1979 Volume 29 Issue 4 Pages 279-286
The genes of IR 28 responsible for resistance to the five bacterial groups I, II, III, IV and V of Xanthomonas oryzae (Uyeda et Ishiyama) Dowson from Japan were analyzed. The resistant variety IR 28, the susceptible variety Toyonishiki and their cross hybrids F1 and F2 plants were tested for resistance to each of the representative isolates of the five bacterial groups; T 7174 for group I, T7147 for group II, T 7133 for group III, H 75373, for group IV and H75304 for group V. Adult plants grown in the experimental paddy field were inoculated by double needle prick method. Three weeks later, the inoculated plants were scored for disease-index number according to the standard proposed by EZUKA and HORINO (1974). With the disease-index number to bacterial groups I and V, F1 means were both very close to IR 28, which showed O.3 for group I and O.1 for group V. For each of the two groups. F2 Segregation in the disease-index number exhibited a wide range from O.O to 7.O, but formed a clear-cut bimodal distribution: one mode with a predorninant number-of plants corresponded to IR 28 and the other with much less plants crresponded to, Toyonishiki, which showed lower disease-index number to group V than to group I most likely because of the relatively weak aggressiveness of the isolate used as group V. The analysis of segregations revealed that one major gene controlled the resistance of IR 28 to bacterial group I and another major gene to bacterial group V, and that the two. genes linked very closely with a recombination value of about 4%.
