HETEROSIS, INBREEDING DEPRESSION AND COMBINING ABILITY IN SORGHUM (SORGHUM BICOLOR (L.) MOENCH)

Abstract

Heterosis, inbreeding depression and combining ability were studied in a 6 X 6 dialleI (excluding reciprocals) from Fl to F4 generations for grain yield and its five components in sorghum (Sorghum bicolor (L.) Moench). Among the different characters studied, highest heterosis in Fl over better parent (87.5"!.) was recorded for grain yield/plant followed by number ofgrains/panicle (50.1%) and number of primaries/panicle (40.5%). All the hybrids which showed higher estimates of heterosis in Fl in general also exhibited high inbreeding depression in F2 and other segregating generations studied. The general (gca) as well as specific combining ability (sca) variances were found significant in all the four (FI-F4) generations for grain yield and its components studied except for number of primaries/panicle in F3 and F4 and for number of whorls/panicle in F2 and F3 generations. The magnitude of sca variance declined in F2 and later generations. The predictability ratio showed preponderance of nonadditive genetic variance for grain yield and additive genetic variance for lOOO-grain weight in sorghum. The study of fl and F2 would be sufficient to assess repeatability of gca effects in advance generations. Four cross combinations, viz SPY 451 XSPY 474, SPY 474 XIS 508, CSV 10 XSPY 451 and CSV lOx SPY 474 were identified as promising, which can be exploited to improve grain yield in sorghum.