Heterosis, combining ability, and breeding potential studies for grain yield and yield components in guinea sorghums [Sorghum bicolor (L.) Moench

Abstract

Relatively low yields of guinea sorghums have been a major obstacle for sustained progress in yield improvement of the race in West Africa. In an attempt to determine why West African sorghums display low yield potential, 7 converted guinea, 4 zerazera, and 2 caudatum sorghums were crossed to three improved A-lines. Parents and hybrids were evaluated for general and specific combining ability at Halfway and College Station, Texas during 1989 and 1990. In general, non-guineas were better combiners than guineas for yield and most yield components. Guineas showed low additive effects for grain yield, seeds/panicle, and seed size. This could be explained by the stability of grain yield of guineas over a wide range of environments. Guineas seem to maintain a relative low yield by reducing the number of seeds/panicle and seed size. Most guinea hybrids showed positive heterosis over the best parent for yield. This indicated that guineas possess some genes or factors contributing to higher yield expression. In general, the guinea hybrids had more primary branches/panicle, more whorls/panicle, greater panicle length, and more exsertion than non-guinea hybrids. Guineas showed some specific combining ability. The principal component analysis indicated that the first component was a measure of yield and yield components, while the second component described architecture of the plant. The best yielding cultivars were non-guinea combinations. Although guinea hybrids showed lower yield, some heterotic response for grain yield existed. For yield and plant architecture, zerazera was found to be related to caffrorum and caudatum. Caudatum and caffroum were less related to conspicuum (guineas). Diversity was found between conspicuum and caffrorum, caudatum, and zerazera. Evolutionary, conspicuums apparently evolved differently from these latter groups. During their evolution, adaptation, and stabilization guineas accumulated primarily genes or factors which contributed to stability of grain yield and to such traits as hard grain with resistance to mold, weathering, and insect damage rather than genes that contributed to high yield. However, contrary to some belief of sorghum scientists, there appears to be breeding value in guineas with regard to improvement of grain yield and related traits.