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Physical mapping of chromosome 4J of Thinopyrum bessarabicum using gamma radiation-induced aberrations

Pu, Jing, Wang, Qing, Shen, Yuefeng, Zhuang, Lifang, Li, Chenxu, Tan, Mengfa, Bie, Tongde, Chu, Chenggen, Qi, Zengjun
Theoretical and applied genetics 2015 v.128 no.7 pp. 1319-1328
Thinopyrum bessarabicum, Triticum aestivum, chromosome translocation, chromosomes, eggs, gamma radiation, genes, germ cells, in situ hybridization, introgression, irradiation, landraces, physical chromosome mapping, pollen, seeds, wheat
KEY MESSAGE : Gamma radiation induced a series of structural aberrations involving Thinopyrum bessarabicum chromosome 4J. The aberrations allowed for deletion mapping of 101 4J-specific markers and fine mapping of blue-grained gene BaThb. Irradiation can induce translocations and deletions to assist physically locating genes and markers on chromosomes. In this study, a 12-Gy dosage of ⁶⁰Co-γ was applied to pollen and eggs of a wheat (Triticum aestivum) landrace Chinese Spring (CS)–Thinopyrum bessarabicum chromosome 4J disomic addition line (DA4J), and the gametes from irradiated plants were fertilized with normal CS eggs or pollen to produce M₁ seeds. Based on genomic in situ hybridization analysis of 261 M₁ plants, we identified 74 lines carrying structural aberrations involving chromosome 4J with the higher aberration rate in treated pollen (31.2 %) than in the treated eggs (21.3 %). We further identified 43 (53.8 %) lines with structural aberrations on chromosome 4J by analyzing another 80 M₁ plants with 74 4J-specific markers, indicating that combining molecular and cytological methods was more efficient for detecting chromosome aberrations. Marker analysis thus was performed prior to cytogenetic identification on M₂–M₄ seeds to detect chromosome structural aberrations. Sixty-eight M₃ lines with structural aberrations on chromosome 4J and six previously obtained chromosome 4J alien lines were then analyzed using 101 chromosome 4J-specific markers. After combining marker results with chromosome aberrations in each line, chromosome 4J was physically divided into 24 segmental blocks with 7 in the short arm and 17 in the long arm. The blue-grained gene BaThb was further mapped into the region corresponding to block 4JL-11. The chromosome aberrations and the physical map developed in this research provide useful stocks and tools for introgression of genes on chromosome 4J into wheat.