Transmission genetics of chromatin from a synthetic amphidiploid to cultivated peanut (Arachis hypogaea L.): Broadening the gene pool of a monophyletic polyploid species

Polyploidy creates severe genetic bottlenecks, contributing to the genetic vulnerability of leading crops. Cultivated peanut is thought to be of monop hyletic origin, harboring relatively little genetic diversity. To introduce variability front diploid wild species into tetraploid cultivated Arachis hypogaea, a synthetic amphidiploid {[A. batizocoi K9484 X (A. cardenasii GK P10017 X A. diogoi GKP10602)](4x)} was used as donor parent to generate a b ackcross population of 78 progeny. Three hundred seventy RFLP loci were map ped onto 23 linkage groups, spanning 2210 cM. Chromatin derived from the tw o A-genome diploid ancestors (A. cardenasii and A. diogoi) comprised mosaic chromosomes, reflecting crossing over in the diploid A-genome interspecifi c Ft hybrid. Recombination between chromosomes in the tetraploid progeny wa s similar to chromosome pairing reported for A. hypogaea, with recombinatio n generally between chromosomes of the same subgenomic affinity. Segregatio n distortion was observed for 25% of the markers, distributed over 20 linka ge groups. Unexpectedly, 68% of the markers deviating from expected segrega tion showed an excess of the synthetic parent allele. Genetic consequences, relationship to species origins, and significance for comparative genetics are discussed.