The results of correlation analysis showed that the POD content of the leaves in the four walnut varieties was significantly positively correlated (P<0.01) with the area of leaf lesions, the expansion ratio of newly added leaf lesions, and the disease index; while the chlorophyll content of the leaves was significantly negatively correlated (P<0.01) with the area of leaf lesions, incidence rate, expansion ratio of newly added leaf lesions, and disease index. The results of principal component analysis showed that specific leaf area, CAT, SOD, MDA and average maximum temperature could be considered as key influencing factors for walnut resistance to anthracnose disease.
