In vitro evaluation of bacteria for the biological control ofMacrophomina phaseolina.

Sixty-four strains ofRhizobium and seven other rhizosphere bacteria were evaluated by streak-plate, double-layer, and spent-culture methods to determine their antibiotic activity againstMacrophomina phaseolina, causative agent of 'ashy stem' blight of beans. Expression of inhibition varied among strains and depended on growth media and screening method. The streak-plate method with yeast extract/mannitol was the best bioassay. Results indicate that root-nodule bacteria have weak biofungicidal potential. A strain ofPseudomonas cepacia (UPR 5C) consistently restricted fungal growth.