Distribution of novel and known repeated elements of Solanum and application for the identification of somatic hybrids among Solanum species

Abstract

Species-specific repetitive DNA probes are a useful tool for the molecular 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 species of the genera Lycopersicon, Nicotiana, and Datura. The clone pSCH15, obtained from S. circaeifolium, represents a new 168-bp repetitive 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% sequence homology) to the Lycopersicon element pLEG15/TGRI previously regarded to be present only in species of the genus Lycopersicon and in S. lycopersicoides. Lower sequence similarity of approximately 80% was observed to repetitive elements of S. brevidens which are organized differently. The repeats exhibited different degrees of specificity: by Southern 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, although in a very low copy number, in Lycopersicon esculentum. Therefore, detection of the repetitive elements pSA287 and pSBH6 in those species in which the respective repeat is less represented depends on exposure time. In contrast, the element pSCH15 is prominently present only in a small number of Solanum wild species and - to some extent - in the diploid breeding lines as revealed after long exposure. Use of these repeated elements for the identification of specific genomes in protoplast-fusion hybrids between Solanum wild species and Solanum breeding lines, or between two breeding lines, was evaluated.

Characterization of a novel satellite DNA sequence from Flying Dragon (Poncirus trifoliata)

“…The distribution and sequence of stDNA may therefore provide insight into phylogenetic relationships among species (King, Jobst & Hemleben, 1995;Stadler et al, 1995;Hemleben, 2000).…”

Cytological and molecular characterization of repetitive DNA sequences of Solanum brevidens and Solanum tuberosum

“…The sequences gave strong Southern hybridization signals not only for S. brevidens, but also for other Etuberosa-group species (Solanum etuberosum and Solanum fernandezianum) (Malkamäki et al 1996). pSB7 is also significantly identical to a tomato-specific repeat, as previously described by Stadler et al (1995). In dot blot analysis, under high stringency conditions (15% mismatch with pSB1 and 5% with pSB7), no hybridization to S. tuberosum or L. esculentum was detectable (Malkamäki et al 1996).…”

“…Depending on the subrepeat of Sb4/2, the homology with pSB7 varied from 78 to 100%. pSB7 also showed 87% homology with a Lycopersicon esculentum derived satellite DNA repeat (pLEG15) (Schweizer et al 1988) and 62% homology with a DNA repeat (pSCH15) isolated from S. circaeifolium (Stadler et al 1995).…”

“…Many tandemly repeated sequences in plants are present in numerous copies in the species from which they were isolated but are present in fewer copies in related species, such sequences are referred to as species-specific repeats (Lapitan 1992). Repetitive DNA sequences have been isolated from many species of the Solanaceae, including Lycopersicon esculentum Schweizer et al 1988), S. tuberosum (Visser et al 1988;Pehu et al 1990;Schweizer et al 1993), Solanum phureja (Visser et al 1988), Solanum acaule (Schweizer et al 1988), Nicotiana tomentosiformis and Nicotiana tabacum (Koukalová et al 1989), S. brevidens (Pehu et al 1990;Preiszner et al 1994), Solanum demissum (Schweizer et al 1993), Solanum circaeifolium and Solanum bulbocastanum (Stadler et al 1995), and Solanum spegazzinii (Gebhardt et al 1995). Some of these sequences have been shown to be useful tools for analyzing the nuclear genomes of hybrids produced by sexual (Watanabe et al 1995) or somatic hybridization (Saul and Potrykus 1984;Schweizer et al 1988;Pehu et al 1990;Xu et al 1993).…”

Transfer of PLRV resistance fromSolanum verrucosum Schlechdt to potato (S. tuberosum L.) by protoplast electrofusion

“…We have used RAPD markers for the identification of somatic hybrids. Other authors have applied different techniques for this purpose such as morphological analysis (Austin et al, 1985), isoenzymatic analysis (Serraf et al,, 1994), RFLP markers (Novy & Helgeson, 1994), primers which amplify simple sequence repeats (Stadler et al, 1995;Menke et al, 1996) and PCR with oligonucleotides which amplify specifically the 5S rDNA spacer region . The problems of RAPD markers with respect to reproducibility of results under the specific conditions in different laboratories, or with respect to equal-sized markers which may not be sequence homologous are well known (Black, 1993).…”