PHENOTYPIC SELECTION OF SUGAR

W i l l i a m 3 . Gabr i e l a

INTRODUCTION

A complex of problems i n t h e maple syrup industry has been ga the r ing f o r c e dur ing t h e p a s t 50 yea r s , l e d by increased costs, reduced ~ r s d u e t i o n , and a dwindling l a b o r supply. V i th in t h e l a s t t w o decades, research has done much t o a l l e v i a t e t h e s e problems. For example, recent. studies an the t e c h n i c a l and mechanical a s p e c t s of sap c o l l e c t i o n have resulted i n an i n c r e a s e of n e a r l y 300 percent i n sap product ion, Although t h i s iaprovement r e q u i r e s a s i z a b l e investment i n new equipment, i t can be made w i t h a sha rp ly reduced l abo r fo rce .

Iaprovements i n t h e b i o l o g i c a l a s p e c t s of sugar-aking, a l though of a long-term n a t u r e , a r e a l s o progress ing . The s e l e c t i o n and elona$ propagat ion of supe r io r phenotypes f o r t h e development of improved s t ra ins of sugar maple f o r sap-sugar product ion have been completed, The next s t e p , c l o n a l and progeny t e s t i n g , i s being taken.

A program f o r t h e improvement of sugar maples for sap volune has been i n i t i a t e d r e c e n t l y a t our p r o j e c t i n Burl ington, Vemont , and is being conducted i n p a r a l l e l wi th t h e experiment i n sap-sugar iaprovement,

The importance of sap product ion i n t h e manufacture of maple syrup is poin ted ou t by t h e f a c t t h a t an average of 34-112 g a l l o n s of sap are r equ i r ed t o make I g a l l o n of s tandard weight syrup (13 pounds), Th i s f i g u r e i s based on an average sap sugar eonten t s f 2 .5 percent*

Also, s ap f low is depending upon f avo rab l e weather conditions, Whenever a cold n i g h t is followed by a warm day, t h e sag usually puns w e l l . Knowing t h e l a r g e volume of sap r equ i r ed t o make syrup, and t h e u n c e r t a i n t y of sp r ing weather i n sou theas t e rn Canada and northeastern United S t a t e s , one can see t h a t t h e sugarmaker must ob ta in as much sap a s p o s s i b l e when t h e cond i t i ons a r e optimuat,

The program f o r t h e s e l e c t i o n of high sap y i e l d i n g trees was conducted i n Maine, New Hampshire, Vermont, Massachuset ts , New Ysrk, Pennsyl~anta~ Ohio, Michigan, and Wisconsin. This broad coverage was made poss ib l e through t h e coopera t ion of s t a t e f o r e s t r y o rgan iza t ions who provided t h e fieldmen f o r making t h e i n i t i a l s e l e c t i o n s - T h i s paper gives the results of t h e f i r s t year of ope ra t i on of t h e program.

Research G e n e t i c i s t , Fo re s t Serv ice , U. S. Dept . of Agriculture, Northeas te rn Fo re s t Experiment S t a t i o n , Burlington, Vermont-

A search o f the literature has shown tha t t h e r e is a gene ra l agreement among researchers t h a t certain t ree c h a r a c t e r i s t i c s are correlated w i t h high sap-voluxle y i e l d . However, no s i n g l e c h a r a c t e r o r combination o f characters were found t h a t s a t i s f a c t o r i l y explained t h e observed phenotypic v a r i a i o w i n sap production.

Toma (1961) repor ted t h a t sap y i e l d increased s i g n i f i c a n t l y w i th dbh, and he noted that l i v e crown r a t io (tree he igh t t o l i v e crown length) was positively correlated with sap y i e l d . But crown l e n g t h a lone showed no cor re la t ion* The author f u r t h e r s t a t e d t h a t t h e combined e f f e c t s of dbh, tree height , c rom d i m e t e r , and l i v e crown r a t i o accounted for only 19 percent o f the pheno&ypic v a r i a t i o n observed. Morrow (1955) and Blum (1971), i n separate similar s t u d i e s , ob ta ined resul ts t h a t w e r e in generak agreement with t hose mentioned above.

Z4arvl1-1 e$ &. (1967) forend Parge differences between trees i n bo th sap volume and s a p sugar. The authors also repor ted a h igh ly s i g n i f i c a n t relation between sap-volume yield and sap-sugar con ten t , based on 18 yea r s of data. Our own observations and those of Morrow (1952) do no t i n d i c a t e a relationship between the characters of sap sugar and sap volume, but i t should be pointed out that t he l a t t e r f i n d i n g s were based on s h o r t e r s tudy periods of 3 t o 5 years*

Sumariz ing the per t inent literature, I f ind an apparen t r e l a t i o n between sap y i e l d and live-crown r a t io and dbh. But a l a r g e p a r t of the phenotypic variation in sap yield cannot be explained s a t i s f a c t o r i l y by differences i n these characters, This leads me to b e l i e v e t h a t much of the unaccounted f o r variation could be inherited. However, I would like t o po in t out t h e p o s s i b i l i t y that some of t h e unaccounted-for v a r i a t i o n may be associated w i t h the inherited tendencies s f t h e f a c t o r s t h a t were found t o be related to sap production,

The methods and criteria t h a t were used i n making s e l e c t i o n s were based on our past experience i n se lec t ing f o r supe r io r sugar product ion , and on the results of exploratory s t u d i e s t h a t were c a r r i e d ou t du r ing the las t 2 years,

The selection of superior sap-producing phenotypes w a s based on sap-flow rate measurements. I n an exploratory s tudy , w e found t h a t sap-flow rate was satisfactorily correlated (rp = 0.55 - 0.93) w i th t h e total sap volume produced during t h e sugaring season (Gabr ie l gal. 1972). This favorable relationship helped t o make t h i s program poss ib l e .

An average sap-flow rate was determined f o r each sugarbush, based on a saesnple u f 100 trees taken along a t r a n s e e t . On a few occas ions t h e nmber sf trees i n t h e sample dropped below 100. The measurements were recorded (Fig. 1); and when a tree with an unusual ly h igh sap-flow r a t e was found, i t received fur the r attention,

Figwe f ,--Completed Farm 1 showing sap VO$ t es t data and o t h e r i n f o r m t i o n p r t b e n t do t h e sugarbushe

Do no& w r i t e in t h i s space

SUGARBUSH - 1 7 ROMSIDE OR FENCELINE TREES

Last H a m e Middle I n i t i a l F i r s t Name

Loeation o f B w h if d i f f e r en t frm

er's address :

No , Rate No a No, No, No, Rate

$%me Gomp let ed :

- T 3 c : n p j i ' = 2s a selection candidate, a tree had to exceed the average

_ I - T e _ , --< A , _ ,i - - 35 :c-r--z.21 s a r r o ~ n d i n g standards by a minimum o f 70 pe rcen t ,

%L 1~2s+ :I] ~ e r c e n t above t h e b e s t performing standard, A Z f trees ,, - z i ~ r ~ c > J by che fieldmen w i l l be c l o s e l y screened according to

3 -- - * - - * -;;,ti ;rsc-d ::T* cable 1, In t h e s c r een ing process the selected

* - - * $ 1 -- -~*-nl, DP 9 ~ 1 1 ; ~ l z e d f o r departing in appearance and proximi ty from its "r r- Ti'-.azz x t t h t3c lowest number of penalties and highest - 2, -- , - -

A d cr%-.:--.lz = ' 1 ~ ::e placed in our select t r ee c a t a l o g u e . S h c e our my;jzrc-- Is in i t s f irst ysar of operation, screening will not - "

x - 11 - z S 2 3 7 L sugaring season,

RESULTS AXD DISGU%SIB?J

" , - 1 - a

, , , - A _ - = 3"cne selection program a f t e r one sugar ing season are - s

-"..-----a- -,c< A A / - $ - - f l q l - g ~ * , A A , .., -_,, to s ta tes , in table 2

T,rzc ~ " a a c e , ic nay seen that t h e selections made this year are -ac i$2r a- , y j2 : _l ;r c<:ntl-,eJ- Eowever, t h i s figure compares fav0rab1y with t h e 3 r ~ ; -.-:-i ' 3 -e-;t~,;s o f t h e now successfully completed sap-sugar program

'"- - i- 5

vdli.=n ,* zi-ces :-rr;. selectedl Correspondence from t h e f i e l d has indicated 5 <c

r- L / r - ,;"?,."" " -

# - --, 2; workloadsB uncooperative sap-flow weather, and 1C 21 --- -- - i. ra-, - :- - "1;4.6 ~ ~ a r l c contributed to "%he relatively small number o f

7 -

--kc2-;i4 > ~ C L 5-41: t x - e z t h a t %were tested and se lected,

- _ _ " = q I - C C * - - j J ~ x - 1 ~ ~ %-YE to begin looking for p o s s i b l e patterns in d -

r ; f ~ ~ : _b;z -:: llixL -5 3e2xes ~r between areas w i t h i n states. Buc t h e present * * -r' - - r

> - - . A li *_ ,c5 - k t election d i f f e r e n t i a l s will be large, 3s seen in t h i s ' f :xgmalZ 2 1 ,

< " * f e z qd;'3*b@#" i - f 4 .-, o f f i e l d selections will receive a final screening 3 , y -7

- -9 i

- - :ye & Y &+ 522 s s a s o n , Characters that w i l l be scored are l i ; t s d in - -

> A - 1 ,B>~~;I:; ;>;;?:I 35 E i g ~ r e I. The screening c r i t e r i a (table 1) w i l l ioe &3;)3 -3 tz r e d - ~ c a :he aunber of selections tha t may owe t h e i r s u p e r i o r - r c

- # - -ulTr

Bj r:r.. t3 +r i - *# - P - T - - ? ,,, , -w-, ,~1-iz1entaI ra ther t han genetic fac tors ,

-3 i I l~;zl-- . , te a sriec-:ion unic, f i g u r e 3 shows a selected tree and 2 5 Note chat we try to use standards t ha t &re comparable

lr: 2 5.;-"2p3qCe C-9 zrAe s l i e c t e d t ree* In t h i s example, t he selected E r e e

- 1 ~ - :c --: z",.. . ; ~ E T G ~ L sa2--f low r a t e of t h e s t anda rds by 88 percent, and ?-. 5 " T - :;id; ? 5 ' Eg ;Dzr(:;-,Rc,

- - -2-Z.S%Ai'i i f e z 1 t h a t i f we iron BUI: a few d i f f i c u l t i e s in t h e f i e l d ,

aria -,C?T?~C"- I,z:,:s, ctx-crihuc.es t h e r i g h t k ind o f weather f o r good sap flow, - - - ~ ~ ~ c c e s ~ F ~ ~ 1 - y conplete t h i s program by t h e end o f next year,

Table 1. -

Chavac t er Index of f a c t o r No. L i m f ts

Diameter = - - * - 0 2 0-10% of se l ec t ed tree diameter

1 "1-20% of selected tree diameter

2 "2-30% of selected tree diameter

3 k 31% and over selected tree diameter

Height * e e . . * O 2 0-10% of selected tree height

1 f 11-20% of selected tree height

2 -+ 21-30% of se l ec t ed tree he igh t

3 k 31% and over selected tf&e height

Live crom r a t i o 4 . 0 2 0-10% of selected tree Live crown r a t i o

I 2 11-20% of selected tree l i v e crown r a t i o

2 2 21-30% of se l ec t ed tree l i v e crown r a t io

3 f 31% and over selected tree l i ve crown r a t i o

D i s t r i b u t i o n . . = . 0 Within 0-25 f e e t of selected tree

1 Within 26-40 feet of selected tree

2 Within 41-60 f e e t a f selected tree

3 Beyond 60 f e e t of selected tree

Insec t dmage, d i sease damage, and topography . . . oa Completely cantparable t o selected tree

1 Some v a r i a t i o n but s t i l l considered comparable

2 Considerable va r ia t ion , conparability qGestionable

3 Not comparable t o selected t ree

a Criteria limits 8 through 3 assigned t o each character fro^ insect

damage through topography. - 23 -

Figure 2.--Partially complered Fom 2 showing individual perfomances of t h e selected tree and i t s standards. Lower part of fam will be cmpleted when selected tree is screened,

12

;AMTlsPW FERm a: SELEmED T E E S PIS, STM

1, Sap P l w Rate

t) I I i i ) nt and Morpholqy Cmparieow o f Standards and Selected Trees

Table 2. -

-- S t a t e Sugarbushes Trees tested F i e l d s e l e c t i o n s

No, - 52

New Hampshire 3 140 5

Vermont 7 518 7

New York

Pennsylvania - - -- --

Ohio -

Michigan

Wisconsin

T o t a l 38 2 ,375 5 5

F i g u r e 3*--This s e l e c t e d t r e e (marked "S") exceeded t h e ave rage of i t s s t a n d a r d s by 98 percent,

LITERATURE CITED

mum, B, N, 3.991, Some correlations between sugar maple tree characteristics and sap sugar y i e l d s . USDA Forest Serv. Res. Note HE-143, 4 p.

Gabriel, W. J., R. S. Walters, and D. W. Seegrist. 1972. The relationship between sap-flow rate and sap volume in dormant sugar maples. USDA Forest Serve Ress Note NE-153, 4 p., illus.

=rvin: 9. We, M. H a r s e l L i , and F. M. Laing. 1967. A correlation between sugar concentration and volume yields in sugar maple--an 18-year study, Forest S c i , 31:347-351.

Morrow, R. R. 1952. Consistency in sweetness and flow of maple sap. J. Fores t , %0:%30-13LI

Morrow, R. R. 1955. Influence of tree crowns on maple sap production. Cornell Univ, Agr, Exp* Sta. Bull. 916, 30 p.

To=, A. KB 1961* Correlations between several tree characteristics of sugar maple (Acer saccharum Marsh.) and maple sap and sugar yields. Unpublished thesis, Mich. State Univ,