High density genetic maps of St. Augustinegrass and applications to comparative genomic analysis and QTL mapping for turf quality traits

Abstract

Background: St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] is a warm-season, perennial turfgrass species well adapted for home lawns and commercial landscapes with economic and ecological value. However, a lack of genomic resources in St. Augustinegrass has hindered the full utilization of genetic variance for maximizing genetic gain and limited our understanding of the species' evolution.

Results: In this study, we constructed the first high-density linkage map for St. Augustinegrass using a genotyping by sequencing (GBS) approach. The integrated linkage map consists of 2871 single nucleotide polymorphism (SNP) and 81 simple sequence repeat (SSR) markers, spanning 1241.7 cM, with an average distance of 0.4 cM between markers, and thus represents the densest genetic map for St. Augustinegrass to date. Comparative genomic analysis revealed inter-chromosome arrangements and independent nested chromosome fusion events that occurred after St. Augustinegrass, foxtail millet, sorghum, and rice diverged from a common ancestor. Forty-eight candidate quantitative trait loci (QTL) were detected for turf quality-related traits, including overall turf quality, leaf texture, genetic color, and turf density. Three hot spot regions were identified on linkage groups LG3 and LG8, where multi-QTL for different traits overlapped. Several leaf development related genes were contained within these identified QTL regions.

Conclusions: This study developed the first high-density genetic map and identified putative QTL related to turf quality, which provide valuable genetic resources for marker-assisted selection (MAS) in St. Augustinegrass.

Keywords: Comparative genomic analysis; Linkage map; QTL; St. Augustinegrass.

Fig. 1

Distribution of molecular markers on parental and integrated genetic maps of St. Augustinegrass. a Map of parent ‘Raleigh’. b Map of parent ‘Seville’. c Integrated map from both parents. A black bar indicates a molecular maker. Linkage group number is shown on x-axis and genetic distance is shown on y-axis (cM)

Fig. 2

Genomic comparison between the St. Augustinegrass and foxtail millet genomes. a, b Dot-plot diagram showing synteny relationships between St. Augustinegrass LGs and foxtail millet chromosomes. Each dot represents a DNA marker. c, d Circos plot showing genome rearrangements between St. Augustinegrass LGs and foxtail millet chromosomes. RLG indicates Raleigh linkage group. SLG indicates Seville linkage group

Fig. 3

Genomic comparison between the St. Augustinegrass and sorghum genomes. a, b Dot-plot diagram showing synteny relationships between St. Augustinegrass LGs and sorghum chromosomes. Each dot represents a DNA marker. c Circos plot showing genome rearrangements between St. Augustinegrass LGs and sorghum chromosomes. RLG indicates Raleigh linkage group. SLG indicates Seville linkage group

Fig. 4

Genomic comparison between the St. Augustinegrass and rice genomes. a, b Dot-plot diagram showing synteny relationships between St. Augustinegrass LGs and rice chromosomes. Each dot represents a DNA marker. c, d Circos plot showing chromosome fusion between St. Augustinegrass LGs and rice chromosomes. RLG indicates Raleigh linkage group. SLG indicates Seville linkage group.