Common bean (Phaseolus vulgaris L.) growth promotion and biocontrol by rhizobacteria under Rhizoctonia solani suppressive and conducive soils

Abstract

Rhizobacteria promote plant growth and disease control. However, in crop management practices cultivar and environmental conditions may also interfere with diseases outcome. This study aimed to evaluate the effect of common bean seed treatment with isolates ALB629 and UFLA285 of Bacillus amyloliquefaciens, combined or not with metalaxyl + fludioxonil, the control of Rhizoctonia solani damping-off and web blight (WB), plant growth parameters and common bean yield. Field and greenhouse trials were carried out in two different locations in Brazil – Lavras, MG (Southeast) with suppressive soil conditions and Boa Vista, RR (North) with a conducive WB condition, using two cultivars of common bean – Pérola and BRS Agreste. The treatments responded differently to either the locations and the cultivars regarding the disease development or plant growth parameters. In Lavras the suppressive conditions did not allow R. solani establishment and promoted higher seed germination and emergency when soils were kept in natural conditions compared to sterile soils. In Boa Vista with conducive conditions, treatments with rhizobacteria associated with fungicide reduced by up to 164% the WB incidence in both cultivars, but the treatment with only ALB629 or UFLA285 also reduced the disease severity. The combination of rhizobacteria with fungicide ensured consistency and stability of results. The common bean yield was higher than the control in 23% and about 500% in Lavras (cv. Perola) and Boa Vista (cv. BRS Agreste), respectively when seeds were treated with ALB629. The use of ALB629 is a plausible strategy for bean seed treatment to control disease and increase bean yield, and therefore an important tool to improve common bean production.