IN-VITRO ACTIVITY OF SORGUM SEED ANTIFUNGAL PROTEINS AGAINST GRAIN MOLD PATHOGENS

Several sorghum seed antifungal proteins (AFP), including sormatin, ch itinase, glucanase, and ribosome-inhibiting protein (RIP), were extrac ted, partially purified using sequential ammonium sulfate precipitatio n, and eluted from a CM-Sephadex column using a linear salt gradient. fluted fractions were tested for bioactivity against Fusarium monilifo rme, Curvularia lunata, and Aspergillus flavus using hyphal rupture, h yphal extension, and spore germination methods. A fraction containing several AFPs was most inhibitory against F. moniliforme, C. lunata, an d A. flavus. Spore germination of all three species was markedly inhib ited by 360 ppm of AFPs. The inhibitory effects were not observed when the protein fraction was boiled, suggesting the involvement of undena tured proteins. Hyphal elongation inhibition was the least sensitive a ssay to detect the inhibitory effects of AFPs on these fungi. F. monil iforme exhibited hyphal rupture at the growing tip at protein levels a s low as 70 ppm. C. lunata required higher protein levels (70-360 ppm) and ruptured only at hyphal tips. A. flavus did not exhibit hyphal di sruption when treated with AFPs.