Systemic acquired resistance inducing chemicals mitigate black scurf disease in potato by activating defense-related enzymes

The potato, being an underground vegetable crop, faces consistent threats from soil- and tuber-borne fungal and bacterial pathogens. Black scurf and stem canker disease caused by the fungal pathogen <i>Rhizoctonia solani</i> Kuhn is a critical global concern in the potato cultivation system. In this study, we evaluated the disease mitigation potential of five systemic acquired resistance-inducing chemicals <i>viz.</i>, salicylic acid, jasmonic acid, <i>β</i>-aminobutyric acid, <i>γ</i>-aminobutyric acid and hydrogen peroxide (H₂O₂). Two common methods, tuber dipping and foliar spray, were utilized in this experiment to evaluate pathogen inhibition on inoculated tubers. The results revealed that all the systemic acquired resistance inducing chemicals were effective in disease suppression in a concentration-dependent manner compared to an inoculated control. Significant differences (<i>P</i> < 0.005) were evident among the various treatment combinations, with salicylic acid being the most effective in alleviating black scurf disease. Maximum reduction in disease incidence compared to the control was observed with salicylic acid (57.89% and 73.68%), followed by jasmonic acid (52.63% and 65.78%) and H₂O₂ (49.99% and 60.52%) under the tuber dipping treatment combinations. Whereas, in the foliar application, the maximum reduction in disease incidence compared to the control was observed with salicylic acid (44.73 and 63.15%), followed by jasmonic acid (42.10 and 60.52%) and H₂O₂ (39.46 and 52.63%). The tuber dipping treatments were significantly more efficacious (<i>P</i> < 0.005) compared to foliar spray for all treatment combinations. The biochemical analysis of defense-related enzymes and metabolites demonstrated the induced resistance activation under these treatments. The activity of peroxidase, polyphenol oxidase, and phenyl ammonia-lyase was significantly higher in treated tubers as compared to inoculated and uninoculated control. The total phenol content was also elevated in treated tubers as compared to the respective control. Altogether, these resistance-inducing chemicals can be successfully included in integrated disease management programs.