Bacillus subtilis e bactérias endofíticas autóctones como agentes de biocontrole para Fusarium solani e bioacúmulo de ferro na cultura da mandioca

Abstract

Cassava is a culture of high socio-economic importance. However, the nutritional value of the root is poor. It contains little protein, vitamins or nutrients, such as iron. In addition, the culture suffers quality and productivity loss due to the occurrence of disease, among which, the main disease is root rot caused by Fusarium solani. In this sense, we conducted trials adopting bacterial isolates beneficial to improving the culture. To evaluate the antagonism against F. solani and the induction of iron accumulation in cassava plants, we used endophytic and autochthonous bacterial isolates and the GBO3 rhizobacteria. Of these, AMRAC31 (Rhizobium radiobacter), MGRTSA05 (Bacillus subtilis), MAIIF2a (Microbacterium imperial) and GBO3 (Bacillus subtilis) promoted growth, iron accumulation and/or absence of root rot symptoms caused by F. solani. New trials were conducted with the most promising bacteria for inducing the accumulation of iron by plants cultivated in nutritive solution. MAIIF2a, MGRTSA05 and GBO3 were capable of inducing significant iron accumulation by plants in ideal conditions and iron deficiency conditions. The isolates also presented fungicide and fungistatic effect, protecting cassava gems and branches against colonization by F. solani after in vitro bacterization. With the combination of the obtained results, we evaluated, in field, the inducing potential of iron accumulation on the more promising isolates in two cultivars previously selected regarding productivity. We concluded that the MGRTSA05 and GBO3, were capable of inducing iron accumulation by cassava plants of cultivar “IAC 576” with significant values regarding the control treatment.