Úrbez-Torres J R, Peduto F, Rooney-Latham S, Gubler W D
Department of Plant Pathology, University of California, Davis 95616.
California Department of Food and Agriculture, 3294 Meadowview Rd., Sacramento 95832.
Plant Dis. 2010 Jun;94(6):785. doi: 10.1094/PDIS-94-6-0785A.
The botryosphaeriaceous fungus Diplodia corticola A. J. L. Phillips, Alves & Luque was shown to be the most prevalent canker and dieback pathogen in cork oaks (Quercus suber L.) in the Iberian Peninsula causing a general decline of the trees as a consequence of canker formation in the trunks (1). In addition, D. corticola has been recently reported as a grapevine pathogen causing cankers in the vascular tissue of 1-year-old canes, spurs, and cordons in Texas (3). In 1998, Jacobs and Rehner reported one isolate of D. corticola from oak in California, but no information regarding the oak species from which the isolate was obtained and its virulence were available in the study (2). In 2009, D. corticola was isolated on potato dextrose agar (PDA) amended with 0.01% tetracycline hydrochloride from symptomatic grapevine cordons and on acidified PDA from the trunk of a canyon live oak tree from Sonoma and Plumas counties, respectively. Two grapevine isolates (UCD1260So and UCD1275So) and one oak isolate (CDFA519) were examined and morphologically compared with previously identified D. corticola isolates CBS678.88 and UCD2397TX from cork oak from Spain and grapevine in Texas, respectively. D. corticola colonies from California were characterized by moderately fast-growing, dark olivaceous, and dense aerial mycelium on PDA. Conidia were obtained from pycnidia formed on pine needles placed on 2% water agar. Conidia were hyaline, contents granular, aseptate, thick walled, ellipsoidal, sometimes becoming dark brown and septate with age. Nucleotide sequences of three genes (ITS1-5.8S-ITS2, a partial sequence of the beta-tubulin gene BT2, and part of the translation elongation factor EF1-α) from D. corticola isolates UCD1260So, UCD1275So, and CDFA519 from California were amplified. All DNA sequences from grapevine and oak tree isolates from California showed 99 to 100% homology with D. corticola isolates previously identified and deposited into GenBank. All DNA sequences obtained from Californian isolates were also deposited into GenBank. Pathogenicity tests were conducted by inoculating detached Vitis vinifera cv. Red Globe dormant canes and canyon live oak branches with agar plugs of isolates UCD1260So, UCD1275So, and CDFA519 (10 inoculations per isolate per host) as described by Úrbez-Torres et al. (3). The same number of grapevine canes and oak branches were inoculated with noncolonized agar plugs as controls. Six weeks after inoculation, the extent of vascular discoloration that developed from the point of inoculation was measured. D. corticola isolates UCD1260So, UCD1275So, and CDFA519 caused an average vascular lesion length of 30.4, 29.6, and 24 mm and 15, 13.2, and 8.6 mm in grapevine dormant canes and oak branches, respectively. Furthermore, D. corticola isolates from grapevine were pathogenic in oak branches and vice versa. Reisolation of D. corticola from discolored vascular tissue of inoculated material was 100%. The extent of vascular discoloration from inoculated grapevine canes and oak branches was significantly greater (P < 0.05) compared with the controls (1.8 and 2 mm, respectively). No fungi were reisolated from the slightly discolored tissue of the controls. To our knowledge, this is the first report of D. corticola causing grapevine cankers and oak trunk cankers in California. References: (1) A. Alves et al. Mycologia 96:598, 2004. (2) K. A. Jacobs and S. A. Rehner. Mycologia 90:601, 1998. (3) J. R. Úrbez-Torres et al. Am. J. Enol. Vitic. 60:497, 2009.
葡萄座腔菌属真菌皮质色二孢菌（Diplodia corticola A. J. L. Phillips、Alves & Luque）被证明是伊比利亚半岛栓皮栎（Quercus suber L.）中最常见的溃疡和枝枯病病原体，由于树干上形成溃疡，导致树木普遍衰退（1）。此外，最近有报道称皮质色二孢菌是一种葡萄病原体，在得克萨斯州导致1年生新梢、短枝和结果母枝的维管组织出现溃疡（3）。1998年，雅各布斯和雷纳报道了从加利福尼亚州的橡树中分离出的一株皮质色二孢菌，但该研究中没有提供关于分离菌株所来自的橡树种类及其毒力的信息（2）。2009年，分别从有症状的葡萄结果母枝上的添加了0.01%盐酸四环素的马铃薯葡萄糖琼脂（PDA）以及索诺马县和普卢默斯县峡谷活橡树树干上的酸化PDA中分离出了皮质色二孢菌。对两株葡萄分离株（UCD1260So和UCD1275So）和一株橡树分离株（CDFA519）进行了检测，并与之前分别从西班牙栓皮栎和得克萨斯州葡萄中鉴定出的皮质色二孢菌分离株CBS678.88和UCD2397TX进行了形态学比较。加利福尼亚州的皮质色二孢菌菌落的特征是在PDA上生长速度适中、呈深橄榄色且气生菌丝浓密。分生孢子从置于2%水琼脂上的松针上形成的分生孢子器中获得。分生孢子无色透明，内含物颗粒状，无隔膜，壁厚，椭圆形，有时随着年龄增长会变成深褐色并产生隔膜。对来自加利福尼亚州的皮质色二孢菌分离株UCD1260So、UCD1275So和CDFA519的三个基因（ITS1 - 5.8S - ITS2、β - 微管蛋白基因BT2的部分序列以及翻译延伸因子EF1 - α的部分序列）的核苷酸序列进行了扩增。来自加利福尼亚州葡萄和橡树分离株的所有DNA序列与之前鉴定并保存在GenBank中的皮质色二孢菌分离株显示出99%至100%的同源性。从加利福尼亚州分离株获得的所有DNA序列也保存在了GenBank中。按照乌尔韦斯 - 托雷斯等人（3）所述的方法，通过用分离株UCD1260So、UCD1275So和CDFA519的琼脂块接种离体的酿酒葡萄品种红地球休眠新梢和峡谷活橡树树枝（每个分离株对每个宿主接种10次）进行致病性测试。用未接种的琼脂块接种相同数量的葡萄新梢和橡树树枝作为对照。接种六周后，测量从接种点开始出现的维管组织变色程度。皮质色二孢菌分离株UCD1260So、UCD1275So和CDFA519在葡萄休眠新梢和橡树树枝中分别导致平均维管病变长度为30.4、29.6和24毫米以及15、13.2和8.6毫米。此外，来自葡萄的皮质色二孢菌分离株对橡树树枝具有致病性，反之亦然。从接种材料变色的维管组织中重新分离出皮质色二孢菌的成功率为100%。与对照（分别为1.8和2毫米）相比，接种葡萄新梢和橡树树枝后维管组织变色程度显著更大（P < 0.05）。在对照的轻微变色组织中未重新分离到真菌。据我们所知，这是关于皮质色二孢菌在加利福尼亚州导致葡萄溃疡和橡树树干溃疡的首次报道。参考文献：（1）A. Alves等人，《真菌学》96:598，2004年。（2）K. A. Jacobs和S. A. Rehner，《真菌学》90:601，1998年。（3）J. R. Úrbez - Torres等人，《美国酿酒与葡萄栽培杂志》60:497，2009年。
