In vivo chromosome doubling of Prunus lusitanica

Prunus lusitanica (2n = 8x) and Prunus laurocerasus (2n = 22x) are evergreen woody shrubs commonly used in landscapes across the United States and Europe. To reduce the difference in ploidy between these species and with the expectation of successful hybridization, an experiment was performed to double the chromosome number of P. lusitanica.

Colchicine was applied at 0%, 0.2%, 0.4%, and 0.8% (w/v), and 125 µM oryzalin as a viscous liquid to the apical meristem of open-pollinated P. lusitanica seedlings. Solutions were semisolidified using 0.55% agar (w/v). Cellular penetration was increased by adding 1% dimethyl sulfoxide (v/v) in all groups except oryzalin. As a result, three chromosome doubled (2n = 16x) plants, one 2n = 12x plant, and 14 cytochimeras (2n = 8x + 16x) were recovered.

Application of 125 µM oryzalin had a meristem-survival rate of 17%, statistically lower than all other treatments. The oryzalin treatment also produced the highest number of altered ploidy seedlings. Oryzalin at 125 µM was the most effective chromosome doubling agent in this experiment. Phenotypic examination indicated that chromosome doubled (2n = 16x) plants displayed shorter stems, thicker leaves, and fewer but larger guard cells than the untreated controls.

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