Mineral fertilizers improve defense related responses and reduce early blight disease in tomato (Solanum lycopersicum L.)

Alternaria solani is one of the most notorious fungal pathogens that causes the destructive early blight (EB) disease of tomato (Solanum lycopersicum L.). Direct application of pesticide is a perilous approach to control disease due to its residual effects, therefore manipulating crop nutrition is a holistic approach to mitigate EB disease by improving the resilience in plants against disease in the sustainable cropping system. Achieving this aim, the effects of plant nutrients viz., nitrogen, phosphorus, potassium (NPK), zinc (Zn), magnesium (Mg) and boron (B) were investigated in controlling early blight disease of tomato. Pathogen infestation camouflaged cell mechanism and disturbed the regulation of key player enzymes (SOD, CAT, POX, PPO and PAL) that weakened the plant immunity, therefore, the plants exhibited 100% disease incidence. Applied nutrients reduced the EB disease by effective interference that leads to the induction of resistance in a host against pathogens to a variable extent. Zn proved strong co-factor for the activation of defense-related enzymes that ultimately managed the EB disease from 60–75% and significantly improved the plant growth and physiological attributes by 30–80% with the significant Pearson correlation among defense-related enzymes and total phenolics. The rest of nutrients were not found to be effective in suppressing disease because the correlation among antioxidant enzymes probably did not facilitate intercellular communications to the desired level to boost up plant immune system.