Allelic Variation Of Vernalization Gene VRN-D1in Common Wheat

Vernalization requirement is one of the most important characteristics related to the adaptability ofcommon wheat （Triticum aestivum L.）. Wheat varieties are classified into winter, facultative and springtypes in growth habit based on their vernalization requirement. Previous studies have shown that theallelic variations at vernalization loci were associated with winter and spring growth habits; however,the molecular basis for the facultative growth habit was not clear. In our previous studies, Vrn-D1b, anew allele at the VRN-D1locus has been found. This sdudy was carried out to determine the effect ofVrn-D1b on vernalization requirement and to understand the distribution of this new allele in variousgeological zones in China. The main results are as follows:1、Five hundred and five F₂plants from Shimai12×Shi4185cross grown in the greenhouse underlong days without any vernalization conditions were studied, and the heading date and number of leavesfor the main stems were recorded. Shimai12is a spring type cultivar and its allelic composition at theknown loci of vernalization genes is vrn-A1vrn-B1Vrn-D1avrn-B3. Shi4185is a facultative cultivar andits allelic composition is vrn-A1vrn-B1Vrn-D1bvrn-B3. The plants carrying allele Vrn-D1b headed28.8days later and had2.8more leaves on average than the plants carrying allele Vrn-D1a. Heading date andnumber of leaves for the plants with Vrn-D1b homozygous allele were similar to those of shi4185.Therefore, we suggest that Vrn-D1b is associated with the facultative growth habit in wheat.2、A high expression level of VRN-D1gene was observed in the unvernalized ten spring accessions（vrn-A1vrn-B1Vrn-D1avrn-B3） compared to ten facultative accessions （vrn-A1vrn-B1Vrn-D1bvrn-B3）.In F₂plants, the expression of VRN-D1gene in the homozygous genotype Vrn-D1a/Vrn-D1a was thehighest, followed by the heterozygous genotype Vrn-D1a/Vrn-D1b, and the lowest in the genotypeVrn-D1b/Vrn-D1b. These results indicated that the effects of VRN-D1alleles on seedling growth habitis probably due to its effects on VRN-D1transcript level.3、Using the gene-specific marker, the distribution of Vrn-D1b among374cultivars from fivemajor wheat ecological regions in China were determined. The highest frequency of Vrn-D1b wasobserved in the Huang-Huai Winter Wheat Region （29.06%）. In the north and the south parts ofHuang-Huai Winter Wheat Region, the frequencies of Vrn-D1b were23.86%and31.64%respectively.In the Yangzi River Winter Wheat Region, the frequency was only6.45%. Vrn-D1b was not detected inother wheat producing regions, such as the North Winter Wheat Region, Northeast Spring WheatRegion, Southwest Winter Wheat Region, and Northwest Spring Wheat Region.