Yu L, Rarisara I, Xu S G, Wu X, Zhao J R
College of Agronomy/Urban Modern Agriculture Engineering Research Center, Kunming University, Kunming, 650214, China.
Department of Food Technology, Chulalongkorn University, Bangkok, Thailand.
Plant Dis. 2012 Nov;96(11):1697. doi: 10.1094/PDIS-05-12-0500-PDN.
Blueberry (Vaccinium spp.) production in southwest and northeast China has grown to over 100,000 ha in the last 20 years thanks to the fruit's high nutritional and economic value. As blueberry acreage increases, the diversity of diseases and challenges for control are gaining more attention. In August 2010, stem and branch blight occurred on Highbush Blueberries (Vaccinium corymbosum L.) at commercial farms in Lijiang and Zongdian, Yunnan Province (southwestern China), with crop damage ranging from 10 to 15%. Typical symptoms of the disease were blight and dieback on the stems with lesions extending along entire branches. Diseased samples (phloem and xylem sectors in the wood) were washed with running tap water, disinfected with 2% sodium hypochlorite, then 70% alcohol, rinsed in sterile distilled water, plated on potato dextrose agar (PDA), and incubated at 28°C. Fungal isolates developed copious, white aerial mycelium that became dark gray after 4 to 5 days and formed black pycnidia after 18 days. Conidia were hyaline, aseptate, thin walled, fusiform, and measured 21 to 27 × 4 to 6 μm. Identity was confirmed by analysis of the ribosomal DNA internal transcribed spacer region ITSI-5.8S -ITS2 with primers ITS1 and ITS4. BLAST searches showed 99% identity with Botryosphaeria dothidea isolates from GenBank (Accession Nos. AB693904 and JF800139). Representative sequences of B. dothidea from Highbush Blueberries from China were deposited into GenBank (Accession No. JX096631). On the basis of morphological and molecular results, the fungus isolated from diseased Highbush Blueberries stem was confirmed to be B. dothidea. Pathogenicity tests were conducted on 2-year-old blueberry seedlings (Highbush Blueberries). Mycelial plugs (2 to 3 mm in diameter) of B. dothidea from actively growing colonies (PDA) were applied to same-size bark wounds in the center of the stems. Inoculation wounds were wrapped with Parafilm. Control seedlings received sterile PDA plugs. Inoculated and control seedlings (five each) were kept in a greenhouse and watered as needed. After 12 days, all of the inoculated but none of the control blueberry seedlings showed dark vascular stem tissue. B. dothidea was reisolated from symptomatic tissues, thus fulfilling Koch's postulates. No symptoms were visible in the control seedlings. B. dothidea has been reported as a pathogen of sycamore (3), olives (1), and peach (2). However, no research has been conducted on stem blight of blueberry caused by B. dothidea in southwest or mainland China. To our knowledge, this is the first report of B. dothidea on blueberry in southwest China. References: (1) M. Chattaoui, et al. Plant Dis. 95:770, 2011. (2) Y. Ko et al. Plant Pathol. Bull. 1:70, 1992. (3) E. Turco, et al. Plant Dis. 90:1106, 2006.
由于蓝莓具有较高的营养和经济价值，在过去20年里，中国西南和东北地区的蓝莓（越橘属）种植面积已增长至超过10万公顷。随着蓝莓种植面积的增加，病害的多样性及防治挑战日益受到关注。2010年8月，中国西南部云南省丽江市和中甸县的商业农场里，高丛蓝莓（Vaccinium corymbosum L.）发生了茎枝枯萎病，作物损失率在10%至15%之间。该病的典型症状是茎部枯萎和枯死，病斑沿整个枝条扩展。将患病样本（木材中的韧皮部和木质部部分）用自来水冲洗，先用2%次氯酸钠消毒，再用70%酒精消毒，然后用无菌蒸馏水冲洗，接种到马铃薯葡萄糖琼脂（PDA）平板上，于28°C培养。真菌分离物产生大量白色气生菌丝体，4至5天后变为深灰色，18天后形成黑色分生孢子器。分生孢子无色，无隔膜，薄壁，梭形，大小为21至27×4至6μm。通过使用引物ITS1和ITS4对核糖体DNA内部转录间隔区ITSI - 5.8S - ITS2进行分析来确认其身份。BLAST搜索显示与来自GenBank的葡萄座腔菌（Botryosphaeria dothidea）分离物（登录号AB693904和JF800139）有99%的同源性。来自中国高丛蓝莓的葡萄座腔菌代表性序列已存入GenBank（登录号JX096631）。基于形态学和分子学结果，从患病高丛蓝莓茎中分离出的真菌被确认为葡萄座腔菌。对2年生蓝莓幼苗（高丛蓝莓）进行致病性测试。从活跃生长的菌落（PDA）中切取直径2至3毫米的葡萄座腔菌菌丝块，接种到茎中部相同大小的树皮伤口处。接种伤口用Parafilm包裹。对照幼苗接种无菌PDA块。接种和对照幼苗（各5株）置于温室中，按需浇水。12天后，所有接种的蓝莓幼苗均出现深色维管束茎组织，而对照幼苗均未出现。从有症状的组织中再次分离出葡萄座腔菌，从而满足了柯赫氏法则。对照幼苗未出现症状。葡萄座腔菌已被报道为悬铃木（参考文献(3)）、橄榄（参考文献(1)）和桃（参考文献(2)）的病原菌。然而，在中国西南部或中国大陆，尚未对由葡萄座腔菌引起的蓝莓茎枯病开展研究。据我们所知，这是中国西南部关于葡萄座腔菌侵染蓝莓的首次报道。参考文献：(1) M. Chattaoui等人，《植物病害》95:770，2011年。(2) Y. Ko等人，《植物病理学通报》1:70，1992年。(3) E. Turco等人，《植物病害》90:1106，2006年。
