Location: Vegetable Crops ResearchTitle: Genomic in situ hybridization reveals both auto- and allopolyploid origins of different North and Central American hexaploid potato (Solanum sect. Petota) species) Author
Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2012
Publication Date: 5/12/2012
Citation: Pendinen, G., Spooner, D.M., Jiang, J., Gavrilenko, T. 2012. Genomic in situ hybridization reveals both auto- and allopolyploid origins of different North and Central American hexaploid potato (Solanum sect. Petota) species. Genome. 55:407-415. Interpretive Summary: Wild potato (Solanum section Petota) species contain different sets of chromosomes with most of the species with two sets diploids, with 24 chromosomes, but with some of the species with four sets with 48 chromosomes termed tetraploids, and some with three sets with 72 chromosomes, termed hexaploids. This research uses a new technique, termed chromosome painting, or more technically genomic in situ hybridization, to see how the hexaploid species growing in North and Central America obtained these duplicated chromosome sets. In the past, ideas of how species obtained these different chromosome sets were determined by how chromosomes behaved when they paired during the sexual process to form sperms and eggs. Chromosome painting, in contrast, uses an entirely new and very powerful technique to investigate this problem by staining “painting” the chromosomes with the DNA of different species that could be the parents of these species with duplicated chromosome sets. The results show two very different modes of formation of these hexaploid species. One mode, exemplified in the hexaploid species technically called Solanum demissum, has all three sets of chromosomes the same, while another hexaploid, technically called Solanum iopetalum, has three very different chromosome sets. We use these data to speculate what are the parents of these two species. These results are very useful for potato breeders in that it informs them of the genetic constitution of these wild species that helps them better plan their breeding programs.
Technical Abstract: Wild potato (Solanum section Petota) species contain diploids (2n = 2x = 24), tetraploids (2n = 4x = 48), hexaploids (2n = 6x = 72), and rare triploids and pentaploids. Determination of the type of polyploidy and the development of the genome concept for section Petota classically was based on the analysis of chromosome pairing in species and their artificial hybrids. In 1990 Hawkes classified all hexaploid Mexican species in series Demissa, and according to a classic five-genome hypothesis of Matsubayashi in 1991, all members of series Demissa are strict allopolyploids. We investigated the genome composition of members of Hawkes’s series Demissa with genomic in situ hybridization (GISH), using labeled DNA of their putative progenitors to include diploid AA or BB or PP genome species or with DNA of tetraploid species of AABB or AAAaAa genomes. GISH analyses support S. hougasii as a strict allopolyploid with one AA component genome, and another BB component genome. Our results also indicate the presence of the P genome of South American species in allohexaploid S. hougasii. However, S. demissum has another genome nature with all three chromosome sets related to the basic A genome similar to the GISH results of polyploid species of series Acaulia. Our results support a more recent taxonomic division of the Mexican hexaploid species into two groups: the strictly allopolyploid Iopetala Group containing S. hougasii, S. iopetalum, and S. schenckii, and an autopolyploid Acaulia Group containing S. demissum and South American species S. acaule and S. albicans.