Cytogenetic features of prior dedifferentiation in lily of the valley (Convallaria majalis L.) tissue culture

Using squashed acetocarmine preparations, the variability of lily of the va lley genome at prior dedifferentiation, beginning from the explant to the e ighth subcultivation, was analyzed. Buds growing above ground were used as explants. Donor plants were of the karyotype K = 2n = 38 = 2(12m + 6sm + 1s a(st)). Even in early culture, aberrant anaphases (17%) and aneuploid metap hases were recorded. However, by the time of the eighth passage, the tissue remained mainly diploid. The proportion of diploid cells was 68%. The kary otype structure of the intact plant in diploid cells was rather stable, des pite certain rearrangements in particular chromosome pairs. Aneuploid cells in lily of the valley culture were characterized by considerable genome ab normalities. The most common mechanism leading to variation in chromosome n umber in vitro involves chromosome breaks at the centromere, which are rare events in lily of the valley cells in vivo. It has been suggested that the preservation of the genome of the intact plant by defined culture conditio ns is necessary for stabilization of the cardenolide-producing cell line.