黄瓜菌根丛枝结构介导的抗根结线虫机制

Root knot nematode （Meloidogyne incognita）disease in cucumber (Cucumis sativus)plants becomes more and more severe and has not been thoroughly controlled. Research confirms that arbuscular mycorrhizal fungi (AMF) can inhibit the occurrence and development of the nematode. Arbuscule structure in arbuscular mycorrhiza is related to retarding infection and expansion of plant soil-borne pathogens, and improving plant disease resistance. Traditional study methods of AMF with molecular biotechniques will be used in the present study to investigate species composition and their arbuscule structure features in cucumber roots, as well as their relationship to nematode disease. The dominant AMF species in cucumber roots which are related to retarding nematodes will be examined. Through enriching these AMF inocula, inoculation with a single species or in combination with different dominant species will be conducted to determine their effects on antognizing nematode. On the basis of obtaining the optimum AMF species which are resistant to nematodes, this study will characterise arbuscular structure features and their regulating defense gene expression, inducing defense response, ultrastructure characters of arbuscule's inhibiting to the nematode, antognizing nematode and reducing the disease, and elucidating nematode resistant mechanisms by the arbuscule structure. The finding of this study is expected to provide a guidance for controlling cucumber nematodes, and help illustrate AMF position in biocontrol of plant soil-borne diseases. It will also provide theoritical foundation and technical support for carrying out the relative research and disease-control practices.

黄瓜根结线虫病害日益严重，尚未得到根本控制。而丛枝菌根真菌能抑制根结线虫的发生发展。其中，丛枝菌根的丛枝结构与拮抗植物土传病原物的侵染扩展、提高植物抗病性有关。本项目围绕设施黄瓜丛枝菌根的丛枝结构特征及其拮抗根结线虫的作用与机制,采用传统丛枝菌根真菌的研究方法，结合分子生物学技术，重点研究：黄瓜根内丛枝菌根真菌种类组成、丛枝结构特征及其与根结线虫病害的关系；确定与抗线虫相关的根内优势丛枝菌根真菌种类，通过扩繁、单菌接种和复合接种，明确不同丛枝菌根真菌优势种类抗根结线虫的作用；在获得抗线虫作用最大的丛枝菌根真菌种类的基础上，通过丛枝结构特征及其调控防御性酶基因表达、诱导防御反应、拮抗线虫的超微结构特征和抑制线虫降低病害的效应研究，以期明确丛枝结构抗根结线虫机制。该研究可望为黄瓜根结线虫的控制提供参考，有助于阐明该真菌在土传病害生防中的地位，以期为开展相关研究和防控实践提供理论依据和技术支持。

从设施栽培黄瓜根系内分离鉴定出丛枝菌根(AM)真菌光壁无梗囊霉(Acaulospora laevis, Al)、摩西管柄球囊霉(Funneliformis mosseae, Fm)、根内球囊霉(Glomus intraradices, Gi)、珠状巨孢囊霉(Gigaspora margarita, GIm)和全球盾巨孢囊霉(Scutellospora aurigloba, SCa)。黄瓜根内着生有典型的泡囊、A型与P型丛枝结构。AM真菌的P型着生率、P/A比率分别与黄瓜根结线虫病害程度具有负相关性。将AM 真菌组合菌剂和南方根结线虫（Meloidogyne incognita, Mi）接种“津优35号”黄瓜，多数AM真菌组合菌剂能够增加黄瓜株高、植株干重和单株产量，其中，以Al +Fm + Ge + Gv组合促生效应最大，以Al + Fm + GIm + SCa 及 Al +Fm + SCa组合的效应最少或无效，Fm + Gi + SCa + GIm 及 GIm + SCa 组合反而降低黄瓜产量；接种AM真菌组合均能显著降低卵囊数和每个卵囊的含卵数量，但Fm + Gi + SCa + GIm组合则增加根内二龄幼虫数、根内雌虫数和根内线虫总数；其他大多数组合能够抑制线虫的繁殖数量，其中，以 Al + Fm +GIm 及Fm+Ge+Gv组合抑制线虫生长发育的作用最大；除GIm + SCa 组合外，其他AM真菌组合均能不同程度的降低线虫为害，防效达31%-83%，以Al + Fm +GIm 组合处理的病情指数最低，防效最大。设施田间试验结果表明，以Al +Fm + Ge + Gv 组合促生增产作用最大，Al + Fm +GIm次之，以 Al + Fm +GIm组合抗病作用最强。这与其显著提高黄瓜叶片内防御酶如过氧化物酶、超氧化物歧化酶和过氧化氢酶活性、诱导植物抗病性与P型丛枝直接拮抗病原物有关。结论认为植物根系丛枝结构中P型丛枝拮抗病原物的效应大于A型的，并且P/A比率>1.3对提高植物抗根结线虫病害以及降低其危害程度的作用更强。 Al +Fm + Ge + Gv及 Al + Fm +GIm组合具有较大的应用潜力。本项目结果对于诠释AM真菌的发育结构特征及其提高黄瓜抗根结线虫作用机制、以及在蔬菜根结线虫病害绿色安全防控技术研发等方面具有重要的理论价值和实际意义。