PRODUCTION OF CHITINOLYTIC ENZYMES AND ENDOGLUCANASE IN THE SOYBEAN RHIZOSPHERE IN THE PRESENCE OF TRICHODERMA-HARZIANUM AND RHIZOCTONIA-SOLANI

Chitobiosidase, endochitinase, endo-beta 1-3-glucanase, and N-acetylgl ucosaminidase were detected in cell-free culture filtrates of the soil borne fungal biocontrol agent Trichoderma harzianum isolate Th008 and the roots of soybean seedlings (Glycine max cv. Williams 82). With the exception of endochitinase, activity of these enzymes also was associ ated with Rhizoctonia solani isolate 2B-12, causal agent of soybean ro ot rot. In greenhouse experiments, soybean seeds inoculated with T. ha rzianum Th008 were planted in a soil mixture infested with R. solani 2 B-12. At 15 days after emergence, the rhizosphere was assayed for chit inolytic enzymes and endoglucanase. Only N-acetylglucosaminidase and e ndochitinase activities in the rhizosphere samples mere significantly elevated above the controls. Using conventional specific enzyme assays and accepted methodologies including HPLC and native and SDS-PAGE sla b-gels, it was determined that T. harzianum Th008 was the source of th e endochitinase in the rhizosphere. On the other hand, the detectable levels of N-acetylglucosaminidase originated from the roots of soybean seedlings. (C) 1998 Academic Press.