Biochemical and molecular fine tuning of antioxidative enzyme in Solanum lycopersicum under the compatible and incompatible interactions with Alternaria solani

Abstract

Abstract Early blight caused by Alternaria solani has been recognised as a serious threat to tomato crop and can adversely affect its productivity worldwide. Studies have been performed to examine the basis of resistance in tomato crop but the progress is still limited. In the current study variations in the antioxidant parameters of three different tomato genotypes with varied resistance (high resistance, moderate resistance and high susceptibility) against Alternaria solani were observed and compared with the healthy non infected plants. Assays of several enzymes and antioxidants, namely Super oxide dismutase (SOD), Catalase (CAT), Ascorbate peroxidase (APX), Guaiacol peroxidase (GPX), and hydrogen peroxide (H2O2) were performed along with the expression analysis of genes encoding these enzymes. The enzymes and metabolites showed differential responses in different genotypes, with the highest concentration of H2O2 in Arka Rakshak (AR) leaves (resistant genotype) after 24 hrs of infection. On the other hand, there were significantly lower levels of H2O2 in CO-3 (highly susceptible genotype) and Pusa Ruby (moderately susceptible genotype). Similarly, SOD, APX, and CAT activities were also found to be highest in the inoculated leaves of the AR genotype. The activity of GPX was highest in Pusa Ruby at 72 hr. Hence, it can be concluded that the early blight tolerance in AR was at least partially due to the increased activities of SOD, APX and CAT under infected state as compared to those of Pusa Ruby and CO-3 genotype. The result suggests that there is a correlation between constitutive induced levels of these enzymes and plant resistance which could be considered as a biochemical markers for studying the plant-pathogen compatible and incompatible interactions.