Biological effectiveness of Bacillus subtilis on common bean bacterial blight

Abstract

Chemical compounds, which are used on beans to manage common bacterial blight (CBB) disease, cause serious damage to natural ecosystems and often fail to control CBB. A greenhouse experiment was conducted to assess the effectiveness of foliar sprays of Bacillus subtilis str. QST 713 against CBB in a susceptible bean cultivar in comparison with copper hydroxide (CH) and its mixes. A concentration of 108 CFU mL− 1 for Xanthomonas axonopodis pv. phaseoli (Xap) was used to inoculate 21-day-old plants after 3 days of first-time treatment applications. The 2nd and 3rd time treatment applications were applied every 7 days after bacterial inoculation. The disease severity, disease infection rate, AUDPC and disease incidence were significantly reduced over the control treatment. The lowest disease severity, incidence and AUDPC were observed from the mix applications with str. QST713 and CH followed by str. QST 713 and CH alone compared to control treatments. The plants treated with mixes and str. QST 713 showed a reduction of the infection rate by 51.21 and 40.36%, and the disease incidence by 53 and 52.25%, respectively. In addition, the lowest bacterial population per gram of fresh weight of leaves was recorded in plants that had been treated with the mix treatments followed by str. QST713 and CH. Results suggest that integrated management with biocontrol agents is the best strategy for effective control of CBB in sustainable and organic agriculture.