XYLELLA FASTIDIOSA: ITS BIOLOGY, DIAGNOSIS, CONTROL AND RISKS
XYLELLA FASTIDIOSA: ITS BIOLOGY, DIAGNOSIS, CONTROL AND RISKS
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DOI：
10.4454/jpp.v92i1sup.2504
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发表时间：
2010-09
影响因子：
2.2
通讯作者：
J. Janse;A. Obradović
中科院分区：
文献类型：
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作者：
J. Janse;A. Obradović
细菌Xylella fastidiosa、xylem-inhabiting vector-transmitted,革兰氏阴性,非常缓慢的增长细菌,是培养和正确地描述在1987年首次在美国是皮尔斯病的原因(PD)的葡萄藤,葡萄(1884年疾病已经观察到)和虚假的原因桃疾病(产后抑郁症)的桃子,碧桃(疾病观察1890年在美国)和1993年在巴西柑橘杂色萎黄病的原因(CVC)或柑橘X疾病。此外，还发现该细菌还能引起一系列所谓的叶枯病，包括杏仁李的杏仁叶枯病或ALS，家李的李子叶枯病或PLS，槭属，山核桃，巴西的小咖啡（CLC， 1995年分离，对柑橘也有致病性），螺旋树，桑树，夹竹桃（OLS），西方Platanus occidentalis，栎树和美洲榆。它也感染苜蓿（矮苜蓿）和长春花（萎蔫症状）。许多野生植物可能携带病原体，但通常没有表现出症状，如草、莎草和树木。给出了主要主机的列表。所有这些疾病都不是种子传播的，主要发生在热带/亚热带地区，尽管叶子焦枯病也发生在寒冷得多的气候中，例如北美东部至加拿大的橡树叶子焦枯病。已经描述了几种致病的细菌品种，它们通常是宿主特异性的（例如，PD菌株如果引入桃或李不会引起疾病）。以下亚种已被描述：(i)苛养木杆菌亚种。苛性虫（错误命名为X. f.亚种）piercei)， PD和LSA，来自栽培葡萄，苜蓿，杏仁和枫的菌株；（ii）苛养X.；多品种、PPD、PLS、桃、榆、梅、鸽葡萄、梧桐和杏仁品种；（iii）苛养X.；pauca， CVC，来自柑橘的菌株，可能还有来自咖啡的菌株（CLC）；（iv）苛养X.；夹竹桃（Nerium oleander， OLS）菌株sandyi；(v)苛养X.；tashke，来自观赏树Chitalpa tashkentensis的菌株。病媒主要是没有潜伏期的神枪手虫和蛙虫或吐痰虫（蝉虫科），并且没有细菌的跨静或跨卵巢传播。该病原体在成年病媒中持续存在，并有能力在前肠中繁殖。在北美，主要的病媒（除非特别说明）是Cuerna costalis (PPD), Draculacephala minerva（绿色神枪手）在加州的ALS中也很重要；蓝绿色神枪手（Graphocephala atropunctata），在介绍玻璃翼神枪手之前最重要的；G. versuta (PPD)；蜜果，效率最高；玻璃翅神射手鸟[原为玻璃翅神射手鸟]；黑锥虫（PPD）、黑锥虫（PPD）、黑锥虫（PPD）、红头神枪手（原红头神枪手）。巴西的CVC病媒有在叶片外部产卵的末端Acrogonia terminalis、costalimai Dilobopterus和Oncometopia fascialis。欧洲当地可能的病媒是绿蝉和草地吐痰虫。fastidiosa在美国西南部是一种新出现的威胁，主要是由于最近建立的玻璃体绦虫，提供比当地媒介更有效的传播，并导致非常严重的葡萄藤，ALS和OLS PD暴发。GWSS最早可能是以植物卵的形式进入加州的。卵沉积在植物组织中。在中美洲和南美洲，由于CVC在柑橘中的迅速蔓延（很可能是通过感染的种植材料的分布），X. fastidiosa已经变得非常有害，导致该地区超过三分之一的树木出现CVC症状，咖啡中也有CLC。在欧洲，根据疾病症状观察，到目前为止，只有少数未经证实的报告称，在科索沃[在Janse（2006年）被错误地称为斯洛文尼亚]和法国的葡萄藤中存在苛养弧菌。由于X. fastidiosa有150多个寄主，其中许多寄主，包括葡萄种植材料，过去和现在都是进口的，因此引进风险（特别是潜伏形式）不可低估。由于没有合适的媒介，所以没有苛养x虫引起的疾病。但也不能排除病原和病媒通过植物材料传入的可能性。此外，本地蝉科（见上文）也可能成为（潜在的）传播媒介。因此，在EPPO地区，鼠疫螺旋体呈A1检疫状态，而以杏仁、桃子和李子为食，宿主范围非常大的玻氏螺旋体最近被列入EPPO警戒名单。与美国北部地区一样，欧洲的葡萄品种非常容易感染镰状弧菌，如果能在南欧冬季存活下来的病媒介在野生宿主（例如，野生和国内的李子和野生樱桃是美国无症状的宿主）中建立起来，并导致春季感染，这确实是一种风险，这种感染很可能持续数年。同样的风险也适用于柑橘类（甜橙、柑橘和橘子）和其他寄主，如在欧洲东南部和西南部广泛种植的杏仁、李子和桃子，特别是在温暖的地中海盆地（那里有温暖的夜晚、定期降雨/高湿度和长生长季节的有利条件）。指出了防止传入和控制最终爆发的可能方法。结论：对欧洲来说，苦毒X. fastidiosa不仅是葡萄和柑橘的威胁，而且是核果（杏仁、桃、李）和夹竹桃的威胁（如GWSS喜欢以夹竹桃为食），一旦形成就很难阻止进入，也很难控制，值得比现在更加重视。欧洲葡萄的抗性很少，甚至没有。病媒控制在美国被证明不是很有效。将植物保持在最佳条件下的栽培措施很重要，但还不够，使用无毒菌株进行交叉保护仍处于起步阶段。
The bacterium Xylella fastidiosa, a xylem-inhabiting, vector-transmitted, Gram-negative, very slow growing bacterium, was cultured and properly described for the first time in 1987 in the USA as the cause of Pierce’s disease (PD) of grapevine, Vitis vinifera (disease observed already in 1884) and as the cause of phony peach disease (PPD) in peach, Prunus persica (disease observed in 1890 in the USA) and in 1993 in Brazil as the cause of citrus variegated chlorosis (CVC) or citrus X disease. Moreover, it was found that the bacterium also causes a number of so-called leaf scorch diseases in Prunus spp. (including almond leaf scorch or ALS in Prunus amygdalus and plum leaf scald or PLS in Prunus domestica), Acer spp., Carya illinoinensis (pecan), Coffea arabica (CLC, in Brazil isolated in 1995 and also pathogenic to Citrus), Hedera helix, Morus rubra, Nerium oleander (OLS), Platanus occidentalis, Quercus spp., and Ulmus americana. It infects also Medicago sativa (alfalfa dwarf) and Vinca major (wilting symptoms). Many wild plants may carry the pathogen with, but more often without showing symptoms, such as grasses, sedges and trees. A list of main hosts is presented. All these diseases are not seed-borne and occur mainly in tropical/subtropical areas, although leaf scorch diseases also occur in much colder climate, e.g. oak leaf scorch in eastern North America up to Canada. Several pathogenic varieties of the bacterium have been described, that are often hostspecific (e.g., the PD strain will not cause disease if introduced to peach or plum). The following subspecies have been described: (i) Xylella fastidiosa subsp. fastidiosa (erroneously named X. f. subsp. piercei), PD and LSA, strains from cultivated grape, alfalfa, almond, and maple; (ii) X. fastidiosa subsp. multiplex, PPD, PLS, strains from peach, elm, plum, pigeon grape, sycamore and almond; (iii) X. fastidiosa subsp. pauca, CVC, strains from citrus and probably those from coffee (CLC); (iv) X. fastidiosa subsp. sandyi, strains from Nerium oleander (OLS); (v) X. fastidiosa subsp. tashke, strains from the ornamental tree Chitalpa tashkentensis. Vectors are mainly sharpshooters and froghoppers or spittlebugs (Cicadellidae) that lack a latent period, and have no transstadial or transovarial transmission of the bacterium. The pathogen shows persistence in the vector adults, and ability to multiply in the foregut. In North America main vectors (for PD unless indicated) are Cuerna costalis (PPD), Draculacephala minerva (green sharpshooter) important also in ALS in California; Graphocephala atropunctata (blue-green sharpshooter), most important before the introduction of the glassy winged sharpshooter; G. versuta (PPD); Hordnia circellata, most efficient; Homalodisca vitripennis [formerly H. coagulata (glassy-winged sharpshooter or GWSS)]; H. insolita (PPD), Oncometopia nigricans, O. orbona (PPD), Xyphon fulgida [formerly Carneocephala fulgida (red-headed sharpshooter)]. CVC vectors in Brazil are Acrogonia terminalis, that lays eggs externally on leaves, Dilobopterus costalimai and Oncometopia fascialis. Local possible vectors for Europe are Cicadella viridis and Philaenus spumarius (meadow spittle bug). X. fastidiosa is an emerging threat in the south-west USA, mainly due to recent establishment of H. vitripennis, providing much more efficient transmission than local vectors, and leading to very serious outbreaks of PD in grapevine, ALS and OLS. GWSS probably first entered California as eggs in plants. The eggs are deposited into plant tissues. In Central and South America X. fastidiosa has become very noxious due to the rapid expansion (most likely via distribution of infected planting material) of CVC in Citrus, leading to more than a third of all trees in the area having symptoms of CVC, and CLC in coffee. For Europe there are until now only a few unconfirmed reports of the presence of X. fastidiosa in grapevine from Kosovo [erroneously mentioned as Slovenia in Janse (2006)] and in France, based on disease symptoms observation. Since X. fastidiosa has more that 150 hosts and many of them, including Vitis planting material, were and are imported, risk of introduction (especially in latent form) must not be underestimated. Absence of the diseases caused by X. fastidiosa will mainly be due to the absence of suitable vectors. However, introduction of the pathogen and vectors with plant material can not be excluded for certain. More- over, also local Cicadellidae (see above) could become (potential) vectors. Therefore, X. fastidiosa has the A1 quarantine status in the EPPO region and H. vitripennis, that has a very large host range and also feeds on almond, peach and plum, was recently put on the EPPO alert list. As in the more northern parts of the USA, Vitis varieties in Europe are very susceptible to X. fastidiosa and this is really a risk should a vector that could survive the winters of southern Europe become established, also in wild hosts (e.g. wild and domestic plums and wild cherry are symptomless reservoirs in the USA) and cause spring infections that would most likely to persist over the years. The same risk holds true for Citrus (sweet oranges, mandarins, and tangerines) and other hosts, such as almond, plum and peach that are widely grown in south-east and south-west Europe, especially in the warmer Mediterranean basin (where a disease-favourable combination of warm nights, regular rainfall/high humidity and long growing season, is present). Possible ways to prevent introduction and to control eventual outbreaks are indicated. The conclusion is that X. fastidiosa is a real and emerging threat for Europe, not only for Vitis and Citrus but also for stone fruits (almond, peach and plum) and oleander (e.g. GWSS likes to feed on oleander), that is difficult to prevent from entering and difficult to control once established, deserving more attention than up till now. Resistance in European grapes is scarce or even absent. Vector control proved not to be very effective in the USA. Cultural practices to keep plants in optimum condition are of importance, but not sufficient and the use of avirulent strains for cross-protection is still in its infancy.