Construction of a high-density genetic linkage map and identification of flowering-related QTL in erect milkvetch(Astragalus adsurgens)

Erect milkvetch(Astragalus adsurgens) is a perennial legume forage crop with economic and ecological value in livestock grazing and soil-erosion control in arid and semiarid areas worldwide. Genomic information and molecular tools to support breeding and research in the species are limited. The objectives of this investigation were to map its genome using DNA markers and to identify quantitative trait loci(QTL)in the species. An F1 mapping population of 250 plants was developed from a cross between two parents with differing flowering-related traits. A high-density genetic linkage map containing 4821 markers on eight linkage groups(LGs) with a total genetic length of 1395 cM and a mean interval of 0.29 cM between adjacent markers was constructed with SLAF-seq technology. Comparative genomic analyses revealed the highest genome sequence similarity(8.71%) between erect milkvetch and Medicago truncatula, followed by Glycine max(7.65%), Cicer arietinum(7.53%), and Lupinus angustifolius(5.21%). A total of 64 significant QTL for flowering-related traits on six LGs were detected, accounting for 9.38 to 19.1% of the associated phenotype variation. Five and 48 key candidate genes for floret number and inflorescence length were identified based on the Glycyrrhiza uralensis genome. These candidate genes were involved in ubiquitination/degradation, pollen development, cell division, cytokinin biosynthetic process, and plant flowering. These findings shed light on the regulation of flowering traits in erect milkvetch and provide genomic resources for future molecular breeding of the crop.