Inhibitory effect of antagonistic bacteria against Sclerotium rolfsii, causal agent of southern blight of common bean

The objective of the present study was to select bacterial strains from the rhizosphere of common bean crop and to determine their potential to control Sclerotium rolfsii under in vitro and in planta conditions. Soil samples were collected in the Municipalities of Ahome, Guasave and Angostura, Sinaloa, Mexico. The strains were evaluated in vitro conditions, afterward the best isolates were tested in planta, and were identified based on 16S region of ribosomal DNA (three samples). Sixty-five bacterial isolates were tested against Sclerotium rolfsii with an inhibition from 2.5 to 65%. Acinetobacter pittii (COHUI06), Pseudomonas putida (SANMI02) and Burkholderia sp. (GLS06) inhibited 55, 60 and 65% under in vitro conditions; and resulted not hemolytic and their molecular identification was based on 16S rDNA. Only Burkholderia sp. exherted the highest percentage inhibition in planta to control S. rolfsii with a reduction of incidence and disease severity of 40 and 50% respectively, and promoted the dry weight of the plant.  A. pitti and P. putida were not efficient in controlling the fungus in planta . Greenhouse and field studies with this bacteria are suggested.