Comparison of triploid and diploid cucumber in long-term liquid cultures

Triploid suspensions generally grew more vigorously in modified MS medium with 2,4-D than those of diploids. The embryogenic potential of 26-month-old auxin-dependent suspension cultures depended on the line. Neither triploid nor diploid BOR (Borszczagowski line) were able to produce somatic embryos. Similarly, 12–20-month-old cytokinin-dependent suspensions from the same triploid line were not capable of regeneration. Only aggregates from 26-month-old auxin-dependent suspension of triploid line 603 differentiated into somatic embryos. In contrast, 18-month-old diploid and triploid liquid cultures of meristematic clumps (LMC) of BOR retained their regeneration potential. The ploidy level of triploid and diploid auxin-dependent suspension cultures was stable during the first 8 months. However, the ploidy level of triploids remained stable over 26 months of culture, whereas 66.7% of diploid cultures underwent chromosome doubling. No ploidy changes were observed among plants regenerated from 18-month-old LMC. Our data suggest that loss of embryogenic potential in suspension culture was independent of ploidy level.