Fungal specificity bottlenecks during orchid germination and development

Area of Science:

• Ecology
• Mycology
• Plant Science

Background:

• Mycoheterotrophic orchids rely on fungal symbionts for early development.
• Mature orchids often associate with ectomycorrhizal fungi shared with forest trees.
• Fungal partner specificity across orchid life stages remains largely uncharacterized.

Purpose of the Study:

• To investigate fungal symbiont specificity in Cephalanthera and Epipactis orchids.
• To compare fungal associations at germination, seedling, and mature plant stages.
• To determine if seedling stages have a narrower fungal partner range than other life stages.

Main Methods:

• Orchid seeds were sown in forest sites and harvested after up to 3 years.
• Fungi associated with seeds, seedlings, and mature plants were identified.
• Cultivation-independent molecular methods were used for fungal identification.

Main Results:

• Most identified fungal symbionts were ectomycorrhizal.
• Fungal associations varied across the three orchid life stages.
• Cephalanthera seedlings utilized a subset of fungi found in seeds and mature plants.
• Epipactis fungal partners were consistent across stages, but lineages affected germination.

Conclusions:

• Orchid seedling stages can exhibit a restricted range of fungal symbionts.
• This narrow mycorrhizal specificity acts as a critical checkpoint in early orchid development.
• Fungal partner breadth increases in germination and mature stages for these orchids.