Oren Emel, Klingeman William, Gazis Romina, Moulton John, Lambdin Paris, Coggeshall Mark, Hulcr Jiri, Seybold Steven J, Hadziabdic Denita
Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN, United States of America.
Department of Plant Sciences, University of Tennessee, Knoxville, TN, United States of America.
PLoS One. 2018 Jan 5;13(1):e0185087. doi: 10.1371/journal.pone.0185087. eCollection 2018.
Thousand Cankers Disease (TCD) of Juglans and Pterocarya (Juglandaceae) involves a fungal pathogen, Geosmithia morbida, and a primary insect vector, Pityophthorus juglandis. TCD was described originally from dying Juglans nigra trees in the western United States (USA), but it was reported subsequently from the eastern USA and northern Italy. The disease is often difficult to diagnose due to the absence of symptoms or signs on the bark surface of the host. Furthermore, disease symptoms can be confused with those caused by other biotic and abiotic agents. Thus, there is a critical need for a method for rapid detection of the pathogen and vector of TCD. Using species-specific microsatellite DNA markers, we developed a molecular protocol for the detection of G. morbida and P. juglandis. To demonstrate the utility of the method for delineating TCD quarantine zones, we tested whether geographical occurrence of symptoms and signs of TCD was correlated with molecular evidence for the presence of the cryptic TCD organisms. A total of 1600 drill cores were taken from branch sections collected from three regions (n = 40 trees for each location): California-J. hindsii (heavy disease incidence); Tennessee-J. nigra (mild disease incidence); and outside the known TCD zone (Missouri-J. nigra, no record of the disease). California samples had the highest incidence of the TCD organisms (85%, 34/40). Tennessee had intermediate incidence (42.5%, 17/40), whereas neither organism was detected in samples from Missouri. The low cost molecular protocol developed here has a high degree of sensitivity and specificity, and it significantly reduces sample-processing time, making the protocol a powerful tool for rapid detection of TCD.
胡桃科核桃属和枫杨属植物的千溃疡病（TCD）涉及一种真菌病原体——致病地丝霉，以及一种主要昆虫媒介——核桃小蠹。千溃疡病最初是在美国西部垂死的黑核桃树上被发现的，但随后在美国东部和意大利北部也有报道。由于寄主树皮表面没有症状或迹象，这种病害通常很难诊断。此外，病害症状可能与其他生物和非生物因素引起的症状相混淆。因此，迫切需要一种快速检测千溃疡病病原体和媒介的方法。我们利用物种特异性微卫星DNA标记，开发了一种检测致病地丝霉和核桃小蠹的分子检测方法。为了证明该方法在划定千溃疡病检疫区方面的实用性，我们测试了千溃疡病症状和体征的地理分布是否与隐匿性千溃疡病生物体存在的分子证据相关。我们从三个地区采集的树枝段上共取了1600个钻芯样本（每个地点40棵树）：加利福尼亚州——黑胡桃（病害发生率高）；田纳西州——黑核桃（病害发生率低）；以及已知千溃疡病区域之外（密苏里州——黑核桃，无该病记录）。加利福尼亚州的样本中千溃疡病生物体的发生率最高（85%，34/40）。田纳西州的发生率处于中等水平（42.5%，17/40），而密苏里州的样本中未检测到任何一种生物体。这里开发的低成本分子检测方法具有高度的敏感性和特异性，并且显著减少了样本处理时间，使其成为快速检测千溃疡病的有力工具。
