Characterization of a Host-Specific Toxic Activity Produced by , Causal Agent of Target Leaf Spot of Sorghum.

Target leaf spot (TLS) of sorghum, caused by the necrotrophic fungus , can cause severe yield loss in many parts of the world. We grew in liquid culture and observed that the resulting culture filtrate (CF) was differentially toxic when infiltrated into the leaves of a population of 288 diverse sorghum lines. In this population, we found a significant correlation between high CF sensitivity and susceptibility to TLS. This suggests that the toxin produced in culture may play a role in the pathogenicity of in the field. We demonstrated that the toxic activity is light sensitive and, surprisingly, insensitive to pronase, suggesting that it is not proteinaceous. We identified the two sorghum genetic loci most associated with the response to CF in this population. Screening seedlings with CF could be a useful approach for prescreening germplasm for TLS resistance.