Synergistic effect of rice straw biochar and Trichoderma harzianum for sustainable mitigation of chickpea collar rot

Chickpea is a versatile crop with respect to its adaptability to different growing regions from temperate to tropical and serve as a crucial food source for both humans and animals. Collar rot (Sclerotium rolfsii) is a destructive soil-borne disease that lead to significant yield losses to chickpea. The wide spread use of chemical pesticides in controlling this disease present dangerous effects to the environment and health, making it essential to provide some sustainable alternatives. The current study assessed the combined application of Trichoderma harzianum and rice straw biochar for mitigation of collar rot under glasshouse conditions. Two rates of biochar (3 and 6%) were used as soil amendment, with and without T. harzianum. In vitro tests indicated a high antagonistic potential of T. harzianum alone in inhibiting mycelial growth of S. rolfsii by about 60%. X-ray diffraction (XRD) spectroscopy based characterization of biochar indicated both crystalline and amorphous mineral phases such as Quartz (SiO2), CaCO3, and CaO. Scanning electron microscope and Energy Dispersive X-ray spectroscopy (EDX) demonstrated that biochar was highly porous and contain other vital elements such as P, K, O, Mg, S, Cl and Si. In pot trial, combined treatment with 6% biochar and T. harzianum effectively decreased the percentage severity index and disease incidence by 32 and 40%, respectively along with simultaneous stimulation of plant growth by up regulating plant defense mechanisms. The combined treatment significantly increased polyphenol oxidase (8.13 Units per g protein per min) as well as phenylalanine ammonia lyase (35 M t-cinnamic acid per mg protein) activities compared to control. These findings suggest that the synergistic effect of rice straw biochar as well as T. harzianum could be a sustainable and environment friendly approach for managing collar rot disease along with growth enhancement of chickpea.