Viana F M P, Cardoso J E, Saraiva H A O, Ferreira M A S V, Mariano R L R, Trindade L C
Embrapa Agroindústria Tropical, Caixa Postal 3761, CEP 6060511-110, Fortaleza, CE Brazil.
Universidade Federal Rural de Pernambuco, Brazil.
Plant Dis. 2007 Oct;91(10):1361. doi: 10.1094/PDIS-91-10-1361C.
In 2003 and 2004, leaves and young fruits of cashew nut plants showing an undescribed disease symptom were observed on plants of an early-dwarf clone in a commercial orchard in Ceará and Piauí states in northeastern Brazil. Initial symptoms consisted of angular, water-soaked, dark-to-black spots on the leaf and at the mid-rib vein surrounding the leaf veins. Eventually, lesions also extended from the mid-rib to the secondary veins, delineating the vein system of the leaf. In young, green fruits, symptoms were large, dark, oily spots surrounded by conspicuous water-soaked areas. A yellow-pigmented colony was consistently recovered from the lesions on nutrient yeast-extract dextrose agar medium (3 g of meat extract, 5 g of peptone, 10 g of dextrose, 5 g of yeast extract, and 18 g of agar per liter). Physiological tests revealed colonies that were gram negative, strictly aerobic, oxidase negative, catalase positive, lacking fluorescent pigmentation on King's B medium, urea hydrolase negative, and able to grow on yeast dextrose calcium carbonate medium yielding yellow colonies. These tests indicated that the bacterium belonged to the genus Xanthomonas. PCR amplification of bacterial DNA using RST2 (1) and Xcv3R (3) primers resulted in identical band patterns to mango isolates Xanthomonas campestris pv. mangiferaeindicae. Restriction fragment length polymorphism analysis of PCR-amplified products of six isolates of X. campestris pv. mangiferaeindicae was conducted with HaeIII and showed different profile patterns on agarose gel, indicating genetic variability among these isolates. Pathogenicity was demonstrated by gently piercing and misting cashew leaves with a bacterial suspension adjusted to 10 CFU/ml. Inoculated plants were enclosed in plastic bags for 24 h and then incubated in a greenhouse (29 ± 1°C). Control plants were misted with sterile water and treated the same way. After 8 days, foliar symptoms similar to those observed in the field developed on all inoculated plants, and reisolated bacteria were characterized and found to be X. campestris pv. mangiferaeindicae. Control plants remained symptomless. To our knowledge, this is the first description of commercially grown cashew plants as host to X. campestris pv. mangiferaeindicae in Brazil. This disease may pose a serious problem to the cashew-growing industry in Brazil. This bacterial pathogen has been reported on mangoes (Mangifera indica) and cashew in India (2) under the former name of Pseudomonas mangiferae-indicae. References: (1) R. P. Leite, Jr. et al. Appl. Environ. Microbiol. 60:1068, 1994. (2) M. K. Patel et al. Curr. Sci. 17:189, 1948. (3) L. C. Trindade et al. Summa Phytopathol. 33:16, 2007.
2003年和2004年，在巴西东北部塞阿拉州和皮奥伊州的一个商业果园里，在一个早矮化克隆品种的腰果植株上，观察到呈现一种未描述病害症状的叶片和幼果。最初症状包括叶片上以及围绕叶脉的中脉处出现角状、水渍状、暗至黑色的斑点。最终，病斑也从中脉扩展至侧脉，勾勒出叶片的叶脉系统。在幼嫩的绿色果实上，症状表现为大的、深色的、油渍状斑点，周围有明显的水渍区域。在营养酵母提取物葡萄糖琼脂培养基（每升含3克肉提取物、5克蛋白胨、10克葡萄糖、5克酵母提取物和18克琼脂）上，始终能从病斑中分离出一个黄色色素菌落。生理测试显示，这些菌落革兰氏阴性、严格需氧、氧化酶阴性、过氧化氢酶阳性、在金氏B培养基上无荧光色素产生、尿素水解酶阴性，并且能够在酵母葡萄糖碳酸钙培养基上生长并产生黄色菌落。这些测试表明该细菌属于黄单胞菌属。使用RST2（1）和Xcv3R（3）引物对细菌DNA进行PCR扩增，得到的条带模式与芒果分离株野油菜黄单胞菌芒果致病变种相同。对六个野油菜黄单胞菌芒果致病变种分离株的PCR扩增产物进行HaeIII限制性片段长度多态性分析，在琼脂糖凝胶上显示出不同的图谱模式，表明这些分离株之间存在遗传变异性。通过用调整至10CFU/ml 的细菌悬液轻轻穿刺和喷雾腰果叶片来证明致病性。接种的植株用塑料袋包裹24小时，然后在温室（29±1°C）中培养。对照植株用无菌水喷雾并以相同方式处理。8天后，所有接种的植株都出现了与田间观察到的相似的叶片症状，重新分离出的细菌经鉴定为野油菜黄单胞菌芒果致病变种。对照植株保持无症状。据我们所知，这是巴西首次将商业种植的腰果植株描述为野油菜黄单胞菌芒果致病变种的寄主。这种病害可能给巴西的腰果种植产业带来严重问题。这种细菌病原体在印度曾以芒果假单胞菌的名称报道于芒果（芒果属）和腰果上（2）。参考文献：（1）R.P.Leite,Jr.等人，应用与环境微生物学60:1068,1994。（2）M.K.Patel等人，当前科学17:189,1948。（3）L.C.Trindade等人，植物病理学综述33:16,2007。
