PREPARATION OF TOMATO MEIOTIC PACHYTENE AND MITOTIC METAPHASE CHROMOSOMES SUITABLE FOR FLUORESCENCE IN-SITU HYBRIDIZATION (FISH)

Fluorescence in site hybridization (FISH) is an increasingly powerful tool with a variety of applications in both basic and applied research . With excellent genetic, cytogenetic and molecular maps available, th e tomato genome provides a good model to benefit from the full potenti al of FISH. Tomato chromosomes at mitotic metaphase are small and not particularly suitable for high-resolution FISH. In contrast, chromosom es at meiotic pachytene are about 15 times longer, and easier to ident ify by their differences in chromosome arm lengths and chromomere patt ern. We have developed a technique for preparing chromosomal spreads o f young pollen mother cells at mid-prophase I which is suitable for FI SH. In a first series of experiments, the hybridization patterns of th ree classes of repetitive DNA sequences were studied in single and mul ticolour FISH.