Kim M-S, Hanna J W, Klopfenstein N B
Department of Forestry, Environment, and Systems, Kookmin University, Seoul, Korea 136-702.
USDA Forest Service, Rocky Mountain Research Station, Forestry Sciences Laboratory, 1221 South Main, Moscow, ID 83843.
Plant Dis. 2010 Dec;94(12):1503. doi: 10.1094/PDIS-07-10-0534.
The loss and decline of native tree species caused by invasive plant pathogens is a major threat to the endangered endemic forests of the Hawaiian Islands (3). Thus, it is critical to characterize existing pathogens to evaluate potential invasiveness. In August 2005, rhizomorphs and mycelial bark fans of genet HI-4 were collected from dead/declining, mature trees of introduced Monterey pine (Pinus radiata) on the southern flank of Mauna Kea, Hawaii (approximately 19°42'55″N, 155°26'48″W, elevation 2,175 m). In March of 2008, three additional genets (HI-11, HI-13, and HI-16) were collected as rhizomorphs at a site named Pu'u La'au (west slope of the Mauna Kea Forest Reserve area, approximately 19°50'00″N, 155°35'35″W, elevation 2,275 to 2,550 m), approximately 20 km west-northwest of the HI-4 collection. These genets were collected from apparently healthy loblolly pine (Pinus taeda) that were introduced, apparently healthy māmane (Sophora chrysophylla; an endemic tree species of Hawaii), dead and dying māmane, and apparently healthy Methley plum (Prunus cerasifera × Prunus salicina) that was planted. All isolates were determined to have identical sequences in the intergenic spacer-1 rDNA region (GenBank Accession No. DQ995357). On the basis of somatic paring tests against North American Armillaria tester strains and 99% nucleotide sequence identities to GenBank Accession Nos. AY190245 and AY190246, these isolates were identified as Armillaria gallica. Past surveys have noted A. mellea sensu lato and A. nabsnona on numerous hosts in Hawaii, including māmane (3,4). However, to our knowledge, this is the first confirmed report of A. gallica in Hawaii, where it was found on māmane, Monterey pine, loblolly pine, and Methley plum. A. gallica has been widely categorized as a beneficial saprophyte, an opportunistic pathogen, or an aggressive pathogen (2). A recent study suggests that A. gallica can be highly pathogenic in some areas of the eastern United States and it is an important component of forest decline (2), especially under increasing stressors such as climate change. The isolation of A. gallica from declining stands on both introduced and endemic hosts under drought conditions suggests this pathogen is a contributing factor to forest decline on the island of Hawaii. Because the māmane tree is an important component of the native forest stands and essential to the endangered palila bird (Loxioides bailleui), which feeds almost exclusively on its green seeds (1), continued monitoring of Armillaria root disease is warranted. References: (1) P. C. Banko et al. J. Chem. Ecol. 28:1393, 2002. (2) N. J. Brazee and R. L. Wick. For. Ecol. Manage. 258:1605, 2009. (3) R. E. Burgan and R. E. Nelson. USDA For. Serv. Tech. Rep. PSW-3, 1972. (4) J. W. Hanna et al. Plant Dis. 91:634, 2007.
入侵性植物病原体导致的本土树种损失和衰退，是夏威夷群岛濒危的地方性森林面临的主要威胁（3）。因此，鉴定现有病原体以评估其潜在入侵性至关重要。2005年8月，从夏威夷莫纳克亚山南侧死亡/衰退的成年引进蒙特里松（辐射松）树上采集到了HI-4遗传体的菌索和菌丝树皮扇（北纬约19°42'55″，西经155°26'48″，海拔2175米）。2008年3月，在名为普乌拉奥的地点（莫纳克亚山森林保护区西坡，北纬约19°50'00″，西经155°35'35″，海拔2275至2550米）又采集到了另外三个遗传体（HI-11、HI-13和HI-16）的菌索，该地点位于HI-4采集点西北偏西约20公里处。这些遗传体取自明显健康的引进火炬松、明显健康的马马内树（夏威夷金叶槐，夏威夷本土树种）、死亡和濒死的马马内树以及种植的明显健康的李梅（樱桃李×李）。所有分离株在基因间隔区-1核糖体DNA区域具有相同序列（GenBank登录号：DQ995357）。基于与北美蜜环菌测试菌株的体细胞配对试验以及与GenBank登录号AY190245和AY190246的99%核苷酸序列同一性，这些分离株被鉴定为高卢蜜环菌。过去的调查已注意到夏威夷众多寄主上存在广义的蜜环菌和纳氏蜜环菌，包括马马内树（3,4）。然而，据我们所知，这是高卢蜜环菌在夏威夷的首次确认报告，在夏威夷它被发现存在于马马内树、蒙特里松、火炬松和李梅上。高卢蜜环菌已被广泛归类为有益腐生菌、机会性病原体或侵袭性病原体（2）。最近的一项研究表明，高卢蜜环菌在美国东部的某些地区可能具有高度致病性，并且是森林衰退的一个重要因素（2），尤其是在气候变化等压力源不断增加的情况下。在干旱条件下，从引进寄主和本土寄主的衰退林分中分离到高卢蜜环菌，这表明该病原体是夏威夷岛森林衰退的一个促成因素。由于马马内树是本土林分的重要组成部分，并且对濒危的帕利拉鸟（贝利氏管舌鸟）至关重要，帕利拉鸟几乎完全以其绿色种子为食（1），因此有必要持续监测蜜环菌根腐病。参考文献：（1）P. C. 班科等人，《化学生态学杂志》28:1393，2002年。（2）N. J. 布拉齐和R. L. 威克，《森林生态与管理》258:1605，2009年。（3）R. E. 伯根和R. E. 纳尔逊，美国农业部森林服务技术报告PSW-3，1972年。（4）J. W. 汉纳等人，《植物病害》91:634，2007年。
