Resistance to common bacterial blight of bean introgressed from Phaseolus coccineus

Abstract

Common bacterial blight, incited by Xanthomonas campestris pv. phaseoli (Smith) Dye, is a major bacterial disease of dry bean (Phaseolus vulgaris L.). Resistance to common bacterial blight has been identified in other Phaseolus species and resistance genes have been introgressed into P. vulgaris. The objective of this study was to characterize in dry bean the inheritance pattern of common bacterial blight-resistance genes derived from P. coccineus. Two common, bacterial blight-susceptible, dry bean cultivars were crossed with different common, bacterial blight-resistant dry bean lines with resistance derived from P. coccineus. F2 progeny were inoculated with Xanthomonas campestris pv. phaseoli strain F19-W and were scored for disease reaction. The ratio of resistant to susceptible plants for F2 populations did not differ significantly from a 1 resistant : 3 susceptible ratio. The F3 segregation was obtained for only one cross and did not differ significantly from a 1 resistant : 2 heterozygous : 1 susceptible ratio, suggesting that the resistance introgressed from P. coccineus into dry bean was controlled by one recessive gene. Additionally, the range of symptom expression within the susceptible class provided evidence of other genes modifying the expression of resistance.