Chromosome painting of telomeric repeats reveals new evidence for genome evolution in peanut

Abstract Interspecific hybridization is an important approach to improve cultivated peanut varieties. Cytological markers such as tandem repeats will facilitate alien gene introgression in peanut. Telomeric repeats have also been frequently used in chromosome research. Most plant telomeric repeats are (TTTAGGG) n that are mainly distributed at the chromosome ends, although interstitial telomeric repeats (ITRs) are also commonly identified. In this study, the telomeric repeat was chromosomally localized in 10 Arachis species through sequential GISH (genomic in situ hybridization) and FISH (fluorescence in situ hybridization) combined with 4’,6-diamidino-2-phenylindole (DAPI) staining. Six ITRs were identified such as in the centromeric region of chromosome B i 5 in Arachis ipaensis, pericentromeric regions of chromosomes A s 5 in A. stenosperma, B ho 7 in A. hoehnei and A v 5 in A. villosa, nucleolar organizer regions of chromosomes A s 3 in A. stenosperma and A di 3 in A. diogoi, subtelomeric regions of chromosomes B ho 9 in A. hoehnei and A du 7 in A. duranensis, and telomeric region of chromosome E s 7 in A. stenophylla. The distributions of the telomeric repeat, 5S rDNA, 45S rDNA and DAPI staining pattern provided not only ways of distinguishing different chromosomes, but also karyotypes with a higher resolution that could be used in evolutionary genome research. The distribution of telomeric repeats, 5S rDNA and 45S rDNA sites in this study, along with inversions detected on the long arms of chromosomes K b 10 and B ho 10, indicated frequent chromosomal rearrangements during evolution of Arachis species.