Histopatologia e influência de nutrientes na intensidade da bacteriose foliar do eucalipto causada por Xanthomonas axonopodis

• Autor(a) principal: Silva, Aderlan Gomes da
• Data de Publicação: 2007
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1077
• topic: Bacteriose do eucalipto; Histopatologia; Nutrição de plantas; Eucalyptus; Bacterial blight; Histopathology; Plant nutrition; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA

This work aimed at to study the pre-penetration and penetration of Xanthomonas axonopodis in eucalyptus leaves, to verify the importance of the stomatal index and of the leaf age in the susceptibility of the plant to the pathogen and to study the influence of the plant nutritional status in the susceptibility to the disease. By means of scanning electron microscopy, it was observed that the bacteria penetrates the leaves by the stomata and that formation of microcolonies has occurred in the substomatal chamber and inside the secretors cavities 6 hours after the inoculation. At the eighty day after the inoculation, the rupture of the epidermis was observed and inside the tissue was a great mass of bacteria involved in a mucilage-like substance. The amount of bacteria increased with the incubation period. The influence of stomata in the susceptibility of the plants to the bacterial blight was studied being used clones with different resistance levels. Samples of leaves of same position in the branch were collected and submitted to the clearing with hydrated clorox and to the light microscopy to evaluate the stomatal index in the plants of different clones and to determine the existence of the relationship between number of stomata and severity of the disease. The severity of the disease didn't link with the stomatal index. To evaluate the influence of the leaf age in the susceptibility to the disease, plants of five clones were inoculated from the first to the sixth leaves. Older leaves presented larger percentage of diseased area. To test the influence of nutrients in the susceptibility to the disease were done three tests in glasshouse and one in commercial nursery. Eucalypts seedlings of hybrid clones from Eucalyptus urophylla x Eucalyptus grandis were cultivated in vases containing sand, and irrigated with different nutrient solutions, with different levels of copper, boron, potassium, calcium and, or nitrogen. The copper, boron and calcium action was variable. The influence of the management of nitrogen and especially of the potassium was consistent in reducing the disease intensity and it presented high use potential. Intermediate levels of nitrogen in the nutrient solution increased the susceptibility of the plants to the bacterial blight. The intensity of the bacterial blight reduced with the increase of the potassium levels. The reduction of the disease was partially explained by a reduction of the relationship nitrogen/potassium and for an increase in the amount of sugars laves. Due to the effect of the potassium in glasshouse, it was tested, in nursery, the effect of the application of KCl in seedlings of two clones of Eucalyptus globulus. The incidence of the bacterial blight reduced with the increase of the concentration of KCl applied, but the incidence of gray mold in the seedlings increased. The management of the mineral nutrition, especially of the potassium, presents great use potential in the control of bacterial blight of eucalypts.