Physical Localization of the Root-Knot Nematode () Resistance Locus in Pepper ().

The root-knot nematode (RKN) severely reduces yields of pepper () worldwide. A single dominant locus, , conferring RKN resistance was previously mapped on the long arm of pepper chromosome P9. In the present study, the locus was fine mapped using an F population of 714 plants derived from a cross between the RKN-susceptible parent ECW30R and the RKN-resistant parent CM334. CM334 exhibits suppressed RKN juvenile movement, suppressed feeding site enlargement and significant reduction in gall formation compared with ECW30R. RKN resistance screening in the F population identified 558 resistant and 156 susceptible plants, which fit a 3:1 ratio confirming that this RKN resistance was controlled by a single dominant gene. Using the CM334 reference genome and BAC library sequencing, fine mapping of markers was performed. The locus was delimited between two markers G21U3 and G43U3 covering a physical interval of approximately 394.7 kb on the CM334 chromosome P9. Nine markers co-segregated with the gene. A cluster of 25 putative nucleotide-binding site and leucine-rich repeat (NBS-LRR)-type disease resistance genes were predicted in the delimited region. We propose that RKN resistance in CM334 is mediated by one or more of these NBS-LRR class genes. The -linked markers identified here will facilitate marker-assisted selection (MAS) for RKN resistance in pepper breeding programs, as well as functional analysis of candidate genes in .