Resistance breeding strategy for Stenocarpella maydis and Fusarium graminearum cob rots in tropical maize

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. GCA effects indicated that inbred WL 110–18 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 ofF.graminearum byS.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.