1 (Sc/er(r~~ora sacchari Miy). and nematodes are presen. i EARLY STAGES OF VARIETAL SELECTION PROGRAM IN FIJI 1

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1 Cane Breeding I i EARLY STAGES OF VARIETAL SELECTION PROGRAM IN FIJI 1 M. Krishnamurthi and S. C. Prasad Agricultural Experiment Station, Fiji Sugar Corporation Limited, Lautoka, Fiji ABSTRACT A new scheme has been designed to select sugarcane varieties based on measurable characters during the early stages of the program. These were based on a single character specifications as demanded by the industry unlike the previous procedure where total performance was considered of greater value. INTRODUCTION The success of any breeding program is mainly dependent on the efficiency and effectiveness of the selection system geared to the requirements of the industry. Often it has been observed that many plant breeders set their goal to achieve improvement on single characters such as resistance to a specific disease, increase of sucrose concentration in juice, etc. Unfortunately, they tend to miss the objective and select for total performance of the varieties while evaluating the experiment. In case of sugarcane, the criterion changes that increase in sugar per unit area is measured. If results were found statistically insignificant, the trials were abandoned. The same situation exists with mutation breeding and varieties obtained through tissue culture. On many occasions, what may be s.tatistically insignificant could be very significant on a national level for a specific character, e.g. increase of sucrose concentration in juice for a variety may only be to 0.4 ton per hectare and statistically insignificant in that particular trial. When calculated on a national level this could give rise to very significant increases. Therefore, the testing and selection should be one which incorporates safeguards and yield results to the situation. The Fijan soils are generally poor and highly deficient in organic matter, phosphorus and potassium. Thus, a plant breeder has to produce varieties which have all the required attributes (high yield of sugar per unit area and good milling qualities such as, uniform fiber i.e to 13.5% with a seasonal average of 12.5%; about tons cane to make a ton of sugar, low impurity loading, etc.). These are substantial demands on any breeding program especially where the worst diseases and pests of cane such 1 (Sc/er(r~~ora sacchari Miy). and nematodes are presen

2 M. KRISHNAMURTHI AND S. C. PRASAD 1112 MATERIALS AND METHODS In any one year, we effected about 1,200 crosses. The seed for planting was drawn from selected 800 crosses with a maximum of $00 seedlings from each cross. In the new system,we usually have a population of 20,000 seedlings in the field in intensive care trial (ICT) as will be described later. The crosses selecteij in the first stage were from the following categories: Commercial x commercial e.g. Homer x Mali ~ Commercial and near commercial polycrosses (Melting pot crosses) lnterspecific crosses e.g. S. officinarum x S, spontaneum: S. officinarum x S. robusrum lntergeneric crosses e.g. S. officinarum x Brianthus. S.,o fficinarum x Riphidium Backcrosses The 20,000 seedlings were planted in ICT in the field. In the ICT, the seedlings were planted at 30 cm spacing in rows which were 75 cm apart giving a population density of 99,000 stalks per ha. The canes when grown were limited to two stalks and supported by wire frames. Five known commercial varieties were planted as standards. Each standard made up a minimum of one percent of the total population. Thus, the standards always constitute five percent of the.total seedling population. The selected population from seedlings i.e. stage 2 and the subsequent selections stage 3 were planted in pots (Daniels and Stevenson31 with three replications each. The same varieties were also planted in 2 m plots in the field so that all fields characters can be assessed under appropriate conditions. The field characters recorded were: flowering stalk length and thickness, tillering, stooling, side shooting, suckering,, trashing, lodging, diseases and general agronomic desirability. The basis of selection for all population for seedlings, stages 2 and 3 were on ratings arrived at after calculating for the standards against their known ratings. The ratings 0 to 9 were used (Daniels and Horsely5); 0 indicated the best of performance and 9, the worst. The discard level was placed a unit below the least performing standard. The known ratings for Fijian standard varieties were as follows: SUC FIB TCH TSA FIJ DOM Ragnar Homer DOM = Downy mildew

3 1113 CANE BREEDING Once the standards were brixed, and the fiber measured and cane weighed, the regression was calculated and the regression line was graphed (Fig RATING OBRIX 23.6 & more & less 20.0 FIGURE I 4 I Established Ratings Regression Line Graph for Sucrose Selection When the different characters were measured for test varieties, the ratings were assigned using the system in Table 1. The data was then entered into computer sheets for storage and analysis. The sample of the sheet is attached as Appendix 1. TABLE 1. System of rating used when measuring varietal characters. Actual ~nown\r$~in~ Given rating Brix Fiber Brix \Fiber' Brix Fiber Ragnar = t 9 Ma na = Mali ~ Waya = LF = = = = = Less 17 plus

4 M. KRlSHNAMURTHl AND S. C.'PRASAD Flbe. U",% & 1sn Ertnbllrhsd Ratlnyr FIGURE 2. Regression Line Graph for Fiber Selection The selections at various stages were made on the following criteria: Characters SUC, FIB. 5,000 x 3 reps SUC, FIB, TCH. 3,000 x li SUC, FIB, TCH, RS. 3 reps TS. All field characters and diseases DOM & FIJ. Seed Multiplication 2 (reps) 2 x 600 x 12 locations TS, RS, SUC, FIB, TCH, Mass stool population TSH, STARCH, All field characters. Randomized block x 6 reps. 4 row x 20 meters Large plots All field and biochemical characters. Large mill test. The stage five selection was based on mass stool population principles (MSP) (Daniels J. et ai4). From the original concept of MSP, the following variations have been introduced: * The entire stool was allowed to grow, i.e. free stooling. This was used for measuring yield. * Although ratoon data da"sii considered for all selection purposes we do not wait for ratoon data for initial s'elec;t[ons. This was incorporated later. I * The trials were in two rep1 ications'in twelve locations.

5 All the selections were based on measurable characters in comparison with the standards. The selections made to date were shown in Table 2. TABLE 2. Selections made from 1971 to 1978 on Stages 1 to 5. Stages ,248 10,000 3,060 17,100 28,516 22,090 22,164 20, ,700 5,107 1,560 4,473 9,915 5,284 5, ,700 3,000 1,175 2,300 3,259 1, ,636 1,874 1,175 1,389 1, RATING WEIGHT IN KG & more 2 1.I

6 M. KRISHNAMURTHI AND S. C. PRASAD 1116 DISCUSSION The current system eliminated human errors calrsed-by the operator as all selections were based on measurable characters, thus minimizing personal bias. The system also eliminated much of the error coming from the environment. Row spacing, soil type, moisture, competition for light, etc. were all made uniform. The interaction to the environment was well tested at stages five and six by having the stage 5 MSP trials at twelve locations in two replications each, and stage six trials in at least four different sites. The interaction assessed for were: soil type; maturity as affected by soil, rainfall, and night temperatures; infection by sugarcane borers and nematodes; and year to year variations on the same location. In essence the interactions were measured on two parameters: within the year over various locations, and on the same location over the years. Such a system, therefore, offered a plant breeder greater latitude of operation than previously possible. However, it must he observed that the system required the facilities of a computer and its operators to measure the various characteristics of large populations. REFERENCES ' 1. Brown, A. H. D., J. Daniels and N. D. Stevenson (1971). Mass selection reservoir and sugarcane selection. Theoretical and App. Genetics 41 : Daniels, J. and A. H. D. Brown (1968). The population approach to sugarcane breeding. 3. and N. D. Stevenson (1971). The reduction of the intergeneration interval in the Fiji breeding program. Prqc. ISSCT 14: (1971). A mass reservoir approach to mutual and geographic selection in sugarcane. Proc. ISSCT 14: 5. - and D. R. Horsely (1971 ). The use of 0-9 scale in fating sugarcane. Characteristics. ISSCT Sugarcane Breeders Newsletter 27.

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