Somaclonal variation in orchids and the application of biotechnology

Orchids have become important floricultural crops in the global market. Desirable plants were selected and mass-propagated by the use of nodes on flower stalks. Micro-propagation of orchids was achieved by either nodal shoot multiplication or through the induction of protocorm-like bodies (PLBs). We have used PLBs for multiplication study by sectioning them transversely, longitudinally, or at 45 degrees, with each sectioned bottom part of PLB producing an average of 12.0-15.2 PLBs after 6 weeks of culture. This implies high multiplication rate of explants through PLB culture. Sectioning methods did not affect PLB production. Somaclonal variation may occur during tissue culture process, with the frequency depending on the genotype, cultural medium, growth hormones, and the way of multiplication. Molecular techniques, such as cDNA suppression subtractive hybridization, were used to compare peloric mutants with the wild type flowers of Phalaenopsis. Several candidate genes, including retroelement, have been identified. The information resulting from these molecular studies will provide clues to peloric mutation. Mutants related to vegetative as well as reproductive growth, such as peloric flowers are being collected from orchid nurseries. These mutants may contribute to our understanding of the development of orchid plants by molecular dissection of gene functions and classical crossing and genetic analysis. A DNA methyltransferase gene (Dnmt) was isolated and shown reduced expression in the semi-peloric flower buds of Phalaenopsis Little Mary.