Controle de fusarium oxysporum f.sp. phaseoli in vitro e em sementes, e promoção do crescimento inicial do feijoeiro comum por Trichoderma harzianum

Abstract

The objective of this study was to evaluate the antagonistic capacity of six isolates of Trichoderma harzianum against Fusarium oxysporum f.sp. phaseoli on infected seeds and its effect on the early stages of growth in bean plants. The isolates were also evaluated in dual culture assays and under in vitro antibiosis at 25°C. Healthy and infected seeds were treated with 2 mL 100 g-1 seeds of the antagonist suspensions (2.5 x 108 conidia mL-1) for healthy evaluation using blotter method at 20 and 25°C. The percentages of pathogen incidence and normal seedlings were evaluated at seven and nine days, respectively. The isolates were applied at 5 x 109 conidia 500 g-1 of sterilized substrate in greenhouse. After 11 days, roots and shoots of the bean plants were measured (12 plants treatment-1). Every isolate of T. harzianum presented in vitro antagonism against the pathogen. The strains CEN202, CEN234, CEN238 and CEN240 offered better control of F. oxysporum on seeds than the positive check, causing a reduction between 35 and 51% in pathogen incidence and 73-81% of normal seedling emergence. The total length of the plants treated with CEN239 (37.43 cm) was longer than the other treatments, with length varying between 27.84 and 33.95 cm. © the Brazilian Phytopathological Society.