Production of Chitinolytic Enzymes and Endoglucanase in the Soybean Rhizosphere in the Presence ofTrichoderma harzianumandRhizoctonia solani

Abstract

Chitobiosidase, endochitinase, endo-β1-3-glucanase, andN-acetylglucosaminidase were detected in cell-free culture filtrates of the soilborne fungal biocontrol agentTrichoderma harzianumisolate Th008 and the roots of soybean seedlings (Glycine maxcv. Williams 82). With the exception of endochitinase, activity of these enzymes also was associated withRhizoctonia solaniisolate 2B-12, causal agent of soybean root rot. In greenhouse experiments, soybean seeds inoculated withT. harzianumTh008 were planted in a soil mixture infested withR. solani2B-12. At 15 days after emergence, the rhizosphere was assayed for chitinolytic enzymes and endoglucanase. OnlyN-acetylglucosaminidase and endochitinase activities in the rhizosphere samples were significantly elevated above the controls. Using conventional specific enzyme assays and accepted methodologies including HPLC and native and SDS–PAGE slab-gels, it was determined thatT. harzianumTh008 was the source of the endochitinase in the rhizosphere. On the other hand, the detectable levels ofN-acetylglucosaminidase originated from the roots of soybean seedlings.