POTENCIAL DE BACTÉRIAS ENDOFÍTICAS DO CACAU PARA O CONTROLE DE FUNGOS DE SOLO E PROMOÇÃO DE CRESCIMENTO RADICULAR NA CULTURA DA SOJA

Abstract

The society concern with the excessive use of agrochemicals in agriculture to control diseases generates great demand for research with environmentally less aggressive control methods, among them biological control. Utilizing antagonistic relations exerted by microorganisms such as antibiosis, competition, parasitism, predation and resistance induction in plants, offering a wide range of opportunities for the use of microorganisms that are still little known as endophytic microorganisms. The objective of this work was to investigate the biological control potential of endophytic bacteria isolated from cocoa against soil pathogens Fusarium solani, Rhizoctonia solani and Sclerotinia sclerotiorum and their action in promoting the root growth of soybean plants. Twenty-two endophytic bacteria were evaluated in vitro for their antagonistic potential by the culture method paired against phytopathogens, using as parameters: the formation of inhibition halo exerted by bacteria, the size of the pathogen colony and the percentage of inhibition of mycelial growth of the pathogen. The parameters used to evaluate the the control potential of endophytic bactéria on soil fungi and the promotion of root growth in vivo were: the percentage of plant emergence, plant height, percentage of abnormal plants, disease severity, root volume, the fresh mass and dry mass of roots, and the aerial and total part of the plants. There were 9 isolates (TCB 02, TCB 7, TCB 08, TCB 10, TCB 11, TCB 11, TCB 17, TCB 18, TCB 19 and TBC 20) that showed more than 75% inhibition for at least one of the pathogens tested in the experiments in vitro, demonstrating high antagonistic potential. The bacterial isolate TCB 10, identified as Paenibacillus and the bacterial isolate TCB 08, identified as Staphylococcus presented an antagonistic potential for the three phytopathogens. The isolates TCB 17, TCB 18 and TCB 19 presented antagonistic potential for S. sclerotiorum. For the tests with the seed treatment the bacterial isolate TCB 10 presented reduction of the severity of R. solani. It was not possible to conclude that the endophytic bacteria promoted the growth of roots in plants.