Shifts of Genomic Organization in Arachis Induced Allotetraploids By Molecular Cytogenetics

Peanut (Arachis hypogaea) is a recent allotetraploid with two subgenomes derived from the hybridization between the diploid wild species, A. duranensis (A genome) and A. ipaënsis (B genome), followed by spontaneous chromosomal duplication. It has a large and complex tetraploid genome, with no reference genome yet available, what hinders the knowledge on its genomic organization and evolutionary history. Studies using induced allotetraploids that mimics peanut genomic background can enlighten some of the effects of hybridization, polyploidization and domestication. To increase our understanding on the changes occurring in the genome after allopoliploidization, cytogenetics analysis were conducted using an induced allotetraploid (A. ipaënsis- ‘K30076’ x A. duranensis ‘V14167’)^4x (IpaDur1), cultivated peanut (spontaneous allotetraploid) and their wild diploid parentals. These allotetraploids shared many similarities; however, IpaDur1 has undergone more alterations than peanut. In IpaDur1, one of the 5S rDNA locus changed position relative to its progenitors; two 45S rDNA loci were lost and at least one pair of chromosomes had an evident hybridization pattern corresponding to recombination between the two component genomes, suggesting some genome instability. Another induced allotetraploid, IpaDur2 (A. ipaënsis- ‘K30076’ x A. duranensis ‘V14167’)^4x is currently being analyzed using plants derived from the first seed multiplication aiming to evaluated genome changes and stability along the early generations. Additionally, comparative studies with the wild A. monticola, the only other natural tetraploid species in the section Arachis that has also A. ipaënsis and A. duranensisas progenitors but with uncertain origin is underway.

This work was supported by the Brazilian Agricultural Corporation (Embrapa); Coordination for the Improvement of Higher Education Personnel (CAPES) and Foundation for Research Support of Federal District (FAP-DF).