ina solution of common table salt dissolved inwater. For Intermediate Trials we select allsound corms from each replication. Forunreplicated Preliminary Trials we select allsound corms of each clone that hasperformed well for all other characters.

% dry weight =dry weightfresh weight___________ x 100

Do not forget to “tare” (deduct) theweight of the paper bag or bakingpan when you weigh fresh and drysamples. And when relative humidityis high, you must weigh dry samplesIMMEDIATELY after removingthem from the oven because theyquickly absorb moisture.

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To estimate specific gravity, make up 1bucket for each specific gravity rating byadding a specific amount of salt to 6 litres ofwater (see Table 2). Treat each corm as aseparate sample. Wash it in water. (It is notnecessary to peel off the skin unless you areusing the same corm for taste testing.) Thenplace it in Bucket 0. If it sinks, move it toBucket 0.5, then Bucket 1.0, then Bucket 2.0,etc, until the corm floats to the surface of thesalt solution. Give the sample the specificgravity rating of the bucket in which it firstfloats, and then average the ratings of thecorms to obtain a mean rating for thereplication (Intermediate Trials) or clone(Preliminary and Hill Trials).

When specific gravity ratings arecompared against Western Samoan taste-testscores, the results are not as consistent as

they are for other crops such as sweet potatoin Tonga. In other words, specific gravity isnot always a good predictor of eating quality,at least in Western Samoa. But we havefound that almost all clones with specificgravity ratings lower than 1.0 have pooreating quality. Also, that most clones withgood eating quality have specific gravityratings of 1.0 or higher. But, that not allclones with specific gravity ratings of 1.0 andhigher have good eating quality. This meansthat we can safely discard clones withspecific gravity ratings lower than 1.0. Whendoing so, we may discard a very few clonesthat have good eating quality, but the numberof ‘mistakes’ is too small to worry about. Inyour location, you will need to evaluatespecific gravity and eating quality of manybreeding clones and local cultivars for severalyears to determine how they are related.

Table 2. How to prepare a series of salt solutions to estimate the specificgravity of taro corms

Specific Amount of salt (grams) Actualgravity to dissolve in 6 liters specificrating of water gravity

0 0 1.00000.5 150 1.01731 300 1.03472 600 1.06803 900 1.10024 1200 1.13165 1500 1.16236 1800 1.1926

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Of course, the best method to determinethe eating quality of breeding clones is toevaluate them in taste tests. And this is theonly method to determine acridity, a veryimportant quality character in taro. However,taste tests are time consuming and only a fewclones can be accurately ‘tasted’ at any onetime. Therefore, taste tests must usuallybe delayed until Intermediate, Advanced, andOn-Farm Trials.

There are several methods of conductingtaste tests, some of them very complicated.However, we have found that a relativelysimple test is accurate enough.

From each replication of the Intermediateand Advanced Trials, we select 2 averagecorms of each breeding clone and each checkcultivar. We peel these corms, then cookthem in the ‘umu’, since this is the mostcommon method of cooking taro in WesternSamoa. Prepare your corms using the mostcommon cooking method in your location.We cut the cooked corms into small pieces,and put each clone (mix the corms) on aseparate plate that has been labelled with acode number (not the actual number thatsome tasters might recognize). We invite atleast 20 Western Samoans to taste severalpieces from each plate and fill out anevaluation form. On this form we ask them torate each clone as 4 (excellent, I like it verymuch), 3 (good), 2 (OK), or 1 (poor, I do notlike it). We also ask them to rate acridity asabsent (-) or present (+). And we also askthem to write remarks about each sample,explaining why they do or do not like it.

Of course, taste is not the only factor thatdetermines the ratings that our tasters give toa sample. They are also influenced by howthe sample looks (colour, ‘wet’), its texture,and the presence of fibres. All these factorsare important in determining eating quality.

Since taro leaves are a popular vegetablein most islands, eating quality of the leaf isalso important. Therefore, you shouldtaste-test the leaves of all clones in theAdvanced Trial that perform well for othercharacters. Harvest leaves at the correctstage, prepare them in a traditional recipe(choose a recipe in which the otheringredients do not disguise the taste of thetaro leaves), and evaluate in a taste test,particularly for acridity and tenderness.

When we asked USP Alafua studentsfrom several different countries to joina taste test, we learned an importantlesson. Judgements about eatingquality vary greatly from country tocountry. For example, a taro clonerated as excellent tasting by a WesternSamoan, may be rated as poor tastingby a Solomon Islander. This meansthat tests must be performed by peoplefrom the location for which the taro isbeing bred.

Acridity means irritation or scratchinessto the mouth and throat.

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Nutritional ValueProtein content, protein-inhibitor content, andvitamin content are very important nutritionalfactors that should be evaluated in your tarobreeding programme. However, mostbreeding programmes cannot afford theexpensive equipment and highly trainedtechnicians required to measure these

nutritional factors. If possible, you shouldestablish a collaborative project with anoverseas institution where you can sendsamples of clones from Advanced Trials foranalysis.

Be sure that you use ‘heat- proof’ labels to identify clones during cooking. We carve a code number into

each corm. Also metal labels and some marking pens will last through the ‘umu’. For boiling, you can cut

the corms into different shapes for identification.

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SUPPLIES

Merchandise Tags for labelling dry weightsStandard quality, white, 1-15/16 x 1-1/4 in., No.6, No. 12-203, 1000 in a box; fromDenney-Reyburn Company, West Chester,Pennsylvania 19380, USA.

White Plastic Labels for labelling pollinationsand basketsDiamond-Lox, white, 5-1/2 x 1/2 in., 1000 in abox; from A.M. Leonard, Inc., P.O. Box 816,Piqua, Ohio 45356-0816, USA.

Flagging Ribbon for markingFlagging, polyethelene or vinyl, 1-3/16 in. wide,many colours, 100 yds/roll; from ForestrySuppliers, Inc., 205 West Rankin St., P.O. Box8397, Jackson Mississippi 39204-0397, USA.

Aluminum Labels for marking field stakesAl Tags, 3/4 x 3 in., 9 in. wire, can bepermanently embossed with pen or pencil, 1000in a box; from Forestry Suppliers, Inc., 205 WestRankin St., P.O. Box 8397, Jackson Mississippi39204-0397, USA.

Field Record BooksLietz Level Book, No. 8152-55, 4-1/2 x 7-1/4 in.,water repellent; from Forestry Suppliers, Inc.,205 West Rankin St., P.O. Box 8397, JacksonMississippi 39204-0397, USA.

Plastic Net Bags for small lots of cormsSold for packaging onions, potatoes, etc.,available in rolls of long tubes that can be cut toany length, and in many bright colours.

Nursery Marking PensPermanent, sunproof, waterproof, fine point, No.UH0960; from The John Henry Company, 5800W. Grand River, P.O. Box 17099, Lansing,Michigan 48901-7099, USA.

Gibberellic AcidPro-Gibb Plus (20% powder) manufactured byAbbott Lab; stock no. 582601, 160 g bottle;available from United Agri Products, 1660Waiwai Loop, Honolulu, Hawaii 96819, USA.

Technical grade, 90% gibberellins, product noG7645; 1, 5 or 10 g; from SIGMA ChemicalCompany, P.O. Box 14508, St. Louis, Missouri63178, USA.

Twist-ties for pollinatingTwist-ems, 6 and 8 in. long, 1000 in a bundle;from Forestry Suppliers, Inc., 205 West RankinSt., P.O. Box 8397, Jackson Mississippi39204-0397, USA.

A - flagging ribbon B- al tag C- diamond-lox labelD - twist-ties E - net fruit bag F - cloth pollinating bag