|Miklas, Phillip - Phil|
Submitted to: Cowpea World Conference Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/8/2005
Publication Date: 9/12/2005
Citation: Fourie, D., Miklas, P.N., Myers, J., Ariyarathne, H. 2005. Identification and genetic mapping of genes conditioning resistance to halo blight in common bean. Regional Partnership to Enhance Bean/Cowpea Consumption and Production in South Africa and Latin America, Sept 12-16, 2005, Dakar, Senegal. p. 19.
Technical Abstract: Halo blight is a seed-borne bacterial disease (caused by Pseudomonas syringae pv. phaseolicola) that infects common bean (Phaseolus vulgaris L.) worldwide. Genetic resistance is the most effective control method. The objective of this research was to analyze resistance to halo blight segregating in 77 recombinant inbred lines (RILs) derived from the cross BelNeb-RR-1 x A55. The lines were challenged by Races 1, 3, 4, 5, 7, and 9 because BelNeb-RR-1 exhibited resistance to Races 1, 5, 7, and 9 and A55 was resistant to Races 3 and 4. Five plants of each RIL were inoculated with each race. Each plant represented a replicate in a RCBD (five replicates). Plants were rated for infection 10 days after inoculation on a 1 to 5 scale with 1 being highly resistant and 5 being highly susceptible. Three major resistance genes, temporarily assigned the symbols Pse-1, Pse-3, and Pse-4 were mapped. The Pse-1 gene that conditions resistance to Races 1, 7, and 9 appears to represent a cluster of individual genes conditioning resistance to separate races. The Pse-1 gene cluster is located on linkage group B4 within a cluster of genes/QTL conditioning resistance to anthracnose, ashy stem blight, bacterial brown spot, Bean golden yellow mosaic virus, and rust. A SCAR marker (B10.520) for MAS of Pse-1 has been developed. Sequence for the 520 bp fragment closely aligns with the sequence of a resistance gene analog (RGA) mapped in the same genomic region. The Pse-4 gene conditions resistance to Race 5 and is also located within a cluster of resistance genes in a different region of linkage group B4, 14.7 cM from the Pse-1 gene cluster. Pse-3 gene conditioned hypersensitive resistance to Races 3 and 4, and was completely linked to the I gene which conditions hypersensitive resistance to Bean common mosaic virus as has been reported previously. Resistance to Races 2, 7, 8 and 9 in the host differential cultivar A43 is conditioned by a single gene. Relationship of this gene with Pse-1 which conditions resistance to Races 1, 7, and 9 is under investigation. Further characterization of these major genes and their co-localization with mapped QTL for resistance to halo blight is discussed. An increased understanding of resistance to halo blight will lead to better breeding methods and resistance gene/QTL deployment strategies for combating this pathogen in East Africa and other regions.