GENETIC VARIABILITY AND YIELD COMPONENTS RELATIONSHIPS IN SOME EARLY MATURING SUGARCANE (Saccharum hybrid spp) GENOTYPES

Abstract

Eight early maturing sugarcane (Saccharum hybrid spp.) genotypes were evaluated in a four-replicated RCB designed experiment for two years each in plant and ratoon crops during 1909/00 to 2001/02 at the farms of Sugar Crops Research Institute, Mardan. The genotypes were S.87-USJ 87T S.86-US.795, S.86- US.642, S.86-US.432, Thatta-7, CP 72- . . 2086 TCP 81-1 Olncluding Mardan-93. Sixteen characters, germination %, hlicrs/70 m2, leaf stalk length, stalk diameter, intcrnodcs/slalk, stalk weight, stalks/70 m2, %, Pol %. purity %, fibre %, CCS % and sugar yield/70rn were studied in stalk yield. Brix planT'crop. Eleven characters, tillers/70 m2, stalk length, stalk diameter, stalk weight, stalks/70 m2. cane yield/70 m2, Brix %, Pol %, fibre %, CCS % and sugar yicld/70 m2 were studied in ratoon crop. Components of variability were evaluated for genotypic, phenotypic and environmental coefficients of variation, broad sense hcritability, expected genetic advances maintaining selection intensity of one genotype selection out of seven; and interrelationships of the characters through path analysis. Genotypes were significantly different in stalk diameter, intcrnodcs/slalk. single stalk weight, fibre content in plant and tillers, stalk length, stalk diameter and fibre content in ratoon (P < 0.01) crops while leaf area, stalk length and cane yield at P < 0.05 in plant crop. G x Y interaction was existed for Brix%, Pol% and CCS% in plant (P < 0.01) and fibre content in ratoon (P < 0.05). Genotypic coefficients of variation were ranged from -0.925% of Pol% to 17.477% of plant height in plant and -2.345% of sugar yield to 27.571% of tillers per 70m2 in ratoon crop. The degrees of genetic determination were ranged from -58.40% to 95.20% in plant and - 47.90% to 99.90% in ratoon crop. The genetic advances were ranged from -0.269% of CCS% to 23.276% of plant height in plant and -1.567% of CCS% to 37.616% of tillers/70m2 in ratoon crop at one genotype out of seven selection intensity. Low genetic advances of quality parameters both in plant and ratoon crops suggested that concentration should be made on cane yield component parameters maintaining quality parameters at a certain commercial acceptable levels during selection. Path analysis gave 38 positive and 42 negative correlation out of total 120 pairs of correlation while 17 positive and 19 negative correlation out of 55 in ratoon crop. Stalk weight, intemodes/stalk and fibre % showed direct positive effect on sugar yield in plant crop and stalk weight, stalk yield, Brix reading, Pol reading and CCS% in ratoon crop. Stalk length; stalk diameter, stalks yield, Brix %, Pol % and CCS% exerted indirect positive effects on sugar yield in plant crop. Genotypes, TCP 81-10, S.86-US.432, S.87-US.1873 and S.86-US642 were significantly (P <0.01) superior than Mardan-93 in cane yields.