Somaclonal variation in Solanum tuberosum detected at the molecular level.

The many reports of phenotypic variation among plants regenerated from tissue culture suggest underlying alterations at the DNA level. This hypothesis was tested with protoplast-derived Solanum tuberosum plants. Random potato-DNA clones were used to probe the genome of individual plants at specific sites. Two out of twelve plants were shown to be variant by Southern-hybridisation with one of the tester-clones. As this clone turned out to represent 25S-rDNA, both somaclonal variants can be regarded as mutants deficient in ribosomal RNA-genes.