Pectic and cellulolytic enzymes produced by Mycosphaerella citrullina and their relation to black rot of squash

Abstract

Polygalacturonase (PG), pectin methylesterase (PME), and cellulase (Cx) were obtained from liquid cultures of Mycosphaerella citrullina and were also extracted from infected squash fruit tissue. The pH optima for PG, PME, and Cx were 4, 7, and 5, respectively. Newly rotted squash tissue from the lesion margin was high in PG activity and low in Cx and PME. Older infected tissue was low in PG and PME but had Cx activity almost three times that from the lesion margin.Infected tissue from the center of the lesion had 18–39% as much pectin as healthy tissue and tissue from the lesion margin had 25–63% as much pectin.