Cytological identification of an Aegilops variabilis chromosome carrying stripe rust resistance in wheat

Aegilops variabilis (UUS^vS^v), an important sources for wheat improvement, originated from chromosome doubling of a natural hybrid between Ae. umbellulata (UU) with Ae. longissima (S^lS^l). The Ae. variabilis karyotype was poorly characterized by fluorescent in situ hybridization (FISH). The FISH probe combination of pSc119.2, pTa71 and pTa-713 identified each of the 14 pairs of Ae. variabilis chromosomes. Our FISH ideogram was further used to detect an Ae. variabilis chromosome carrying stripe rust resistance in the background of wheat lines developed from crosses of the stripe rust susceptible bread wheat cultivar Yiyuan 2 with a resistant Ae. variabilis accession. Among the 15 resistant BC₁F₇ lines, three were 2S^v + 4S^v addition lines (2n = 46) and 12 were 2S^v(2B) or 2S^v(2D) substitution lines that were confirmed with SSR markers. SSR marker gwm148 can be used to trace 2S^v in common wheat background. Chromosome 2S^v probably carries gametocidal(Gc) gene(s) since cytological instability and chromosome structural variations, including non-homologous translocations, were observed in some lines with this chromosome. Due to the effects of photoperiod genes, substitution lines 2S^v(2D) and 2S^v(2B) exhibited late heading with 2S^v(2D) lines being later than 2S^v(2B) lines. 2S^v(2D) substitution lines were also taller and exhibited higher spikelet numbers and longer spikes.