Physical mapping and chromosomal location of the photoperiod response gene Ppd2 in common wheat

Duration from sowing to flowering is of critical importance for crop adaptation. Breeding for the optimal flowering time is one of the major factors, which confer maximal yields in a given environment. The timing of flowering is modulated primarily by responsiveness to photoperiod and temperature, and there are large differences in sensitivity among genotypes. In most spring wheat cultivars the duration of the vegetative period is strongly influenced by genes controlling photoperiod response. In this paper we report the photoperiod responses of a set of 'Chinese Spring' substitution and partial deletion lines of homoeologous group 2 chromosomes studied under natural short days. We confirmed the presence of dominant genes Ppd1 and Ppd2 on chromosomes 2D and 2B, respectively, and compared the effects of Ppd1 and Ppd2 for daylength response. The photoperiodic responses of partial chromosome deletion lines of 'Chinese Spring' allowed us to map Ppd2 physically between breakpoints 0.27 and 0.53 of the short arm of chromosome 2B. This result is consistent with the finding of a possible location of Ppd2 based on molecular marker studies. A dosage effect of the dominant gene Ppd2 was shown.