Bacterial spot of Japanese-type plum and others stone seed fruits, caused by Xanthomonas arboricola pv. pruni, is a serious disease in warm and humid environments. Chemical control is costly and often ineffective. Therefore, in areas where bacterial spot is a problem, the use of resistant cultivars is an important part of a management program for reducing the risk of loss from this disease. However, the selection of resistant genotypes is difficult because there are no rapid and reliable methods to evaluate the severity of disease on leaves and twigs. The aim of this work was to test screening techniques to identify resistant genotypes under field conditions and to classify three Japanese plum varieties according to their reaction to bacterial spot. Among the screening techniques compared, leaf severity was more reliable than the mean number of leaf spots. The number of twig cankers per meter and the mean of cankers in the first 10 cm from the twig base were both reliable, but the last technique is faster and easier to apply. 'Irati' exhibited the highest level of resistance, among the other cultivars.
Prunus salicina; stone seed fruits; disease resistance; stone seed fruits breeding
