Chromosome doubling in monohaploid and dihaploid potatoes by regeneration from cultured leaf explants

Plants were regenerated from cultured excised leaf segments of monohaploid (2n=x=12) and diphaloid (2n=2x=24) potato (Solanum tuberosum L.) and a sample has been studied cytologically. In the case of monohaploids, a single leaf regeneration cycle resulted in almost total recovery of doubled monohaploid plants (2n=2x=24), whilst 50% of the plants regenerated from doubled monohaploid leaves had doubled again to the doubled double monohaploid (or homozygous tetraploid, 2n=4x=48) level. Regeneration from dihaploid leaf pieces also gave a good proportion (60%) of doubled genotypes. Very few mixoploids and very few aneuploids were found. These results, together with the general applicability of the method to a large number of potato cultivars, suggest that it can be used as a simple and reliable method of obtaining homozygous tetraploid potatoes.