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Vernalization, photoperiod and the poorly defined earliness per se (Eps) genes regulate flowering in plants. This thesis used elite hexaploid wheat varieties and focused on an Eps QTL on 1DL, and photoperiod QTLs on 1BL and 5AL short day QTL using doubled haploid (DH) populations. Four independent backcross two F5 (BC2F5) populations with 70 lines each of a cross between Spark and Rialto derived from BC2F2 by single seed decent (SSD), and four independent pairs of near isogenic lines (NILs) in the background Rialto were used for 1DL. Genomics and bioinformatics approach was used to design genome specific primers for genes on 1DL, 1BL and 5AL QTL regions using the Brachypodium distachyon syntenic genes. Resequencing genes on 1DL revealed that Spark and Cadenza have a chromosomal deletion including several genes. The equivalent region in Rialto and Avalon is intact. The DH, SSD and NILs all showed that the 1DL deletion was associated with early flowering. Recombinants from the BC2F5 populations indicate that the 1DL deletion likely contains the candidate gene(s). The 1DL QTL was defined as a discrete Mendelian factor. The 1BL QTL was short day specific for Spark X Rialto and Avalon X Cadenza but the QTL was observed under both short and long day conditions for Charger X Badger. The gene TaFT3 a homologue of the HvFT3/Ppd-H2 is suggested as the candidate for the 1BL QTL because two mutant alleles, a deletion and a conserved amino acid change seem to account for most of the variation under short days. Twenty-five varieties from Sweden segregate for the FT3-1B and loss of function mutation results in delayed flowering under short days. This thesis describes evidence that has allowed prioritization of candidate genes for the QTLs. The data from this thesis is useful for understanding wheat adaptation and marker assisted selection. |
