Somatic hybrids have been obtained between potato and Solanum bulbocastanum PI 245310, a Mexican diploid (2n=2x=24) species. Through restriction fragment length polymorphism (RFLP) and randomly amplified polymorphic DNA (RAPD) analyses it was found that the somatic hybrids contain each chromosome of the diploid parent and that the synteny of RFLP markers noted with tomato, potato and S. brevidens is largely maintained in S. bulbocastanum. RFLP analyses of BC1 progeny of two different hybrids indicated that a substantial number of markers were either lost or were heterozygous, in marked contrast with results previously noted with S. brevidens. A RAPD map for all 12 chromosomes of S. bulbocastanum was prepared and marker transmission was followed in three BC2 populations. Results with chromosomes 3, 8 and 10 from these populations are compared.

The Solanum brmidens genome (2n = 2x = 24) was examined with randomly applied polymorphic DNA (RAPD) markers in a second backcross population derived from a S. brevidens + S. tuberosum somatic hybrid. RAPD markers cosegregated into 12 different S. brevidens synteny groups. Most synteny groups were nonrecombinant. However, nearly 40% of the S. brevidens synteny groups detected in this population were recombinant deletions that carried at least one, but not all, synteny group-specific RAPD markers. All S. brevidens synteny groups (except chromosome 5) were involved in recombination, and recombination occurred within most intervals between markers. About 20% of the recombinant S. brevidens synteny groups involved a single synteny group-specific marker. The inheritance of some single-marker representatives was followed in four BC3 families. At least nine changes in S. brevidens synteny groups had occurred during backcrossing. Six of the nine changes involved translocation of S. brevidens markers between nonhomologous S. brevidens chromosomes, and three S. brevidens markers may have been introgressed into the potato genome.