RFLP analysis and genomic in situ hybridization (GISH) in somatic hybrids and their progeny between Lycopersicon esculentum and Solanum lycopersicoides

RFLP (restriction fragment length polymorphism) and GISH (genomic in situ hybridization) analyses were employed to identify the chloroplast and nuclear genomes of the somatic hybrids and progeny between tomato 'Ohgata zuiko' and Solanum lycopersicoides ('LA2386'). A random distribution of the chloroplast genotype was determined using a cloned 19.6-kb BamHI fragment (Bal) of tobacco chloroplast DNA. Eight selected hybrids were analyzed for their chromosomal compositions; 4 were tetraploids (2n = 48) with an equal number of chromosomes derived from each parent as accurately determined by GISH, and the other 4 were hexaploids, containing an average of two sets of tomato chromosomes and one set from the wild parent. RFLP analysis with six tomato nuclear probes of known chromosomal locations revealed no major variation among the 44 hybrid plants surveyed. However, it also showed the presence of both parent-specific alleles and the loss of some and the presence of a few non-parental alleles, indicating rearrangement and/or recombination of the nuclear DNA. The relevance of the molecular and cytological methods and the potential use of somatic hybrids for plant breeding are demonstrated.