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To identify genes in wheat (T. aestivum L.), The first step is detecting chromosomes that carry interesting traits. In order to search out chromosomes involved in heading date and grain weight, reciprocal sets of chromosome substitiution lines in duplicate between two winter wheat cultivars, Cheyenne and Wichita, were used. Two experiments were sown in adjacent in complete block designs with two replications for each duplicate. Heading dates recorded when 50% of plants in a plot had their spikes emerged. Heading date was considered as the number of days from an arbitrary date to the time of heading. Grain weight was determind by weighing 250 grains for each genotype in two
replications. The populations of P 1 , P2, F 1 and F2 derived from the cross of Wichita xCheyenne were sown in field for estimating the minimum number of effective genes contributing heading date. Heading date was recorded for each plant when the main spike had emerged. Results showed that Wichita carries major genes on 3A, 3D that accelerate heading date and Cheyenne had major genes on 3A, 3D and 6A that delay heading date. In addition, Cheyenne carries genes for heading date with minor effects on 1D and 4D. Wichita carries genes with major effects on 3A and 3D and genes with minor effects on 2A and 6A that increase grain weight. However, Cheyenne carries genes with major effects on 3A and 3D and genes with minor effects on 6A and 7A that decrease grain weight. The minimum number of effective genes contributing to heading date in field conditions was estimated (2.38) and standard error of this estimate was (0.91), that almost coincide with results obtained from chromosomal experiments.