Submitted to: Molecular Breeding
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/12/2007
Publication Date: 4/2/2007
Citation: Larson, S.R., Mayland, H.F. 2007. Comparative Mapping of Fiber, Protein, and Mineral Content QTLs in Two Full-Sib Families Derived From Interspecific Hybrids of Leymus (Triticeae) Wildryes. Molecular Breeding. Interpretive Summary: Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and mineral content are important components of forage quality in grasses. Elevated K / (Ca + Mg) ratios substantially increase the risk of grass tetany (hypomagnesemia) in grazing animals. Elevated K / (Ca + Mg) ratios are relatively common in cool-season grasses, especially during rapid early spring growth, and are a leading cause of non-infectious disease and mortality in ruminant livestock. The objectives of this study were to identify and compare chromosome regions controlling CP, NDF, ADF, Al, B, Ca, Cl, Cu, Fe, K, Mg, Mn, Na, P, S, Si, Zn, and KRAT in two experimental breeding populations of Leymus wildrye. The chromosome maps were constructed using 555 DNA markers that were informative in both breeding populations and 67 DNA markers that have been mapped in other grass species. Significant genetic variation and QTLs were detected for all traits. Three different chromosome regions were associated with ADF variation in both populations, including one that also affected NDF, and four different chromosome regions were associated with K / (Ca + Mg) ratios in both breeding populations. Likewise, other chromosome regions were also associated with Ca, CP, Mn, and S variation in both breeding populations. These results provide information and tools that will be used to breed new Leymus wildrye forages and help identify and characterize genes that control fundamentally important processes of mineral uptake and fiber synthesis in grasses and other plants.
Technical Abstract: Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and mineral content are important components of forage quality in grasses. Elevated K / (Ca + Mg) ratios (KRAT) substantially increase the risk of grass tetany (hypomagnesemia) in grazing animals, which is a serious problem associated with some cool-season grasses. The objectives of this study were to map and compare QTLs controlling CP, NDF, ADF, Al, B, Ca, Cl, Cu, Fe, K, Mg, Mn, Na, P, S, Si, Zn, and KRAT in two full-sib Leymus triticoides x (L. triticoides x L. cinereus) TTC1 and TTC2 families. Significant genetic variation and QTLs were detected for all traits, with evidence of homologous QTLs for ADF (LG1a, LG5Xm, LG7a), NDF (LG7a), Ca (LG1b), CP, (LG5Xm), KRAT (LG3b, LG6b, LG7a, LG7b), Mn (LG2b, LG3b, LG4Xm), and S(LG3a) in both TTC1 and TTC2 families. Moreover, the direction of QTL effects was the same for 13 of the 14 homologous QTLs in both families. The TTC1 and TTC2 KRAT QTLs on LG7a and LG7b were located near homoeologous marker loci, suggesting possible correspondence of QTLs between genomes of allotetraploid Leymus. Another 88 QTLs were unique to one family or the other, but many of these clustered to common genome regions. Unique TTC1 QTLs for Al, Mn, and Fe content correspond to a gene controlling aluminum tolerance mediated by citrate secretion in other Poaceae species. These results support development of Leymus wildrye forages and help identify and characterize genes controlling mineral uptake and fiber synthesis.