Microdissection and Chromosome Painting of the Alien Chromosome in an Addition Line of Wheat - <i>Thinopyrum</i><i> intermedium</i>

<div><p>In this study, chromosome painting was developed and used to identify alien chromosomes in TAi-27, a wheat - <i>Thinopyrum</i><i>intermedium</i> addition line, and the chromosomes of the three different genomes of <i>Th. Intermedium</i>. The smallest alien chromosome of TAi-27 was microdissected and its DNA amplified by DOP-PCR was used as a probe to hybridize with metaphase chromosomes of TAi-27 and <i>Th</i><i>. intermedium</i>. Results showed that hybridization signals were observed in all regions of a pair of the smallest alien chromosomes and the pericentromeric area of another pair of alien chromosomes in TAi-27, indicating that the probe from microdissected chromosome is species specific. In <i>Th</i><i>. intermedium</i>, 14 chromosomes had wide and strong hybridization signals distributed mainly on the pericentromere area and 9 chromosomes with narrow and weak signals on the pericentromere area. The remaining chromosomes displayed a very weak or no signal. Sequential FISH/GISH on <i>Th</i><i>. intermedium</i> chromosomes using the DNAs of microdissected chromosome, <i>Pseudoroegneria</i><i>spicata</i> (<b>St</b> genome) and pDbH12 (a <b>J^s</b> genome specific probe) as the probes indicated that the microdissected chromosome belonged to the <b>St</b> genome, three genomes (<b>J^s</b>, <b>J</b> and <b>St</b>) in <i>Th</i><i>. intermedium</i> could be distinguished, in which there is no hybridization signal on <b>J</b> genome that is similar to the genome of <i>Th</i><i>. bessarabicum</i>. Our results showed that the smallest alien chromosomes may represent a truncated chromosome and the repetitive sequence distribution might be similar in different chromosomes within the <b>St</b> genome. However, the repetitive sequence distributions are different within the J^s genome, within a single chromosome, and among different genomes in <i>Th</i><i>. intermedium</i>. Our results suggested that chromosome painting could be feasible in some plants and useful in detecting chromosome variation and repetitive sequence distribution in different genomes of polyploidy plants, which is helpful for understanding the evolution of different genomes in polyploid plants.</p>