Purcifull D E, Hiebert E, Petersen M A, Simone G W, Kucharek T A, Gooch M D, Crawford W E, Beckham K A, De Sa P B
Department of Plant Pathology, University of Florida, Gainesville 32611-0680.
Plant Dis. 1998 Dec;82(12):1386-1390. doi: 10.1094/PDIS.1998.82.12.1386.
Conspicuous, unusual nuclear inclusions in stained epidermal strips of leaves implicated a virus (designated isolate 2932) as the cause of foliar mosaic in a watermelon plant (Citrullus lanatus) received for analysis from South Florida in 1990. In greenhouse tests, mechanically inoculated plants of Cucurbita pepo (Small Sugar pumpkin and Early Prolific Straightneck squash) and watermelon (Crimson Sweet) developed mosaic or mottle symptoms. Isolate 2932 caused foliar symptoms in 16 cultivars of Cucurbita pepo, including Freedom II and Prelude II, and in six cultivars of watermelon. None of five cultivars of melon (Cucumis melo) or 11 cultivars of cucumber (Cucumis sativus) developed consistent, distinctive symptoms, but all of these cultivars were systemically infected based on back-inoculations to squash. No systemic infection of mechanically inoculated plants of 25 species representing 13 noncucurbitaceous plant families was detected. Crystalline nuclear inclusions, cytoplasmic amorphous inclusions, and cytoplasmic cylindrical inclusions were detected by light and electron microscopy in leaf tissues of infected squash and watermelon. Electron microscopy of squash leaf extracts revealed filamentous particles, and 86% of 159 particles measured ranged from 800 to 890 nm in length. The virus was transmitted in a nonpersistent manner by Myzus persicae from squash to squash in two of three trials. Immunodiffusion tests with polyclonal antisera prepared to partially purified 2932 or its capsid protein showed that the isolate was antigenically different from papaya ringspot virus type W, watermelon mosaic virus 2, and zucchini yellow mosaic virus. In limited testing of field samples of squash and watermelon since 1990, no additional isolates of the 2932 type have been found. The characteristics of isolate 2932 obtained thus far indicate that it is a distinct potyvirus. It is tentatively named watermelon leaf mottle virus to distinguish it from other potyviruses commonly isolated from cucurbits in Florida.
1990年从南佛罗里达州送来分析的一株西瓜植株（西瓜属）叶片的染色表皮条中出现明显、异常的核内含体，这表明一种病毒（命名为分离株2932）是叶片花叶病的病因。在温室试验中，用机械接种法接种西葫芦（小糖南瓜和早丰直颈南瓜）和西瓜（绯红甜蜜）植株后，它们出现了花叶或斑驳症状。分离株2932在16个西葫芦品种（包括自由二号和前奏二号）以及6个西瓜品种中引起了叶片症状。5个甜瓜品种（甜瓜属）和11个黄瓜品种（黄瓜属）均未出现一致、明显的症状，但根据对南瓜的回接结果，所有这些品种均被系统感染。在代表13个非葫芦科植物科的25种植物的机械接种植株中未检测到系统感染。通过光学显微镜和电子显微镜在受感染的南瓜和西瓜叶片组织中检测到了结晶核内含体、细胞质无定形内含体和细胞质柱状内含体。对南瓜叶提取物进行电子显微镜观察发现了丝状颗粒，在测量的159个颗粒中，86%的长度在800至890纳米之间。在三项试验中的两项试验中，桃蚜以非持久性方式将该病毒从南瓜传播到南瓜。用针对部分纯化的2932或其衣壳蛋白制备的多克隆抗血清进行免疫扩散试验表明，该分离株在抗原性上与西瓜花叶病毒W型、西瓜花叶病毒2型和小西葫芦黄花叶病毒不同。自1990年以来，在对南瓜和西瓜田间样本进行的有限检测中，未发现2932型的其他分离株。迄今为止获得的分离株2932的特征表明它是一种独特的马铃薯Y病毒。暂时将其命名为西瓜叶斑驳病毒，以将其与佛罗里达州通常从葫芦科植物中分离出的其他马铃薯Y病毒区分开来。
