Controle biológico de doenças foliares e murchas do tomateiro pelo uso rizobactérias

Abstract

The search on alternative control of diseases to replace the use of pesticides has been the subject of agricultural research. Rhizobacteria are known by controlling diseases and promoting growth in several crops. The objectives of this work were to evaluate the efficacy of six rhizobacteria pre-selected for the control of Ralstonia solanacearum and Fusarium oxysporum f. sp. lycopersici (FOL) in greenhouse, and to relate this behavior with the production of compounds "in vitro", as well as evaluate the protection of tomato plants against foliar diseases under field conditions. It was evaluated the ability of these rhizobacteria to produce chitinases, amylases, lipases, antibiotic compounds and to solubilize phosphate. The seed microbiolization with rhizobacterium DFs1420 (Bacillus sp.) reduced the severity of the bacterial wilt 66% at 14 days after inoculation and AUDPC 70%, respectively, the first and second assays. This control may be associated with the production of compounds responsible for the antibiosis observed "in vitro". Streptomyces (DFs1296 and DFs1315) and Bacillus sp. (DFs1414) significantly reduced fusarium wilt. The control observed can be attributed to the chitinolytic activity and/or antibiosis in the presence of volatile compounds. Three field trials were carried out in field. The foliar diseases severity was monitored over time. The rhizobacteria were capable of protecting plants against Septoria lycopersici. DFs1414 and DFs1421 (Pseudomonas sp.) were the most stable, providing protection in two consecutive trials. The rhizobacteria DFs1296 and DFs1420 were able to control late blight (Phytophthora infestans) in two trials. DFs1296 also had the ability to protect against these and other diseases when sprayed weekly in the plant canopy.In general, the control achieved by these rhizobacteria, by seed microbiolization or by foliar application, did not differ from treatments using recommended chemical in weekly applications.