Utley Curtis, Nguyen Tivonne, Roubtsova Tatiana, Coggeshall Mark, Ford Tim M, Grauke L J, Graves Andrew D, Leslie Charles A, McKenna James, Woeste Keith, Yaghmour Mohammad A, Seybold Steven J, Bostock Richard M, Tisserat Ned
Bioagricultural Sciences and Pest Management, Colorado State University, Ft. Collins.
Department of Plant Pathology, University of California, Davis.
Plant Dis. 2013 May;97(5):601-607. doi: 10.1094/PDIS-07-12-0636-RE.
Thousand cankers disease (TCD) of walnut is a result of feeding in the phloem by the walnut twig beetle (WTB), Pityophthorus juglandis, and subsequent canker formation caused by Geosmithia morbida around galleries. TCD has caused extensive morbidity and mortality to Juglans nigra in the western United States and, in 2010, was discovered in the eastern United States, where the tree is a highly valuable timber resource. WTB and G. morbida also have been found in J. regia orchards throughout major production areas in California, and the numbers of damaged trees are increasing. We tested the susceptibility of walnut and hickory species to G. morbida in greenhouse and field studies. Carya illinoinensis, C. aquatica, and C. ovata were immune. All walnut species tested, including J. ailantifolia, J. californica, J. cinerea, J. hindsii, J. major, J. mandshurica, J. microcarpa, J. nigra, and J. regia, developed cankers following inoculation with G. morbida. J. nigra was the most susceptible, whereas J. major, a native host of the WTB and, presumably, G. morbida, had smaller and more superficial cankers. Canker formation differed among maternal half-sibling families of J. nigra and J. cinerea, indicating genetic variability in resistance to G. morbida. Our inoculation studies with G. morbida have corroborated many of the field observations on susceptibility of walnut and hickory species to TCD, although the ability of the WTB to successfully attack and breed in walnut is also an important component in TCD resistance.
核桃千溃疡病（TCD）是由核桃小蠹（WTB，即胡桃小蠹，Pityophthorus juglandis）在韧皮部取食，随后由围小丛壳菌（Geosmithia morbida）在蛀道周围形成溃疡所致。TCD已在美国西部导致黑核桃大量发病和死亡，2010年在东部地区也被发现，而东部地区的黑核桃是一种极具价值的木材资源。在加利福尼亚州主要产区的核桃果园中也发现了核桃小蠹和围小丛壳菌，且受害树木数量不断增加。我们在温室和田间研究中测试了核桃和山核桃属物种对围小丛壳菌的易感性。美国山核桃、水生山核桃和卵叶山核桃具有免疫性。所有测试的核桃物种，包括日本胡桃、加州核桃、灰核桃、辛氏核桃、大果核桃、胡桃楸、小果核桃、黑核桃和普通核桃，在接种围小丛壳菌后都形成了溃疡。黑核桃最易感，而大果核桃是核桃小蠹以及推测的围小丛壳菌的原生寄主，但溃疡较小且较浅。黑核桃和灰核桃的母系半同胞家系之间溃疡形成情况不同，这表明对围小丛壳菌的抗性存在遗传变异。我们对围小丛壳菌的接种研究证实了许多关于核桃和山核桃属物种对TCD易感性的田间观察结果，不过核桃小蠹成功侵袭和在核桃中繁殖的能力也是TCD抗性的一个重要组成部分。
