Piriformospora indica and Bacillus velezensis reduced titres ofPRSV and CMV and suppressed symptoms of snake gourd mosaic disease

Pre-endophytic colonization of snake gourd (Trichosanthes cucumerina L.) with Piriformospora indica (1% w/v), followed by individual pre-colonizations with Bacillus velezensis (108 CFU mL-1) and arbuscular mycorrhizal fungi (AMF; 1% w/v), significantly mitigated the incidence and severity of snake gourd mosaic disease under laboratory and field conditions. The endophytic treatments effectively suppressed the titres of Papaya ringspot virus (PRSV) and Cucumber mosaic virus (CMV), as confirmed by DAC-ELISA and DAS ELISA analyses. Among the treatments, P. indica pre-colonization resulted in the lowest viral load and delayed symptom expression, followed by B. velezensis and AMF. Enhanced activities of defense-related enzymes viz., peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, catalase and ascorbic acid oxidase were recorded in P. indica-colonized plants, indicating the induction of systemic resistance. SDS-PAGE analysis revealed the induction of a novel 31.57 kDa protein in AMF-treated plants, while, P. indica and B. velezensis colonization altered overall protein profiles relative to the control. Field evaluations demonstrated a marked reduction in disease incidence (88.36% in P. indica, 92.95% in B. velezensis and 99.74% in AMF treatments at 90 DAS), improved vegetative growth and yield, with P. indica recording the highest yield (7.04 kg plant-1).