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

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 Bi5 in Arachis ipa？nsis, pericentromeric regions of chromosomes As5 in A. stenosperma, Bho7 in A. hoehnei and Av5 in A. villosa, nucleolar organizer regions of chromosomes As3 in A. stenosperma and Adi3 in A. diogoi, subtelomeric regions of chromosomes Bho9 in A. hoehnei and Adu7 in A. duranensis, and telomeric region of chromosome Es7 in A. stenophylla. The distributions of the telomeric repeat, 5S r DNA, 45 S r DNA 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 r DNA and 45 S r DNA sites in this study, along with inversions detected on the long arms of chromosomes Kb10 and Bho10, indicated frequent chromosomal rearrangements during evolution of Arachis species.

Progress on genetic and genomic research for enhanced oil content and quality in peanut

Peanut or groundnut （ Arachis hypogaea L. ） is an important source of vegetable oil in the world. Genetic enhancement for high yield and high oil content has greatly contributed to enhanced pro-ductivity of peanut and increased supply of peanut oil. Further improving oil content and quality of peanut is still crucial for increasing productivity of arable land and market competitiveness of peanut oil. Based on investigation among the peanut germplasm accessions including wild Arachis species, the oil content could be as high as 65%. Heterosis has been observed for oil content in hybrids derived from diverse crossing parents. Segregates with enhanced oil content have been obtained by pyramiding different genes or alleles with major and minor additive effects. Improved testing techniques for oil content in breeding lines with reduced cost have accelerated breeding progress for high oil content. SSR markers associated with oil content have been identified by association and linkage analysis. The stability of oil content in peanut across seasons and locations is highly associated with cold tolerance, high nutrition efficiency and drought tolerance. Recent progress on improving fatty acids in particular marker assisted backcrossing breeding has contributed to higher quality peanut oil and other products. High oil peanut lines with im-proved resistance to aflatoxin production have been developed. The wild Arachis species would be of great value for peanut breeding in increasing oil content.