Molecular cytogenetic analysis of Triticum aestivum-Leymus racemosus reciprocal chromosomal translocation T7DS·5LrL/T5LrS·7DL

Abstract

In order to induce chromosome translocation between wheat chromosomes and chromosome 5Lr of Leymus racemosus, the microsporocytes during meiosis of T. aestivum-L. racemosus disomic addition line DA5Lr were irradiated by 60Co γ-rays 800 R (100 R/min). Before flowering, the treated spikes were emasculated and bagged. After 2–3 d, the emasculated flowerets were pollinated using pollens from T. aestivum cv. Chinese Spring. One plant with two translocation chromosomes involved in both the long and short arm of 5Lr was detected in the M1 by GISH. The plant was crossed with line DA5Lr, and its progenies with one 5Lr and two translocation chromosomes were analyzed for chromosome pairing behavior in their pollen mother cells (PMCs). A cross-shaped configuration at diplonema and Z-shaped or ring-shaped quadrivalent configuration at metaphase I were observed, indicating that the two translocation chromosomes were reciprocal translocation. Chromosome C-banding indicated that the wheat chromosomes involved in the reciprocal translocation belonged to A- or D-genome. Fluorescence in situ hybridization using pSc119.2 and pAs1 as the probe found that only pAs1 signals were present in the wheat chromosome segments of the two translocation chromosomes. Combining these results, the reciprocal chromosomal translocation was designated as T7DS·5LrL/5LrS·7DL. The two translocation chromosomes were found to be transmitted together in the gametes of heterozygous reciprocal translocation plants with the transmission ratios of 59.4% in the female gametes and 83.9% in the male gametes, revealing preferential pollen transmission. In the self-fertilized progenies of the heterozygous reciprocal translocation, a line with the homozygous translocation line with a pair of translocation chromosome T7DS·5LrL was identified. The T7DS·5Lr translocation line was highly resistant to wheat scab and can be used as a potential and new source in wheat improvement for scab resistance.