Construction of an integrated linkage map and trait dissection for bacterial blight resistance in field pea (Pisum sativum L.)

Field pea (Pisum sativum L.) is a grain legume crop that is cultivated for either human or livestock consumption. Development of varieties adapted to damaging abiotic and biotic stresses is a major objective for field pea breeding. Bacterial blight is a serious disease caused by the pathogenic agents Pseudomonas syringae pv. syringae and Pseudomonas syringae pv. pisi. A recombinant inbred line (RIL) genetic mapping population was generated by crossing the susceptible genotype Kaspa to the resistant genotype PBA Oura. Previously described sets of single-nucleotide polymorphism and simple sequence repeat markers were assigned to a genetic linkage map of the Kaspa × PBA Oura population, which contained 358 markers spanning 1070 cM with an average marker density of 1 locus per 3.0 cM. Combination with multiple previously published maps (including that of Kaspa × Parafield) subsequently generated an integrated structure with much higher marker density of 1 locus per 0.85 cM. The Kaspa × PBA Oura and Kaspa × Parafield RILs were screened at the seedling stage for resistance to both pathovars. Totals of four and two QTLs for resistance to infection by P. syringae pv. syringae were detected in the Kaspa × Parafield and Kaspa × PBA Oura populations, respectively. A single common genomic region associated with P. syringae pv. pisi resistance was identified in both mapping populations. To integrate information on bacterial blight resistance from various QTL mapping studies, the relevant regions were extrapolated on to the integrated map through use of common flanking markers. The resources generated in this study will support map enhancement, identification of marker-trait associations, genomics-assisted breeding, map-based gene isolation and comparative genetics.