|Zapata, Mildred -|
|Beaver, James -|
Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 16, 2010
Publication Date: May 21, 2011
Citation: Zapata, M., Beaver, J.S., Porch Clay, T.G. 2011. Dominant gene for common bean resistance to common bacterial blight caused by Xanthomonas axonopodis pv. phaseoli. Euphytica. 179:373-382. Interpretive Summary: The common bacterial blight pathogen (Xanthomonas axonopodis) is a limiting factor for common bean (Phaseolus vulgaris) production worldwide and there is little resistance to this disease in most commercial common bean varieties. Different strains of common bacterial blight vary in their ability to cause disease in common bean. Some common bean lines also react with different levels of disease symptoms when they are inoculated with different strains of common bacterial blight. These results indicate that there may be independent genes controlling resistance to different strains. This study investigated the genetics of resistance of the variety PR0313-58 to a common bacterial blight strain, through the analysis of segregation patterns in several generations of a cross between PR0313-58 and the susceptible variety, ‘Rosada Nativa.’ Response to bacterial infection was tested under greenhouse conditions and in the field. The genetic analysis indicates that a single dominant gene controls the resistance of PR0313-58 to the common bacterial strain. This resistance gene co-segregates with a molecular marker, SAP6, which can be used for selecting for resistance to common bacterial blight in the laboratory. This is the first published report of a single resistance gene controlling resistance to common bacterial blight in common bean. These results will provide information for improving common bean selection techniques in breeding programs and they will further our knowledge about the interaction between the bacterial pathogen and the common bean host.
Technical Abstract: The common bacterial blight pathogen [Xanthomonas axonopodis pv. phaseoli (Xap)] is a limiting factor for common bean (Phaseolus vulgaris L.) production worldwide and resistance to the pathogen in most commercial cultivars is inadequate. Variability in virulence of the bacterial pathogen has been observed in strains isolated from Puerto Rico and Central America. A few common bean lines show a differential reaction when inoculated with different Xap strains, indicating the presence of pathogenic races. In order to study the inheritance of resistance to common bacterial blight in common bean, a breeding line that showed a differential foliar reaction to Xap strains was selected and was crossed with a susceptible parent. The inheritance of resistance to one of the selected Xap races was determined by analysis of segregation patterns in the F1, F2, F3 and F4 generations from the cross between the resistant parent PR0313-58 and the susceptible parent ‘Rosada Nativa’. The F1, F2 and F3 generations were tested under greenhouse conditions. Resistant and susceptible F3:4 sister lines were tested in the field. The statistical analysis of all generations followed the model for a dominant resistance gene. The resistant phenotype was found to co-segregate with the SCAR SAP6 marker, located on LG 10. These results fit the hypothesis that resistance is controlled by a single dominant gene. The symbol proposed for the resistance gene is Xap-1 and for the bacterial race, XapV1.