Maize cob rot caused by Fusarium graminearum and Stenocarpella maydis affects grain yield and quality. The objective of this study was to investigate the appropriateness of multiple infection as a selection and breeding strategy for multiple resistance to F. graminearum and S. maydis. Twelve tropical inbred lines with varying resistance to either or both pathogens were mated in a full diallel and the progeny and their parents evaluated for reaction to single or multiple infection. Under multiple inoculation, S. maydis suppressed colonization of cobs by F. graminearum. General combining ability (GCA) effects indicated that inbred WL 118-10 effectively transmitted resistance to both diseases. Hybrids' resistant to S. maydis was also resistant to F. graminearum, but the reverse was not true. Therefore, efficient screening should initially involve screening for S. maydis followed by F. graminearum. Overall, the suppression of F. graminearum by S. maydis shows that multiple infection cannot be used as an appropriate breeding strategy to obtain multiple resistance. The use of F. graminearum and S. maydis separately is, therefore, the best breeding strategy.Pathogen culture and inoculation: The pathogens were initially isolated from infected cobs obtained from NaCRRI fields. Inoculum was prepared wileyonlinelibrary.com Plant Breeding 132, 83-89 (2013)

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Alectra vogelii (benth) is parasitic weed which causes significant yield reductions in cowpea (Vigna unguiculataWalp) in Africa. The objective of this study was to identify the type of gene action controlling the trait for resistance to Alectra vogelii in cowpea and estimate the heritability of the trait. Seven genotypes of cowpea were mated in half diallel and their F 2 progeny, including parents, were evaluated for reaction to Alectra vogelii infection in the field in two locations at Ilonga and Hombolo Agriculture Research Stations. Highly significant (P < 0.001) differences were found for Alectra emergency and infestation at Ilonga. General combining ability (GCA) and specific combining ability (SCA) effects for Alectra shoot emergency and infestation were significant (P < 0.05). The estimate of Baker's ratio for Alectra shoot emergency and infestation were 0.62 and 0.66, respectively. This indicates that both additive and non-additive gene actions influenced the trait for resistance to Alectra emergency and infestation. Narrow sense heritability estimates were 41.28 and 44.39 for shoot and emergency, respectively. These results imply that introgression of a desirable trait in an elite genotype would involve careful crossing with a resistance genotype, accompanied by selection in the advanced population.

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