Condições favoráveis à mancha foliar causada por Xanthomonas axonopodis em eucalipto

• Autor(a) principal: Neves, Daniela Andrade
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4450
• topic: Eucalipto; Xanthomonas axonopodis; Bacteriose do eucalipto; Eucalyptus; Bacterial blight; Xanthomonas axonopodis; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA

Xanthomonas axonopodis has become one of the main leaf pathogens in Brazilian eucalyptus plantations. It causes leaf spots and defoliation in nursery seedlings and young plants in the field. There is, however, little information on the conditions favoring the infection. This work studied the establishment and development of bacterial leaf spot caused by X. axonopodis in eucalyptus at different leaf ages, under different leaf wetting periods and temperatures. Disease severity increased with leaf age, being higher in the third fully expanded leaf pair, from apex to base. In addition, higher level of bacterial colonization was found in the third leaf pair expressed as colony forming units (cfu)/cm2 leaf area. The presence of free water on the leaf surface, for 12 h pre-inoculation, was essential for increasing disease severity. However, the extension of the leaf-wetting period caused a reduction in the disease severity. The optimum temperature range for disease development was between 26 and 30ºC. The results allowed to determine the optimum conditions for the disease establishment. Plants should be kept in fog room for 12 h pre-inoculation and then immediately transferred to growth room at 26 - 30ºC. Evaluations of severity should be carried out at 20 days after inoculation in the fourth leaf pair, from apex to base, and defoliation at 30 days after inoculation. Such conditions are to be used in resistance studies, such as selection of resistant genotypes and should be taken into consideration when defining control strategies based on the management of cultivation conditions.