Quantitative trait locus mapping of five significant quality traits such as crude protein content of tetraploid hybrid crested wheatgrass in multiple environments

Agropyron is an important germplasm material of the genetic improvement for Gramineae forage and Triticeae crops. In the present research, in order to determine the stable and major quantitative trait loci (QTLs) controlling five significant quality traits, a total of 115 individuals from F₂ segregation population of tetraploid hybrid crested wheatgrass and their parents were used as materials. On the basis of the ultra-high density molecular genetic linkage map of tetraploid crested wheatgrass constructed with single nucleotide polymorphism (SNP) markers, we first determined QTLs for the phenotypic data of five quality traits in three different environments (Hohhot-2018, Hohhot-2019 and Tongliao-2019) in 2 years (2018 and 2019) by Map QTL 6.0 software. The results showed that a total of 28 QTLs controlling quality traits of wheatgrass were located on 11 linkages (LGs), including LG1, LG2, LG3, LG4, LG6, LG7, LG8, LG9, LG12, LG13 and LG14. Among them, there were two QTLs for crude protein content (CPC), four QTLs for water-soluble carbohydrate content (WSCC), 12 QTLs for starch content (SC), five QTLs for phosphorus content (PC) and five QTLs for calcium content (CC), which accounted for 10.1% to 21.6% of the phenotypic variation and all were major QTLs of genetic contribution rate >10%. However, only six stable QTLs were detected at least in two environments and in the mean environment data, including one for CPC (qCpc4-1), one for WSCC (qWscc4-2), two for SC (qSc1-2, qSc9-12), one for PC (qPc4-4) and one for CC (qCc4-2). These QTLs determining five traits would provide a theoretical basis for further fine mapping and the molecular marker-assisted selection of elite gene in tetraploid crested wheatgrass.