Timing and intensity of upregulated defensive enzymes is a key factor determining resistance in chickpea to Ascochyta rabiei

Abstract Ten genotypes comprising five resistant genotypes namely PBG 7, GLK 08–104 and GL 12021 (desi), ILWC 292 and C. judaicum 182 (wild); one moderately resistant genotype HC 5 (desi); three susceptible genotypes GLK 14313 and L552 (kabuli) and C. pinnatifidum 212 (wild) and one highly susceptible wild genotype ILWC 115 characterized on the basis of disease severity scale to Ascochyta blight caused by infection of Ascochyta rabiei were investigated for elicited biochemical responses. These genotypes were sown separately in Ascochyta screening plot and in control plot under normal conditions to study the response of enzymatic antioxidants and signalling molecules in leaves at four different stages of infection i.e. S0 (pre-inoculatory) stage, S1 stage (7 days after infection), S2 stage (20 days after infection), S3 stage (30 days after infection). The specific activity of superoxide dismutase increased during S0 and S1 and catalase activity was enhanced at later stages of infection. The specific activities of peroxidase, ascorbate peroxidase and glutathione reductase increased with the incidence of disease in resistant genotypes as compared to susceptible genotypes. The timely upregulation and more intensity of defensive enzymes such as SOD, APX-GR followed by CAT and POD in the resistant genotypes as compared to susceptible genotypes might be responsible for resistance to Ascochyta blight. The higher accumulation of H2O2 in resistant genotypes and higher MDA content in susceptible genotypes also contribute to their differential tolerance behaviour towards infection. The upregulation of defensive enzymes at later stages of infection in GLK14313, L552, C. pinnatifidum 212 and their lower activities in ILWC115 might be responsible for their susceptible behaviour indicating that the time and intensity of induced defensive mechanism is an important contributing factor towards disease tolerance.