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We examined the effects of five antimitotic agents using Antirrhinum majus L. 'Maryland True Pink' on the induction of adventitious shoots resulted in increase of frequencies of chromosome doubling without plant growth regulators.

Chromosome numbers of wild species in the genus Epidendrum have previously been reported in the range of 2n= 24-240. However, the ploidy levels of cultivars in the given genus originating from interspecific hybridization among several wild species have never been reported. To elucidate their ploidy levels, we analyzed the chromosome number of cultivars and related wild species. Four wild species showed a new record of chromosome number in the present study, namely, E. radicans 2n=38, 80, E. secundum 2n=60, and E. cinnabarinum 2n=64. Six cultivars examined were revealed to have more chromosomes than the wild species, with a range of 2n= 84-164, suggesting that the cultivars have high polyploid levels. A significant correlation between the nuclear DNA amount and the chromosome number in wild species as well as cultivars was observed. Those cultivars originated from hybridization. Thus, the results from the present study suggest that the polyploid cultivars in this genus could have resulted from pollination involving unreduced gametes during breeding.