A Protocol for the Induction of Polyploids in Phalaenopsis Orchids by In Vitro Method Without Using Anti-microtubule Agents

Abstract

Polyploidy plays an important role in the breeding of many crops as well as horticultural plants of the world. It is also important for the variety improvement of Phalaenopsis orchids. Most of the commercial orchids are tetraploids. However, most of the wild species of Phalaenopsis are diploid. Thus, a barrier to hybridization between these two groups of varieties limits the source of germplasm available for the breeding programs. Hence, a simple technique to scale up the ploidy level of diploid species is needed. Traditionally, chemical induction using anti-microtubule agents such as colchicine or oryzalin is used for polyploid induction. However, there are several disadvantages to these methods, such as complicated procedures, problems of toxicity to plants, and the occurrence of unfavorable chimeras. Search for alternate procedures might give better result to achieve the same objective. Due to the occurrence of endopolyploid cells in the tissues of protocorms and PLBs of the orchid, there is a chance to regenerate polyploid plants from these cells. A protocol for dissecting protocorms or PLBs in tissue culture without using anti-microtubule agents and the use of flow cytometry with 4,6-diamidino-2-phenylindole (DAPI) staining is described in details in this chapter. This is a simple, effective, and reliable technique to produce large numbers of polyploid plants in Phalaenopsis orchids. It might have a great impact on new variety development of the orchid in the future.