Abstract
1. This paper presents the results of experiments concerning physiological specializations of Cladosporium fulvum. Fifty-four isolates, obtained from nine prefectures in Japan, were used for race classification using differential tomato varieties as Ponderosa (susceptible), Leaf Mold Resister No. 1 (cf1), Vetomold (cf2) and V-121 (cf3). These isolates were identified as race 0(51 isolates) and race 3(3 isolates), according to Day's system.
Furthermore, on the basis of minor differences in pathogenicity, the race 0 were separated into four subraces as race 0(0), 0(1), 0(3) and 0(1·3).
2. Other thirteen resistant varieties than before stated differential ones were inoculated with ten isolates which belonged to above races and subraces, respectively. Stirling Castle showed low resistant reaction to race 0(1) and highly resistant reactions to other races. Another twelve varieties showed highly resistant reactions to all isolates.
3. In few cases, susceptible lesions were found on the matured plants of resistant varieties, i. e., L.M.R. No. 1, Antimold B and V-121. The isolates obtained from L.M.R. No.1 and Antimold B were identified as race 0 and the isolate obtained from V-121 was identified as race 3 which was pathogenic on this variety.
4. Two types, angular and circular, of the lesion of leaf mold can be observed on the tomato leaves. It was found that one variety forms always angular or circular lesions, when inoculated with any races. On the variety which the palisade parenchyma are interrupted by the vein tissues, lesions are angular. The other hand on the varieties which the palisade parenchyma are not interrupted but continue over the veins, lesions are circular.
