Activity of antifungal proteins against mold in sorghum caryopses in the field

Sorghums were stressed with pathogenic fungi and sprinkling to determine re lationships between changes in chitinase and sormatin in caryopses and grai n mold resistance. Panicles of 10 cultivars differing in mold resistance an d accumulation of antifungal proteins (AFPs) were inoculated at anthesis wi th Fusarium moniliforme and Curvularia lunata spores. Panicles were sampled at 30 and 50 daps after anthesis, and caryopses were evaluated for chitina se and sormatin using western blots. Sprinkling panicles (to mimic rainfall ) decreased sormatin and chitinase in most cultivars. Inoculation decreased AFPs in susceptible cultivars, but resistant cultivars maintained or incre ased AFPs in caryopses. Grain mold resistance corresponded to induction of AFP synthesis in response to sprinkling, fungal stress, and/or adverse fiel d conditions. Sormatin and chitinase appear to be an active part of the def ense mechanism of the caryopsis against grain mold.