Homoeologous Chromosome Pairing and Alien Introgression in Backcrossing Progenies Derived from Hybrids Solanum tuberosum (+) Mexican 2x (1 EBN) B-Genome Potato Species

Abstract

We applied a genomic in situ hybridization (GISH) to analyze the genomic constitution of and meiotic pairing in interspecific somatic hybrids, and in a wide subset of backcrossing derivatives (BC1–BC5), from three interspecific combinations involving the cultivated potato, Solanum tuberosum (AAAA genome), and three diploid (1 EBN) wild Mexican potato species (genome BB)—S. tarnii, S. pinnatisectum, and S. bulbocastanum. The theoretically expected genomic composition was detected in the somatic hybrids (AAAABB) and in the BC1 progeny (AAAAB), whereas in the subsequent BC2–BC4 generations, the partial loss of alien chromosomes was observed and almost all the BC5 genotypes showed a complete chromosome elimination of wild species. GISH revealed a homoeologous pairing between the chromosomes of the A- and the B-genomes in each of the hybrid progenies. Using GISH, we selected introgression lines with a single chromosome of the wild species in a potato genome background, as well as introgression lines with intergenomic recombinant chromosomes. Moreover, via molecular screening, BC hybrids with diagnostic markers for the R-genes conferring resistance to late blight disease and to the quarantine pest of the potato–Columbia root-knot nematode—were selected. The potential application of the results obtained for the planning of introgressive schemes directed to the breeding of advanced lines with multiple disease and pest resistance is discussed.