RESULTS AND DISCUSSION

Transcription

1 Breeding RECURRENT SELECTION FOR LARGE STALK SIZE OF SUGARCANE esearch Institute, Pasuruan 67126, Indonesia This research aims to develop population of large stalk size of sugarcane clones fop'breeding purposes. The approach uses recurrent selection in combination with Hawaiian melting pot technique. Through this approach, stalk size could ba increased significantly. The observed negative effects were on stalk population, piping and rendement. It seems that recurrent selection is an effective approach to improve observable characters of sugarcane clones. Key words: Stalk size, sugarcane, recurrent selection, breeding., INTRODUCTION The idea of selecting large stalk size was coined by Hawaiian breeders (HSPA4). A*valuable wild relative of commercial sugarcane, Saccharurn spontaneum, is well known among breeders for its prolific stooling ability and small stalk size. While prolific stooling is desirable, small stalk size is not. Unfortunately, small stalk size is a partially dominant trait. Since the beginning, most breeders have been attempting to utilize S. spontaneum germplasm and repeatedly backcross toward the commercial parent type until progeny with acceptable stalk size can be selected. Using commercial clones with extremely large stalk size to initiate crosses with S. spontaneum will probably be beneficial. This approach would allow the breeder to achieve intermediate stalk size as early as possible during the backcrossing process. This research aims to develop a population of large stalk size of sugarcane clones for breeding purposes., a MATERIALS AND METHODS Our approach to develop the population of large stalk size is using recurrent selection as described by Hull5. Hull's approach was also applied by Breauxl to enhance sucrose content of sugarcane varieties in 'Louisiana. The procedure is to: (a) select the largest stalk size phenotypes available; (b) intercross these 397

2 clones; (c) grow large seedling populations; (d) select rigidly for stalk size; and (e) intercross the selections to produce still another improvement cycle. The program started in 1986 using 54 varieties as initial parents (SO) in a melting-pot procedure. Some 291 clones (Sl) were selected for stalk size out of 62,168 seedlings during March 2-11, The second cycle was started in Some 372 clones (S2) were selected out of 120,625 seedlings in February Samples of 25 clones were taken ra om each cycle for evaluation in critical experiment. The experiment was planted in July 1990 at the Indonesian Sugar Research Institute, Pasuruan. It was arranged in a randomized complete block design with four replications. Each clone plop was planted with 24 buds in one row of three meters. Sane agronomic characters were observed and analyzed using orthogonab contrasts in analysis of variance. Germination was counted a month after and stalk number at three and six months. Stalk diameter was measured from the mid-internode in the middle of the stalk at six months. Stalk length to the top visible dewlap was measured twice at six months and again at early haryest. Since flowering stalks differ in their dewlap arrangement, measurement of flowering stalks was done between the lowest point and the seventh internode (Clements2, KSC6). Percent flowering was observed in April Two millable stalks were ~ut at random at early harvest. Brix was measured with a Bausch and Lomb precision refractometer and pol was assessed with a Schmidt and Haensch polarimeter. Purity and rendement were assessed as a function of Brix and direct pol reading (Tan8, TIM RENDEMEN9). Pithiness was assessed a3 percent of internodes; pipe diameter was measured on the seventh internode from the base in two stalks, averaged. ( I I ', I Late harvest was done at the end of July 1991, when purity and rende were assessed for the second time. RESULTS AND DISCUSSION At the start of the improvement program the av parents was 2.66 cm. Through the two cycles of recurrent selection, average stalk diameter was increased significantly to the average of 3.26 cm and 3.27 cm respectively (Tables 1 and 2). Although tremendous increase of stalk size could be achieved in the initialrcycle, there was practically no increase from cycle 1 to cycle 2,as indicated bycno significant difference of S1 vs S2 contrast (Table 2). The fact that ainong clones (within cycles) component is a significant source of variation for stalk size (Table 2) indicates that it should still be possible through tighter selection intensity to achieve further improvement.

3 ,' I I, ThBLE 2. Analysis of variances of pre-harvest observations. I,? >. 7 - k : ', 1., I, 1 L. Degrees Mean Squares fsource of of #Germi- Stalk # Stalk # Diameter Stalk Flowering a?' k;] ~$fi~\tiohs Freedom I nation (3 Mo) (6 Mo) Length 2 i ,895.60Y * 216' ' :O " is$ 81 I 1 >' * Significant at 1% level. B This experiment 'showed that an adverse side-effect of increasing " stalk diameter bas reduced staik dumber per unit space. It M ras pronounced at bot 3 and 6'fnonth counts (Tables 1 and 2). While large sl.alk e is desirable, less ;tooling - $"got. Geimidhtion, 'stalk, length a& flowering were barely affected. i ' <,( 2,, ' k,,, it(: ' \ : I,. * 399

4 BREEDING The more pronounced deleterious effects,of increasiong stalk, size were on the frequency and size of piping and the reduction of rendement, These phenomena are presented in Tables 3 and 4. Pithiness and purity were barely affected. This finding was supported by Mariotti7 in his path analysis. It was shown that there1 has been a negative correlation coefficient' between kndement and stalk diameted as a component of cane weight, that is, the bigger the diameter, the less the, rendement. The close association of piping and stalk size,was probably due; to rapid growth. Evans' experience (Evans') showed that hollowing in the stalk: is generally associated with rapid growth, i.e, they are large cells in which1 the vacuole is not completely filled with sap, central core pithiness'could welli be associated with very rapid growth and there would be a tendency for such tissues to dry out on full maturit TABLE 3. Mean of I Early Harvest,%,!.>.,,. Late uarvest Cycles Stalk Pithiness Piping Purity Rend. Purity Rendement length (%) freq. diam. (%) (%) (%I a b r I The most frequently used parent varieties at Pasuruan are vartieties with small, to medium stalk size. The outstanding performance of Ps 61 in multilocation/ yield trials is overlooked by planters due to the fact that its stalk diameter is too small. It seems that released varieties should meet a minimum stalk size, standard. Although negative correlations cannot be neglectid, this program offers some advantages on the Pasuruan breeding program. CONCLUSION 1 i J ' ', ',,*',#. I, I1 / Through a recurrent selection procedure stalk, size,,could, be increased significantly. Although disadvantageous,negative correlations qould,not be neglected, this procedure offers, some advantages for the Pasuruan breeding program. The observed deleterious effects were on stalk population, piping and rendement. It seems that recurrent selection described by Hull5 in combination with Hawaiian melting-pot technique is an effective way to characters of sugarcane varieties.

5 -- UKARSO AND S. SASTROWIJONO he11 4. Analysis of variances of post-harvest observations 0 ' ACKNOWLEDGMENTS Thdnks' to 'Mr.'Kabul Agus Wahjudi for his help in data processing. REFERENCES 1. Breaux, R.D. (1984). Bfeeding to enhance sucrose content of sugarcane varieties in Louisiana. Field Crops Research Clements, H.F. (1980). Sugarcane crop logging and crop control. Principles and practices. The University Press of Hawaii, Honolulu. 3. Evans, H. (1966). Investigations on the occurrence of pithiness in cane. ISSCT Sugarcane Breeders' Newsletter 17: HSPA (1984). Annual Report. Hawaiian Sugar Planters' Assoc. Exp. Sta. 5. Hull, F.N. (1945). Recurrent selection and specific combining ability in corn. J. Amer. Soc. Agron. 37: KSC. (1980). Procedures manual for a sugarcane ripening log, a method for preharvest sampling, field experiment procedures. Kenana Sugar Company, Sudan. (internal publication). 401

6 7. Mariotti, J.A. (1973). A path-analysis of yield components in sugarcane. ISSCT Sugarcane Breeders' Newsletter 32: I1 th 1984, BP3G ha I \ $ LA SELECTION RECURRENTEl POUR LE DIAMETRE DES TIGES' DANS LA CANNE A SUCRE \ G. Sukarso et S. Sastrowijono RESUME ' polycroisement. Ainsi, le diamktre des tiges fut augment6 de fa~on ~ignificative. Les effets negatifs associts portent sur le nombre de tiges, la formation de lihge et le rendement. I1 apparait que la selection rkcurrente est efficace pour amtliorer des caracthres m~rphologiques des clones de canne 8 sucre. Mots clts: Diamhtre,des tiges, canne 8 sucre? sklection rtcurrente, amklioration varittale. 10

7 SELECCION RECURRENTE PARA MAYOR TAMANO DEL TALL0 DE LA CANA DE AZUCAR I ' RESUMEN El objetivo de la investigaci6n es desarrollar una poblaci6n con un mayor tamaiio del tallo para prop6sitos de mejoramiento. El esquema utiliza la seleccidn recurrente junto con la tkcnica de policruzamiento Hawaiiano. A travts de este 403