2Ai-2染色体在小麦部分同源染色体代换背景中的遗传

用中间偃麦草2Ai-2染色体特异的EST-PCR标记检测5个小麦-中间偃麦草二体异代换系(包括端体代换系)与普通小麦中国春(CS)杂交后代群体，研究外源染色体2Ai-2通过杂种向后代的传递率及其结构变异，并用基因组原位杂交进行验证。结果表明，第二部分同源群不同染色体代换背景对外源染色体传递的影响不同，在2B代换系的杂种中外源染色体或片段显示优先传递，而在2D代换系的杂种中其传递力则较低，2B代换背景更有利于2Ai-2染色体或片段的传递；外源染色体在杂种后代传递过程中会发生变异，在多数组合中，变异出现在着丝粒处；与短臂相比，外源染色体长臂更容易在世代中丢失；端体代换系中的外源染色体端体在杂种后代传递过程中容易丢失，且也会发生结构变异。基因组原位杂交结果证明了分子标记跟踪外源染色体的可靠性。

Genetic Behaviour of Thinopyrum intermedium Chromosome 2Ai-2 in Different Wheat Chromosome Substitution Backgrounds of Group 2

Thinopyron intermedium is one of the important gene sources for high resistances to barley yellow dwarf virus, stripe rust as well as tolerances to cold and drought in wheat (Triticum aestivum L.) breeding. Several wheat–Th. intermedium addition lines, substitution lines, and translocation lines have been developed as breeding materials, including the 2Ai-2 substitution lines with high resistances to the GPV and GAV strains of barley yellow dwarf virus. The aim of this study was to provide cytogenetical evidence on the behavour of 2Ai-2 chromosome of Th. intermedium in different wheat chromosome substitution backgrounds. Five wheat–alien disomic (or ditelosomic) substitution lines were crossed with common wheat variety Chinese Spring to generate the BC₁ and F₂ populations, and the two populations were detected using EST-PCR markers specific to 2Ai-2 chromosome and genomic in situ hybridization (GISH). In the F₂ generation, plants with 2Ai-2 accounted for 83.1% and 82.4% in offsprings of the 2Ai-2 (2B) substitution lines N420 and N439, respectively, which were higher thantheexpected ratio of 75%; whereas, the observed ratios in offsprings of the 2Ai-2 (2D) substitution lines N431 and N452 were 67.6% and 53.8%, respectively, which were lower than the expected value. Especially, the observed value in the hybrids of N452 was significantly different from the expected value (P < 0.01), inferring that the alien chromosome or fragment might be preferentially transmitted into F₂ generation in 2Ai-2 (2B) substitution lines through the corresponding gametes. On the contrary, the transmission ratio of the alien chromosome or fragment was low in 2D-subsititution background. It was concluded that the effect of different substitution background on the transfer of the 2Ai-2 chromosome was different. In addition, in both 2B and 2D subsititution backgrounds, the transmission ratio of the alien chromosome or fragment was obviously higher through male gametes than female gametes. Furthermore, many plants with 2Ai-2 in F₂ and BC₁ were detected using 2Ai-2-specific EST-PCR markers in a limited region, but not in other region, indicating that the alien chromosome was unstable when it was transmitting from hybrid to subsequent generations. From the results, it was inferred that most chromosome variances occurred near centromere. Compared with the short arm, the long arm of the alien chromosome was lost more often in the next generations. The F₂ plants with 2AS-substitution background (N530) were very few when detected with 2Ai-2S-specific EST-PCR marker(s).The difference between observed and expected values was significant (P < 0.01), suggesting that the alien telosome might be lost freguently. Structure variationoftelosome 2Ai-2S was also observed inthe offsprings with2AS-substitution background. GISH results confirmed that the EST-PCR markers can be used effectively in tracing the alien chromosome in wheat background.