Variation of Seed Dormancy and After-ripening in Tetraploid Wheat (Triticum durum, T. turgidum, T. turanicum, T. carthlicum, T. polonicum)

In western Canada, durum wheat cultivars (Triticum durum) have low to moderate lev-els of seed dormancy and are susceptible to pre-harvest sprouting. The aim of this study was to evaluate the dormancy level of Canadian durum wheat cultivars and to identify tetraploid wheat accessions with elevated levels of seed dormancy. First, the level of seed dormancy and length of after-ripening of ۱۷ North American durum wheat cultivars were evaluated. The plants were grown under field conditions in ۱۹۹۵ and ۱۹۹۶, harvested at maturity (Zadok’s Growth Stage ۹۲, ZGS ۹۲), dried at room temperature for one week, and assessed for level of seed dormancy over seven weeks of after-ripening at ۲۰C. Seed dormancy was characterized by the extent of germination at ۲۰C. The results indicated that five durum cultivars exhibited moderate levels of seed dormancy at maturity while the remaining cultivars were non-dormant. Likewise, a rapid loss of dormancy (within ۲-۳ weeks of after-ripening) was characteristic of all durum cultivars. In a second experiment, ۷۸ accessions of T. turgidum, T. turanicum, T. carthlicum, T. polonicum, and T. durum from the USDA germplasm collection grown under field conditions in ۱۹۹۵ and ۱۹۹۶ were evaluated for seed dormancy with the idea of identifying potential sources of increased seed dormancy. At ZGS ۹۲, eighteen accessions were classified as dormant. Accession ۹۳-۲۸۲ was the only highly dormant genotype in this study. The seven most dormant acces-sions, identified in two years of field tests, were tested for length of the dormancy period. Accession ۹۳-۲۸۲ was the only genotype that had a longer period of dormancy than the durum cultivar, Kyle. The intensity of seed dormancy was quantified at five germination temperatures. A dormancy index was calculated from germination data at ۱۰ and ۲۰°C. The dormancy indices of tetraploid accessions ۹۳-۶۲ and ۹۳-۱۷۷ were ۳۷% higher than that of the durum cultivar Kyle.

Keywords:

Temperature , After-ripening , Dormancy index , Seed dormancy , Seed Germination , Tetraploid wheat