Genetic variability of restorer lines in rice (Oryza sativa L.)

Analysis of variance (ANOVA) for both locations revealed highly significant (P0.01) differences among restorer lines, CMS lines and restorer lines x CMS [cytoplasmic male sterility] lines for all traits. Estimates of genetic variance of restorer lines for traits measured were highly significant based on F-test, except for number of productive tillers. Confidence interval estimates for all traits were significantly different from zero except number of productive tillers. This indicates that estimates obtained were significant and that the genetic variability exists for these traits. The GCA [general combining ability] of the CMS lines for grain yield revealed that IR 68888 A was the best combiner, followed by IR 68897 A. For most traits, restorer lines contribute a high percentage to the total variation, 81.50% for percent seed set and 75.03% for grain yield. Combined mean performance across locations revealed that hybrids derived from IR 68888 A had the highest mean yield (6652.33 kg/ha). Twenty-five percent (15/60) of hybrids evaluated at UPLB exhibited 16.73-44.29% yield advantage over the yield check, PSB Rc72H (5814 kg/ha). At PhilRice CES, three hybrids (5%) out yielded the maturity check PSB Rc28 (9157 kg/ha). At UPLB [Univ. of the Philippines at Los Banos, College, Laguna], restorers crossed to IR58025A had the highest mean yield (5916.95 kg/ha) followed by crosses made to IR68888A (5844.07 kg/ha). In the Maligaya trials, hybrids of IR68888A recorded a mean yield of 7460.59 kg/ha, followed by hybrids of IR 68897A at 7381.23 kg/ha. The results indicate that location-specificity should also be considered in breeding and selection of F1 hybrids. The 65 SSR markers were polymorphic. A total of 266 alleles ranging from 2 to 8 alleles/locus and a mean of 4.09 alleles/locus were detected. The Nei and Li genetic similarity coefficients among restorers and CMS ranged from 0.22 to 0.71. Twenty-four percent of the total alleles detected were rare (63/266) and these were distributed throughout the entire chromosomes of the rice genome