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J. Fungi 2018, 4(2), 58;

Observations on the Early Establishment of Foliar Endophytic Fungi in Leaf Discs and Living Leaves of a Model Woody Angiosperm, Populus trichocarpa (Salicaceae)

School of Plant Sciences, The University of Arizona, 1140 E. South Campus Drive, Tucson, AZ 85721, USA
National Museum of Natural Science, 1 Guancian Rd., Taichung 40453, Taiwan
Department of Biology, University of San Francisco, Harney 219C, 2130 Fulton Street, San Francisco, CA 94117, USA
Department of Ecology and Evolutionary Biology, The University of Arizona, 1041 E. Lowell St., Tucson, AZ 85721, USA
Author to whom correspondence should be addressed.
Received: 1 May 2018 / Revised: 11 May 2018 / Accepted: 13 May 2018 / Published: 16 May 2018
(This article belongs to the Special Issue Fungal Endophytes in Plants)
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Fungal endophytes are diverse and widespread symbionts that occur in the living tissues of all lineages of plants without causing evidence of disease. Culture-based and culture-free studies indicate that they often are abundant in the leaves of woody angiosperms, but only a few studies have visualized endophytic fungi in leaf tissues, and the process through which most endophytes colonize leaves has not been studied thoroughly. We inoculated leaf discs and the living leaves of a model woody angiosperm, Populus trichocarpa, which has endophytes that represent three distantly-related genera (Cladosporium, Penicillium, and Trichoderma). We used scanning electron microscopy and light microscopy to evaluate the timeline and processes by which they colonize leaf tissue. Under laboratory conditions with high humidity, conidia germinated on leaf discs to yield hyphae that grew epiphytically and incidentally entered stomata, but did not grow in a directed fashion toward stomatal openings. No cuticular penetration was observed. The endophytes readily colonized the interiors of leaf discs that were detached from living leaves, and could be visualized within discs with light microscopy. Although they were difficult to visualize within the interior of living leaves following in vivo inoculations, standard methods for isolating foliar endophytes confirmed their presence. View Full-Text
Keywords: Cladosporium; colonization; microscopy; Penicillium; Populus; stomata; Trichoderma Cladosporium; colonization; microscopy; Penicillium; Populus; stomata; Trichoderma

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Huang, Y.-L.; Zimmerman, N.B.; Arnold, A.E. Observations on the Early Establishment of Foliar Endophytic Fungi in Leaf Discs and Living Leaves of a Model Woody Angiosperm, Populus trichocarpa (Salicaceae). J. Fungi 2018, 4, 58.

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