Identification of QTLs Associated with Improved Resistance to Ascochyta Blight in an Interspecific Pea Recombinant Inbred Line Population

Ascochyta blight of pea (Pisum sp.), caused by Peyronellaea pinodes, often results in serious yield losses. Some accessions of Pisum fulvum Sibth. & Sm. previously showed high levels of resistance and could be used as sources of new resistance genes. The objectives of this study were to develop a single nucleotide polymorphism (SNP)-based linkage map and identify genomic regions associated with Ascochyta blight resistance. A population (PR-19) consisting of 144 recombinant inbred lines (RILs) developed from a cross between P651 (P. fulvum) and Alfetta (Pisum sativum L.) was used. These RILs were evaluated for Ascochyta blight resistance under field conditions in Saskatchewan, as well as under greenhouse conditions. The RILs were genotyped using an Illumina GoldenGate array panel of 1536 SNPs. A wide range of variation was observed in Ascochyta blight scores and other agronomic traits. Disease scores were positively correlated (P < 0.001) with lodging and were negatively correlated (P < 0.001) with days to flower, plant height, days to maturity, and grain yield. A total of 733 SNP markers were assigned to six linkage groups covering 682.1 cM of the pea genome. Nine quantitative trait loci (QTLs) were identified for Ascochyta blight resistance, which individually explained 7.5 to 28% of the total phenotypic variation. In addition, five QTLs each were identified for plant height, days to maturity, and grain yield, four QTLs for days to flower, and two QTLs for lodging. The QTL abIII-1 was consistent across locations and years, whereas abI-IV-2 was significant at both locations in 2014. These QTLs can be utilized for development of molecular markers associated with Ascochyta blight resistance.