Improvement of Seedling Vigor of Smooth Bromegrass (Bromus inermis Leyss.) by Recurrent Selection for High Seed Weight¹

Abstract

Three polycross populations of smooth bromegrass (Bromus inermis Leyss.) derived by recurrent phenotypic selection for high seed weight averaged higher in seed weight and seedling vigor and lower in fertility index than five check varieties. Selection for high seed weight had little effect on mean performance or variability for traits other than seed weight and seedling vigor. Seed and forage yields were maintained at high levels.In average seed weight over 2 years, the three successive selected populations were, respectivdy, 6, 20, and 30% higher than the mean of two check clones selected to represent the mean of the initial material. Close agreement was obtained between space‐planted and seeded‐row tests for relative seed weight (r = .98). Phenotypic variance for seed weight increased with each successive cycle of selection.Selection for increased seed weight resulted in superior seedling vigor as measured by ability to emerge from a 5‐cm planting depth, weight per seedling, and seedling yield per unit area. The seedling vigor advantage of large‐seeded strains was greatest during early stages of seedling growth. Topcross progenies of 50 plants selected for high seed weight and seed set from cycle 3 were 45% higher in average weight per seedling 1 month after planting in the field than were five check varieties.

Agronomic assessment of two populations of intermediate wheatgrass—Kernza® (Thinopyrum intermedium) in temperate South America

“…The effects of seed size on plant growth have been studied mostly in annual species but also in perennials, though no consensus has been reached yet. While some studies report that large seeds promote higher rates of seedling growth (Arnott, 1969;Bretagnolle et al, 1995;Glewen & Vogel, 1984;Kosiński, 2008;Leger et al, 2019;Peterson et al, 1989;Smith et al, 2003;Thomas, 1966;Trupp & Carlson, 1971), other studies highlight the limited effect of large seeds that is quickly lost (Beveridge & Wilsie, 1959;Lewis & Garcia, 1979;Naylor, 1980;Smart & Moser, 1999). As in other perennial crops, there is controversy about the effects of seed size on seedling growth in Kernza as well (Cattani & Asselin, 2022;Hunt & Miller, 1965), and there are no studies on the effects of seed size on the growth and development of adult plants.…”

Registration of ‘Plainsmen’ tall wheatgrass

“…Seed size, as indicated by 1,000‐seed weight, of Plainsmen was also significantly greater than that of Jose, as reported in Table 1. Although the relationship of seed weight and seedling vigor was not evaluated during the development of Plainsmen, there are many studies reporting the positive correlation between seed test weight and seedling vigor in grasses (Asay et al., 1996; Berdahl & Ries, 1997; Trupp & Carlson, 1971).…”

Relationships and influence of yield components on spaced‐plant and sward seed yield in perennial ryegrass

“…Although floret site utilization is a common index used to explain differences in realized seed yield, it is a very onerous trait to measure in a breeding programme. For this reason, floret site utilization has been related to the ratio of clean seed mass to total spike biomass, termed fertility index (Jessen & Carlson, 1985; Raeber & Kalton, 1956; Trupp & Carlson, 1971). From a breeding perspective, fertility index is far more pragmatic to collect and could indicate higher economic floret site utilization per se or a more compact and lighter spike, such as is found in wheat.…”