Flowering time is an important trait for cereal crops including wheat (Triticum ssp.) to adapt to the environment and succeed in the seed production. In our recent study (Nishimura et al. 2018), we identified that an emmer wheat accession derived from Ethiopia, TN26, harbored an early flowering allele of Vrn-A3 with two insertions at the promoter region (this allele was named as Vrn-A3a, while Vrn-A3 without the insertions was designated as Vrn-A3b). It was suggested that a GATA box sequence in one of the insertions affected the expression of Vrn-A3, which resulted in the early flowering. To evaluate potential of Vrn-A3a to apply for wheat breeding, we analyzed the distribution of Vrn-A3a in polyploid wheat species and investigated its effect on the heading time of hexaploid wheat. From the investigation using 194 tetraploid accessions and 168 hexaploid accessions, we identified that all durum accessions did not harbor Vrn-A3a, while 20 dicoccum, 9 turgidum, 9 German spelta and 15 Japanese aestivum accessions harbored Vrn-A3a. This result reveals that tetraploid and hexaploid wheat varieties with Vrn-A3a are quite limited and the presence of Vrn-A3a is exceptional. The analysis using RILs of hexaploid accessions segregated for Vrn-A3a and Vrn-A3b did not show any significant effect of VrnA3a on heading date, but Vrn-A3a clearly affected the heading date of the tetraploid RILs (Nishimura et al. 2018). These results suggest that Vrn-A3a can be used directly for the early flowering breeding of durum cultivars. On the other hand, it is necessary to clarify the difference of Vrn-A3a effect between tetraploid and hexaploid wheat if Vrn-A3a is used for breeding of hexaploid wheat.

Nishimura, K., R. Moriyama, K. Katsura, H. Saito, R. Takisawa, A. Kitajima, T. Nakazaki. (2018). The early flowering trait of an emmer wheat accession (Triticumturgidum L. ssp. dicoccum) is associated with the cis-element of the Vrn-A3 locus. Theor Appl Genet. 131: 2037-2053.