Nuclear Genome Organization of Asymmetric Intergeneric Somatic Hybrid Plants between Lycopersicon esculentum × L. pennellii and Solanum melongena

Asymmetric somatic hybrids were obtained by PEG/DMSO fusion of protoplasts of a kanamycin-resistant (KmR+) interspecific tomato hybrid L. esculentum × L. pennellii with protoplasts of S. melongena eggplant. Elimination of tomato chromosomes was directed by application of 100, 250, 500, 750, and 1000 Gy of γ-rays to the donor protoplasts. The hybrid nature of selected KmR+ calli was confirmed by RAPDs, PCR amplification of the NptII gene, and Southern hybridization. Flow cytometry revealed that asymmetric hybrid plants were regenerated only from selected somatic hybrid calli that had a ploidy level close to 4n. The amount of donor DNA in three somatic hybrid plants was quantified by dot-blot hybridization with tomato species-specific probes, and was found to be 5% to 7%. Therefore, presence of four to five tomato chromosomes in asymmetric hybrid plants has been calculated. Detection of tomato-specific chromosomes in hybrid plants by RFLP analysis will be presented.