Natural variation in wheat requirement of long exposures to cold temperatures to accelerate flowering (vernalization) is mainly controlled by the Vrn-1, Vrn-2, Vrn-3, and Vrn-4 loci. The first three loci have been well characterized, but limited information is available for Vrn-4. So far, natural variation for Vrn-4 has been detected only in the D genome (Vrn-D4), and genetic stocks for this gene are available in Triple Dirk (TDF, hereafter). We detected heterogeneity in the Vrn-1 alleles present in different TDF stocks, which may explain inconsistencies among previous studies. A correct TDF seed stock from Japan carrying recessive vrn-A1, vrn-B1, and vrn-D1 alleles was crossed with three different winter cultivars to generate F2 mapping populations. Most of the variation in flowering time in these three populations was controlled by a single locus, Vrn-D4, which was mapped within a 1.8cM interval flanked by markers Xcfd78 and Xbarc205 in the centromeric region of chromosome 5D. A factorial ANOVA for heading time using Vrn-D4 alleles and vernalization as factors showed a significant interaction (P<0.0001), which confirmed that the Vrn-D4 effect on flowering time is modulated by vernalization. Comparison of the different Triple Dirk stocks revealed that Vrn-B1, Vrn-D1, and Vrn-D4 all have a small residual response to vernalization, but Vrn-D4 differs from the other two in its response to short vernalization periods. The precise mapping and characterization of Vrn-D4 presented here represent a first step toward the positional cloning of this gene.
Bibliographical noteFunding Information:
This work was supported by the United States Department of Agriculture Cooperative State Research, Education, and Extension Services National Research Initiative competitive grants 2007-35301-17737 and 2007-35301-18188 and Grant-in-Aids for Research Programs of Wheat and Barley Production from the Ministry of Agriculture, Forestry and Fisheries of Japan and for Young Scientists (B) (20780002) from Japan Society for the Promotion of Science (JSPS).
ASJC Scopus subject areas
- Agronomy and Crop Science