Destructive Phytophthora on orchids: current knowledge and future perspectives

Area of Science:

• Plant Pathology
• Mycology
• Horticulture

Background:

• The genus Phytophthora, meaning "plant destroyer," was first described by Anton de Bary.
• Phytophthora species have caused devastating losses in various plant species, including orchids, since their discovery.
• Phytophthora palmivora was first reported on Dendrobium maccarthiae in Sri Lanka over a century ago, marking the beginning of Phytophthora's impact on orchids.

Purpose of the Study:

• To provide a comprehensive review of Phytophthora diseases affecting orchids.
• To highlight the historical aspects, symptoms, pathogens, taxonomy, distribution, host range, and management strategies for Phytophthora in Orchidaceae.
• To discuss current diagnostic methods, mating types, races, and future research perspectives for controlling these devastating diseases.

Main Methods:

• Literature review synthesizing information on Phytophthora diseases in orchids.
• Analysis of historical records, pathogen characteristics, and geographical distribution.
• Compilation of data on host-pathogen interactions, diagnostic techniques, and management strategies.

Main Results:

• Twelve Phytophthora species are known to infect orchids, with five major species (P. palmivora, P. nicotianae, P. cactorum, P. multivesiculata, P. meadii) causing significant economic losses.
• These Oomycetes thrive in moist environments ( > 80% RH) at temperatures between 16-28°C.
• Anthropogenic factors contribute significantly to disease dissemination in cultivated orchids, alongside water management, cultivation practices, and agro-chemicals as primary control options.

Conclusions:

• Phytophthora diseases represent a major threat to orchid cultivation globally, necessitating effective management strategies.
• While conventional methods like water management and agro-chemicals are currently employed, eco-friendly approaches such as resistant cultivars and biological control are still in early development.
• Further research into advanced techniques like transgenic approaches and RNAi technology is crucial for sustainable long-term management of Phytophthora in orchids.