Karyotype stability and genome-specific nucleolar dominance in peanut, its wild 4x ancestor, and a synthetic AABB polyploid

J. G. SEIJO; KOVALSKY, EVELIN IVANA; CHALUP, L.; SAMOLUK, S; FAVERO, A; ROBLEDO, G

Iguazú

Congreso; International Congress of Genetics; 2018

Internationa Society of Genetics

ABSTRACT:Allopolyploidy is a significant evolutionary process involved in the origin of many crops,including peanut (Arachis hypogaea L.). The process usually results in a series ofchromosome, genomic and epigenetic rearrangements in the derived polyploids. Here,we examined the chromosomal consequences undergone by AABB tetraploids ofArachis after the genome merger. For that objective, different chromosome markersand DNA contents were compared among peanut, its wild tetraploid ancestor, and thediploid genome donors A. duranensis Krapov. & W.C. Gregory (AA, female) and A.ipaënsis Krapov. & W.C. Gregory (BB, male). The analysis also included an artificiallysynthesized allotetraploid using A. ipaënsis as a female [(A. ipaënsis x A.duranensis)4x]. The karyotypes in the natural (originated ?10,000 yr ago) and newlysynthesized allopolyploids have largely maintained the patterns of heterochromatin andribosomal RNA loci detected in the diploid progenitors. Intergenomic translocationswere not evident using genome in situ hybridization, and the DNA contents of theallotetraploids corresponded to the expected sum of those observed in their parentalspecies. The analysis of ribosomal DNA loci and their association with nucleolarorganizing regions revealed a rapid establishment of nucleolar dominance in favor ofthe A genome. The large macrostructural stability of karyotype observed here afterpolyploidization has not been frequently cited for polyploid crop plants. This stability issignificant for peanut breeding, since it suggests that effective introgression of wilduseful alleles into cultivated peanut may potentially occur in most of the extension ofthe A and B chromosome complements.Funding Agency: ANPCYT-MINCYT and CONICET, Argentina