Inheritance studies in Sevier X Odessa wheat cross

A genetic study was made of the F3 progenies of a cross of pure lines of Odessa X Sevier wheats. The characters in which these parents were contrasted and upon which a study was made included (a) awns, (b) spike density, (c) grain color, (d) length of culm, (e) number of culms per plant, and (f) number of spikelets per spike. From this cross three classes of awns were obtained, viz., (a) a homozygous group resembling the Odessa parent, (b) a homozygous group resembling the Sevier parent, and (c) a heterozygous group segregating for awn classes. In the homozygous hybrids there is a greater variation than is found in the parents. In both groups of true-breeding strains there is a tendency for the awns to be longer than those of the corresponding parental group. A good 1:2:1 ratio was obtained in awn segregation. There was a 1:2:1 ratio in spike density segregation. In the two homozygous groups there were found spikes considerably more compact than the spikes of either parent and some considerably more lax than was found in either parent. The true-breeding dense hybrids have, on the whole, shorter internode lengths than either parent, and the true-breeding lax hybrid had, on the whole, longer internode lengths than has the lax parent. In a few cases both the dense and the lax parental spike forms were recovered. Although a poor F3 ratio was obtained in grain color segregation, observations in F4 and F5 indicate that inheritance of this character is probably due to a one-factor difference. No genetical data for chaff color were obtained because of the similarity of the chaff color in the parents. Black markings occurring on the Odessa parent and on some of the progeny were too strongly influenced by environment to permit a determination of the ratios. There was little difference in the mean length of culms for the parents. The mean length for the hybrids as a group was slightly longer than the mean for the taller parent. There was considerably greater variation in the mean length of the hybrid families than there was in the means of the parental families. The variation reached both above and below the extremes of the parents. Too few parental rows decrease the weight of conclusions on culm length, number of culms, and number of spikelets. The average number of culms per plant in the hybrid was between the averages for the two parents. The average of the hybrids, however, was considerably toward the average of the parent bearing the greater number of culms. The lowest number of spikelets per spike in the hybrid is fewer than the least number in the parent with the lower average. The greatest number of spikelets per spike in the progeny is in excess of the greatest number of the high parent. The average number of spikelets per spike in the hybrids is between the average of the parents but is very near the average of the high spikelet bearing parent. None of these differences are statistically significant. There is perhaps segregation for the number of spikelets, but its nature was not determined.