Harnessing <i>Trichoderma asperellum</i>: Tri‐Trophic Interactions for Enhanced Black Gram Growth and Root Rot Resilience

Root rot caused by Macrophomina phaseolina, a common soil-borne disease in black gram, is managed with chemical fungicides, leading to toxicity and degradation of beneficial soil microbes. Existing bioagents, like talc formulation, cause leaching, clogging, and reduced productivity. The development of liquid bio-formulation via drip irrigation is crucial to mitigate biotic stress and maximize yield. This study aims to investigate the efficacy and survivability of liquid formulation of Trichoderma asperellum against root rot and its growth promotion. The results showed that Tv1 effectively inhibited M. phaseolina (66.67%), under in vitro condition. The vigor index of 4025.00 and the spore load of 1 × 10⁸ cfu/mL were recorded from plant growth promotion and spermosphere study @ 5 mL/kg of seeds with formulation. The study found that combined application of seed treatment @ 5 mL/kg of seed and soil application @ 10 mL/L of water significantly reduced disease incidence (9.1%) against control (74.3%), with increased biomass index. There are 32 mVOCs profiled during the tritrophic interaction in roots of black gram and they were up or downregulated, viz., mollugin, pentadecanoic acid, cyclopropaneoctanoic acid, 2-octyl-, methyl ester, rhodopin, dodecanoic acid, 1,2,3-propanetriyl ester by involved in defense mechanism and biosynthetic pathways like jasmonic acid, glyconeogenic and act as acyl-CoA: acyltransferase 2 inhibitor. The results of this study confirmed that liquid formulation performs better in growth promotion, survivability on seed surface, and managing root rot of black gram compared talc-based formulation.