The location of the photoperiod gene, Ppd2 and an additional genetic factor for ear-emergence time on chromosome 2B of wheat

Abstract

The major photoperiod gene Ppd2 was identified on chromosome 2B of wheat using homozygous recombinant lines developed from a cross between Chinese Spring (CS) and the substitution line CS (Marquis 2B). Genetic analysis of these lines, using disease marker genes on the long arm of chromosome 2B, the yellow rust (Puccinia striiformis) gene Yr7 and the stem rust (P. gra minis) genes Sr9g and Sr16, showed these genes segregated independently from Ppd2. It was concluded that Ppd2 is located on the short arm of chromosome 2B. The classification of the disease resistance genes was used to identify a second gene(s) influencing the ear emergence time of the lines within each of the Ppd2 and ppd2 gene classes. The second gene(s) was associated with the disease genes on the long arm of chromosome 2B. The early allele of this gene(s) was found on Marquis chromosome 2B and the late on Chinese Spring 2B, so that early alleles of the two gene(s) influencing ear emergence time in this study were dispersed between the parental chromosomes. Following a winter sowing in the field, differences in ear emergence time were associated with the Ppd2 locus and the gene(s) on the long arm. Following a spring sowing, differences were confined to the gene(s) on the long-arm only. This confirms the photoperiodic sensitivity of Ppd2 and suggests that the second genetical effect was acting independently of the environment. © 1983, The Genetical Society of Great Britain.