放牧因子与VA菌根的相互作用对鸭茅养分吸收和生长发育的影响

探讨了放牧因子与VA菌根的相互作用对鸭茅(Dactylis glomerataL.)养分吸收和生长发育的影响。菌根效应表现在不施磷肥条件下的鸭茅地上部生育与地上、地下部的磷素营养上,但对地上部生育的效应因刈割次数的增加而降低,对地上、地下部磷素营养的效应因土壤镇压而降低。菌根对鸭茅钙素营养的效应只见于不施磷肥条件下的土壤镇压处理,而在相同条件下菌根却降低了鸭茅的镁含量。说明VA菌根对鸭茅磷素营养和生长发育的效应与土壤磷营养有关,而且因地上部的过度采食和土壤镇压而降低。     

菌根与植被恢复

菌根不仅可促进植物的营养吸收、生长发育、抗病、抗逆,而且在保持良好的土壤结构、控制水土流失方面具有直接的作用。在我国西北许多地区,菌根菌与植物间的共生关系已被中断,要恢复该地区的植被,治本的方法应是重建植物与菌根菌的共生关系,形成健康的生态系统。文中还提出了菌根技术在植被恢复中的应用策略。     

Parasitic plant infection is partially controlled through symbiotic pathways

Legumes are unique in interacting with Rhizobium , arbuscular mycorrhizal (AM) fungi, and parasitic plants. To dissect common parts of these three plant–organism interactions, infection by Orobanche crenata was studied in mutants with altered symbiotic phenotypes of Medicago truncatula and Pisum sativum . Orobanche crenata inoculation of mutant lines carrying defective mutation in the genes dmi2 / sym19 and dmi3 resulted in an increase in O. crenata establishment. Similarly, inoculation of mutants carrying mutation in the gene sunn / sym29 that controls the autoregulation mechanism of the symbiosis, also lead to a significant increase in haustoria formation. Altogether, our results suggest that parasitic plant infection is partly controlled by both the conserved symbiotic pathway that mediates symbiont recognition and establishment and the autoregulation mechanism that regulates the extent of colonisation by Rhizobium and AM fungi.     

Glomus mosseae bioprotection against aster yellows phytoplasma (16srI-B) and Spiroplasma citri infection in Madagascar periwinkle

The bio-control potential of arbuscular mycorrhizal fungus Glomus mosseae against two pathogenic microorganisms aster yellows (AY) phytoplasma and Spiroplasma citri has been examined in Madagascar periwinkle (Catharanthus roseus). G. mosseae had a positive influence on healthy C. roseus plants and S. citri infection. It provided bioprotection against S. citri pathogen and induced significant degree of resistance to spiroplasma infection. Besides, symptom expression significantly reduced and shoot height, leaves number, root fresh and dry weight increased in spiroplasma-infected plants treated with mycorrhiza fungus. Although, G. mosseae had no positive effect on phytoplasma disease. The root architectures were affected by the phytoplasma pathogen, and the root surface area dramatically decreased in G. mosseae treated AY-infected periwinkles compared with the control. Nitrogen and Phosphorus concentrations notably increased in spiroplasma + G. mosseae compared with control plants. Potassium concentration did not differ significantly in all mycorrhizal treated and untreated infected plants except in G. mosseae treated healthy plants. The spore density and root colonization rate did not vary in both pathogen treatments G. mosseae + spiroplasma and G. mosseae + phytoplasma. To our knowledge, this is the first report showing the bioprotective effect of G. mosseae on S. citri. The possible mechanisms involved in complex interaction between plants, cell wall-less bacteria and arbuscular mycorrhizal fungi (AMF) are discussed and the underlying mechanisms for the functioning of AMF are hypothesized.     

Biocontrol of the pathogen Phytophthora parasitica by arbuscular mycorrhizal fungi is a consequence of effects on infection loci

The impact of colonization by the arbuscular mycorrhizal fungus (AMF) Glomus mosseae on tomato root necrosis caused by the soil-borne pathogen Phytophthora parasitica was investigated. Studies in situ permitted infection loci to be identified and the effects of the AMF on numbers to be elucidated. Effects were significant and, 7 and 16 days after inoculation with zoospores of the pathogen, roots of plants colonized by the AMF had 39% and 30%, respectively, fewer infection loci than those that were not. Concurrent studies of the rate of spread of necrosis within roots showed no changes caused by the AMF. At harvest, 26 days following inoculation with the pathogen, 61% of roots of noncolonized plants were necrotic compared with only 31% in AMF-colonized plants. It is concluded that effects on numbers of infection loci are one mechanism via which AMF achieve biocontrol of this pathogen in tomato. Measures of the effects of the AMF on root system architecture suggest that no significant changes occur and are thus not the reasons for the reduction in infection loci. The implications of these data for agricultural practice and biocontrol research are discussed.     

混合接种菌根真菌对喜树幼苗生长及喜树碱含量的影响

通过温室盆栽接种试验,研究了蜜色无梗囊霉(Acaulospora mellea)、弯丝硬囊霉(Sclerocystic sinosa)及二者混合接种(分别记为Am、Ss和Am-Ss)对喜树幼苗生长及喜树碱含量的影响.结果表明:丛枝菌根的形成促进了喜树幼苗的生长,菌根幼苗的生物量优于无菌根幼苗,混合接种Am-Ss的菌根幼苗显著高于无菌根幼苗和单接种的菌根幼苗.丛枝菌根形成影响了喜树幼苗的喜树碱代谢,菌根幼苗根、叶片和全株的喜树碱含量均显著高于无菌根幼苗,并且混合接种处理的喜树幼苗喜树碱含量最高.     

Responses of field grown tomato plants to arbuscular mycorrhizal fungal colonization under varying intensities of drought stress

The effects of root colonization by the arbuscular mycorrhizal (AM) fungus Glomus intraradices Schenck and Smith on growth, flower and fruit production, and fruit quality were studied in field-grown tomato plants exposed to varying intensities of drought stress. Inoculated (M+) and non-inoculated (M−) tomato seedlings were exposed to varying intensities of drought stress by adjusting irrigation intervals. Mycorrhizal plants had significantly higher uptake of N and P in both roots and shoots regardless of intensities of drought stress. AM inoculation also significantly increased shoot dry matter and the number of flowers and fruits. The fruit yields of M+ plants under severe, moderate, mild drought-stressed conditions were higher than M− plants by 24.7%, 23.1%, 16.2% and 12.3%, respectively. Furthermore, M+ plants produced tomato fruits that contain significantly higher quantities of ascorbic acid and total soluble solids (TSS) than M− plants. Mycorrhizal effects increased with increasing intensity of drought. The overall results suggest that mycorrhizal colonization affects host plant nutritional status, water stratus and growth under field conditions and thereby alters reproductive behaviour, fruit production and quality of fruits under both well-watered and drought-stressed conditions.     

Molecular analysis of the Arbuscular mycorrhiza symbiosis

The molecular analysis of the arbuscular mycorrhizal (AM) symbiosis started at the beginning of this decade. The paper summarises the work of the ‘Laboratorium für Molekulare Genetik arbuskulärer Mykorrhiza’ at the MPI für terrestrische Mikrobiologie in Marburg on three major topics. Firstly, the plant response to the mycorrhizal colonisation was analysed using both, targeted and non‐targeted approaches. As an example, the localisation of the gst1 mRNA in potato mycorrhiza is shown. Second, molecular techniques were established to analyse gene expression of the fungal partner of the symbiosis. We present a differential RNA display analysis of spore germination in two AM fungi and the cloning of a gene from Glomus mosseae that shows expression at all stages of the fungal life cycle. In the last part, we introduce the work we are carrying out with a new root endophytic fungus, Piriformospora indica. Infection experiments on maize showed that despite the fungus performs as a root necrotroph, it has a positive effect on plant growth.     

Growth and competitiveness of the New Zealand tree species Podocarpus cunninghamii is reduced by ex-agricultural AMF but enhanced by forest AMF

The composition of arbuscular mycorrhizal fungi (AMF) communities found in agricultural systems has been found to be very different to that of forest. The implications of this, if any, for the restoration of indigenous forest on ex-agricultural land is poorly understood. This study investigated the effect that AMF communities isolated from ex-agricultural and forest soils have on the growth of an indigenous New Zealand tree species (Podocarpus cunninghamii). The forest AMF community was isolated from a remnant stand of P. cunninghamii forest and the ex-agricultural AMF from a retired grazing grassland. In addition, the study examined how the two AMF communities affected the competitiveness of P. cunninghamii when grown in competition with an invasive grass species (Agrostis capillaris), which is frequently dominant on ex-agricultural land in New Zealand. P. cunninghamii growth was significantly decreased by inoculation with ex-agricultural AMF compared to forest AMF. Furthermore, the forest AMF community was able to significantly increase P. cunninghamii root production when in competition with A. capillaris. The findings suggest that when attempting to restore indigenous forest on ex-agricultural land, inoculation of tree seedlings with appropriate forest AMF may improve their growth and survival.     

菌根真菌对3种兰花幼苗生长作用研究

菌根真菌在兰科植物生活史中具有重要作用。为获得促进兰科植物生长的共生真菌,阐明菌根真菌对兰科植物的作用,本研究对从野生建兰中分离获得的3株共生真菌进行形态学和系统进化分析,并将3株真菌与建兰、硬叶兰和铁皮石斛幼苗在不同浓度燕麦琼脂培养基(OMA)条件下共培养,进行比较研究。结果表明,3株真菌分属于胶膜菌属(Tsc)、角担菌属(Cej3)和蜡壳菌属(Sec),且菌丝和菌落特征存在明显差异;系统进化分析发现,Tsc菌株与Cej3菌株亲缘关系较近,与Sec菌株亲缘关系较远;与兰科植物共培养结果表明,Tsc菌株可在全部OMA浓度条件下与3种兰科植物幼苗建立共生关系,且定殖率均为100%;Cej3菌株和Sec菌株与3种兰科植物在不同OMA浓度条件下定殖时间及定殖率存在差异,且具有一定的专一性;与对照组相比,与真菌共生的兰科植物幼苗的平均鲜重、干重、苗高、根长增长率均明显提高。本研究结果为深入研究兰科植物与真菌共生的分子机制奠定了一定的理论基础,并为兰花种质资源的保护提供了参考。