Patogênese de Aspergillus niger e biocontrole da podridão vermelha do sisal por Trichoderma spp.

Abstract

Sisal (Agave sisalana) is a crop of great importance in the semi-arid region of Northeastern Brazil, contributing to the creation of jobs and income in areas with few alternatives for agricultural production. The red rot disease of sisal caused by the fungus Aspergillus niger is the main problem of the crop, causing a continuous decline of the plant, expressed as reduction in cultivated area, production and yield. The biological control is a viable alternative for control of sisal red rot, and fungi of the genus Trichoderma spp. have been pointed out in several studies as biocontrol agents for several plant diseases. There are very few studies about this crop and the definition of disease control methods demands a comprehensive knowledge of the disease. Thus, this work aimed at evaluating some components of the pathosystem sisal - A. niger in sisal seedlings and at selecting isolates of Trichoderma for control of sisal red rot disease. It was observed that disease symptoms only appeared in plants with lesions in the stem, and that isolates of A. niger obtained from the environment, and not from sisal plants, nor from sisal producing areas were pathogenic, although with lower aggressiveness when compared to strains isolated from sisal plants with red rot symptoms. A method for testing in vitro antagonism between A. niger and Trichoderma isolates with the use of sisal stem discs was developed. The in vitro testes allowed the selection of four promising Trichoderma spp. isolates. However, when these isolates were evaluated in the field under the semi-arid environmental conditions of the municipality of Miguel Calmon, they did not efficiently control sisal.