Costa H S, Guzman A, Hernandez-Martinez R, Gispert C, Cooksey D A
Department of Entomology, University of California, Riverside, CA 92521, USA.
J Econ Entomol. 2006 Aug;99(4):1058-64. doi: 10.1603/0022-0493-99.4.1058.
Xylella fastidiosa Wells is a bacterial pathogen that causes a variety of plant diseases, including Pierce's disease (PD) of grapevine, almond leaf scorch, alfalfa dwarf, citrus variegated chlorosis, and oleander leaf scorch (OLS). Numerous strains of this pathogen have been genetically characterized, and several different strains occur in the United States. The dominant vector in southern California is the glassy-winged sharpshooter, Homalodisca coagulata (Say) (Hemiptera: Cicadellidae). The high mobility of this insect, and its use of large numbers of host plant species, provides this vector with ample exposure to multiple strains of X. fastidiosa during its lifetime. To learn more about the ability of this vector to acquire, retain, and transmit multiple strains of the pathogen, we developed a polymerase chain reaction (PCR)-based method to detect and differentiate strains of X. fastidiosa present in individual glassy-winged sharpshooter adults. Insects were sequentially exposed to plants infected with a PD strain in grapevine and an OLS strain in oleander. After sequential exposure, a few insects tested positive for both strains (7%); however, in most cases individuals tested positive for only one strain (29% PD, 41% OLS). In transmission studies, individual adults transmitted either the PD or OLS strain of the pathogen at a rate (39%) similar to that previously reported after exposure to a single strain, but no single individual transmitted both strains of the pathogen. PD and OLS strains of X. fastidiosa remained detectable in glassy-winged sharpshooter, even when insects were fed on a plant species that was not a host of the strain for 1 wk.
桑氏木质部小菌（Xylella fastidiosa Wells）是一种细菌病原体，可引发多种植物病害，包括葡萄的皮尔氏病（PD）、扁桃叶焦枯病、苜蓿矮化病、柑橘杂色黄化病和夹竹桃叶焦枯病（OLS）。该病原体的众多菌株已进行了基因特征分析，在美国存在几种不同的菌株。南加州的主要传播媒介是玻璃翅叶蝉，即凝翅扁头叶蝉（Homalodisca coagulata (Say)，半翅目：叶蝉科）。这种昆虫的高移动性以及它对大量寄主植物物种的利用，使得该传播媒介在其生命周期中有充足的机会接触多种桑氏木质部小菌菌株。为了更多地了解这种传播媒介获取、保留和传播多种病原体菌株的能力，我们开发了一种基于聚合酶链反应（PCR）的方法，用于检测和区分单个玻璃翅叶蝉成虫体内存在的桑氏木质部小菌菌株。昆虫依次接触感染了葡萄中PD菌株和夹竹桃中OLS菌株的植物。依次接触后，少数昆虫对两种菌株检测均呈阳性（7%）；然而，在大多数情况下，个体仅对一种菌株检测呈阳性（29%为PD，41%为OLS）。在传播研究中，单个成虫传播病原体的PD或OLS菌株的比例（39%）与之前接触单一菌株后报道的比例相似，但没有单个个体传播两种病原体菌株。即使昆虫以一种并非该菌株寄主的植物物种为食1周，桑氏木质部小菌的PD和OLS菌株在玻璃翅叶蝉体内仍可检测到。
