Allelic variation at the Vrn-A1, Vrn-B1, Vrn-D1, Vrn-B3 and Ppd-D1a loci of Pakistani spring wheat cultivars

Abstract

Flowering time in bread wheat (Triticum aestivum L.) is controlled by vernalization and photoperiod response, and earliness per se genes. The genetic basis of flowering time has not been investigated in Pakistani bread wheat. This study was, therefore, conducted to determine the allelic composition at Vrn-A1, Vrn-B1, Vrn-D1, Vrn-B3 and Ppd-D1a loci of 59 Pakistani spring bread wheat cultivars. These cultivars, along with 4 isogenic lines for vernalization genes were characterized with previously reported DNA markers designed for detecting allelic variation at 4 Vrn (Vernalization) and 1 Ppd (Photoperiod) loci. Spring habit Vrn-A1a allele was found in 36% cultivars either alone or with spring habit Vrn-B1 and Vrn-D1 alleles. Two wheat cultivars had the dominant Vrn-A1c allele, whereas none of the cultivars had Vrn-A1b. Spring habit Vrn-B1 was the most frequent allele (64%) present either alone or with Vrn-A1a, Vrn-A1c and Vrn-D1. Spring habit Vrn-D1 was found in 61% cultivars. Vrn-D1 was singly found in 25% cultivars and along with Vrn-B1 in 29% cultivars. Dominant Vrn-B3 was absent in all cultivars studied. All cultivars except Era had the photoperiod insensitive allele PpdD1a. We did not find any association between the flowering time and Vrn allelic composition of the studied cultivars. This indicated that the partial vernalization requirement of cultivars with Vrn-B1 and Vrn-D1 alleles is probably fulfilled during Pakistani growing season. Earliness per se and the photoperiod sensitive loci other than Ppd-D1 need to be investigated to further understand the genetic basis of flowering time in Pakistani wheat.

Comparison of Economically Important Loci in Landraces and Improved Wheat Cultivars from Pakistan

“…The absence of Vrn‐A1 in WLRs and its presence in 44.6% of HWCs indicated an exotic origin. The frequency of the dominant Vrn‐A1 genotype was reported to be 25.0% in global germplasm (Stelmakh, 1998), 44.2% in Chinese germplasm (Zhang et al, 2008), 56.0% in wheats from California and Argentina (Fu et al, 2005), 85.0 to 90.0% in Canadian spring wheat (Iqbal et al, 2007), 36.0% in Pakistani cultivars (Iqbal et al, 2011), 82.9% in wheats from the Pacific Northwest USA region (Santra et al, 2009), 98.0% in modern cultivars from Russia (Leonova et al, 2003), 41.0% in CIMMYT germplasm (van Beem et al, 2005), and 57.6% in Indian cultivars (Singh et al, 2013). Vrn‐D1 predominates in cultivars from Asia (Stelmakh, 1990), Japanese and Chinese landraces (Gotoh, 1979), and particularly in subtropical regions where the growing season is longer.…”

Allele frequencies in the VRN-A1, VRN-B1 and VRN-D1 vernalization response and PPD-B1 and PPD-D1 photoperiod sensitivity genes, and their effects on heading in a diverse set of wheat cultivars (Triticum aestivum L.)

“…Under field conditions, however, the various environmental factor combinations experienced in different years result in considerable variability in the phenotypic effects of the individual alleles of these genes, often leading to contradictory findings (Snape et al 1985; Worland 1996; Worland et al 1998; Kato et al 2000). In addition, although a lot of information is available on the allele compositions and effects of individual vernalization response and photoperiod sensitivity genes separately, there are much less data available on the frequency distributions and phenotypic effects of the various allele combinations in the three VRN - 1 and in the two PPD - 1 genes together (Blake et al 2009; Andeden et al 2011; Iqbal et al 2011; Díaz et al 2012). …”

Allelic variance at the vernalization gene locus Vrn-D1 in a group of sister wheat (Triticum aestivum) lines and its effects on development

“…However, Tanio & Kato (2007) showed that the effect of Ppd-B1a could be as strong as that of Ppd-D1a. Beales et al (2007) demonstrated that the photoperiod insensitivity determined by the Ppd-D1a locus in wheat was due to a 2089 bp upstream fragment deletion in the coding region and subsequently designed a pair of gene-specific primers for detecting allelic variation at this locus (Iqbal et al 2011). Other genes such as Ppd-A1 and Ppd-B1 may also play important roles in cultivar adaptation (Beales et al 2007).…”