Quantitative-genetic parameters of sorghum growth under striga infestationin Mali and Kenya

To estimate quantitative-genetic parameters of sorghum for resistance to th e hemi-parasitic weed striga [Striga hermonthica (Del.) Benth.] and for agr onomic traits, 36 diallel F-2 populations and their nine parental lines wer e evaluated under severe striga infestation at two locations each in Mall a nd Kenya, Location means for grain yield ranged from 132 to 254 g/m(2). F-2 populations outyielded lines on average by 18%. For striga emergence trail s, F-2 heterosis values ranged from -36% to 232% among populations. Genetic and genotype x environment interaction variances of lines and F(2)s were h ighly significant for all traits. Broad-sense heritabilities for areas unde r striga severity progress curves and grain yield were 0.83 and 0.90 in lin es, and 0.81 and 0.89 in F(2)s, respectively. General and specific combinin g ability, and their interaction effects with locations were significant fo r most traits. F-2 superiority for grain yield under striga infestation dem onstrates the potential merit of heterozygous cultivars in the target areas . Significant genotype x environment interaction entails multilocational te sting to identify stable resistance. A combination of resistance with strig a tolerance is recommended to breeders.