High-Density Linkage Map Construction and QTL Mapping of Multiple Traits in Field Pea

In this study, four recombinant inbred (RI) populations derived from crosses of cultivated field pea accessions were used to generate high-density linkage maps of pea for the purpose of identification of quantitative trait loci (QTL) associated with agronomical, yield and nutritional traits.  RILs from Orb x CDC Striker, CDC Sage x CDC Centennial, Carrera x CDC Striker and 1-2347-144 x CDC Meadow were genotyped using genotyping-by-sequencing (GBS) method involving double digestion of genomic DNA with PstI and MspI.   DNA of individual RIL was ligated with a barcode adapter and pooled as 48-plex libraries.  Each library was sequenced in a single lane on Illumina Hiseq using V4 sequencing chemistry.  An average of 3.56 million reads per RIL were generated after quality trimming and were used for SNP allele calling.   Polymorphic SNPs identified in each population (an average of 2380) were used to construct linkage maps and these maps were integrated with the existing linkage maps (250-350 SNP markers) based on 1536 Golden Gate array SNP genotyping.   The integrated linkage maps covered an average distance of 1050 cM and an average of 720 loci were mapped in each population.  Fourteen QTLs associated with Mycosphaerella blight resistance, lodging resistance, zinc and iron concentrations of seed were identified in Carrera x CDC striker population.  The LOD thresholds of these QTLs ranged from 3.2 to 17.6.  Details of these QTLs will be presented.