Somatic hybridization between Solanum tuberosum and S. cardiophyllum

The wild diploid Mexican species, Solanum cardiophyllum Lindl. (2n = 2x = 24), is resistant to important potato diseases. However, introgression of resistance to the tetraploid cultivated potato (S. tuberosum L.) (2n = 4x = 48) by conventional crossing is not feasible due to the difference in their endosperm balance number between these species. Somatic hybrids between S. cardiophyllum and S. tuberosum were produced for the first time by electrofusion of protoplasts isolated from young leaves of each parental line. The hybrid nature of the regenerated plants was confirmed based on morphology, chromosome number and DNA species-specific RAPD markers. All the somatic hybrids produced a violet pigmentation on their stems and petioles, which resembled the wild partner. Most of the hybrid plants had 2n = 72 chromosomes and exhibited a morphology intermediate between the two fusion parents, but with a tendency towards cultivated potato. These plants flowered and set fruit when backcrossed with their S. tuberosum...