Improving Seed Retention and Germination Characteristics of North American Basin Wildrye by Marker-Assisted Gene Introgression

Abstract

Basin wildrye [Leymus cinereus (Scribn. and Merr.) Á. Löve] and creeping wildrye [Leymus triticoides (Buckley) Pilg.] are native perennial grasses cultivated for seed used for fire rehabilitation and revegetation in western North America. Although L. cinereus produces large spike inflorescences with many seeds, it is prone to seed shattering. Seed can be harvested before shattering, but often displays poor germination and seedling vigor. Conversely, L. triticoides has fewer seeds per spike, but relatively strong seed retention. Both species are allotetraploid (2n = 4x = 28) and form fertile hybrids used for breeding and genetic research. A dominant, major-effect seed-shattering gene (SH6) from L. cinereus was previously identified in an L. triticoides backcross population. In this study, a DNA marker was used to select the recessive L. triticoides seed-retention allele (sh6) in cycle six (C6) of a L. cinereus × L. triticoides breeding population and evaluate gene × harvest date effects on seed yield and germination characteristics in a full-sib family derived from homozygous (sh6/sh6) and heterozygous (SH6/sh6) C6 parents. Although seed yields of shattering genotypes were 19.4% greater than non-shattering genotypes on the first harvest dates, yields of non-shattering genotypes were 167% greater on the last harvest dates. Seed harvested on the last harvest date reached 50% germination 4.2 days (26.4%) earlier and displayed 20.5% higher upper percentage germination limits than seed harvested on the first harvest date. Results indicate that the sh6 seed-retention gene will improve basin wildrye seed retention and indirectly improve seed germination by enabling later harvest dates.