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Title: The potential role of water in spread of conidia of the Neotyphodium endophyte of Poa ampla

item Dugan, Frank

Submitted to: Mycological Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2007
Publication Date: 6/4/2007
Citation: Tadych, M., Bergen, M., Dugan, F.M., White, J.F. 2007. The potential role of water in spread of conidia of the Neotyphodium endophyte of Poa ampla. Mycological Research. 111: 466-472.

Interpretive Summary: Neotyphodium species are fungi that are symbiotic (mutualistic) in grasses. The symbiosis often confers protection of the grass from insects, but also can have the effect of inducing toxicosis in grazing livestock. It has become conventional wisdom that transmission of these endophytic fungi occurs solely via infected seed or vegetative plant parts. However, several recent studies have noted that conidia of these fungi are sometimes produced on host leaf surfaces. These observations led us to the question of how such conidia might be disseminated. The present study demonstrates that water is essential for release from leaf surfaces of conidia of the Neotyphodium sp. mutualistic with the grass Poa ampla. Artificial wind (compressed air) lacking water droplets did not discharge conidia, but water sprays were effective in inducing discharge.

Technical Abstract: Endophytes of the genus Neotyphodium are mutualistic fungi that colonize many cool season grasses. Neotyphodium endophytes are asexual but related to the ascomycete genus Epichloe. They do not produce obvious structures external to the host and for most of the life cycle are asymptomatic and systemic in the aboveground organs of infected host plants. Infected seeds and vegetative organs of the host are the only known modes of propagation of these asexual endophytes. However, in the last decade certain Neotyphodium-infected grass species have been shown to produce Neotyphodium hyphae, conidiophores and conidia on leaf surfaces. Poa ampla is among the hosts for which this has been demonstrated. Our experimental results indicate that air currents containing water droplets (sprays) release conidia growing on leaf surfaces of Poa ampla, and such sprays also release conidia growing on thin layers of agar spread on glass slides (slide cultures). Air currents of compressed air alone (lacking water droplets) did not dislodge conidia from either leaves or slides.