Somaclonal variation in cucumber (Cucumis sativus L.) plants regenerated via embryogenesis

Plants were regenerated via embryogenesis from leaf explant-derived callus of cucumber ( Cucumis sativus L. cv. Hokus). Somaclonal variation was evaluated in the regenerated plants (R, generation) and in the selfed progeny (R2). Considerable variation was found in the young R, plants, but it was of a transient nature. Mature R, plants showed slight abnormalities which were not directly transmitted to the progeny. Seed production of the R,s was variable and very poor, as was seed germination. This is probably caused by dysfunctioning of generative tissue and cells and might have a genetic base. Of eight R2 lines analysed, one was tetraploid and five expressed a low extent of variability, probably of a genetic nature. Most of the R2 plants were phenotypically normal. In a yield analysis, genetic variation useful for improvement of crop performance has not been detected. It is suggested that in cucumber the generative phase acts as a sieve for genetically based somaclonal variation.