In vivo and in vitro phosphate-dependent polygalacturonase production by different isolates of Botrytis cinerea

Abstract

Eleven isolates of Botrytis cinerea, coming from different host plants of various geographical locations and isolated in different years, were compared with isolate BC1 for: (a) their in vitro and in vivo total polygalacturonase (PG) production; (b) pattern of PG isoenzymes formed in the presence of inorganic phosphate (KH2PO4) or AMP; and (c) for their ability to cause lesions on leaves of French bean and tomato. All isolates were strongly phosphate-dependent for in vitro PG production, showing a complete lack of activity when phosphate was absent from the growing medium. In the presence of AMP four isolates had in vitro a PG production significantly higher than with KH2PO4 and five isolates showed also the specific induction of the synthesis of a PG1-like isoenzyme, as occurring with BC1. Under the same conditions, three isolates showed no PG synthesis. All isolates were characterized by the production of cathodic forms of PGs comprising at least a PG1- or a PG2-like isoenzyme. Seven isolates produced two isoenzymes with an electrophoretic mobility equal to that of PG1 and PG2 of isolate BC1. The results point to a low level of intraspecific variation for the isoenzyme pattern of the different B. cinerea isolates. All isolates gave rise to spreading lesions on French bean and tomato leaves when glucose and KH2PO4 were present in the inoculum drops, but not when both compounds were absent. Differences in total PG production did not affect the ability to cause spreading lesions or to infect the two host plants used.