DNA stability contrasts with chromosome variability in Allium fistulosum calli

RAPD analysis was applied to assess the degree of DNA polymorphism in A. fistulosum calli of high chromosomal instability. Nineteen of 24 randomly selected RAPD primers revealed scorable polymorphism between calli and seeds (reference material). Polymorphic band frequency was 55/237 in seeds and 36/233 in calli; variability on the DNA level was thus lower in calli than in seeds (15.4% vs. 23.2% of band positions). UPGMA analysis of Jaccard's coefficients confirmed the genetic similarity of the analyzed cultures. The most distinctive DNA changes in calli involved coincident loss of original bands or the appearance of novel bands. Seven such changes (4 losses, 3 gains) were observed. Our results suggest that changes on the chromosomal level and on the DNA level occurred independently of each other and that different callus lines underwent similar genetic changes during culture, presumably due to strong selection pressure effected by standard in vitro conditions.