Abstract
Spathiphyllum wallisii Regel, which has the beautiful contrast of deep green leaves and a white spathe, is evaluated highly as an indoor ornamental plant. In order to breed new and valuable varieties of Spathiphyllum, crossing with wild species is effective. The breeding of tetraploids is useful for the development of fertile progeny by interspecies or intergeneric crossing. In this study, to establish effective breeding methods for tetraploids, the effects of the in vitro treatments of removing a suitable number of unexpanded leaves before sterilization, leaving a suitable number of leaf primodia remaining with the apical meristem, and the conditions of colchicine treatment were investigated in S. wallisii Regel ‘New merry’. The preparative methods, leaving four or five unexpanded leaves before sterilization and cutting off apical meristematic tissues with three or four-leaf primodia, decreased the contamination rate and sterilization damage of explants. The rate of apical meristems identified as polyploid was increased to 31.3% on fourteen-day colchicine treatment on MS medium, after growing on MS medium containing both NAA at 0.1 µM and BAP at 10 µM for one month. The leaves of the resulting tetraploids showed a broad-shaped form compared to the diploids, and spathes of tetraploids were slightly smaller than those of diploids.
