Tissue culture techniques are now widely used to produce commercially grown
orchids. This process takes about 8-12 months to produce plantlets large enough to
withstand the rigours of nursery conditions. However, during the acclimatization phase,
tissue-cultured plantlets undergo a lag phase before they are able to establish. In nature,
orchid plants rely on their close association with mycorrhiza fungi for growth and
development. Thus, we have developed a method to infect in vitro orchid roots with
mycorrhiza. Stage III micropropagated orchid plantlets were artificially inoculated with
mycorrhiza strain MS6A (isolated from Mokara Sunkist) in vitro. The roots of the
plantlets were harvested 5, 8 and 20 weeks after inoculation to study the stages and
development of mycorrhiza infection. Using biological microtechniques, the orchid roots
were cut into sections of 8m thickness and stained with 1% Toludine Blue O. The slides
were examined under light microscope and the developmental stages of mycorrhiza in the
cells were examined. The aim is to study the developmental stages of the association of
mycorrhiza strain MS6A (isolated from Mokara Sunkist) in Vanda Tan Chay Yan orchid
plantlets in vitro. Orchid roots after 5 weeks of infection had masses of fungal hyphae at
the velamen region. At week 8, intracellular fungal aggregates have spread to the cortical
cells. At week 20, coils of fungal hyphae, also known as pelotons, have infected cells
near the central vascular cylinder. This was similar to the infection pattern observed in
plants in vivo.