Gene Locations for Heading Date Using Reciprocal Chromosome Substitutions in Winter Wheat 1

Heading date, which is one of the developmental stages of wheat ( Tritlcum aestivum L.) that contribute to maturity, is therefore significant trait from an economic standpoint. Reciprocal sets of chromosome substitution lines in duplicate between two hard red winter wheat cultivars, Cheyenne and Wichita, were used to identify chromosomes that carried genes for heading date. The materials were planted in the field at Lincoln, NE using a randomized complete block design with three replications. Heading dates were recorded when 50% of the plants in the two center rows of each four‐row plot had the basal spikelets emerged from the boots. Heading dates were converted to number of days to heading from 1 May for statistical analyses. Wichita appeared to carry major genes controlling heading date on chromosomes 3A and 3D, while Cheyenne carried major genes on 3A, 3D, and 6A. The genes from Wichita accelerated heading of Cheyenne and those from Cheyenne delayed heading of Wichita. Three types of responses were obtained with respect to the duplicates of each substitution line. In the first type, one duplicate differed significantly from its recipient parent but the duplicates did not differ significantly. This behavior could indicate a genetic control of heading date, with Cheyenne chromosomes 1D, 2D, 4D, and 5A having minor effects in Wichita background. In the second type, two lines had significant differences between duplicates and also between one duplicate and its recipient parent. This type of response suggested that there were differences in the genetic backgrounds of the duplicates and that additional backcrosses were needed. In the third type, two lines had significant differences between duplicates but none between either duplicate and its recipient parent, indicating a possible environmental effect.