Incidence and severity of the common blight in bean plants inoculated with Rhizobium phaseoli

Abstract

The common bacterial blight Xanthomonas axonopodis pv. phaseoli is a disease that attacks the bean crop (Phaseolus vulgaris), is present 83% of the areas of seed production and up to 79% in commercial fields and reduces yields up to 55%. The inoculation of Rhizobium in plants as a promoter of plant growth, nitrogen fixer, to the synthesis of indoleacetic acid, produces in the plant greater vigor and tolerance to diseases. The behavior of the incidence and severity of common blight of bean plants inoculated with Rhizobium phaseoli and X. axonopodis pv. phaseoli. For this, strains of Rhizobium (FM-1, N-2, PS-3, M-4, BJ-5) of root nodules of bean plants and Xanthomonas (Xant 1) of necrotic leaf spots were isolated. The isolates were identified based on cellular, colonial and biochemical morphological characteristics. The greenhouse and field trials were carried out on seeds inoculated with 10⁶ cfu mL^-1 of Rhizobium and a second application 10 days after planting. Subsequently, 15 days after emergence of the bean, Xanthomonas axonopodis was inoculated directly by sprinkling directly into the plant. After 30 days of greenhouse cultivation, it was observed that the severity of common blight was lower in plants with nodules in the root (14.5%), than in the control (46%), it was also found that plants inoculated with Rhizobium phaseoli BJ -5 developed greater vigor, stem diameter, dry weight, number of leaves and root length. In the field, the inoculation with strain BJ-5 also showed lower severity (25.6%) compared to the control (55.8%) and it turned out to have better growth in the plant. The inoculation of beans with Rhizobium phaseoli allows the crop to be nutritionally and phytosanitarily favored.