Evaluating the efficacy of 'Trichoderma' spp and 'Bacillus substilis' as biocontrol agents against 'Magnaporthe grisea' in rice

Abstract

Rice blast causes yield losses to rice farmers worldwide. Although this problem is currently being addressed through the use of resistant rice varieties, fungicide and rotation farming, these methods alone do not form a durable, long lasting solution in mitigating disease. Here we obtained Trichoderma isolates from soil and tested their efficacy as biocontrol agents against Magnaporthe grisea. Twenty-two Trichoderma isolates were identified and used in dual culture assays to determine antagonistic ability before isolates showing promise were administered to rice plants grown in greenhouse conditions where the efficacy of these isolates was tested individually or as dual inoculums with Bacillus substilis UKM1. The results showed that the dual inoculation of biocontrol agents caused significant (p =0.05) inhibition of M. grisea as compared to a single agent. In addition, we observed the inhibitory effect of Trichoderma T2 under SEM where the hypha of the biocontrol agent coiled and possibly enzymatically degraded the pathogen. Trichoderma T2 in combination with B. substilis UKM1 gave the highest reduction in pre-post damping off, disease infection and disease severity caused by M. grisea in greenhouse conditions. From the greenhouse experimentations, the biocontrol agents were more efficient in inhibiting rice blast when applied prior to transplantation as compared to when applications were made at seed setting stage.