Distribution Of Vrn-D1b Allele In Chinese Wheat Cultivars And Its Response To Cold Treatment

Vernalization requirement is one of the most important characteristics related to the adaptability of common wheat(Triticum aestivumL.). Vernalization requirement is mainly determined by allelic variations at three loci, Vrn-A1, Vrn-B1 and Vrn-D1. Different allelic variations endowed common wheat with distinct vernalization requirement. So far three alleles, Vrn-D1 a, Vrn-D1 b and vrn-D1, were discovered at the Vrn-D1 locus. Vrn-D1 a conferred spring growth habit; vrn-D1 was associated with winter growth habit and the new allele Vrn-D1 b, recently discovered in Chinese wheat cultivars was related to facultative growth habit. But the distribution and the response to cold treatment of Vrn-D1 b were not clear.A total of 689 wheat accessions from the four wheat zons, Northern Spring Wheat Zone(NSWZ), Northern Winter Wheat Zone(NWWZ), Yellow and Huai River Reaches(YHRR) and Southern Spring Wheat Zone(SSWZ), including landrances, improved cultivars and the cultivars introduced from overseas, were detected to distinguish the alleles at the Vrn-D1 locus. In addition, the response to cold treatment of Vrn-D1 b was studied in both NILs and F5 sister lines.The main results are as follows:1. The results showed that Vrn-D1 a, Vrn-D1 b and vrn-D1 were present in 27.3, 20.6 and 52.1%, respectively, of all 689 accessions. Vrn-D1 a was mostly distributed in NSWZ and SSWZ, accounting for 56.5% and 68.3% of the accessions respectively. Vrn-D1 b was common in YHRR, accounting for 30.3% of the accessions, and vrn-D1 was predominant in NWWZ, accounting for 94.4% of the accessions.2. A comparison between the Vrn-D1 b genotype and the vrn-D1 genotype from the same cultivar Shiluan 02-1 showed that without vernalization the Vrn-D1 b genotype reached the double ridge(DR) stage 27 days earlier than the vrn-D1 genotype. Vernalization responses, expressed as a reduction in the number of days to reach the DR stage following cold treatment, at 4°C for 20, 30 and 40 days, were 62, 67 and 75 days, respectively, for the Vrn-D1 b genotype, and 74, 87 and 98 days, respectively, for the vrn-D1 genotype, suggesting vernalization requirement of two alleles were distinct and Vrn-D1 b was less responsive to cold treatment than that of vrn-D1. The similar result was shown when the comparison between the Vrn-D1 b genotype and the vrn-D1 genotype of F5 sister lines crossed from Shi 4185 and Shijiazhuang 8 was made.3. Both vrn-D1 and Vrn-D1 a alleles were found in the cultivars introduced from overseas. But none of the foreign cultivars carried the Vrn-D1 b allele. Pedigree analysis indicated that the Vrn-D1 b allele originated from China and the landraces from YHRR, such as Mazhamai, Xibei 60 and Xiaofoshou were most probably the donor of the Vrn-D1 b allele.