Relationships Among Components of Seed Yield in Blue Grama¹

Abstract

High caryopsis weight in forage plants generally increases seedling emergence, vigor, and establishment. Breeding for improved caryopsis weight in blue grama [Bouteloua gracilis (H.B.K.) Lag. ex Steud.] can be successful only if variations in average caryopsis weight of a plant are not simply a result of variations in the components of caryopsis yield. The objectives of this study were to determine the effects of spikes/culm, spikelets/spike, and fertility on caryopsis weight and the effects of spikes/culm, spikelets/spike, fertility, and caryopsis weight on yield/culm. In a 1,080−plant, spaced field nursery, average caryopsis weight varied among plants from 25 to 70 mg/100. Multiple regression and path analysis indicated that spikes/culm, spikelets/spike, and fertility accounted for only 5% of the variation in caryopsis weight. These components of yield, with caryopsis weight, accounted for 86% of the variation in caryopsis yield/culm. In a polycross nursery of 60 plants selected from the previous nursery primarily for high caryopsis weight, blue grama clones differed significantly in all of the components of caryopsis yield/culm. Blocks in the polycross nursery differed significantly in all components of yield/culm except average caryopsis weight of a plant. These results suggest that it would be possible to select blue grama plants for both high caryopsis weight and high seed yields.

Seed Yield Variation in Blue Grama and Little Bluestem Plant Collections in Southern Manitoba, Canada

“…In comparison, Roos and Quinn (1977) obtained 100‐caryopses weights ranging from 74.5 to 98.0 mg among plants from two young (2–3 yr) and two old (35–40 yr) little bluestem populations in New Jersey. The large amount of variation in caryopsis weight seen in this study indicates that selection for this trait can be effective with selection within or among plant collections, as indicated earlier by Wilson et al (1981) Native grasses can benefit from larger caryopses because this trait enhances seedling emergence and stand establishment (Carren et al, 1987a, 1987b).…”

“…The mean 100‐caryopses weights among all blue grama plants ranged from 17.4 to 64.1 mg in 1994 (data not shown). Wilson et al (1981) reported a similar range from 25 to 70 mg 100 caryopses −1 among individual plants from four blue grama collections. For little bluestem, 100‐caryopses weights among all individual plants ranged from 46.8 to 163.1 mg in 1994 (data not shown).…”

“…However, plants generally showed a predominance of culms with a certain number of seedheads, which reflects the genetic influence on this trait. Improvement of seedhead number per culm in blue grama has already been accomplished in the cultivar, Lovington (Wilson et al, 1981), and the large variation for this trait seen in little bluestem indicates the same potential for improvement.…”

“…Clearer trends may be evident with additional plant collections covering a wider geographical range than in this study. Selection for culms per plant in blue grama has already produced the cultivars Lovington and Hachita (Wilson et al, 1981)…”

“…He found that the local Kansas ecotypes produced the highest seed yield; northern ecotypes from near Waterton, ND showed earlier anthesis and low seedset; and southern ecotypes with late maturation succumbed to autumn frosts. Selection in blue grama has improved different seed yield traits such as culms per plant (Lovington and Hachita), spikes per culm (Lovington), spikelets per spike (Hachita), and fertility (PM‐K1482) (Wilson et al, 1981) Similar studies characterizing morphology and seed yield in blue grama and little bluestem populations in Canada could not be found in the literature. Ecotypic variation in blue grama and little bluestem populations caused by habitat differences, as described by Miller (1967), demonstrates the need to characterize populations of these species in western Canada.…”