Management of Collar Rot of Chickpea (Cicer Arietinum) by Trichoderma Harzianum and Plant Growth Promoting Rhizobacteria
Collar rot (Sclerotium rolfsii) of chickpea (Cicer arietinum) is one of the devastating soil-borne diseases of fungal origin, due to which 10-30% yield loss is recorded annually according to severity of the disease. Management of collar rot of chickpea is not feasible in the absence of effective soil fungicides. However, Trichoderma harzianum and plant growth promoting rhizobacteria (PGPR) have shown high efficacy against this disease in vitro as well as in the field. We used T. harzianum (104, 106 and 108 spore/ml) and two PGPRs (Pseudomonas fluorescens strain 4 and P. aeruginosa) as foliar spray with the fresh and heat inactivated microorganisms. Foliar application of T. harzianum (108 spore/ml) and P. fluorescens strain 4 (108 cfu/ml) showed maximum efficacy in reducing plant mortality as compared to the control. Foliar application of fresh-and heat-inactivated (121°C for 10 min) P. fluorescens strain 4, and T. harzianum reduced 15-25% plant mortality but P. aeruginosa showed very little disease control of 10-15%. However, regarding plant growth promotion, it was observed that fresh-and heat-inactivated P. fluorescens strain 4 showed maximum efficacy followed by fresh and heat inactivated P. aeruginosa and T. harzianum as compared to the control. The disease-controlling efficacy was also associated with the increase in phenolic acid synthesis in chickpea plants. The control of chickpea collar rot by biocontrol agents is safe and ecologically sound and appears to be a healthy approach to the disease control.