The Journal of Pacific S tudies Volume : 7 , 1 981 , pp . 81-104

THE PHENOMENON OF VARIETAL YIELD DECLlNEOF SUGAR CANE WITH PARTICULAR REFERENCE TO FIJI

Prem C Prasad

Introduction

The varietal yield decline of sugar cane (Saccharum Officinarum L.) is a complex problem being dependent not only upon vigour of the crop but also upon physical environmental conditions. The deterioration of soil physical and chemical properties, ratoon stunting disease, presence of nematodes and poor quality of management practices all contribute in varying proportions to the decline of yield in sugar cane. By virtue of its importance, research on sugar cane breeding has an international dimension.

Sugar cane is essentially a tropical crop g rown predominantly between the latitudes 30 0 N and 300 S, with the approximate limits of its c ultivation defined by the 20 0 c annual isotherm, a nd a minimum rainfall of between 1400mm and 1 650mm (Klages, 1954: Campbell, 1967). The temperature and rainfall regimes place the major cane growing areas in the Af, Aw, Am, Cf, and Cw cl imatic zones as classified by the Koppen (1923) system. The areal limits of sugar cane cultivation are f u rther set by the annual ~so-potential evapotranspiration lines which e x tend =rom 1000mm in the southern hemisphe r e to 3000mm

11 1

in the northern hemisphere. The boundaries defined above, together with differences in soil physical and chemical properties, and variations in physiography and cultural practices, indicate that the crop is able to survive commercially in a diverse range of ecological conditions. A feature common to sugar cane wherever it is grown commercially, however, is the phenomenon of varietal yield decline, that is, the tendency of sugar cane yield of any variety to decrease over time. In recognition of this problem the sugar industry in every country has developed an active research programme in sugar cane breeding. It is not an exaggeration to state that the survival of any sugar industry depends on the strength of its breeding programme.

In this paper an attempt will be made to survey varietal yield decline in a number of selected countries, and to examine the factors responsible for this problem.

The Phenomenon of Varietal Yield Decline of Sugar Cane

Ever since the era of expansion of commercial cultivation of sugar cane, the problem of declining yield of all varieties has been of great importance to growers and millers alike. In general, the decline of yield takes two forms: (a) a sudden and spectacular collapse of a variety, triggered off by diseases, pests or genetic defects; and (b) a gradual decline in yield, which is a more commonly observed phenomenon. A feature which is common to both these cases is that they tend to occur after a period of relatively high production.

It is now generally accepted that varietal yield decline is caused by a number of factors which contribute to the phenomenon in varying proportions. Amongst the factors cited are: (1) declining fertility of soils,

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(2) the development of unfavourable physical conditions in the soils, (3) the cumulative effects of diseases and pests, (4) the existence of symptomless or unidentified diseases.

Examples of the Varietal Yield Decline Phenomenon

A notable example of the phenomenon of varietal yield decline is provided by N:Co310, a variety which had a high place amongst the famous sugar cane of the world. Bred in Coimbatore, India in 1938, the parentage of the variety was Co421 and Co312. The fertilized flowers from these varieties were propogated at the South African Sugar Experiment Station and the resulting variety of N:Co310 soon outweighed the long proclaimed advantages of the varieties grown then which included Co281, Co301 and Co291. The significant feature of N:Co310 was an extremely low incidence of virus diseases, the number of diseased stools being less than one percent of the original plants. The variety N:Co310 flourished for several decades and made significant contributions to the sugar cane production of several countries. For instance, in Natal it contributed 2.6 percent to the total sugar production in 1949-50 season and by 1961-62 its percentage had increased to 56.5. However, today the variety has been surpassed by others and hardly any is now grown.

For the period 1940-62, the varieties grown in Barbados (Figure 1) and Hawaii (Figure 2) were analyzed. These examples were chosen for the following reasons: (1) while in Hawaii the cUltivation of sugar cane and its processing is highly mechanized, this is not the case in Barbados; (2) in Hawaii, sugar cane is grown on a plantation scale while in Barbados there is a mixture of small holding and plantation systems; (3) in Barbados sugar cane is not always grown under optimum conditions of water supply or crop husbandry, whereas in Hawaii these and other requirements for maximum crop growth are ensured;

33

~ V> <11

!!' a >

CIJ .po

1 00 1 :::::::~ ~

9 0

60

50

40

30

20

10

Year

Figure 1: Diagram of variety percentages in commercial cultivation in Barbados. (Adapted from Ste ven so n, 1965.)

~ '" . ~ OJ c

(Xl 0

V1 >

1940 1945

Ye ar

Figure 2: Diagram of variety percentages in commercial cultivation in Hawaii. (Ad apted fr om Steven so n, 196 5.)

(4) the crop cycle in Barbados is about 15 months while in Hawaii it is for 24 months or even up to 36 months in the Hutchinson Plantation; and (5) sugar cane grown in Barbados is of a vertical variety and t herefore its energy and water use patterns are mar kedly different to the varieties grown in Hawaii where the crop lodges after the eighth month.

Doubtless, the factors mentioned above affect the survival capacity of any var iety. Given these differences and differences in t he physical environment compounded by cultural practices In the two countries, a contrasting pattern of var ietal y ie ld dec line eme rges (Figure 1 , 2). In Barbados, one dominan t vari ety, namely B3 7161 contribute d more than 50 percent of cane c r ushed fo r the decad e a round "1945-55 . The development o f this vari ety was one of the mos t significant advances in the s u gar cane breeding programme s o f Barbados.

In order to a s s es s the importanc e o f any v a r iety t o t h e total sugar cane p r oduced in a c ountry, a scale , taking into account the percentage of a variety g r own in a year, is propose d be l ow:

Var iety producing percent o f t otal sugar cane produced

Le ss t han 20

20 - 40

40 - 60

60 - 80

80 - 10 0

Qualitative description

p oo r

Minor

Ma j o r

Dominant

Exclus i v e

Prior t o 19 47 , s even var ieties were grown in Barbado s and except for B29 35 , all f al l in the poor category. Sub sequently, t he variety B3 7161

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was dominant, and by 1962 five other varieties were developed of which only two, namely B4744 and B49119, fell in the minor category; the remainder were all poor varieties. An important feature of the Barbados varietal change is that in any given year, no variety qualifies for the exclusive category; and therefore every year the sugar cane production is derived from two or more varieties, the maximum number being 9 varieties in 1944. From 1958 onwards, there were about five minor varieties, contributing almost equally to the total production.

In contrast, the Hawaiian varietal situation was totally different. While there were no exclusive or dominant varieties, only the variety 32-8560 could be considered as minor. Thus, in Hawaii, the sugar cane produced during 1940-62 comprised four to nine varieties, indicative of a trial period during which nO ,one variety made the greatest impaet. Also, considering the unique features of the Hawaiian sugar industry mentioned earlier, it appears that a high yield is obtained by growing a larger number of varieties rather than only one or two. There are obvious advantages in growing numerous varieties at the same time, since this safeguards the industry from attacks of pests or diseases which might be specific to a given variety. In this event the unaffected varieties may continue to produce high yields. The mixture of a number of varieties of sugar cane also reflects the economics of sugar cane production in Hawaii where security is sought in numbers. It should also be mentioned that because of the length of the crop cycle, the varieties grown in Hawaii are normally not grown elsewhere, and this factor may also in part explain a different pattern.

In Australia, during 1933, POJ2878 became a commercial variety and revitalised the industry, but its yield began to decline within a decade and it was abandoned. Then in 1935, the variety

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Co290 was introduced; this contributed 474,000 tons in 1940 but abruptly declined in productivity until it was withdrawn as a commercial variety. In Mackay district, the variety Q28 was first crushed in 1943, and it revolutionized cane growing, reaching the position of third in importance in the state by 1949, when 907,000 tons were harvested; yet within two decades its productivity declined sharply, and today it is totally absent from the plantation.

Analysis of the varieties of sugar cane grown in four principal regions of Fiji reveals some features common to all the districts. But each district also possesses its own distinctive characteristics. This finding stresses the fundamental role of micro-environmental factors such as microclimates; topography, drainage and soils in determining the decline of yields. Apart from these external factors, the sugar cane crop is itself susceptible to diseases, pests and ratoon stunting diseases. The research station of the Fiji Sugar Industry has directed most of its research toward breeding better varieties in an attempt to solve its own immediate problem of varietal yield decline, and at the same time contribute to a more general long-term global problem which links all sugar cane producing countries.

Data on the varieties of sugar cane grown in four principal regions of Fiji is available from the Fiji Sugar Corporation. The period 1949-65 was selected for this study because of the comparability of available data with that of other countries. Recently, the Fiji Sugar Corporation has begun publi~hing more detailed information on the varietal situation in the annual reports, and future studies on this topic should incorporate this new information. The changes in varieties of sugar cane in the four principal regions are depicted in Fiqure 3, and these will be discussed in total and aiso by individual districts.

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00 \.0

CHANGES IN VARIETIES OF SUGAR CANE GROWN IN FOUR PRINCIPAL REGIONS OF FIJI

"t> ~

~ ~ u ~

'" ~ " " .e ~ c ~ u ~

~

'" " .. ... 2 '0 C .. ~ ~ ...

." .. ~ ~ u .. co ~

" " 2 ~

" .. u

! 2 o " GO

. ~ ~ ...

LAUTOKA MILL

1950 195 5

PENANG MILL

1950 1955

RA RAWA I MIL L

1960 1965 195 0 1955 196 0 1965

LABASA MILL

196 0 1965 1950 1955 1960 1965

(a) Overall varietal changes in all four mills

Several observations can be made about changes in the varieties which apply to all four districts. First, the total sugar cane crushed in any given year is made up of several varieties, although there may be two or even three major varieties. Second, a major variety in one district may not have the same status in another. Third, where the same varieties are grown in two or more districts, they tend to occur over the same period. Fourth, the rapid decline in yield of a given variety in one district does not necessarily mean that the pattern will be similar for another district.

(b) Changes in varieties at individual mills

(i) Lautoka Mill

Four major varieties, namely Badila, Ajax, Pinda and Ragnar have contributed to the bulk of the tonnage of sugar cane crushed at Lautoka Mill during 1949-65. Varieties such as POJ2878, Galba, Horner and Spartan appear to have made a negligible contribution to the total tonnage crushed. It appears that uround 1960 there was a significant change in the sugar cane varieties grown in the Lautoka district. This period saw the emergence of Pindar and Ragnar and a greater dependence upon fewer varieties, while in the period ' prior to this, a large number of varieties contributed to the total tonnage.

(ii) Rarawai Mill

In the Rarawai district, there is evidence of a change in the varieties grown, around 1960. Prior to this date there were three major varieties, namely Badila, Pompey and Galba.

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After 1960, only Pindar and Ragnar were the major varieties. The variety Mantor did not make a significant contribution.

(iii) Penang Mill

The main varieties grown for the Penang Mill were Badila, Galba, and Ragnar. Minor varieties included Ajax, Pompey, POJ2878, and Pindar. The major changes in varieties occurred around 1960. Prior to this date Galba and Badi1a were the dominant varieties, but subsequent to 1960, Ragnar contributed to about 80 percent of the tonnage crushed, with the balance being made up by Pindar. A decade earlier, two principal varieties and three minor varieties were grown in the Penang district.

(iv) Labasa Mill

The changes in varieties grown in the Labasa district are more complex compared with the other three. There is a larger number of minor varieties including Pompey, POJ2878, Ajax, Corvus and Cros. The two major varieties, namely H109 and Ragnar, have contributed to the bulk of the sugar production. It appears that 1960 was an important turning point since it saw the decline of earlier varieties and the emergence of Ragnar and Pindar upon which this district became dependent.

The analysis shows that while there are certain similarities in the four districts, each region has its distinctive pattern with respect to the varietal situation. The pattern for each district stresses the difference in microclimate, topography, and the physical and chemical properties of the soil in determining the s uitability of each variety. The emergence, f ruition and deterioration of each variety may be ttributed to the physical environment, cultural

practices and crop characteristics.

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The foregoing discussion indicates that in time all varieties of sugar cane decrease in productivity to the point of economic unacceptability and have to be replaced by others. This fate is irrespective of the level of technology, or the crop husbandry practised. The observation of Francis Bacon: "that which man altereth not for the better time altereth for the worse" is particularly relevant to the global problem of varietal yield decline of sugar cane.

Sugar Cane Breeding Research

Because of the importance of varietal yield decline, the problem has been studied at the international level. Humbert (1959) discussed the physical and chemical properties of soils, their microbiological populations, and the rotation of crops in relation to the decrease in sugar cane yields. The main conclusion reached in this study was that modifications of the environment of the root system of sugar cane brought about by cultural practices may lead to inability of the soil to support continuing high yields.

The genetic aspects of yield decline have been critically examined by Mangelsdorf (1959) who stated:

The multiplicity of known pathogens suggests that the causes of yield decline are likely to differ in differe nt varieties and in different situations. In one situation, for example, the dec line may be due to the buildup of an i nitially scarce strain of the Phythium fungus; in another area, a new race of nematodes may be responsible. Regardless of cause, the threat of the yield decline can be best

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countered by active breeding and testing programmes. Ample genetic diversity of the breeding programme will help to ensure sources of resistance to the various negative factors as they develop. The more comprehensive the programme, the more promptly will a decline of the standard variety be detected once it occurs ...

In Hawaii, the biological causes of the deterioration of sugar cane varieties were studied by Martin et.al. (1959) who included cultural, environmental, and genetic causes in their consideration of this complex problem. They pointed out that the significant increase in yield of recovered sugar per hectare over a period of fifty years was due to the combined effects of: (1) replacement of declining varieties by higher yielding ones, and (2) an improved cultural practice and control of insects and diseases. Their investigation showed that the most important soil fungus causing a reduced yield was the root rot organism Phythium graminicolon. The effects of certain nematodes which were also found to decrease cane growth were not assessed because of the great variations in numbers and genera.

Steiner (1959) reported that the nematode infestation in the cane soils of Puerto Rico reached immense proportions, with population densities reaching hundreds of millions per square metre; up to twelve different genera were identified and named, while research is continuing on the biological identification of others. The symptoms of nematode infections were described as stunted growth of root, systems, rotting of roots, irregular growth of stools, sickly appearance of plants, and thin stalks. All of these effects contribute to a decreased yield per hectare. It is also commonly acknowledged that ratoon

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stunting disease is a major cause of varietal yield decline. Differences in the rate of deterioration have been found related to the degree of varietal resistance. In Louisiana, Abbott (1959 ) i nvestigated the ratoon stunting disease problem and identified the effects of ret rot, mossaic and phythiurn root rot on noble cane and the variety D74, which failed in the 1920 ' s.

As it is not possible to review the developments in sugar cane varieties in all countries concerned, an account of selected developments are given below in a historical perspective.

(i) Java

In Java the main impetus to a cane breeding programme was given by the presence of sereh disease, which caused extensive losses on the sugar plantations. All attempts to find an immune variety among the imported noble canes were unsuccessful. In order to monitor the disease special seed nurseries at an altitude of 450m -900m were established. Before 1890 several varieties were imported and tested for disease susceptibility and amongst these Loethers, Fidji, Batijanrn white and black Manila and Borneo are the best known.

The term "noble" sugar cane was first applied by Dutch researchers to various forms of S. Officinarurn which were tall and thick varieties with diameter of more than two inches. This luxuriant variety dominated the sugar industry for centuries. The process of 'nobalization' of sugar can refers to the crossing of wild Saccharum species with S. Officinarum, and afterwards back-crossing the selected progeny (Barnes, 1964), with the objective of maintaining a high juice quality by developing new varieties.

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Perhaps, the most important variety of sugar cane obtained in the nobalization programme of Java was POJ2878. In later breeding work this variety and other hybrids were used in further nobalization and in crosses between different nobalization stages to give improved commercial varieties. Two of these, POJ3016 and POJ3067, both seedlings of POJ2878 together occupied more than 85 percent of the cane area of Java in 1960. During the Japanese occupation, sugar cane breeding was discontinued but started again under the auspices of the Republic of Indonesia.

(ii) Barbados

In Barbados the systematic breeding programme of sugar cane commenced in 1902 using three different approaches.

(a) The hybridization method developed by Kobus in Java in which varieties shedding pollen were used as females and planted in a chessboard fashion with male varieties which shed pollen abundantly. Seed was collected from the females only. Seedlings from this experiment were described as Barbados Natural Hybrid (BNH) but none of them were ever planted commercially.

(b) An emasculation method was suggested by Bovell (1899). Stevenson (1965) described the method thus: "young unopened flowers of the variety to be used as female were emasculated by hand, and later fertilized with pollen from selected males. The work was done under a dissecting microscope upon a platform 8 feet high and required care and delicacy". Initially only a few crossed seedlings were obtained but later more were produced and were used e x tensively in the high rainfall districts of Barbados. The symbol BH denoted Barbados Hybrid, of which none was used as a commercial variety even though the t e chnique was employed until 1917.

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(c) Selfing, "the objects of which were to obtain an idea of transmission of unit characters to the progeny and in order to gain some knowledge of the value of different Barbados seedlings as the starting point for further work" (Stevenson, 1965).

Selfing was carried out with standard commercial varieties, and seedlings which had reached the "select variety trial" stage; resulting seedlings were given the symbol BSF (Barbados Self Fertilized).

As well as with the routine breeding programme in Barbados, considerable research in the laboratory was directed towards a detailed study of the genetics and cytology of selfing in sugar cane, and its application to the production of improved commercial varieties.

(iii) Mauritius

Scientific breeding of cane started in Mauritius in 1891, and the most important of the early nob~e cane seedlings to attain commercial popularity were 33P, SSP, and 87P. In 1930 organized breeding work on a substantial scale commenced and in the same year an important noble cane seedling, M171/30 was bred and planted commercially on a large scale.

Nobalization work was first used in the Mauritius breeding programme in 1931 by back crossing the imported POJ2878 with locally produced, and introduced, noble varieties. The well known M134/32 was bred in 1932 and within ten years was the major estate variety in the island, being grown in a wide range of environmental conditions.

Sugar cane breeding in Mauritius is noted for the use made of a vigorous seedling found locally. This variety known as Uka Marot used previously in

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an attempt to breed commercial canes directly, but yielded seedlings of very poor juice quality. In 1939, crosses were made by Stevenson to produce the parents of M147/44 and other commercial varieties which later replaced much of the area under M134/32. Uka Marot also contributed to the parentage of Ebene 1/37 which was grown on a large scale in Mauritius being well adapted to the cold, high rainfall areas.

(iv) Hawaii

Breeding research cOITmenced in Hawaii as early as 1904 but suffered a serious setback in the following year when importation of sugar cane was prohibited due to the accidental importation of a dangerous pest, Perkiniella saccharicida Kirk. At this time the only variety on the island was Uka which was practically infertile. This restriction in breeding activity did, however, produce one important variety, H109, a seedling of Lahaina (Otaheite) which subsequently became the major plantation variety.

In recent years, the Hawaiian breeding programme has been yielding more than a million seedlings for testing per year. A unique approach for sugar cane breeding developed in Hawaii is referred to as the "Melting pot" method. In this technique a large number of varieties, often several hundred arrows in all, are brought together in a special crossing rack holding many containers of the preservative solution, and their

" "ons relative to one another are changed "ly during the flowering period. The process

I ination occurs almost randomly and the ntag of the resulting seedling is known only

on the site of the seed bearing parent. This system of cane breeding is still used in Hawaii, and it has made a fundamental contribution to cane breeding.

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varieties which have attained commercial prominence in Hawaii include 37-1933, for many years the standard cane of irrigated areas, and the unirrigated variety 49-5, and 50-7208. An important reason underlying the success of sugar cane production in Hawaii is that the growing season of the crop is two years or more, and this has a direct bearing on the high quality of sugar produced. Several Hawaiian varieties have been grown unsuccessfully in other countries simply because the rather special circumstances required for their cultivation are found only in Hawaii.

(v) India

Unlike many other sugar cane growing countries, the subtropical environment of India provides new challenges in cane breeding. Here vast areas of sugar cane are in the subtropical climatic regimes which rule out the possibility of growing noble cane varieties or a variety of a comparable type on account of the temperature extremes experienced in these regions. High summer temperatures alternate with winter frosts in many areas to provide an environment to which the original native varieties of S. barberi and S. Sinense were well adapted, with low sugar yields.

Work at the cane breeding station in Coimbatore began in 1912 when Barber made the first deliberate cross between a noble cane variety and S. Spontaneum. The best of early Coimbatore hybrids were Co281 and Co290, and these found immediate application in subtropical regions not only- in India but also in Australia, Louisiana, Natal, Argentina, and Brazil. They were particularly adapted to poor soils of low fertility.

One of the originators of sugar cane breeding programme was Venketraman who carried out research in this field for about a quarter of a century.

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Among his most notable achievements was the development of an early ripening variety of sugar cane which was bred by crossing cane varieties with sorgum. However, the resultant variety never gained commerical prominence. In 1936, he calimed that he obtained hybrids from sugar cane and bamboo crosses, and again these were not developed commerically.

(iv) Fiji

In Fiji, the sugar cane breeding programme is carried out systematically in well defined steps. From the Table 1 it is clear that cane breeding is a complex procedure where a large number of potentially suitable varieties are considered and each successive step eliminates hundreds of varieties. During 1978, for instance, two varieties were released for Fi j i conditions, namely Kaba and Ono, but the original population numbered several thousands.

Table 1

stages of Sugar Cane Breeding Programme (Adapted from Krishnamurthi, 1978)

Steps

The process of crossing

1 Production of

e edlings

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Comments

In 1978, some 900 crosses were made, using about 1500 parent material.

About 30,000 seedlings were produced of which 20,000 were selected and planted in the field.

Table 1 (contd)

Testing of sugar fibre, and yield

Field testing, planted in three single stools and also two metre plots in the field

Seed multiplication phase and testing at the mill-level

! Release of sugar cane varieties to about 12 locations to assess the interaction with the physical environment.

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About 5,000 varieties were selected and planted. These were planted in three single stools and after 12 months of growth tested for sugar fibre and yield. Select 3,000 for continuation. Assessment of all field characteristics stooling, tillering, suckering, side shotting, flowering, tracking diseases, germination, stalk length and thickness and general agronomic desirability. In 1978, there were about 2,600 varieties in ratoon phase and 3,000 varieties in the plant phase. Disease testing was also carried out for Fiji's two major diseases Fiji disease, and downy mildew.

In 1978, about 650 varieties were available for distribution.

Of the possible 650 varieties, about 50 were selected for large scale trials.

Conclusion

The varietal yield decline of sugar cane is a problem shared by all sugar cane growing countries. This paper shows that, in time all varieties loose their vigour and reach a point of productivity which is economically unacceptable. The primary function of anyon-going research programme in cane breeding is to develop varieties which surpass the declining varieties in yield. A newly released variety is tested over a period of time, and during the transition phase several varieties are grown to test their suitability to the particular environment. This paper establishes that exclusive varieties are only notional, and at anyone time dominant or major varieties exist.

Although experimental tests may indicate the high potential of a number of varieties, they may not necessarily develop their full potential in the environment where they are grown. Thus, release of varieties which are found to be unsuitable and hence not grown subsequently is a common feature of varietal development programmes.

varietal yield decline is caused by a number of trigger mechanisms. Amongst the most commonly cited are: the deterioration of crop itself, the inability of the crop to adjust to the physical environment and the invasion by pests and diseases, early detection of the problem causing yield decline can lead to the adoption of remedial measures, although economic considerations often outweigh their prolonged usuage.

Regardless of technological sophistication, 1 sugar cane growing countries face the

r oblem of varietal yield decline and have v e loped their own research programmes to combat

this perpetual hazard. In Fiji, the cane breeding programme commenced over 75 years ago and during this period several drought resistant

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varieties have been developed successfully, thereby solving the immediate problem of decline in yield. In a broader context, this research has made significant contribution to the long­term global" programme of sugar cane breeding.

Acknowledgement

I am grateful to Dr W. C. Clarke who made valuable comments on the first draft of this article. Mr Alan Robson also assisted me in the revision of the manuscript and several of his comments have been incorporated in the tex t. Dr David Routledge also read the first draft and made valuable suggestions.

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Reference

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Sugar Cane Techn. 10th Congress.

Barnes, A.C. 1964. The Sugar Cane. Interscience Publishers. New York.

Bovell, J.R. 1899. Report on Agricultural Experiments Conducted at Barbados 1898 to 1900.

Campbell, R.B. 1967. Sugar, Oil, and Fibre Crops Part II -Sugar Cane. In: Irrigation of Agricultural Lands. American Society of Agronomy, Madison, USA. Chapter 33:649-654. Edited by Ragan, R.M., Raise, R.R. and Edminister, T.W.

Chang, J.R. 1961. Microclimate of sugar cane. Raw. Sugar Planters Rec. 56:195-225.

Chang, J.R. 1968. Climate and Agriculture: An Ecological Survey. Aldine, Chicago. 304pp.

Espenshade, E.B. (Ed.) 1972. Goode's World Atlas. 15th Edition. Rand McNally and Cog. Chicago, USA.

RumQert, R.P. 1959. Soil as a factor in varietal yield decline. Proceeding of 10th Congress. ISSCT:51-59.

Klages, K.R.W. 1942. Sugar. In: Ecological Crop Geography. Chapter XXVI:451-471. McMillan Company, New York.

Krishnamurthi, 1978. FSC. Agricultural Experimental station, Lautoka. Fiji Sugar Yearbook. 1978:75-76.

Koppen, W. 1923. Klimakunde.

Die Klimate der Erde: Grundriss der Walker de Gruyter Co. Berlin, 369pp.

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Mangelsdorf, A.J. 1953. Sugar Cane breeding in Hawaii. Part II, 1921 to 1952. Hawaiian Planters' Rec. 54, No.3.

Prasad, P.C. 1972. Evapotranspiration by sugar as influenced by meteorological factors. Unpublished PhD Dissertation. University of Hawaii, 293pp.

Prasad, P.C. 1979. The variability of rainfall in Fiji. Paper presented to the 49th ANZAAS Congress Section 21: Geographical Sciences. University of Auckland, N.Z. 15pp.

Prasad, P.C. 1981. Preliminary study of irrigation needs of sugar cane in Fiji. Report prepared for Department of Agriculture, Fiji. Mimeograph. University of the South Pacific, 55pp.

Steiner, G. fields. 85:86.

1959. A most serious pest in Puerto Rico cane Proc. Int. Soc. Cane Tech. 10 Congress.

Stevenson, G.C. 1965. Genetics and breeding of sugar cane. Longmans, London.

Thompson, G.D. and J.P. Boyce. 1967. Daily measurements of potential evapotranspiration from fully canopied sugar cane. Agric. Met. 4~ 267-79.

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