Genetic dissection of seed production traits and identification of a major-effect seed retention QTL in hybrid Leymus (Triticeae) wildryes
Many native grasses display seed shattering and other seed production problems. Basin wildrye [Leymus cinereus (Scribn. & Merr.) Á. Löve] and creeping wildrye [L. triticoides (Buckley) Pilg.] are perennial Triticeae grasses native to western North America. In this study, variation in the number of florets per inflorescence, percent seed set, seed mass, seed shattering, and seed dormancy was measured in clonally replicated multiyear field evaluations of 164 progeny derived from a backcross between a creeping x basin wildrye hybrid and a true creeping wildrye tester. Genomewide quantitative trait locus (QTL) scans detected independent gene effects for all five traits and one pleiotropic QTL, located on Triticeae homeologous chromosome group 6, associated with major seed shattering (43.1% R2, 26.9 log of odds likelihood ratio [LOD]) and seed dormancy (24.1% R2, 10.6 LOD) effects. We hypothesize that a dominant basin wildrye gene creates an abscission that promotes seed disarticulation but hinders seed development and seed ripening in the creeping wildrye backcross family. Alignments of Leymus chromosome 6 expressed sequence tag markers to the rice (Oryza) genome reveal well-defined correspondence of Leymus wildrye and American wildrice (Zizania palustris L.) seed shatter QTLs.