Molecular Analysis of a Large Subtelomeric Nucleotide-Binding-Site-Leucine-Rich-Repeat Family in Two Representative Genotypes of the Major Gene Pools of Phaseolus vulgaris

In common bean, the B4 disease resistance (R.) gene cluster is a complex cluster localized at the end of linkage group (LG) B4, containing at least three R specificities to the fungus Colletotrichum lindemuthianum. To investigate the evolution of this R cluster Since the divergence of Andean and Mesoamerican gene pools, DNA sequences were characterized front two representative genotypes Of the two Major gene pools of common heart (BAT93: Mesoamerican; JaloEEP558: Andean). Sequences encoding 29 B4-CC nucleotide-binding-site-leucine-rich-repeat (B4-CNL) genes were determined-12 from JaloEEP558 and 17 front BAT93. Although sequence exchange events were identified, phylogenetic analyses revealed that they were not frequent enough to lead to homogenization of B4-CNL sequences within a haplotype. Genetic mapping based on pulsed-field gel electrophoresis separation confirmed that the B4-CNL family is a large family specific to one end of LG B4 and is present at two distinct blocks separated 13), 26 W. Fluorescent in situ hybridization oil meiotic pachytene chromosomes revealed that two B4-CNL blocks are located ill the subtelomeric region of the short arm of chromosome 4 oil both sides of a heterochromatic block (knob), suggesting that this peculiar genomic environment. may favor the proliferation of a large R gene cluster.