Genetic Changes Over Six Generations in a Pedigree Breeding Programme in Sorghum

Six consecutive generations (F1 to F6) of a cross between CSV 8R and SPV 104 were studied during rabi (postrainy) season at Hyderabad. The F3-f6 progenies have undergone assortive mating. They were also subjected to selection for grain yield and seed size. The grain yield was highest in F1 followed by successive depression in F2 and f3 generations. After marginal increase in F4, the yield levels were almost consistent in subsequent generations. There was decrease in plant height and increase in days to flower and seed size in later generations. Heterosis over superior parent was highest (27.3%) for grain yield. It was mainly governed by dominance gene effect (h). The highest inbreeding depression for grain yield was observed in F3 due to segregation of heterozygous plants which had selective advantage over the relatively homozygous plants in F2 and high magnitude of dominance which governs the yield heterosis. The change in mean phenotypic value of other characters has been due to correlated response.