Disease incidence, severity, and AUDPC-based evaluation of two bush bean varieties

Bush bean ( Phaseolus vulgaris L.) is a legume crop of economic value that is valued for its nutritional content and contribution to food security. Bush bean production is increasing in Bangladesh, particularly in Sylhet, but several diseases reduce yield under humid subtropical climatic conditions. This study was conducted during the Rabi season to assess major bush bean diseases, including their incidence, severity, causal pathogens, and impact on yield and quality. Two bush bean varieties were selected for the study: BARI Bush Bean-1 (V 1 ) and a local line (V 2 ), and they were evaluated in pot and laboratory trials. Three major diseases, anthracnose, Alternaria leaf spot, and common bacterial blight, were found to be dominant. Morphological characterization confirmed Colletotrichum lindemuthianum as the causal agent of Anthracnose and Alternaria alternata as the pathogen of Alternaria leaf spot, while Bacterial blight was diagnosed on the basis of characteristic symptoms. Mean differences between varieties were observed in the incidence and severity of the disease. Disease levels were consistently higher for the local variety, where bacterial blight showed the highest incidence (50% in V 1 and 70% in V 2 ), anthracnose (33% in V 1 and 58% in V 2 ), and Alternaria leaf spot (29% in V 1 and 70% in V 2 ). Disease severity ranged between 17 and 29% among the diseases. Disease occurred at 14–35 days after transplanting and was maximum at 42–63 days. Area under the disease progress curve (AUDPC) showed bacterial blight to be the most virulent followed by Alternaria leaf spot and anthracnose with AUDPC values of 513.31 & 838.26, 605.26 & 860.85, 626.50 & 887.1 for V 1 and V 2 , respectively. The findings recognize the vulnerability of local bush beans in Sylhet region to major diseases and highlight integrated disease management methods in Sylhet region. It needs further experiment and evaluation for more comprehensive information especially including farmer’s field experiment, control measures in future.