Responses to selection for seed weight and seedling vigour in Phalaris

Abstract

Significant responses were obtained to three cycles of directional selection for seed weight, seedling weight, leaf size, and rate of leaf appearance in a broadly based P. tuberosa population. The responses were linear in both the high and low directions, and the realized heritabilities of the characters were 0.35, 0.12, 0.61, and 0.38 respectively. Leaf size was positively correlated with seedling weight and negatively correlated with rate of leaf appearance. Selection for high seed weight resulted in marked correlated increases in seedling weight and leaf size, but selection for heavy seedlings or large leaves did not significantly increase seed weight. Selection for light seedling or small leaves, on the other hand, led to a correlated decrease in seed weight. A hybrid population obtained by crossing the parents of the high leaf size line with those of the high rate of leaf appearance line had seedlings nearly as heavy as those of the high seedling weight line and significantly heavier than the mean of the two parent lines. This effect, together with other evidence of the effect of inbreeding on all characters, indicated some degree of directional dominance, particularly for leaf size. Plants in the high seed weight line matured earlier and had fewer heads. However, because they had heavier seeds and more seeds per head, there was no apparent decrease in seed yield per plant in this line, compared with the control population. Areas of the spikelets and leaf sheaths were greater in the high seed weight line, but areas of the flag and penultimate leaves were unchanged, and there was no evidence that increases in seed weight were accompanied by increases in the amount of photosynthetic area available to each developing seed. It was concluded that selection for large leaves is a relatively efficient means of increasing seedling weight, but results in a reduced rate of leaf appearance and possibly a slower rate of tillering. Selection for seed weight, though inefficient, exploits a source of variation largely untapped by direct selection for seedling weight.

Improving Warm-Season Forage Grasses Using Selection, Breeding, and Biotechnology

“…In virtually all the studies that have been done to date, seed size or weight has been an important component of seedling establishment capability (Asay & Johnson, 1987;Voight et al,l987, Kneebone, 1956). Breeding for improved seed size can result in strains with improved seedling growth and establishment (Trupp & Carlson, 1971;Wright, 1977;Clements and Latter, 1973).…”

Daylength and Temperature Effects on Emergence and Early Growth of Sericea Lespedeza

“…P OOR EMERGENCE and seedling growth of forage crops has been associated with low seed germination (Pfeiffer et al, 1972;Haskins and Gorz, 1975), reduced seedling elongation (Haskins and Gorz, 1975), low rate of leaf appearance (Clements and Latter, 1974), and low seed (Ries and Everson, 1973;Clements and Latter, 1974;Haskins and Gorz, 1975) or seedling weight (Clements and Latter, 1974). Slow seed germination and poor seedling establishment are major problems in sericea lespedeza, a summer perennial legume grown in the southeastern USA for forage and soil conservation (Logan et al, 1969).…”

Effects of day-night temperature combinations under constant day length on emergence and early growth of sericea lespedeza genotypes

“…Recommended sowing time of sericea is early spring as soon as the risk of a frost (temperatures below 0°C) has passed. Emergence and seedling growth of forage crops has been associated with seed germination, seedling elongation (Haskins and Gorz 1975) and seed or seedling weight (Clements and Latter 1974). Slow seed germination and poor seedling establishment are major problems in sericea lespedeza (Logan et al 1969).…”