Reação de genótipos de pessegueiro a bacteriose causada por Xanthomonas arboricola pv. pruni

Abstract

The bacterioses of peach caused by Xanthomonas arboricola pv. pruni is an of the majors diseases of the peach orchard in Brazil and in the most of producing regions of the world. The use of resistant cultivars is a tool to reduce disease progresses in commercial orchards. This work aimed to evaluate and classify peaches genotypes which the sensitivity to Xanthomonas arboricola pv. pruni. Thus, three experiments were performed to evaluate the reaction of genotypes of peach in different situations. In the experiment under natural conditions, it was evaluated the incidence, severity and defoliation caused by bacterial spot. The genotypes showed different levels of sensitivity, and the genotypes Conserva 985, Conserva 1129, Conserva 871 and 'Tropic Snow' were the most resistant, while ‘Bonão’, Conserva 1125, 'Atenas' and Conserva 1153 was the most susceptible ones. In laboratory, it was evaluated the severity of bacterial spot in detached peach leaf, inoculated with Xanthomonas arboricola pv. pruni in eight genotypes of peach, selected in the experiment under natural conditions. It was measured the activated of some biochemical compounds related to the pathogenesis in two resistant genotypes and two susceptible ones. Based on the results, it was concluded that the detached-leaf bioassay, inoculated by infiltration, is possible to use for identify resistant bacterial spot genotypes. The genotypes that showed the lowest rates of disease were Conserva 985 and Conserva 1129, while Conserva 1153, Atenas and Conserva 1125 showed the highest rates; it was not possible to identify a biochemical compound related to bacterial spot resistance. In a controlled environment (greenhouse), it was evaluated the progression of the disease in young plants through the levels of bacterial spot severity on the leaves, using the same genotypes of the experiment in the laboratory. The results were similar with the previous results confirming the resistance of Conserva 985 and Conserva 1129, and the susceptibility of Conserva 1153 and ‘Atenas’ to bacterial spot caused by Xanthomonas arboricola pv. pruni.