F2 linkage results are presented in Table 1 with a=XY, b=fy, c=xY, and d = xy for the gene pairs listed in the form of Xx and Yy. Percentage recombination was obtained from the ratio of products following Immer and Henderson (1943) . There is a single dominant gene which results in delayed flowering ("late" ) vs. non-delayed ("early") flowering for the recessive allele, under a 20-hr daylength using incandescent light (unpublished results and Buzzell et al., 1974).