Consensus Genetic Map Construction for Field Pea (Pisum sativum L.), Trait Dissection of Biotic and Abiotic Stress Tolerance and Development of a Diagnostic Marker for the er1 Powdery Mildew Resistance Gene

Field pea (Pisum sativum L.) is a cool-season legume that is cultivated worldwide for both human consumption and stockfeed. Genetic improvement is essential for enhanced crop production and management of field pea, especially to deliver superior varieties adapted to various biotic and abiotic stresses. A detailed understanding of the genetic basis of such stress tolerances is hence desirable. Genetic linkage maps based on single nucleotide polymorphisms (SNP) and simple sequence repeat (SSR) markers have been developed from two recombinant inbred line (RIL) populations generated by crossing phenotypically divergent parental genotypes. The Kaspa x Yarrum map contained 428 loci across 1910 cM, while the Kaspa x ps1771 map contained 451 loci across 1545 cM. Data from these maps were combined through bridging markers with those from previously published studies to generate a consensus structure including 2028 loci distributed across seven linkage groups (LGs), with a cumulative length of 2387 cM at an average density of one marker per 1.2 cM. Trait dissection of powdery mildew resistance was performed for both RIL populations, identifying a single genomic region of large magnitude in the same genomic region on Ps VI, which were inferred to correspond to the er1 gene. Equivalent studies of the Kaspa x ps1771 RIL population identified a major quantitative trait locus (QTL) for boron tolerance that coincided with the disease resistance-controlling locus, permitting strategies of co-selection for these desirable traits. Resequencing of the PsMLO1 candidate gene from resistant and susceptible genotypes allowed design and validation of a putative diagnostic marker for powdery mildew resistance. The availability of a highly saturated consensus map, linked markers for key biotic and abiotic stress tolerances and a diagnostic marker for the agronomically important er1 gene provide important resources for field pea molecular breeding programs.