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

大赖草(Leymus racemosus，2n=28)是小麦科多年生野生种，生长于海滨和旱地。它旺盛的生长和习性表明这种植物对生物和非生物胁迫具有耐受性。本研究以携带大赖草一条或一对染色体的普通小麦植株为材料。在这项研究中，我们首先分离了重复的DNA序列，这些DNA序列可以作为每个总状乳杆菌染色体的标记。以这些DNA序列为探针，进行原位杂交，绘制出总状乳杆菌染色体的表意图形。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给后代。相反，‘J2’染色体是从雄配子优先传递的。附加系表现出不同的形态变化，如锥形穗状花序和芒的外延。在雨季中期收获含有S杂染色体的小麦群体，对穗和种子进行反复干燥和浸泡，以检测其对穗发芽的耐受性。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。在这项研究中，我们意外地发现了一个重复序列，命名为tai-Family，它在普通小麦的着丝粒区域显示了信号，尽管它最初在总状花序染色体中被鉴定为末端异染色质序列。Tai1家族是在普通小麦染色体着丝粒区域发现的第一个重复序列。

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.