Induction of systemic resistance (ISR) against sheath blight of rice caused by Rhizoctonia solani Kuhn using biological seed treatment with Trichoderma

Abstract

Sheath blight caused by Rhizoctonia solani Kuhn has recently noticed one of the most important diseases of rice on almost all the high yielding varieties in major rice growing area. In our study morphologically and molecu-larly characterized thirty rhizospheric isolates of Trichoderma (T. harzianum and T. virens) from different locations of Uttarakhand were evaluated for their mycoparasitic ability, disease (sheath blight) suppressing potential and inducing systemic resistance against Rhizoctonia solani. Maximum inhibition in hyphal growth (58.9 %) against R. solani was recorded with isolate PB 2 followed by PB 3 (53.4 %) in confrontation assay. Under glass house con-dition, minimum disease severity (13.6%) was recorded in the treatment where seeds were treated with PB 22 and this treatment also exhibited highest total phenol content (394 ?l/g) 168 hours after pathogen inoculation. Total phenol content was also increased maximally (466 ?l/g) before pathogen inoculation in the treatment where seeds were treated with PB 22. Moreover, high quality ISR activity was recorded with isolates PB 21, 3, 1, 4, 23, 2 and 16 as they reduced more than 34 percent disease and total phenol contents 456 ?l/g, 449 ?l/g, 442 ?l/g, 440 ?l/g and 440 ?l/g, 438 ?l/g and 431 ?l/g were recorded for respective isolates indicated induction of resistance in paddy against sheath blight disease caused by R. solani.