Three novel Nicotiana debneyi specific repetitive DNA elements derived from a RAPD marker

The RAPD marker UBC418(1050), tightly linked in coupling with the Nicotiana debneyi gene for resistance to black root rot (Chalara elegans Nag Raj and Kendrick; Syn. Thielaviopsis basicola [Berk. and Broome] Ferraris), has be en cloned and sequenced. The terminal 10 bases of this RAPD marker exactly match the sequence of the primer UBC418. UBC418(1050) was restricted into 6 subfragments of 75, 91, 110, 174, 274, and 336 bp (the accession numbers f or these 6 subfragments in the GenBank Data Base are U84217, U84218, U84219 , U84220, U84221, and U84222, respectively) by combined restriction with Hi ndIII and RsaI. The entire UBC418(1050) marker and its 6 subfragments were used as probes in RFLP analyses. The RFLP analyses were performed on 'Delgo ld' tobacco (Nicotiana tabacum L.), the tobacco plants (2n = 48) recovered from the somatic hybrids between 'Delgold' and N. debneyi, the 'Delgold' to bacco translocation line carrying the N. debneyi gene for resistance to bla ck root rot, the 'Delgold' tobacco addition lines carrying various N. debne yi chromosomes, and an additional 27 species in the genus Nicotiana. The an alyses indicated that UBC418(1050) is composed of at least 6 different repe titive DNA elements that are independently interspersed in N. debneyi genom es. Three of them (subfragments of 91, 274, and 336 bp) are N, debneyi spec ific. The N. debneyi specific repetitive DNA elements are distributed prima rily within the taxonomic section (Suaveolentes) to which N. debneyi belong s.