Gene effects, heterosis and inbreeding depression for grain sorghum characters

Two crosses between grain sorghum (Sorghum bicolor L. Moench), BR 007A x BR 012R and BR 001Ax BR 012R originated two F-i hybrids (BR 303 and BR 304) a nd the advanced inbreeding generations F-2 and F-3, establishing nine genot ypes, which were evaluated in two planting dates (normal and succession). S everal yield and forage quality characters were evaluated. The objectives o f this study were to obtain the estimated heterosis and inbreeding depressi on in F-2 and F-3 generations, to evaluate the possibility of F-2 seeds use in commercial sown, to verify also the estimated gene effects associated t o heterosis and inbreeding depression. In sucession planting, comparing wit h normal planting, the grain sorghum hybrids showed small grain production, green matter and dry matter weight and higher protein content. For the two grain sorghum hybrids, the estimated heterosis was positive to grain yield and dry matter and was negative to protein and fiber content, at the two p lanting date. The estimated inbreeding depression was positive to grain yie ld, making impossible the commercial utilization of F-2 seeds. The estimate d additive gene effects had importance to quality characters in grain cross BR 007A x BR 012R, while the dominance effects were predominant to yield c haracters of the two hybrids and planting dates. The dominance effects expl ained most of the heterosis and inbreeding depression expressed of several characters in two crosses.