Dormancy Spreads Seed Germination over a Long Period with a Discontinuous Procession in Aegilops tauschii, the D-genome Donor Species of Bread Wheat

Synthetic hexaploid wheat and its utilization for wheat genetic improvement in China

Synthetic hexaploid wheat (Triticum turgidumxAegilops tauschii) was created to explore for novel genes from T. turgidum and Ae. tauschii that can be used for common wheat improvement. In the present paper, research advances on the utilization of synthetic hexaploid wheat for wheat genetic improvement in China are reviewed. Over 200 synthetic hexaploid wheat (SHW) accessions from the International Maize and Wheat Improvement Centre (CIMMYT) were introduced into China since 1995. Four cultivars derived from these, Chuanmai 38, Chuanmai 42, Chuanmai 43 and Chuanmai 47, have been released in China. Of these, Chuanmai 42, with large kernels and resistance to stripe rust, had the highest average yield (>6 t/ha) among all cultivars over two years in Sichuan provincial yield trials, outyielding the commercial check cultivar Chuanmai 107 by 22.7%. Meanwhile, by either artificial chromosome doubling via colchicine treatment or spontaneous chromosome doubling via a union of unreduced gametes (2n) from T. turgidum-Ae. tauschii hybrids, new SHW lines were produced in China. Mitotic-like meiosis might be the cytological mechanism of spontaneous chromosome doubling. SHW lines with genes for spontaneous chromosome doubling may be useful for producing new SHW-alien amphidiploids and double haploid in wheat genetic improvement.