Production of Leymus racemosus chromosome addition lines of common wheat and their evaluation as breeding materials

大赖草（Leymus racemosus，2n=28）是小麦族多年生野生种，生长于海滨和旱地。其旺盛的生长和习性表明该植物具有生物和非生物胁迫的耐受性。本研究选择了携带大赖草一条或一对染色体的普通小麦植株。在这项研究中，我们首先分离出可用作每个总状百合染色体标记的重复DNA序列。以这些DNA序列为探针进行原位杂交，绘制了总状百合染色体的示意图。目前已获得8个二体附加系和4个单体附加系。剩下的两条染色体没有传递给后代。相反，“J2”染色体优先从雄配子传递。异附加系表现出穗状花序变细、外稃具芒等形态变化。在雨季中期收获一个含有总状赖草杂染色体的小麦植株群体，将穗和种子反复干燥和浸泡。在这项研究中获得的所有附加系现在都与其他机构的植物病理学家合作进行评估。在本研究中，我们意外地发现了一个被命名为TaiI家族的重复序列，它在小麦的着丝粒区域显示出信号，而它原本被认为是一个在总状小麦染色体上的末端异染色质序列。TaiI家族是第一个在普通小麦染色体着丝粒区发现的重复序列。

Leymus racemosus (2n=28) is a wild perennial species in Triticeae and grows in seashore and dry land. Its vigorous growth and habit suggest that this plant has tolerance to biological and abiological stresses. In this research, common wheat plants carrying one or a pair of chromosomes of Leymus racemosus were selected. For this study, we first isolated repetitive DNA sequences that could be used as the markers for each L.racemosus chromosome. By in situ hybridization using these DNA sequences as the probes, we drew an ideogram of the chromosomes of L.racemosus. We have now already obtained eight disomic addition lines and four monosomic addition lines. The remaining two chromosomes were not transmitted to the progeny. By contrast, chromosome 'J2' was transmitted preferentially from the male gametes. The addition lines showed various morphologic changes, such as tapered spikes and awned lemma. The tolerance for pre-harvest sprouting were examined by the following method : A population of wheat plants including miscellaneous chromosome(s) of L.racemosus was harvested in the middle of rainy season, and the spikes and seeds were repeatedly dried and soaked. All addition lines obtained in this research are now evaluated in cooperation with plant pathologists in the other institutions. In this study we unexpectedly found that one repetitive sequence, named TaiI-family, showed the signals on the centromeric regions of common wheat though it had been originally characterized as a terminal heterochromatin sequence in L.racemosus chromosomes. TaiI-family is the first repetitive sequence found in the centromeric regions of common wheat chromosomes.