Cytological Comparison of Amplified Chromosome Segments in Four Tobacco Doubled Haploids
Atypical quadrivalents, which appear to be the result of pairing between amplified homologous segments in nonhomologous chromosomes, have been found in tobacco (Nicotiana tabacum L.) doubled haploid (DH) × cultivar hybrids. The purpose of this study was to determine if the same amplified chromosomes are involved in these quadrivalents in different DH lines. Chromosome pairing was studied in hybrids between four DHs, of which two were derived from ‘NC95’ and the other two from ‘C139’. Results of this study indicate that all four of the DHs contain two homologous amplified chromosomes regions. The chromosomal locations of both of these amplified segments in three of the DHs appear to be the same. One of the amplified segments in the fourth DH is located on the same and the other on a different chromosome than in the other three DHs. The difference in location of one of the amplified segments in this fourth DH could be the result of a translocation or the amplification of nontandem multigene families. That similar genetic sequences have been amplified in all four DHs studied suggests there may be some specificity to the DNA amplification that occurs as a result of anther culture in tobacco.
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