Allelic variation at the VERNALIZATION-A1, VRN-B1, VRN-B3, and PHOTOPERIOD-A1 genes in cultivars of Triticum durum Desf.

The durum wheat varieties from Ukraine, Russia, and Kazakhstan are characterized by the specific allelic composition of the VRN genes that sharply distinguish them from the Triticum durum varieties from other countries. For numerous varieties, the VRN alleles which previously were not found in tetraploid wheat were identified. The ability of wheat to adapt to a wide range of environmental conditions is mostly determined by the allelic diversity within genes regulating the vernalization requirement (VRN) and photoperiod response (PPD). In the present study, allelic variation in the VRN1, VRN3, and PPD-A1 genes was investigated for 134 varieties of Triticum durum from different eco-geographic areas. It was shown that varieties from Russia and Ukraine have a specific allelic composition at the VRN genes, which in quantity and quality differed from European and American cultivars. A large number of varieties of T. durum from Russia carry the dominant Vrn-A1a.1 allele, previously identified mainly in hexaploid wheat. For some varieties from Eastern Europe and Asia, Vrn-A1i and vrn-A1b.3 recently revealed in wheat were also identified. Polymorphism of the VRN-B1 promoter region, distinguishing all three variants of this sequence (VRN-B1.f, VRN-B1.s, and VRN-B1.m), was detected. It was found that the dominant Vrn-B1c allele is commonly found in varieties of T. durum from Russia and Ukraine, but not Europe or USA. Furthermore, many Ukrainian and Russian varieties carry the dominant alleles of the both VRN-A1 and VRN-B1 genes simultaneously, while varieties from Europe and America carry the dominant allele of VRN-A1 alone. Finally, a high frequency of the Vrn-B3a allele, which previously was found only in some accessions of hexaploid wheat, was observed for varieties from Ukraine and Russia. It was revealed that the Ukrainian pool of T. durum varieties is currently the largest genetic source of the dominant Vrn-B3a allele in wheat in the worldwide.Peer reviewe

Novel alleles of the VERNALIZATION1 genes in wheat are associated with modulation of DNA curvature and flexibility in the promoter region

In wheat, the vernalization requirement is mainly controlled by the VRN genes. Different species of hexaploid and tetraploid wheat are widely used as genetic source for new mutant variants and alleles for fundamental investigations and practical breeding programs. In this study, VRN-A1 and VRN-B1 were analysed for 178 accessions representing six tetraploid wheat species (Triticum dicoccoides, T. dicoccum, T. turgidum, T. polonicum, T. carthlicum, T. durum) and five hexaploid species (T. compactum, T. sphaerococcum, T. spelta, T. macha, T. vavilovii).Peer reviewe

The New Wheat Vernalization Response Allele Vrn-D1s is Caused by DNA Transposon Insertion in the First Intron

Vernalization requirement in hexaploid bread wheat (Triticum aestivum L.) is largely controlled by a series of homoeologous VERNALIZATION (VRN) genes, VRN-A1, VRN-B1 and VRN-D1. Here we analyse sequence from the promoter and first intron of VRN-D1 in 77 hexaploid accessions, representing five wheat species (T. compactum, T. sphaerococcum, T. spelta, T. vavilovii and T. macha) from different eco-geographic areas within 35 countries. Polymorphism was detected for promoter area of VRN-D1 gene. This polymorphism was caused by mutations which are associated with a new haplotype of the Vrn-D1 gene. Analysis of VRN-D1 intron-1 revealed a novel insertional mutation within the ‘vernalization critical’ region in T. spelta and T. compactum. This allelic variant, termed here Vrn-D1s, is predicted to result in vernalization non-responsive alleles. Analysis of the 844 bp insertion revealed it to be a novel transposable DNA-element not previously described in Triticum (DTA_Chimera_KF800714), belonging to the hAT superfamily. Lastly, we describe a PCR-based assay that discriminates the wild-type vrn-D1 allele from the predicted spring Vrn-D1s allele.Peer reviewe

Origin and Distribution of the VRN-A1 Exon 4 and Exon 7 Haplotypes in Domesticated Wheat Species

The high adaptive potential of modern wheat to a wide range of environmental conditions is determined by genetic changes during domestication. Genetic diversity in VRN1 genes is a key contributor to this adaptability. Previously, the association between the transitions C->T within the fourth and seventh exons of VRN-A1, the distinguishing pair haplotypes Ex4C/Ex4T and Ex7C/Ex7T, and the modulation of such agronomically valuable traits as the vernalization requirement duration, frost tolerance and flowering time of wheat have been shown. However, this polymorphism was analyzed in only a few cultivars of Triticum aestivum L., and not in other wheat species. In the present study, VRN-A1 exon 4 and exon 7 were investigated in six tetraploid and five hexaploid wheat species carrying different VRN-A1 alleles. An allele-specific polymerase chain reaction (PCR) assay was optimized to identify the VRN-A1 exon 7 haplotypes. It was found that polymorphism of the VRN-A1 exon 7 originated in wild tetraploid wheat of Triticum dicoccoides Körn, while the mutant exon 4 of this gene originated later in domesticated hexaploid wheat of T. aestivum. Both these polymorphisms are found in all hexaploid wheat species. Analysis of the VRN-A1 exon 4 and exon 7 haplotype combinations found that intact exon 7 and mutant exon 4 are associated with analogous types of exon 4 and 7, respectively. With the exclusion of the Vrn-A1c (IL369) and Vrn-A1j alleles, identified only in hexaploid wheat, all dominant VRN-A1 alleles carry intact exons 4 and 7 (Ex4C/7C haplotype). The Ex4C/4T/7T haplotype was detected in numerous accessions of hexaploid wheat and is associated with the presence of multiple copies of VRN-A1. Overall, modern domesticated hexaploid wheat T. aestivum includes most possible combinations of the VRN-A1 exon 4 and exon 7 haplotypes among polyploid wheat, which are present in different proportions. This contributes to the high adaptive potential to a broad range of environmental conditions and facilitates the widespread distribution of this species throughout the world

Additional file 2: Table S1. of Novel alleles of the VERNALIZATION1 genes in wheat are associated with modulation of DNA curvature and flexibility in the promoter region

“The VRN-A1 and VRN-B1 alleles of hexaploid wheat accessions”. (DOC 118 kb