Efeito de rizobactérias no crescimento micelial de Sclerotinia sclerotiorum e na germinação e sanidade de sementes de soja

Abstract

White mold caused by Sclerotinia sclerotiorum is an important disease for the soybean crop to present dissemination facility, causing losses of up to 100 % in production. The use of rhizobacteria has shown great potential in the control of plant pathogens, being an environmentally friendly alternative to reduce the use of pesticides in soybean production. The objective of this work was to isolate and to select rhizobacteria from soybean plants as antagonistic capacity to S. sclerotiorum in vitro and to evaluate the effect of these isolated on germination and sanity of soybean seeds. The tests were performed at the Laboratory of Plant Pathology, Federal University of Pampa - Campus Itaqui. Isolation of rhizobacteria was made from soybean roots, randomly drawn from three distinct points from three soybean crops in the cities of Uruguaiana, Itaqui and Maçambara of the Rio Grande do Sul State. From the isolates obtained was performed an in vitro test to assess the effect of rhizobacteria on mycelial growth rate index (MIGS) S. sclerotiorum. For this, each rhizobacterian isolated was peaked in the four extremes of the Petri dish, except in the control group and a 0.5 cm fungal mycelium disk was placed in the center of all plates. The plates were placed in BOD at 25 ° C with a photoperiod of 12 hours. The evaluation consisted of daily measurements of the pathogen until the witness reaches the edge of the plate. The best isolates in vitro test were assessed for their effect on health and germination of soybean seeds. Seeds of soybean were microbiolized bacterial suspension in the concentration OD₅₄₀=0,5 = 0.5 for five minutes. Next was mounted paper roll test and kept in BOD at 25 ° C. Eight days after germination were evaluated and the incidence of fungi on seeds . The experimental design was completely randomized with four replications. The data were submitted to analysis of variance and the means of each treatment, grouped by the Scott- Knott test at 5 % probability. 47 rhizobacterian isolates were obtained where 21.27 % had some degree of control on the MIGS when compared to the control. The rhizobacterium I1 was the most efficient, with 70.3 % inhibition of MIGS S. sclerotiorum. The germination and health soybeans only isolated M8 showed good results on germination and control of phytopathogens.