Organelle analysis of symmetric and asymmetric hybrids between Lycopersicon peruvianum and Lycopersicon esculentum.

The organelles of somatic hybrids obtained from symmetric and asymmetric fusions between the Lycopersicon species L. peruvianum and L. esculentum were analyzed by DNA hybridization methods. In the asymmetric fusions the L. peruvianum protoplasts were gamma-irradiated at a dose of 50, 300 and 1,000 Gy. The organelles were characterized using the Petunia chloroplast probe pPCY64 and the mitochondrial EcoRI-SalI fragment of the Pcf gene. In all symmetric and asymmetric hybrid plants, a total of 73 being analyzed, only one of the parental chloroplast genomes was present, except for one hybrid plant which harbored both parental chloroplast genomes. No recombination and/or rearrangement in the chloroplast genome could be identified with the pPCY64 probe. Irradiation of the L. peruvianum protoplasts did not significantly reduce the fraction of asymmetric hybrids with L. peruvianum chloroplasts. A novel mitochondrial restriction pattern was present in 5 out of 24 hybrids tested. In 9 hybrids novel combinations of chloroplasts and mitochondria were found, indicating that both organelle types sorted out independently.