Genetic Behavior of 2Ai-2 Chromosome in Thinopyrum intermedium–Wheat Substitution Lines

The aim of this study was to provide cytogenetical evidence on the behavior of chromosome 2Ai-2 from Thinopyrum intermedium in different wheat (Triticum aestivum L.) chromosome substitution backgrounds. Five wheat-alien disomic or ditelosomic substitution lines were crossed with the common wheat variety Chinese Spring to produce the BC1 and F2 populations, which were tested with expressed sequence target (EST)-PCR markers specific to chromosome 2Ai-2 and genomic in situ hybridization (GISH) analysis. In the 2Ai-2(2B) substitution background, the alien chromosome or its fragment was transferred to offspring with higher ratio than the expected ratio, whereas the transmission ratios were much lower than the expectation in the 2Ai-2(2D) background. The 2Ai-2 chromosome was transferred preferentially through heterozygosis in the 2Ai-2(2B) background. Structural changes of 2Ai-2 occurred frequently in progenies, most of which were near the centromere. Compared with the short arm, the long arm of the alien chromosome was lost more frequently in the next generations. The F2 plants with 2AS-substitution background were rare when detected with 2Ai-2S-specific EST-PCR marker(s), suggesting that the alien telosome might be lost frequently. Structural variation of the telosomic chromosome 2Ai-2S was also observed in the offspring with 2AS-substitution background. The GISH results confirmed that the EST-PCR markers can be applied in tracing the alien chromosome in wheat background.