Epiphytic bacteria from various bean genotypes and their potential for bicontrol of Xanthomonas axonopodis pv. phaseoli

Abstract

Naturally occurring epiphytic non-pathogeni bacteria were isolated from reproductive tissue of various bean genotypes grown in the field and screened for both in vitro and in vivo antagonism to Xanthomonas axonopodis pv. phaseoli (formely X. campestris pv phaseoli). Of the 22 potential bacterial antagonists screened in vitro (at 27 + l0C), only 3 isolates exhibited antagonism to X. a. pv. phaseoli. Two of the 3 isolates were identified as Bacillus spp. and the third as Pseudomonas fluorescens. When screened in vo in the greenhouse, all three bacterial, antogonists delayed the development of common bacterial. blight, symptoms for 2-3 days, when spray-inoculated prior to phaseoli. The rate of common bacterial blight disease development was significantly reduced. Bean plants treated with bacterial antagonists had smaller disease lesions than the phosphate buffer, treated controls. These results suggest that phylloplane microflora from beans influence the development of common bacterial blight on the bean crop. These antagonists are promising potential biocontrol agents for bean common bacterial blight disease.

Keywords: Epiphytic bacteria, biocontrol, Phaseolus vulgaris, Xanthomonas , axonopodis. pv. phaseoli

Tanzania J. Agric.,SC., (1999) Vol. 2 No.1, 19-26