Correlations between antioxidative enzyme activities and resistance to Phytophthora leaf blight in taro

The present study aimed to investigate the correlations between the activities of antioxidative enzymes (AOEs) and Phytophthora colocasiae Racib. (Pc) incidence in taro (Colocasia esculenta (L.) Schott) under induced epiphytotic conditions. The activities of AOEs in leaf tissues of taro were increased significantly (up to 7.6-fold) under Pc infestation compared with the control. Spot diameter had significant negative correlations with superoxide dismutase (SOD, r = –0.42), catalase (CAT, r =–0.36), ascorbate peroxidase (APX, r = –0.47), polyphenoloxidase (PPO, r = –0.41) and monodehydroascorbate reductase(MDAR, r = –0.44) activities. The number of sporangia was negatively correlated with guaiacol peroxidase (GPX, r = –0.375)and MDAR (r = –0.51) activities. The percentage of leaves infected and the infected leaf area were negatively correlated with GPX (r= –0.392 and –0.369, respectively), but they were positively correlated with the number of sporangia produced by Pc infection (r = 0.571 and 0.721, respectively). All the AOE activities were positively correlated with each other and negatively correlated with disease incidence. Spot diameter had a close association with disease severity, suggesting that this parameter could be reliable for the screening of taro genotypes for Pc. SOD,CAT, APX, PPO, and MDAR, exhibited strong roles in combating Pc infestation, as evidenced by the correlation matrix and principal component analysis (PCA). Taro genotype ‘RCMC–5ʹshowed resistance to Pc, with low disease incidence and higher AOE capacity than the other genotypes, suggesting the potential of this genotype for use in taro breeding programs.