Effect of the continuous selection of large and small wheat seed on yield, bushel weight, varietal purity, and loose smut infection

The experiments described in this paper were undertaken to show the effect of continuous selection of large or small seed wheat of a small-kernelled variety on varietal purity and behavior. Purplestraw wheat was grown in 1921 between plats of Abruzzes rye and Fulcaster (Bearded Purplestraw) wheat and the resulting crop of Purplestraw seed was sorted into large and small sizes. In the following years of the experiment the large seed was sorted annually from the crop of the large-seed plats of the previous harvest and the small seed from the crop of the small-seed plats. Increased grain yields were obtained in all years but the first from the use of large wheat kernels. The gains from using large seed in comparison with small seed varied from approximately 0.3% in 1924 to 18.7% in 1926. The bushel weight of the grain produced by large seed was heavier in four of the six years of the experiment, but the differences were small and not conclusive. Large seed produced a higher percentage of large kernels than small seed in each of the five years that data were recorded. The five-year average percentage of large kernels in the large-seed plats was 35.5 as compared to 17.8% in the small-seed plats. Hybrid kernels of natural crosses between wheat and rye, being small, were sorted automatically into the small seed in 1922 and 1923, the years following the growing of the seed plats in the vicinity of rye. In the crop of 1922 there were an average of 19 F1 wheat-rye hybrids in each of the seven small-seed plats as compared to 1 wheat-rye hybrid in all seven large-seed plats. Seed from unsorted Purplestraw straw wheat produced an average of one wheat-rye hybrid to the 40th-acre plat. In 1923, an average of six wheat-rye hybrids were present in each of the small-seed plats and two hybrids in all seven large-seed plats. Extra small seed from the threshing machine taken from unsorted Purplestraw seed wheat grown near rye produced an average of about 21 wheat-rye hybrids in each of two 40th-acre plats in 1923. The Purplestraw seed from which the extra small seed was obtained produced only two wheat-rye hybrids in 110 40th-acre plats. Seeds of fully awned wheat rogues, which may be due to natural crossing between Purplestraw X Fulcaster, were sorted into the large seed, being themselves large, and the number present in the large-seed plats increased rapidly in each of the four years in which data were recorded. In 1924 there were 13 times as many bearded heads in the large-seed plats as in the small-seed plats, and in 1927 there were over 64 times as many. Unsorted Purplestraw seed in 1927 produced over twice as many bearded heads as small seed, but the large seed produced 29 times as many as the unsorted seed. Three times as many loose-smutted heads occurred in the plats sown with small seed as in the plats sown with large seed in 1926 and over five times as many in 1927. Small-seed plats contained four times as many loose-smutted heads as unsorted Purplestraw seed.