Bulletin of the U.S. Department of Agriculture Volume 863-875 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1920 Excerpt: ...The means for these two F2 generations were 2.94 0.01 and 2.96 0.02 mm., respectively. The variation as determined by the frequency distribution and the coefficient of variability was much greater in F2 than in Ft or in the parental forms, the coefficient of variability of the F, generation being 6.30 0.30 mm. and of the F2 generations of 1916 and 1918, 10.20 0.27 and 11.82 0.48 mm., respectively. Thirty-two F3 lines, representing all F2 types of density, were grown. Thirteen of these F2 plants appeared to give homozygous progeny in the F3 generation. The writers recognize that too few plants were grown in F3 to determine with certainty which forms were homozygous. Eight of these 13 lines were continued in F4, and five of these appeared to be homozygous. These results show that a considerable number of the F3 plants selected bred true in F3, although no conclusion as to the actual percentage can be made. The five types which proved to be homozygous in F4 gave mean densities as follows: 378-1, mean 2.57 0.01 mm.; 378-11, mean 2.64 0.01 mm.; 378-14, mean 3.37 0.02 mm.; 378-23, mean 2.55 0.01 mm.; 378-31, mean 2.58 0.01 mm. Selection 378-88 gave the highest coefficient of any third-generation line. Two heads were selected which bred true in F4 for densities near the Manchuria parent. 182694--20--Bull. 869 2 The Svanhals parent gave a mean of 2.71 0.01 mm. and the Manchuria one of 3.46 0.01 mm. in 1918. No sorts were obtained which were homozygous for densities very different from those of the parents. FAMILY MANCHURIA (360) X STEIGUM (17). The parental forms of the Manchuria and Steigum cross gave nearly the same average density in 1916. In 1918 the Manchuria parent gave about the same average dens...