Improving seed retention and germination characteristics of North American basin wildrye by marker-assisted gene introgression

Authors: Larson, Steven; Jones, Thomas; Johnson, Linnea; Waldron, Blair

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2020
Publication Date: 11/8/2020
Citation: Larson, S.R., Jones, T.A., Johnson, L.M., Waldron, B.L. 2020. Improving seed retention and germination characteristics of North American basin wildrye by marker-assisted gene introgression. Agronomy. 10(11). Article 1740. https://doi.org/10.3390/agronomy10111740.
DOI: https://doi.org/10.3390/agronomy10111740

Interpretive Summary: Basin wildrye and creeping wildrye are native perennial grasses cultivated for seed used for fire rehabilitation and other large-scale revegetation needs in western North America. Like many wild plants, these grasses display traits that complicate seed production. Although basin wildrye produces large stems with many seeds, it is prone to seed shattering during the latter stages of seed ripening. Seed can be harvested before shattering, but it often lacks germination and seedling vigor traits needed to compete with invasive annual weeds. Conversely, creeping wildrye has relatively strong seed retention but produces fewer seeds per stem. A dominant seed-shattering gene from basin wildrye was previously identified in an experimental population of hybrids that were genetically 75% creeping wildrye and 25% basin wildrye. This seed shattering gene was also associated with slower germination rates so it was hypothesized that the seed-retention gene of creeping wildrye could be used to improve seed retention and seed germination of basin wildrye. In this study, a DNA marker was used to introgress the seed-retention gene from creeping wildrye to basin wildrye and evaluate the seed yield and seed germination characteristics of shattering and non-shattering genotypes from 22 to 99 days after pollination. Although seed yields of shattering genotypes were 19.4% greater than non-shattering genotypes on the first harvest date, yields of non-shattering genotypes were 167% greater on the last harvest date. 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 creeping wildrye seed retention gene will improve seed retention and seed germination of basin wildrye.

Technical Abstract: Basin wildrye (Leymus cinereus) and creeping wildrye (L. triticoides) are native perennial grasses cultivated for seed used for fire rehabilitation and other large-scale revegetation needs in western North America. Like many wild plants, these grasses display traits that complicate seed production. Although L. cinereus produces large spike inflorescences with many seeds, it is prone to seed shattering during the latter stages of seed ripening. Seed can be harvested before shattering, but it often lacks germination and seedling vigor traits needed to compete with invasive annual weeds. Conversely, L. triticoides has relatively strong seed retention but produces fewer seeds per spike. A dominant, major-effect seed-shattering gene (SH6) from L. cinereus, which also decreased germination rates, 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 an L. cinereus x L. triticoides breeding population and to evaluate seed yield per spike and germination characteristics of shattering and non-shattering genotypes from 22 to 99 days after pollination. Although seed yields of shattering genotypes were 19.4% greater than non-shattering genotypes on the first harvest date, yields of non-shattering genotypes were 167% greater on the last harvest date. 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 germination.