Evaluation of phenotypic, physiological and biochemical attributes connected with resistance in tomato against Alternaria solani

Abstract

Early blight (EB) disease caused by fungus Alternaria solani is one of the world's most catastrophic Solanum lycopersicum L. diseases. This study was aimed to check the response of 29 different tomato genotypes toward EB disease with the help of phenotypic (percent disease index and growth inhibition index), physiological (total chlorophyll content and carotenoids) and biochemical attributes [total protein content (TPC), total phenolics (TP) and activities of catalase (CAT), peroxidase (POX), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL)] at 30 and 60 DAI (days after inoculation). The experiment consisted of all 29 inoculated and uninoculated genotypes of tomato which were placed in greenhouse. The results obtained from investigated parameters grouped eight genotypes as resistant, seven as moderately resistant, six as moderately susceptible and eight as susceptible to the infection of the pathogen. Moreover, from the findings of physiological and biochemical attributes in the grouped genotypes, possible resistance mechanisms activated in the host were also predicted. Activation of defense responses was revealed by elevated biochemical attributes in all inoculated genotypes and changes were more obvious in resistant and moderately resistant tomato genotypes due to the least reduction of health markers. Among antioxidant enzymes, CAT contributed maximum to resistance, as the enzyme activity was highest in resistant genotypes.