【作者】 李敏；

【导师】 李晓林；

【作者基本信息】 中国农业大学 ， 植物营养学， 2005， 博士

【摘要】 越来越多的研究表明,丛枝菌根(Arbuscular Mycorrhiza,AM)真菌在维护植物健康方面发挥着关键作用。在作物土传病害发生发展过程中,土壤中AM真菌多样性及其与其它微生物尤其是病原物比率和动态平衡、以及由此而引起的寄主植物生理生化的变化是近年来菌根领域研究的热点问题。作者在田间和盆栽条件下探索了AM真菌对西瓜生长的影响、以及与枯萎病发生发展的关系,在此基础上,应用电镜技术和化学分析等方法比较深入系统的研究了AM真菌诱导西瓜抗枯萎病作用的机制。 首先在大田条件下证实,苗期接种AM真菌在移栽至大田后能显著降低西瓜枯萎病的发病率、病情指数、根际和根内镰刀菌(Fusarium oxysporum f.sp.niveum)繁殖体的数量;提高叶片光合速率和水分利用效率,并能增加植株地上部氮、磷、硼和锌等元素的含量,表现出促进植株生长,改善西瓜品质的效果。 在温室盆栽条件下接种AM真菌显著促进西瓜植株的生长,增加植株干重;抑制镰刀菌对西瓜根系侵染;降低枯萎病发病率和病情指数,减轻西瓜枯萎病的危害。西瓜苗根系AM真菌的丛枝着生率与枯萎病的病害等级呈显著的负相关。不同AM真菌的效应之间差异显著,对枯萎病的防治效果依次为Glomus versiforme>Glomus mosseae>Gigaspora rosea。对不同抗性的西瓜品种而言,AM真菌对高感枯萎病品种的防治效果优于抗病品种。并且AM真菌与镰刀菌的不同接种时间和顺序影响西瓜枯萎病的发生发展。试验证实AM真菌与镰刀菌之间存在竞争,有拮抗关系。 菌根化西瓜苗根分泌物,能有效抑制镰刀菌孢子萌发和菌落的生长,非菌根苗的根分泌物则能刺激孢子萌发和菌落生长。菌根化西瓜苗根分泌物能促进西瓜生长,抑制枯萎病的发生发展,而且这种抑制效应,随着西瓜苗根系菌根化程度的提高和分泌物的增加而增强。 在土壤速效磷含量较低的条件下,接种G.versiforme和施磷能促进西瓜苗生长,减轻枯萎病的发病程度,增加西瓜苗氮、磷、钾等元素的含量,但施磷减少了锌、铜的含量,部分地抑制了菌根的发育。初步证实AM真抑制镰刀菌侵染和发育、提高西瓜苗对枯萎病的抗性与其改善植株磷营养状况有关。 在AM真菌提高西瓜抗病性的生化作用机制研究中,首先证实预先接种G.versiforme,后接种镰刀菌的植株根内丙二醛含量、组织自动氧化速率和细胞膜透性均低于单接镰刀菌的处理。证明菌根化西瓜苗在遇到镰刀菌侵染时其自我调节和恢复正常状态的能力显著提高,从而维护了膜系统的稳定性。试验还进一步证实,双接种G.versiforme和镰刀菌的植株根内过氧化物酶、苯丙氨酸解氨酶、β-1,3-葡聚糖酶和几丁质酶活性均高于单接镰刀菌的处理,且酶的活性峰值出现较早。试验表明AM真菌能在一定范围内诱导西瓜植株与抗病有关的防御性酶类,使根系对镰刀菌侵染产生快速反应。 总之,AM真菌具有提高西瓜抗病性的作用,其机制包括改善植株矿质营养状况、促进西瓜生长、降低病原物的数量、调节生物膜透性和提高防御性酶活性等方面。而其在分子水平上的调控机制需进一步研究。更多还原

【Abstract】 Arbuscular mycorrhizal (AM) fungi have been shown to play a key role in maintaining plant health. Community diversity of AM fungi, AM fungi/pathogen ratios, their dynamic balance in the soil, and their influence on plant physiology and metabolic process during the development of soil-borne diseases have become central topics in the field of mycorrhizas. The author started working on interactions between AM fungi and Fusarium oxysporum f.sp. niveum on growth and wilt disease of watermelon (Citrullus lanatus). Then a series of experiments was carried out systematically to study the mechanisms of increasing resistance to fusarium wilt by watermelon induced by AM fungi.Firstly, the influence of AM fungi and E oxysporum f.sp niveum on growth and wilt disease of watermelon were investigated in field. Pathogen propagules in roots and the rhizosphere, the extent of root infection by F. oxysporum f.sp niveum, wilt disease incidence and disease index of watermelon seedlings inoculated with AM fungi were significantly reduced. AM fungal inoculation also increased net photosynthetic rate, transpiration rate, water use efficiency and the concentrations of N, P, B and Zn in the leaves. Consequently, AM fungal inoculation promoted the growth, yield and quality of watermelon.Watermelon seedlings inoculated with Gigaspora rosea, Glomus mosseae, and Glomus versiforme were grown in pots under greenhouse conditions. AM inoculation increased growth and dry weight of the seedlings and significantly decreased percentage root infection by F. oxysporum f.sp. niveum wilt disease incidence and disease index. The relationship between root arbuscule colonization by AM fungi and disease severity showed a negative correlation. The mycorrhizal effects of the three AM fungi were clearly different, with the degree of disease control following the sequence G. versiforme> G mosseae>Gi.rosea. In addition, the effectiveness of disease control by AM fungi were greater on susceptible cultivars than on resistant cultivars. The development of wilt disease was influenced by inoculation time and sequences of AM fungi and the pathogen. The data suggest that there competition or antagonism occurred between the AM fungi and F. oxysporum f.sp. niveum.Spore germination and colony growth of F. oxysporum f.sp. niveum were restrained by exudates from mycorrhizal watermelon seedling roots and stimulated by non-mycorrhizal roots. The exudates from mycorrhizal seedlings significantly increased growth and reduced wilt disease severity of watermelon seedlings, and the control effect increased as the degree of mycorrhizal colonization and exudates from mycorrhizal watermelon seedlings roots increased.In a low available phosphorus soil, G versiforme inoculation and phosphorus fertilization increased seedling growth, reduced wilt disease severity in watermelon seedlings, and increased the concentrations of N, P and K. However, Zn and Cu concentrations were decreased and mycorrhizal development of watermelon seedlings was partly inhibited by P fertilization. This indicates that the increase in wilt-resistance induced by inoculation with AM fungi was related to their function in improving plant P nutrition.Regarding the biochemical mechanisms of wilt-resistance induced by AM fungi, the MDA content, autoxidation rate and cell membrane permeability of the roots inoculated with both G. versiforme and F. oxysporum f.sp. niveum were lower than in roots treated only with F. oxysporum f.sp. niveum. These results suggest that the mycorrhizal status of the seedlings infected with F. oxysporum f.sp. niveum enhanced the self-regulation capability, thereby maintaining the stability of the plant cell membranes. On the other hand, double inoculation with G. versiforme and F. oxysporum f.sp. niveum, produced higher peroxidase (POD), phenylalanine ammonia lyase (PAL), β-1, 3-glucanase and chitinase enzyme activities in the seedlings compared with those inoculated with F. oxysporum f.sp. niveum alone. The peak of enzyme activities in the former treatment appeared earlier as compared with the lat更多还原