8-azaguanine-resistant carrot cell mutants and their use as universal hybridizers

We isolated a carrot cell mutant resistant to 8- azaguanine. Into this line a second mutation for resistance to ~-amanitin was introduced. The double mutant was shown to be selectable in e-amanitin and counter-selectable in HAT medium. Resistance to Azg and sensitivity to HAT were correlated with an alteration of the enzyme HPRT. The properties of the double mutant as universal hybridizer were verified in a fusion with wild-type carrot protoplasts.