In situ hybridization in Vitis vinifera L

Cytological studies of metaphase chromosomes in Vitis vinifera L. were restricted to the determination of the chromosome number for a long time. Analyses at the chromosome level both in meiotic and somatic metaphase plates of grapevine were limited by the size of the chromosomes. Only few approaches to establish a karyotype by measuring homogeneously stained metaphase chromosomes have been made because of their small size (0.8-2.0 mu m) and similar length. For the differentiation chromosome-specific markers have to be developed. Apart from cytogenetic methods as C-, N-banding or silver staining in situ hybridization could be a useful tool for the characterization of chromosomes. In 1969, a method for radioactive in situ hybridization was described. Since, it has been developed and in the 1980s it was more and more replaced by fluorescent in situ hybridization (FISH) which is widely used for the detection of DNA sequences now. FISH is extremely valuable in studying karyotypes with small and similarly sized chromosomes in plants. Nevertheless, no studies in grapevine have been reported yet. For establishing this method in grapevine we intended to detect the satellite chromosomes by in situ hybridization. In the chromosomes the rRNA genes are located in the region proximal to the secondary constriction in form of several hundreds tandemly repeated units. As an rDNA probe we used pTA 71 from common wheat. In the present paper we demonstrate that fluorescent in situ hybridization can be used as a new, additional method for characterizing the chromosomes and for physical mapping of interesting DNA sequences (genes) on chromosomes of grapevine.