DNA polymorphism in Cab locus of tomato induced by tissue culture

Plants were regenerated from callus induced from leaf disc explants of a tomato F1 hybrid heterozygous for three marker loci anthocyaninless (a), without anthocyanin (aw), and hairless (hl). Regenerants were studied for somaclonal variation at the phenotypic level by scoring for variation in the marker loci, and at the DNA level by probing geomic DNA blots with a chlorophyll a/b binding protein (Cab-3C) cDNA sequence. While no variation was observed at the phenotypic level in over 950 somaclones studied, DNA polymorphism for the Cab locus could be detected in two out of 17 somaclones tested. Tissue culture induced variation at the phenotypic level for specific loci is very low (less than 0.001 for a, aw or hl) but DNA sequence changes are induced at much greater frequency (approximately 0.1 for a multicopy gene family such as Cab).