First Report of the Root-Rot Pathogen, Armillaria Gallica, on Koa (acacia Koa) and ‘ōhi‘a Lehua (metrosideros Polymorpha) on the Island of Kaua‘i, Hawai‘i

HomePlant DiseaseVol. 101, No. 1First Report of the Root-Rot Pathogen, Armillaria gallica, on Koa (Acacia koa) and ‘Ōhi‘a Lehua (Metrosideros polymorpha) on the Island of Kaua‘i, Hawai‘i PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of the Root-Rot Pathogen, Armillaria gallica, on Koa (Acacia koa) and ‘Ōhi‘a Lehua (Metrosideros polymorpha) on the Island of Kaua‘i, Hawai‘iM.-S. Kim, N. R. Fonseca, R. D. Hauff, P. G. Cannon, J. W. Hanna, and N. B. KlopfensteinM.-S. KimSearch for more papers by this author, N. R. FonsecaSearch for more papers by this author, R. D. HauffSearch for more papers by this author, P. G. CannonSearch for more papers by this author, J. W. HannaSearch for more papers by this author, and N. B. KlopfensteinSearch for more papers by this authorAffiliationsAuthors and Affiliations M.-S. Kim , Department of Forestry, Environment and Systems, Kookim University, Seoul 02707, Korea N. R. Fonseca , Departamento de Fitopatologia, Universidade Federal de Viçosa, Minas Gerais, 36570-000, Brazil R. D. Hauff , Division of Forestry and Wildlife, Department of Land and Natural Resources, Honolulu, HI 96813 P. G. Cannon , USDA Forest Service, Forest Health Protection, Region 5, Vallejo, CA 94593 J. W. Hanna N. B. Klopfenstein , USDA Forest Service, Rocky Mountain Research Station, Moscow, ID 83843. Published Online:31 Oct 2016https://doi.org/10.1094/PDIS-07-16-1043-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Koa (Acacia koa) and ‘ōhi‘a lehua (Metrosideros polymorpha) are the two most dominant native tree species in Hawai‘i. Their populations are continuously decreasing, primarily because of forest disease (Dudley et al. 2007; Keith et al. 2015) and other biotic disturbances. In April 2015, Armillaria rhizomorphs were collected from woody hosts on the island of Kaua‘i, Hawai‘i. Based on somatic pairing tests, isolates were assigned to two genets or clones (Kōke‘e-3 and Nu‘alolo-2) of the same species. Subsequently, these two genets were identified as A. gallica on the basis of pairing against 18 tester isolates representing six North American Armillaria spp. and translation elongation factor 1α (tef1) nucleotide sequences (GenBank accession nos. KX772408 for Kōke‘e-3 and KX772409 for Nu‘alolo-2). From 15 replications of somatic incompatibility tests, both genets showed reasonably high intraspecific compatibility (colorless antagonism) with three A. gallica tester isolates (average 62%), but low compatibility with closely related Armillaria spp. (average 1 to 31%). Sequences of tef1 for both genets showed an identity of 98% (KF156775) and 97% (KF156772) to A. gallica with 99 to 100% coverage. In Hawai‘i, A. gallica has been reported on the Big Island of Hawai‘i on Monterey pine (Pinus radiata), loblolly pine (P. taeda), māmane (Sophora chrysophylla), and Methley plum (Prunus sp.) (Kim et al. 2010). This study identified four new host associations in Kaua‘i, but only two of these hosts showed both signs and symptoms of root disease. Genet Kōke‘e-3 comprised one isolate collected from a dying, mature koa tree in the west Pu‘u ka Pele Forest Reserve (22°05′38.34″ N, 159°41′27.42″ W, elevation 876 m) approximately 1.45 km northwest of Lua Reservoir. The crown of the koa tree showed severe dieback (>75% dead) with decayed roots and flaccid/senescing leaves. Genet Nu‘alolo-2 consisted of five isolates collected at the head of Nu‘alolo trail (22°07′46.08″ N, 159°39′35.82″ W, elevation 1,124 m), approximately 5.07 km northeast of the Kōke‘e-3 collection. These isolates were collected from koa and ‘ōhi‘a lehua with crown dieback/thinning and root decay, in addition to apparently healthy karaka nut (Corynocarpus laevigatus; introduced from New Zealand) and ‘āla‘a (Pouteria sandwicensis; endemic in Hawai‘i). Koa symptoms at Nu‘alolo trail were similar to those associated with the Kōke‘e-3 genet, except <25% of the crown was dead/dying at the time of collection. Above-ground symptoms on mature koa trees from each site were similar to koa-wilt disease caused by Fusarium oxysporum f. sp. koae (Dudley et al. 2007); however, the koa-wilt pathogen was not recovered from root samples from either tree. Interestingly, A. gallica genet Nu‘alolo-2 was collected from diseased ‘ōhi‘a lehua (50 cm dbh), symptomless karaka nut, and symptomless ‘āla‘a, which were all growing in close proximity. A. gallica has a wide host range, it displays diverse ecological behaviors, and phylogenetic studies suggest it likely comprises a species complex (Kim et al. 2012). It can act as an opportunistic and/or primary pathogen (Brazee and Wick 2009), especially under stressors, such as climate change. Although A. gallica was isolated from multiple hosts in forests of Kaua‘i and the Big Island of Hawai‘i, continued surveys are needed to document distribution of A. gallica on diverse native and exotic tree species throughout the Hawaiian Islands, especially in relation to climate change.References:Brazee, N. J., and Wick, R. L. 2009. For. Ecol. Manage. 258:1605. https://doi.org/10.1016/j.foreco.2009.07.016 Crossref, ISI, Google ScholarDudley, N. S., et al. 2007. Native. Plant J. 8:259. Crossref, Google ScholarKeith, L. M., et al. 2015. Plant Dis. 99:1276. https://doi.org/10.1094/PDIS-12-14-1293-PDN Link, ISI, Google ScholarKim, M.-S., et al. 2010. Plant Dis. 94:1503. https://doi.org/10.1094/PDIS-07-10-0534 Link, ISI, Google ScholarKim, M.-S., et al. 2012. Phytopathology 102:S4.63. Link, ISI, Google ScholarDetailsFiguresLiterature CitedRelated Vol. 101, No. 1 January 2017SubscribeISSN:0191-2917e-ISSN:1943-7692 Metrics Article History Issue Date: 22 Dec 2016Published: 31 Oct 2016First Look: 12 Sep 2016Accepted: 6 Sep 2016 Page: 255 Information© 2017 The American Phytopathological SocietyCited byArmillaria gallicaCABI Compendium, Vol. CABI CompendiumFirst Report of Armillaria Root Disease Pathogen, Armillaria gallica, on Rhododendron and Quercus rubra in Georgia, U.S.A.J. W. Hanna, N. B. Klopfenstein, M. M. Cram, R. O. Olatinwo, S. W. Fraedrich, and M.-S. Kim24 February 2021 | Plant Disease, Vol. 105, No. 4Molecular Genetic Approaches Toward Understanding Forest-Associated Fungi and Their Interactive Roles Within Forest Ecosystems4 May 2018 | Current Forestry Reports, Vol. 4, No. 2