Identification, pathogenicity and abundance of Paracremonium pembeum sp. nov. and Graphium euwallaceae sp. nov.--two newly discovered mycangial associates of the polyphagous shot hole borer (Euwallacea sp.) in California

Shannon Colleen Lynch; Mathias Twizeyimana; Joey Sal Mayorquin; Danny Ho Wang; Francis Na; Mukaddes Kayim; Matthew T Kasson; Pham Quang Thu; Craig Bateman; Paul Rugman-Jones; Jiri Hulcr; Richard Stouthamer; Akif Eskalen

doi:10.3852/15-063

Identification, pathogenicity and abundance of Paracremonium pembeum sp. nov. and Graphium euwallaceae sp. nov.--two newly discovered mycangial associates of the polyphagous shot hole borer (Euwallacea sp.) in California

Mycologia. 2016 Mar-Apr;108(2):313-29. doi: 10.3852/15-063. Epub 2016 Jan 6.

Authors

Affiliations

¹ Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521Center for Conservation Biology, University of California, Riverside, California 92521.
² AgBiome, Inc., 104 T.W. Alexander Drive, Building 1, Research Triangle Park, North Carolina 27709.
³ Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521.
⁴ Department of Plant Protection, Faculty of Agriculture, University of Çukurova, Balcali 01330, Adana, Turkey.
⁵ Division of Plant and Soil Sciences, West Virginia University, Morgantown, West Virginia 26506.
⁶ Forest Protection Research Center, Vietnamese Academy of Forest Sciences, 46 Dong Ngac Road, Duc Thang, Northern Tu Liem, Hanoi, Vietnam.
⁷ Department of Entomology, University of Florida, Gainesville, Florida 32611.
⁸ Department of Entomology, University of California, Riverside, California 92521.
⁹ School of Forest Resources and Conservation, University of Florida, Gainesville, Florida 32611.
¹⁰ Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521 akif.eskalen@ucr.edu.

PMID: 26740544
DOI: 10.3852/15-063

Abstract

Fusarium euwallaceae is a well-characterized fungal symbiont of the exotic ambrosia beetle Euwallacea sp. (polyphagous shot hole borer [PSHB]), together inciting Fusarium dieback on many host plants in Israel and California. Recent discoveries of additional fungal symbionts within ambrosia beetle mycangia suggest these fungi occur as communities. Colony-forming units of Graphium euwallaceae sp. nov. and Paracremonium pembeum sp. nov., two novel fungal associates of PSHB from California, grew from 36 macerated female heads and 36 gallery walls collected from Platanus racemosa, Acer negundo, Persea americana and Ricinus communis. Fungi were identified based on micromorphology and phylogenetic analyses of the combined internal transcribed spacer region (nuc rDNA ITS1-5.8S-ITS2 [ITS barcode]), elongation factor (EF 1-α), small subunit (18S rDNA) sequences for Graphium spp., ITS, EF 1-α, calmodulin (cmdA), large subunit of the ATP citrate lyase (acl1), β-tubulin (tub2), RNA polymerase II second largest subunit (rpb2) and large subunit (28S rDNA) sequences for Paracremonium spp. Other Graphium spp. recovered from PSHB in Vietnam, Euwallacea fornicatus in Thailand, E. validus in Pennsylvania and Paracremonium sp. recovered from PSHB in Vietnam were identified. F. euwallaceae was recovered from mycangia at higher frequencies and abundances in all hosts except R. communis, in which those of F. euwallaceae and P. pembeum were equal. P. pembeum was relatively more abundant within gallery walls of A. negundo and R. communis. In all hosts combined F. euwallaceae was relatively more abundant within PSHB heads than gallery walls. All three fungi grew at different rates and colonized inoculated excised stems of P. americana and A. negundo. P. pembeum produced longer lesions than F. euwallaceae and G. euwallaceae on inoculated avocado shoots. Results indicate PSHB is associated with a dynamic assemblage of mycangial fungal associates that pose additional risk to native and nonnative hosts in California.

Keywords: ambrosia fungi; avocado; fungal associates; fungal pathogens; mycangia; symbiosis.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Animals
Ascomycota / classification*
Ascomycota / genetics
Ascomycota / isolation & purification*
California
Coleoptera / microbiology*
Female
Persea / microbiology
Phylogeny
Plant Diseases / microbiology