Reação de linhagens elites de feijoeiro à Xanthomonas axonopodis pv. phaseoli, agente causal do crestamento bacteriano comum

Abstract

Common bacterial blight (CBB) is one of the most important diseases that affect the common bean crop (Phaseolus vulgaris L.) and the major bacteriosis that affects this crop. The CBB is caused by Xanthomonas axonopodis pv. phaseoli and Xanthomonas axonopodis pv. phaseoli var. fuscans. Under conditions of temperatures between 28 and 30°C and high humidity, the disease develops in the host, causing yield losses of up to 45%. This disease is of great relevance, due to its wide distribution and its great potential for seed transmissibility and may remain viable for several years in plant residuals and seeds. The use of resistant cultivars is one of the most efficient measures in the control of CBB. In doing so, the objective of this study was to evaluate the resistance of common bean lines to common bacterial blight. A total of 115 bean lines were evaluated, including susceptibility and resistance patterns, Pérola and BRS Campeiro, respectively. The experimental design was arranged in randomized blocks, with two replications and each repetition consisted of one pot with three plants, conducted in a greenhouse. The inoculation of the suspension and the evaluation of the disease severity were performed using the method proposed by Zapata (2006). The evaluation was 14, 21 and 28 days after inoculation (DAI) and it was estimated the area under the disease-progress curve (AUDPC). A total of 75 lines (65.2%) were considered potential resistance sources and most of them are of the carioca and black groups. The VC 36 line presented the lowest severity mean score (mean = 1), followed by the CXII-13, CV-6, CNFP 10794, RPXI-7, BRS Campeiro, MB 89, CXII-1, BRS Timbó, RPCVIII 7, CXIII1.7B, VC 19, VC 21, BRS Esteio and CXII-8, with severity mean scores ranging from 1.15 to 1.85. The evaluation at 28 days after inoculation of Xap was shown to be promising for the selection of resistance lines to CBB.