Effects of Genotype and Seed Size on Speed of Emergence and Seedling Vigor in Nine Spring Wheat Cultivars1

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Abstract
Rapid seedling establishment is an important attribute for successful crop production in short‐season areas. A study was done to determine the role of seed size, speed of emergence and rate of plant development in seedling vigor of nine spring wheat, Triticum aestivum L., cultivars. Six field studies, comprised of three seeding dates in each of 2 years, were conducted. Each study included nine spring wheat cultivars divided into two seed sizes arranged in a randomized complete block design with four replications. Logistic curves were fitted to emergence data expressed as percentage of final number of seeds emerged in a 46 cm row length. Each curve was characterized by median emergence time, the most useful measurement for speed of emergence, and maximum rate of emergence. Cultivar differences were observed in both years for speed of emergence, Haun stage, and seedling shoot dry weight. The average number of growing degree‐days (GDD) required for emergence in 1982 and 1983 were 109 and 103, respectively. With respect to Haun stage, approximately 68 GDD were required per phyllochron (interval between the appearance of successive leaves). ‘Potam’, ‘Siete Cerros’, and ‘Glenlea’ were found to require significantly fewer GDD per phyllochron interval on the third seeding date of 1983. The relative performance of cultivars was similar for speed of emergence, Haun stage and seedling shoot dry weight. Plants grown from small seeds emerged faster but accumulated less shoot dry weight than plants grown from large seeds. There was no cultivar by seed size interaction observed for speed of emergence and seedling shoot dry weight. Seed size, speed of emergence, and Haun stage all contributed to differences between cultivars in seedling vigor. Seed size accounted for approximately 50% of the variation in seedling shoot dry weight. It was concluded that selecting for seedling vigor could be done by selecting for seed size, speed of emergence and/or rate of plant development.