Abstract
Ascochyta blight (AB) is an important disease of pea which can cause severe grain yield loss under wet conditions. In our previous study, we identified two quantitative trait loci (QTLs) abIII-1 and abI-IV-2 for AB resistance and these QTLs were consistent across locations and/or years in an inter-specific pea population (PR-19) developed from a cross between Alfetta (Pisum sativum) and P651 (P. fulvum). The objectives of this study were to fine map the abIII-1 and abI-IV-2 QTLs using a high density single nucleotide polymorphism (SNP)-based genetic linkage map and analyze identified markers in heterogeneous inbred family (HIF) populations. Selective genotyping of 51 PR-19 recombinant inbred lines was performed using genotyping-by-sequencing (GBS) and the resulting high density genetic linkage map was used to identify eight new SNP markers within the abI-IV-2 QTL, whereas no additional SNPs were identified within the abIII-1 QTL. Two HIF populations HIF-224 (143 lines) and HIF-173 (126 lines) were developed from F6 RILs PR-19-224 and PR-19-173, respectively. The HIF populations evaluated under field conditions in 2015 and 2016 showed a wide range of variation for reaction to AB resistance. Lodging score had significant positive (P < 0.001) correlation with AB scores. HIFs were genotyped using SNP markers within targeted QTLs. The genotypic and phenotypic data of the HIFs were used to identify two new QTLs, abI-IV-2.1 and abI-IV-2.2 for AB resistance within the abI-IV-2 QTL. These QTLs individually explained 5.5 to 14% of the total phenotypic variation. Resistance to lodging was also associated with these two QTLs. Identified SNP markers will be useful in marker assisted selection for development of pea cultivars with improved AB resistance.
Highlights
Ascochyta blight (AB), caused by Peyronellaea pinodes
Four recombinant inbred line (RIL) each tested for abI-IV-2 (PR-19-57, PR-19-132, PR-19-176, and PR-19-224) and abIII-1 (PR-19-04, PR-19-65, PR-19-115, and PR-19-173) had heterozygous alleles within QTLs, i.e., these lines were segregating for markers associated with AB, which is a prerequisite for heterogeneous inbred family (HIF) development
HIFs had a small range of variation for days to flower (DTF) and days to maturity (DTM) at different station years, while plant height and grain yield had a wide range of variation among tested HIF lines
Summary
Ascochyta blight (AB), caused by Peyronellaea pinodes Fine Mapping Ascochyta Resistance in Pea low to moderate levels of resistance (Kraft et al, 1998; Zhang et al, 2006). A higher level of resistance was identified in wild pea (P. fulvum) accessions (Clulow et al, 1991; Wroth, 1998; Fondevilla et al, 2005; Jha et al, 2012). Fondevilla et al (2005) reported the highest level of resistance in accession P651 (P. fulvum) compared to other wild peas, P670 Elatius) were identified upon evaluation of 44 wild pea accessions which had the potential for improvement of AB resistance (Jha et al, 2012). The most promising accession, P651 (P. fulvum) was utilized for resistance breeding (Sindhu et al, 2014; Jha et al, 2016)
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