The use of transmissible hypovirulence for the biological control of Ophiostoma, the causal agent of Dutch elm disease

美国榆树的自然种群和城市种群已经被荷兰榆树病（DED）的病原体--蛇舌属病原真菌所摧毁。 对这种病原体的控制集中在杀真菌剂以阻止真菌的生长或杀虫剂以控制昆虫媒介的传播，然而这两种选择都不是非常有效。一个有吸引力的替代使用化学农药或杀菌剂是一个有吸引力的生物控制的发展，O。新乌尔米。 这至少需要一种对真菌具有拮抗性的试剂，该试剂可传播给田间现存的真菌种群，并且非常特异性地使脱靶效应最小化。弱毒力是病原体对其宿主的毒力降低，并且可以由许多原因引起，包括线粒体DNA突变、核基因组突变或真菌病毒的存在。我们打算通过开发用于DED生物防治的工程化dsRNA载体的传染性疾病防治来扩展用于真菌病原体管理的传染性低毒力的应用。 通过真菌病毒诱导的弱毒力可以很容易地应用于O。作为加拿大西部疾病前线的目标种群，novo-ulmi基本上由两个非常大的克隆组成，营养体相容性障碍很少见。我们测定了一种新的双链RNA有丝分裂病毒OnuMV 1c的基因组序列。novo-ulmi在疾病的前线，并证明了菌株之间的传播。 存在于细胞质中的部分病毒已在密切相关的物种中描述，并预期可传播给O。新乌尔米。通过我们对O. Novo-Ulmi我们已经鉴定了几个被认为是致病性和真菌适合度所必需的基因座。 我们打算通过插入特异于已鉴定的O. novo-ulmi基因位点选择性下调对真菌存活至关重要的基因。利用RNAi技术构建低病毒基因工程菌，为真菌病害的生物防治提供了新的途径。

Natural and urban populations of the American elm have been devastated by pathogenic fungi of the genus Ophiostoma, the causal agent of Dutch elm disease (DED). Control of this pathogen has focused on fungicides to stem the growth of the fungus or pesticides to control the spread of the insect vector however neither option has been very effective. An attractive alternative to the use of chemical pesticides or fungicides is the development of a biological control for O. novo-ulmi. This requires, at minimum, an agent that is antagonistic to the fungus, is transmissible to extant populations of the fungus in the field, and is very specific to minimize off-target effects. Hypovirulence is the decreased virulence of a pathogen towards its host and can result from many causes including mitochondrial DNA mutations, nuclear genome mutations or the presence of mycoviruses. We intend to extend the application of transmissible hypovirulence for the management of fungal pathogens by the development of a transmissible disease control using engineered dsRNA vectors for the biological control of DED. Induction of hypovirulence via mycoviruses could readily be applied to O. novo-ulmi as the target population at the western Canadian disease front is essentially composed of two very large clones and vegetative compatibility barriers are rare. We have determined the genome sequence of a new dsRNA mitovirus OnuMV1c isolated from an infected O. novo-ulmi at disease front and demonstrated its transmission between strains. Partitiviruses, which reside in the cytoplasm, have been described in closely related species and are expected to be transmissible to O. novo-ulmi. Through our work on the genomics of O. novo-ulmi we have identified several gene loci thought to be integral to pathogenicity and fungal fitness. We intend to embark on the re-engineering of viral dsRNAs by the insertion of silencing RNA (siRNA) specific to identified O. novo-ulmi gene loci to selectively down-regulate genes critical to fungal survival. The development of RNAi engineered hypoviruses could provide a new approach for biological control that would be applicable to many fungal pathogens.