Role of Antioxidant Enzymes, Hydrogen Peroxide and PRProteins in the Compatible and Incompatible Interactions of Cowpea (Vigna unguiculata)Genotypes with the Fungus Colletotrichum gloeosporioides

Several diseases, such as anthracnose, which are caused by the fungus species Colletotrichum gloeosporioides, negatively affect the cultivation of the cowpea (Vigna unguiculata). This work was conducted to measured the time-course activities and evaluate the possible roles of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and hydrogen peroxide (H2O2), and the pathogenesis-related proteins (PR-proteins), peroxidase (POX), β-1,3-glucanase (GLU) and chitinase (CHI), in the resistant (TE97) and susceptible (BR3) cowpea genotypes in response to C. gloeosporioides infection. During infection, the SOD activity was increased, while the CAT activity was decreased in TE97. The APX activity in TE97 was similar to that in BR3 at 12 to 24 after infection (HAI). These data were consistent with the increased production and accumulation of leaf H2O2 within this time period in TE97; the generation of H2O2 was also observed in BR3, but to a lesser extent. The fungal inoculation also induced changes in the PR-proteins analyzed. Overall POX, GLU and CHI activities were higher in the resistant genotype TE97 compared with those in the susceptible genotype BR3. Altogether, these results showed that H2O2 and the PR-proteins play important roles in the interactions of cowpea and C. gloeosporioides.