Transmission of Atkinsonella hypoxylon (Clavicipitaceae) by cleistogamous seed of Danthonia spicata (Gramineae)

Atkinsonella hypoxylon is a systemic parasite of the grasses Danthonia spicata, D. compressa, and Stipa leucotricha. The means by which this fungus and other Balansiae (Balansia, Balansiopsis, Epichloë, and Myriogenospora) are transmitted from one plant to another is poorly understood. Host grasses of A. hypoxylon normally produce spikelets of open, wind-pollinated chasmogamous flowers at the apex of the flowering culm and spikelets of self-pollinated cleistogamous flowers in the lower leaf sheaths of the same culm. Plants of D. spicata infected by A. hypoxylon regularly produce cleistogamous spikelets in the lowermost leaf sheaths, although chasmogamous spikelets are aborted by hypothallus development. Embryos of the seeds resulting from these flowers were surrounded by hyphae. The seeds were germinated and when the plants flowered, they produced deformed flowering culms and hypothalli, indicating that A. hypoxylon is transmitted from parent to offspring through cleistogamous seed.