和梨黒斑病の防除に関する基礎的研究（ⅩⅣ） : 日本梨の黒斑病に対する抗毒性とカタラーゼ活性

Resistant variety, Nijisseiki variety (susceptible) cultured by the culture solution containing much N, P₂O₅, Fe₂O₃ (N : standard density) and the old, unshaded, unpreserved leaves showed the resistance to the black spot disease caused by an imperfect fungus, Alternariakikuchiana TANAKA. Catalase activity in the leaves of the above-mentioned cases was higher than in other cases. Although in the leaves of Nijisseiki variety cultured by the culture solution containing much K₂O, and in younger mature leaves, the catalase activity was higher, however, the leaves was susceptible to this disease. Catalase activity was raised in the leaves, when the fungus was inoculated to the tissue of pear leaves. Catalase activity had a tendency to inactivate the toxicity of toxin produced by this fungus. From the experimental results mentioned above. the auther concludes that catalase activity organizes a part of antitoxic resistance, although it is not so powerful as ascorbic acid oxidase