Seed-Yield Components, Reproductive Health, and Ecological Fitness of Six Snake River Wheatgrass Populations

Abstract

We compared six Snake River wheatgrass (Elymus wawawaiensis J. Carlson & Barkw.) populations, including Destination Germplasm (released 2023), ‘Discovery’ (2007), and ‘Secar’ (1980), for seed-yield components, a reproductive-health score, ecological fitness, and persistence of fitness. In two consecutive years, we measured fecundity in a transplanted trial at North Park Farm (Hyde Park, UT) and survivorship (stand percentage) in a seeded trial at Nephi, UT. Across the six populations, seed yield per spike exceeded spike number in importance as a seed-yield component, seeds per plant exceeded seed mass, seeds per spike exceeded both spike number and seed mass, and seed area exceeded seed-specific mass. Compared to Discovery, from which it was derived, in 2022 (2023) at North Park, Destination displayed 61.1% (113.0%) greater seed yield per plant, 45.3% (81.6%) greater seed number per plant, and 14.4% (18.1%) greater seed mass (P < 0.05). Destination's greater seed yield than Discovery in 2022 was accounted for by increases in seed mass, spike number, and seeds per spike in roughly a 1:2:1 ratio, though the latter was not significant (P > 0.05). At Nephi in 2023 (2024), Destination displayed a 65.8% (32.1%) stand, while Discovery's stand was much lower at 34.0% (14.1%). Destination's reproductive-health score (15 of 16 possible points) exceeded Secar's (4) and Discovery's (1). Relative ecological fitness (and its persistence) was 1.000 (1.000) for Destination, 0.302 (0.662) for Discovery, and 0.147 (0.711) for Secar. By all measured parameters, Destination shows greater promise for rangeland revegetation and restoration efforts than Secar or Discovery.