Evaluation of sorghum genotypes for their reaction to major grain molds and mycotoxin-producing fungi in two climates of Ethiopia

Use of resistant genotype is considered to be the most feasible means to mitigate sorghum grain damage by grain mold in a climate favourable for fungal invasion and subsequent mycotoxin contamination. Field-based experiments were conducted at Babile and Haramaya for two consecutive cropping seasons to evaluate 20 sorghum genotypes for their reaction to grain molds as well as aflatoxin and fumonisin contamination. Aspergillus flavus and Fusarium verticillioides with spore concentrations of 10(6) ml(-1) were inoculated by spraying into the inflorescence, when the anther emerged from approximately 50-70% of the spikelets. Mycotoxin analysis was done using enzyme-linked immunosorbent assay (ELISA). The results revealed that the sorghum genotypes evaluated for their reactions to A. flavus and F. verticillioides inoculation had significantly different responses. Variety Melkam was identified as a susceptible genotype to F. verticillioides and variety Birhan was found resistant to both fungal species. Variety Long Muyera was the most susceptible to both toxigenic fungi. Long Muyera was contaminated with aflatoxin B1 and total fumonisin above the maximum tolerable limit of 10 mu g kg(-1) and 2000 mu g kg(-1), respectively. Though the sorghum genotype Birhan was resistant to A. flavus, its aflatoxin B1 contamination was relatively high. In this study, it was recognized that none of the tested sorghum genotypes exhibited possession of multiple resistance to the inoculated toxigenic fungi. Therefore, it is commendable to select and use genotypes, which are resistant to specific toxigenic fungi for a particular location, where the problem exists.