Construction of a high-density genetic map using specific-locus amplified fragment sequencing and quantitative trait loci analysis for tillering related traits in Psathyrostachys juncea perennial grass.

Abstract

Russian wildrye (RWR, Psathyrostachys juncea) is an outcrossing perennial grass that plays a crucial role in foragaing and rangeland restoration due to its tiller producing capabilities, nevertheless, a genetic map has yet to be constructed due to a shortage of efficient and reliable molecular markers. This also limits the identification, localization, and cloning of economically important traits related to tiller density during breeding. Therefore, this study aimed to create a F1 mapping population with 147 individual lines and their two parents, which were selected based on varying tiller densities. We then used this mapping population to conduct specific-locus amplified fragment sequencing (SLAF-seq) to generate SLAF markers and discover single nucleotide polymorphisms (SNPs). Initially, we generated a total of 1,438.38 million pair-end reads with an average sequencing depth of 84.92 in the maternal line, 79.34 in the parental line, and 27.05 in each F1 individual line, respectively. Following the filtering of low-depth SLAF tags, a total of 558,344 high-quality SLAFs were identified. A total of 1,519,903 SNP markers were obtained, and 62,424 polymorphic SNPs were discovered. From these, 4,644 polymorphic SNPs were selected and used for the construction of a genetic map encompassing seven linkage groups. The genetic map spanned 1,416.60 cM with an average distance of 0.31 cM between adjacent markers. Comparative analysis between the seven linkage groups of RWR SLAF tag and the whole-genome sequences in barley (Hordeum vulgare L.) revealed homology values ranging from 17.5% to 34.6%, and the collinearity between the RWR linkage groups and the barley homology groups ranged from 0.6787 to 0.9234, with an average value of 0.8158. Additionally, 143 significant quantitative trait locus (QTLs) with Logarithm of Odds (LOD) value greater than 2.5 for five tiller related traits were detected using three consecutive years of phenotypic trait data from the F1 population, further verifying the map's reliability.