Gene effects, heterosis and inbreeding depression for grain sorghum characters

Abstract

Two crosses between grain sorghum (Sorghum bicolor L. Moench), BR 007A x BR 012R and BR 001A x BR 012R originated two F₁ hybrids (BR 303 and BR 304) and the advanced inbreeding generations F₂ and F₃, establishing nine genotypes, which were evaluated in two planting dates (normal and succession). Several yield and forage quality characters were evaluated. The objectives of this study were to obtain the estimated heterosis and inbreeding depression in F₂ and F₃ generations, to evaluate the possibility of F₂ seeds use in commercial sown, to verify also the estimated gene effects associated to heterosis and inbreeding depression. In sucession planting, comparing with 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 planting date. The estimated inbreeding depression was positive to grain yield, making impossible the commercial utilization of F₂ seeds. The estimated additive gene effects had importance to quality characters in grain cross BR 007A x BR 012R, while the dominance effects were predominant to yield characters of the two hybrids and planting dates. The dominance effects explained most of the heterosis and inbreeding depression expressed of several characters in two crosses.