Detection methods and in vitro elimination techniques for orchid viruses: A review

The maximum number of genera in the family Orchidaceae are well represented by their floricultural importance and are exported globally for trade exchanges. However, economic loss due to viral diseases has a profound impact on the orchid trade industry worldwide. Further, enduring phytosanitary certificates and undergoing stringent quarantine measures for virus-free orchids pose a major setback during the exchange of breeding materials between regions or countries. Fortunately, the spread of orchid viruses can be effectively controlled if proper diagnosis of viral diseases is made at an early stage and strict application of appropriate eradication methods are deliberated in a holistic approach. This bibliographic review highlights the substantial advancements in the diagnostic and eradication techniques of orchid viruses during the past few decades. The review shows that PCR-based techniques, which are represented as the "gold standard" method, are the most widely used diagnostic tools because of their accuracy, simplicity, and sensitivity. Considering the large diversity of orchids, only 7.2% of the genera belonging to the sub-families Epidendroideae, Orchidoideae, Cypripedioideae, and Vanilloideae have been detected for virus infection. The tribes Podochileae, Thaieae, Nervilieae, Gastrodieae, Xerorchideae, Triphoreae, Wullschlaegelieae, Tropidieae, Sobralieae, and Neottieae of the family Orchidaceae are under-represented. In vitro techniques, including meristem culture, thermotherapy, chemotherapy, and their combinations, represent the most desirable and effective approaches for orchid viral elimination. The use of cryotherapy, a simple technique based on cryopreservation, should have a high priority for viral elimination from infected orchids. This review could pave the way forward for comprehensive research on the production of virus-free orchids.