Studies on factor(s) in sweet potato which specifically inhibits germ tube growth of incompatible isolates of <italic>Ceratocystis fimbriata</italic>

Abstract

Sweet potato root contained a factor or factors which differentially inhibited the growth of various isolates of Ceratocystis fimbriata. The factor scarcely inhibited germ tube growth of sweet potato isolate, compatible to sweet potato. On the other hand, the growth of prune, oak, taro and almond isolates, all incompatible to sweet potato, was strongly inhibited. The germ tube growth of coffee and cacao isolates, incompatible to sweet potato, were less inhibited. Inhibitory factor was distributed through various fractions when centrifuged on a sucrose density gradient. The germ tube growth of pre-germinated oak isolate became less sensitive to the inhibitory factor after being treated with pronase, suggesting the interaction of the factor with some protein-containing surface structure of the fungal cell. Treatment of the factor by phospholipase c, lipase and pronase caused no changes in its inhibitory activity, whereas periodate treatment partially inactivated the factor. These results suggest that this inhibitory factor constitutes one of the factors determining the specificity in sweet potato-C. fimbriata interactions.