DISTRIBUTION OF NOVEL AND KNOWN REPEATED ELEMENTS OF SOLANUM AND APPLICATION FOR THE IDENTIFICATION OF SOMATIC HYBRIDS AMONG SOLANUM SPECIES

Species-specific repetitive DNA probes are a useful tool for the molec ular identification of somatic hybrids. Therefore, the distribution of three repetitive DNA elements of Solanum was investigated in Solanum wild species, Solanum breeding lines, and in more distantly related sp ecies of the genera Lycopersicon, Nicotiana, and Datura. The clone pSC H15, obtained from S. circaeifolium, represents a new 168-bp repetitiv e element; it shows 73-79% sequence similarity to repetitive elements of S. brevidens and Lycopersicon species. The 163-bp element in pSBH6, cloned from S. bulbocastanum, turned out to be very similar (95% sequ ence homology) to the Lycopersicon element pLEG15/TGRI previously rega rded to be present only in species of the genus Lycopersicon and in S. lycopersicoides. Lower sequence similarity of approximately 80% was o bserved to repetitive elements of S. brevidens which are organized dif ferently. The repeats exhibited different degrees of specificity: by S outhern hybridization the element represented by the clone pSBH6 could be detected in almost all Solanum species investigated here but only after long exposure to X-ray film. The previously described ''Solanum- specific'' element represented by the clone pSA287 was also found, alt hough in a very low copy number, in Lycopersicon esculentum. Therefore , detection of the reptitive elements pSA287 and pSBH6 in those specie s in which the respective repeat is less represented depends on exposu re time. In contrast, the element PSCH15 is prominently present only i n a small number of Solanumwild species and - to some extent - in the diploid breeding lines as revealed after long exposure. Use of these r epeated elements for the identification of specific genomes in protopl ast-fusion hybrids between Solanum wild species and Solanum breeding l ines, or between two breeding lines, was evaluated.