Controle de Guignardia citricarpa, agente causal da Mancha Preta dos Citros / Control of Guignardia citricarpa, causal agent of Citrus Black Spot

AUTOR(ES)

Maria Beatriz Calderan Rodrigues

DATA DE PUBLICAÇÃO

2006

RESUMO

Citriculture is an extreme important rural activity in social and economical national context in Brazil. Orange is 49% of total brazilian fruit production. However, thousands of tons are lost due to the action of phytopathogens annually. The Black Spot of Citrus (BSC) is responsible for great lost in various citrus producers regions all around the world, being already designed as a phytosanitary barrier, mainly in European market. For in natura fruit consuming, the fruit esthetic is a limiting factor, where BSC compromises the market of fresh affected fruits. Chemical control of plant pathogens is the most commonly way used to minimize damages in citriculture by BSC, although the application of such products implies in high costs, not only for farmers but also for environment, causing soil and water contamination and increasing the selection pressure on pathogen population. On this way, the biocontrol became an attractive way, as a strategy that permits a minor environmental impact besides the plant protection against phytopathogens. For this application, are necessary researches based on utilization of biocontrol techniques, as for example, the using of microorganism producers of hydrolytic enzymes. Such enzymes, like quitinases, endoglicanases and β-glicosydases are able to digest the fungal and bacterial cell wall. In this work, 24 strains of G. citricarpa were evaluated about the sensibility to fungicides used in field for BSC control: piraclostrobin and carbendazin, in dosages of 0,5, 1,0 and 2,0 mg a.i./mL, aiming to verify the effect of selection pressure caused by continuous use of this compounds. Two of these strains presented resistance to carbendazim in all evaluated dosages, showing that the use of this agrochemical may select resistant individuals, resulting a non-efficiency of this compound for BSC control. An alternative to minimize this kind of effect must be the application of this compound in combination to others active principles. The celullolitic and chitinollitic activities of 96 fungi strains widely spread phylogenetically were evaluated for selection of potential biological control agents. Four strains that presented major activity of each enzyme, besides two Trichoderma lineages, were tested as potential biological control of G. citricarpa in an experiment with ‘Valência’ orange leaves, comparing the action of these biocontrolers with commercial fungicides. Although a better pathogen control was achieved in leaves treated with piraclostrobin, two fungi strains revealed to have the similar efficiency to fungicide, inhibiting the development of G. citricarpa, suggesting the possible future utilization of biocontrol methods to Black Spot of Citrus.

ASSUNTO(S)

phytopathogenic fungi orange mancha preta plant disease resistência genética controle biológico biological control fungo fitopatogênico genetic resistance laranja black spot doença de planta

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