In vitro induction of tetraploids in Colophospermum mopane by colchicine

Colophospermum mopane is an ecologically and economically important tree in subtropical southern Africa with ethnobotanical and medicinal uses. The effect of colchicine on the polyploidisation of seeds of C. mopane was studied in vitro. Seeds of C. mopane were imbibed in colchicine solutions of 0.05, 0.1 and 1.0% (w/v) for 24, 48 and 96 h before transfer to 1/8 MS basal medium. Ploidy levels of the surviving in vitro grown seedlings were determined using flow cytometry. Of a total of 45 surviving seedlings, 44% were found to be tetraploids, one was a chimera while the remainder were diploids. Tetraploid induction occurred in seedlings derived from seeds imbibed for 48 h at 0.05% and 0.1% (w/v) colchicine solutions. In comparison to the control plants, tetraploids showed morphological differences such as an earlier induction of enhanced growth of lateral branches and smaller leaflets and multiple shoots per single cultured seed. Treatments with colchicine concentrations greater than 0.1% and exposure times of more than 48 h were severely detrimental to growth and survival.