Emanuel Isabel Brooke, Ralston Timothy I, Chatfield James, Draper Erik, Veil Jason, Peduto Hand Francesca
The Ohio State University, 2647, Plant Pathology, Columbus, Ohio, United States;
The Ohio State University, 2647, Extension, Wooster, Ohio, United States;
Plant Dis. 2021 Mar 17. doi: 10.1094/PDIS-12-20-2612-PDN.
Japanese apple rust, caused by the heteroecious and demicyclic rust fungus Miyabe ex G. Yamada, can affect juniper ( spp.), where the telial stage of this disease occurs, and apple or crabapple ( spp.), where the aecial stage occurs (Yun, 2010). Leaf samples displaying symptoms and signs of rust disease were collected in August 2020 from 14 different crabapple cultivars ('Amerspirzam' [American Spirit], 'Amsalzam' [American Salute™], 'Excazam' [Excalibur], 'Guinzam' [Guinevere], 'Hargozam' [Harvest Gold], 'Mary Potter', 'Orange Crush', 'Prairie Maid', 'Professor Sprenger', 'Pumpkin Pie', 'Rawhide', 'Select A' [Firebird], 'Shotizam' [Show Time], 'Sinai Fire') in the crabapple research plot of Secrest Arboretum (Crablandia) in Wooster, OH. Samples displayed adaxial leaf lesions with brown necrotic centers surrounded by a red-yellow coloration, corresponding on the abaxial side to lesions containing brown-orange aecia, producing aeciospores, surrounded by a dark red-orange coloration (Supplemental Figure 1). One to multiple lesions were present per symptomatic leaf. DNA was extracted from symptomatic leaf tissue containing fungal material on all 14 cultivars using the DNeasy Plant Mini Kit (QIagen) and the D1/D2 region of the 28S rDNA was amplified using primers NL1 and NL4 (O'Donnell 1993) according to Dagar et al. (2011). GenBank BLAST sequence analysis of all 14 sequences resulted in 99.83-100% sequence identity to with with 99% query coverage (MN605735). Sequences from all samples were deposited in GenBank under Accession Nos. MW131119.2-131125.2 and MW131127.2-131132.2. Morphological features were characterized for the three representative cultivars 'Amerspirzam' (American Spirit), 'Orange Crush' and 'Pumpkin Pie' (Supplemental Figure 2). Aecia were hypophyllous, roestelioid, with cornute, yellow-brown, peridia with lacerate sides. Peridial cells appeared yellow and were long-linear rhomboid, verrucose with long papillae, smooth outer walls and echinulate inner walls, measuring 45 - 78 × 16 - 27 µm (average 65 × 21 µm), 51 - 82 × 16 - 30 µm (average 66 × 23 µm), and 47 - 93 × 14 - 31 µm (average 64 × 24 µm), respectively (n=50 per cultivar). Aeciospores were globose, 20 - 26 × 18 - 24 µm (average 23 µm × 20 µm), 21 - 28 µm × 19 - 24 µm (average 24 µm × 21 µm), and 21 - 27 µm × 18 - 23 µm (average 23 µm × 21 µm), respectively, with a slightly coronate surface and dark yellow walls 1.6 - 2.7 µm (average 2 µm), 1.4 - 2.4 µm (average 2 µm), and 1.3 - 2.5 µm (average 1.8 µm) thick, respectively (n=50 per cultivar). The telia, known to occur on spp., were not observed. Specimens from these three cultivars were deposited into the U.S. National Fungus Collections (BPI 923889, 923888, 923887). Japanese apple rust has been officially reported in parts of Eastern Asia and the Eastern United States and is also known to be present in parts of Far East Russia and Ontario, Canada (Yun et al., 2009; CAB International, 2008). This report constitutes the first confirmed instance of causing Japanese apple rust in Ohio. Because infected trees tend to be highly symptomatic, this disease poses a significant threat to the nursery and landscape industries as it can decrease the market value of ornamental varieties and affect yield and crop quality in varieties used for fruit production.
日本苹果锈病由山田耕太郎（G. Yamada）鉴定的山田宫部锈菌（Miyabe ex G. Yamada）引起，该锈菌为转主寄生菌，具有半生活史。它可侵染桧柏属（spp.）植物，在其上产生冬孢子堆阶段的病症，还可侵染苹果或海棠属（spp.）植物，在其上产生性孢子器阶段的病症（Yun，2010年）。2020年8月，从俄亥俄州伍斯特市塞克雷斯特树木园（Crablandia）的海棠研究区14个不同的海棠品种（‘Amerspirzam’[美国精神]、‘Amsalzam’[美国致敬™]、‘Excazam’[王者之剑]、‘Guinzam’[桂妮薇儿]、‘Hargozam’[丰收金]、‘Mary Potter’、‘Orange Crush’、‘Prairie Maid’、‘Professor Sprenger’、‘Pumpkin Pie’、‘Rawhide’、‘Select A’[火鸟]、‘Shotizam’[表演时刻]、‘Sinai Fire’）上采集了显示锈病症状和病征的叶片样本。样本叶片正面出现病斑，病斑中心为褐色坏死，周围有红黄相间的色泽，叶片背面相应位置为病斑，病斑内含有褐色橙色的性孢子器，产生性孢子，周围有深红色橙色的色泽（补充图1）。每个有症状的叶片上有1至多个病斑。使用DNeasy植物微量提取试剂盒（QIagen）从所有14个品种有症状且含有真菌材料叶片组织中提取DNA，并根据Dagar等人（2011年）的方法，使用引物NL1和NLr4扩增28S rDNA的D1/D2区域。对所有14个序列进行GenBank BLAST序列分析，结果显示与序列（MN605735）的序列同一性为99.83 - 100%，查询覆盖率为99%。所有样本的序列已存入GenBank，登录号为MW131119.2 - 131125.2和MW131127.2 - 131132.2。对三个代表性品种‘Amerspirzam’（美国精神）、‘Orange Crush’和‘Pumpkin Pie’的形态特征进行了描述（补充图2）。性孢子器生于叶背（下叶），呈柱状，具角状，黄褐色，包被侧面撕裂。包被细胞呈黄色，为长线性菱形，具疣，有长乳头，外壁光滑，内壁具小刺，大小分别为45 - 78×16 - 27 µm（平均65×21 µm）、51 - 82×16 - 30 µm（平均66×23 µm）和47 - 93×14 - 31 µm（平均64×24 µm）（每个品种n = 50）。性孢子呈球形，大小分别为20 - 26×18 - 24 µm（平均23 µm×20 µm）、21 - 28 µm×19 - 24 µm（平均24 µm×21 µm）和21 - 27 µm×18 - 23 µm（平均23 µm×21 µm），表面略有冠状突起，黄色壁厚1.6 - 2.7 µm（平均（2 µm）、1.4 - 2.4 µm（平均2 µm）和1.3 - 2.5 µm（平均1.8 µm）（每个品种n = 50）。已知在桧柏属植物上产生的冬孢子堆未被观察到。这三个品种的标本已存入美国国家真菌收藏库（BPI 923889、923888、923887）。日本苹果锈病在东亚部分地区和美国东部已被正式报道，在俄罗斯远东部分地区和加拿大安大略省也有发现（Yun等人，2009年；国际应用生物科学中心，2008年）。本报告是俄亥俄州首次确认由引起日本苹果锈病的实例。由于受感染树木往往症状明显，这种病害对苗圃和园林产业构成重大威胁，因为它会降低观赏品种的市场价值，并影响用于水果生产品种的产量和作物品质。
