Department of Plant Pathology, Iowa State University, Ames, IA, USA.
Mycologia. 2011 Sep-Oct;103(5):1028-36. doi: 10.3852/10-417. Epub 2011 Apr 6.
The laurel wilt pathogen Raffaelea lauricola was hypothesized to have been introduced to the southeastern USA in the mycangium of the redbay ambrosia beetle, Xyleborus glabratus, which is native to Asia. To test this hypothesis adult X. glabratus were trapped in Taiwan and on Kyushu Island, Japan, in 2009, and dead beetles were sent to USA for isolation of fungal symbionts. Individual X. glabratus were macerated in glass tissue grinders, and the slurry was serially diluted and plated onto malt agar medium amended with cycloheximide, a medium semiselective for Ophiostoma species and their anamorphs, including members of Raffaelea. R. lauricola was isolated from 56 of 85 beetles in Taiwan and 10 of 16 beetles in Japan at up to an estimated 10 000 CFUs per beetle. The next most commonly isolated species was R. ellipticospora, which also has been recovered from X. glabratus trapped in the USA, as were two other fungi isolated from beetles in Taiwan, R. fusca and R. subfusca. Three unidentified Raffaelea spp. and three unidentified Ophiostoma spp. were isolated rarely from X. glabratus collected in Taiwan. Isolations from beetles similarly trapped in Georgia, USA, yielded R. lauricola and R. ellipticospora in numbers similar to those from beetles trapped in Taiwan and Japan. The results support the hypothesis that R. lauricola was introduced into the USA in mycangia of X. glabratus shipped to USA in solid wood packing material from Asia. However differences in the mycangial mycoflora of X. glabratus in Taiwan, Japan and USA suggest that the X. glabratus population established in USA originated in another part of Asia.
被认为引入美国东南部的月桂叶枯萎病原体拉菲尔榕小卷蛾（Raffaelea lauricola），其介体是原产于亚洲的红树南美象甲（Xyleborus glabratus）。为了验证这一假说，2009 年在台湾和日本九州岛诱捕了成年红树南美象甲，并将死亡的甲虫送往美国以分离真菌共生体。将单个红树南美象甲在玻璃组织研磨器中粉碎，将浆糊连续稀释并涂在添加环己酰亚胺的麦芽琼脂培养基上，该培养基对半知菌，包括拉菲尔榕小卷蛾在内的及其无性型是半选择性的。从台湾的 85 只甲虫中分离到了 56 株 R. lauricola，从日本的 16 只甲虫中分离到了 10 株，每只甲虫的估计数量为 10 000 CFUs。下一个最常分离到的物种是 R. ellipticospora，该菌也从在美国诱捕的红树南美象甲中分离到，此外，还从台湾的甲虫中分离到了另外两种真菌，R. fusca 和 R. subfusca。从台湾收集的红树南美象甲中很少分离到三种未鉴定的拉菲尔榕小卷蛾和三种未鉴定的奥氏蜜环菌。在美国佐治亚州同样诱捕的甲虫中，从甲虫中分离到了 R. lauricola 和 R. ellipticospora，数量与从台湾和日本捕获的甲虫相似。结果支持了拉菲尔榕小卷蛾是通过从亚洲运往美国的实木质包装材料中的红树南美象甲的介体传入美国的假说。然而，台湾、日本和美国红树南美象甲的介体真菌区系存在差异，表明在美国建立的红树南美象甲种群起源于亚洲的另一个地区。
