Submitted to: Plant Genome Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 13, 2009
Publication Date: N/A
Technical Abstract: Photoperiod response plays a major role in determining the climatic adaptation of wheat, and variation is commonly associated with Ppd loci on group two chromosomes. Seventy-three soft winter wheat (SWW) cultivars from the eastern U.S. were tested for photoperiod response in growth chambers. Flowering data were collected on fully vernalized plants grown under Long Days (LD; 16 hr) or Short Days (SD; 10hr). The SWW cultivars differed widely in their photoperiod response from highly sensitive cultivars that flower only under long day conditions to insensitive cultivars that flower under short day conditions. Association mapping was performed using the Ppd-D1 allele-specific maker, SNPs at Ppd-B1, SSR markers on chromosome 2B and genome-wide DArT markers in order to investigate the contribution of Ppd loci on flowering time in this set of cultivars. The Ppd-D1a allele was in 36% of the entries tested and all cultivars that carry the allele were insensitive to photoperiod. This locus had highly significant effects on flowering in LD and SD treatments, indicating a major role on photoperiod response and earliness. Approximately one-third of the cultivars tested had medium to low sensitivity to photoperiod in the absence of the Ppd-D1a allele, including two historic varieties. Significant effects were observed for SSR markers on chromosome 2B mapping near the Ppd-B1 locus for flowering date in SD and for photoperiod effect. These data suggest that insensitivity at Ppd-B1 was introgresesed at an early stage and plays an important role in regulating flowering time in these germplasm.