Identification of a short rDNA spacer sequence highly specific of a tomato line containing Tm-1 gene introgressed from Lycopersicon hirsutum

• Published in: Theoretical and applied genetics Vol. 80; no. 5; pp. 602 - 608
• Main Authors: Levesque, H, Vedel, F, Mathieu, C, Courcel, A.G.L. de
• Format: Journal Article
• Language: English
• Published: Germany 01.11.1990
• Subjects: cloning; DNA; genes; genetic recombination; genetic resistance; interspecific hybridization; introgression; linkage (genetics); molecular sequence data; nucleic acid hybridization; nucleotide sequences; probes (equipment); restriction fragment length polymorphism; ribosomal DNA; Solanum habrochaites; Solanum lycopersicum var. lycopersicum; Tobacco mosaic virus; tolerance
• ISSN: 0040-5752; 1432-2242
• DOI: 10.1007/bf00224218

We studied rDNA restriction fragment length polymorphism between two tomato lines used for F1 hybrid seed production: line A, containing the Tm-1 gene responsible for tobacco mosaic virus tolerance introgressed from the wild species Lycopersicon hirsutum, and line B, a tobacco mosaic virus sensitive line. Hybridization patterns led to distinct rDNA maps with two size classes, 10.4 and 10.7 kb, in line A and a single, 8.9-kb class in line B. Size differences were located in the intergenie sequence (IGS). A highly specific 54-bp TaqI fragment was cloned from the line A IGS and used in dot blot experiments to probe total DNA from line A, line B, and their F1 hybrid. It proved capable of discriminating B from A and the hybrid. This probe could thus serve to screen inbreds in commercial seed lots where line A is used as male. This fragment showed 80-90% sequence homology with the 53-bp subrepeats previously characterized in a region of the tomato IGS close to the 25S rRNA gene. Preliminary comparison of rDNA in line A and several wild related species indicated that the L. hirsutum H2 genotype was the closest to line A. rDNA variations between line A and this wild genotype could be explained by recombination during the introgression process involving numerous backcrosses or by an important intraspecific polymorphism. Our results strongly suggest that Tm-1 and the rDNA were introgressed together into tomato from L. hirsutum through linkage drag.