Nuclear DNA content and isozyme variation in relation to morphogenic potential of strawberry (Fragaria × ananassa) callus cultures

Callus cultures of strawberry cv. Redcoat (2n = 8x = 56) initiated from greenhouse and in vitro leaf explants were examined at various culture periods for morphogenic response, changes in nuclear DNA content, and isozyme banding patterns of four enzymes. The flow cytometric analysis of nuclear DNA content revealed the occurrence of polyploid and aneuploid changes as a function of ageing of callus cultures. The calli initiated from in vitro leaf explants were more prone to such changes than those initiated from greenhouse leaf explants. The in vitro morphogenic ability of callus cultures was affected by the ploidy changes, but the latter were not the only cause for loss in regeneration potential of long-term callus cultures. The isozyme phenotypes of esterase, phosphoglucomutase, phosphoglucoisomerase, and leucine aminopeptidase did not change with the chromosomal variation in callus cultures. Key words: strawberry, Fragaria × ananassa, callus culture, flow cytometry, nuclear DNA content, isozyme.