Sand culture of mycorrhizal plants

In this work, a sand culture system for ecto- or arbuscular mycorrhizal plants was developed. Nutrients were added into the sand at a constant rate using solutions with similar concentrations of nutrients as those found in forest soil solutions. Plants grew well in the system and inoculated plants developed abundant ecto- or arbuscular mycorrhizas. To test the suitability of the culture system for studies on metal toxicity, aluminium was added to the nutrient solutions of non-mycorrhizal and mycorrhizal spruce seedlings. Measurments of labile Al in the solution draining from the sand revealed that Al was mainly present as phytotoxic monomeric Al. In addition, concentrations of Ca²⁺, Mg²⁺ and SO₄^2— ions which have the potential to alleviate Al toxicity, were similar in the draining as in the nutrient solutions. After 10 weeks of exposure to 400 μM Al, taproot growth as well as Ca and Mg uptake of the seedlings were impaired by Al. Mycorrhizal colonization had no effect on the degree of inhibition of these processes. We conclude that this culture system is suitable for investigations on effects of Al and other toxic metals on mycorrhizal tree seedlings.     

Arbuscular mycorrhizal fungal spore-associated bacteria affect mycorrhizal colonization,plant growth and potato pathogens

Arbuscular mycorrhizal (AM) fungi and their bacterial associates are essential living components of the soil microbiota. From a total of 385 bacteria previously isolated from spores of AM fungi (AMB), 10 were selected based on ability to inhibit growth of plant pathogens. Effects of these isolates on AM fungal colonization, plant growth in potato (Solanum tuberosum L.) and inhibition of pathogens was investigated. AM fungal root colonization of potato was 7-fold higher in the presence of the Pseudomonas FWC70 isolate in a greenhouse and was 6–9-fold higher in the presence of the three isolates Pseudomonas FWC70, Stenotrophomonas FWC94 and Arthrobacter FWC110 in an outdoor pot experiment. Several growth traits of potato were stimulated by the Pseudomonas isolates FWC16, FWC30 and FWC70 and by the Stenotrophomonas isolate FWC14. All three Pseudomonas isolates showed inhibition against Erwinia carotovora, Phytophthora infestans and Verticillium dahliae but Stenotrophomonas isolates were variable. Protease(s), siderophores and indole acetic acid were produced by all isolates. Chitinase(s) were produced by all Stenotrophomonas and phosphate-solubilizing activity by all Pseudomonas isolates, the Stenotrophomonas FWC14 isolate and the Arthrobacter FWC110 isolate. We conclude that some AMB are multifunctional and production of extracellular enzymes and bioactive compounds are likely mechanisms for their multifunctional activities. Our results show that some AMB are likely to contribute to the often described ability of AM fungi to inhibit pathogens, acquire mineral nutrients and modify plant root growth.     

菌根共生参与基因对不同品种小麦菌根侵染的响应

为研究不同小麦品种之间丛枝菌根(Arbuscular mycorrhiza，AM)侵染率差异的分子机制，于2017～     

Effect of peat on mycorrhizal colonization and effectiveness of the arbuscular mycorrhizal fungus Gigaspora margarita

Abstract

The influence of the addition of Chinese peat and Canadian peat on arbuscular mycorrhizal colonization, mycorrhizal effectiveness and host-plant growth was investigated in a pot experiment. Chinese peat or Canadian peat was mixed with Masa soil (weathered granite soil) at different levels (0, 25, 50, 100, 150 or 200 g kg^?1) into which an arbuscular mycorrhizal fungus (AMF) Gigaspora margarita Becker & Hall was inoculated, and seedlings of Miscanthus sinensis Anderess were planted. There was a significant increase in plant growth with increasing amounts of Chinese peat. The growth-promoting effect of the AMF on the host was enhanced when the addition of Chinese peat was increased from 25 to 100 g kg^?1. Root colonization and the number of spores proliferating increased with increases at low levels of Chinese peat (from 25 to 100 g kg^?1), and decreased gradually with higher Chinese peat increments. Although plant growth and root colonization with the addition of Canadian peat increased slightly, Canadian peat suppressed mycorrhizal effectiveness. In contrast to Canadian peat, the addition of Chinese peat improved considerably the physical and chemical properties of the soil, which might result in the promotion of AM formation and mycorrhizal effectiveness.     

Mineral acquisition by arbuscular mycorrhizal plants

Arbuscular mycorrhizal fungi (AMF) benefit plants by allowing them to grow and produce in relatively harsh mineral stress environments. This has been attributed extensively to ability of AMF to expand the volume of soil for which mineral nutrients are made available to plants compared to what roots themselves would contact. This article reviews the effects of AMF on enhancing/reducing acquisition of phosphorus (P), nitrogen (N), sulfur (S), boron (B), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), zinc (Zn), copper (Cu), manganese (Mn), iron (Fe), aluminum (Al), silicon (Si), and some trace elements in plants. The nutrients enhanced most in host plants grown in many soils (e.g., high and low soil pH) are P, N, Zn, and Cu, but K, Ca, and Mg are enhanced when plants are grown in acidic soils. Many AMF have also the ability to ameliorate Al and Mn toxicities for plants are grown in acidic soil.     

Leucaena leucocephala seedling response to vesicular-arbuscular mycorrhizal inoculation in soils with varying levels of inherent mycorrhizal effectiveness

Summary The symbiotic effectiveness of vesicular-arbuscular mycorrhizal (VAM) fungi present in widely differring tropical soils was evaluated in a greenhouse experiment. Small volumes of field soil, a standard inoculum (Glomus aggregatum) or both were introduced into a fumigated sand-soil medium amended with nutrients for optimum VAM activity. Leucaena leucocephala (Lam.) de Wit var. K8 was grown in the medium as an indicator plant. VAM effectiveness was monitored as a function of time by determining the P status of pinnules. The soils differed from each other with respect to the time their endophytes required for the expression of initial and maximum effectiveness and in the level of maximum effectiveness they exhibited. The effect of mycorrhizal inoculation, calculated as the ratio of the areas enclosed by the effectiveness curve of G. aggregatum to that enclosed by the effectiveness curves of test soils, was found to be a good indicator of the response of L. leucocephala to inoculation of soils with G. aggregatum Hawaii Institute of Tropical Agriculture and Human Resources Journal series No. 3285     

丛枝菌根真菌领域专利情报分析

丛枝菌根真菌 (AMF) 与植物共生在提高植物的抗逆性、抗病性和维护植物健康方面发挥着关键作用，其在农业、林业和生态环境等方面的应用受到广泛关注。本研究基于incoPat科技创新情报平台，检索了2019年前国内外丛枝菌根真菌的专利产出，对专利申请数量、主要申请人、技术构成等方面进行了分析，以揭示国内外丛枝菌根真菌领域的研发状况、技术发展趋势和产学研合作情况。近年来，中国丛枝菌根真菌领域专利数量急剧增加，AMF产品化不断加强，AMF应用领域从农业领域向污染修复领域拓展，结合现代生物、信息技术等新兴技术的AMF检测技术和研究方法正在快速发展，新的研发充分考虑了AMF产品化和应用的结合；我国在丛枝菌根真菌领域的专利申请人多隶属高校和科研院所，企业参与度较低。AMF菌种扩繁和污染修复领域的应用已成为焦点，生物和信息新技术成果正引入AMF检测技术的开发；中国在丛枝菌根真菌领域的产学研合作研发亟需加强。     

Controls over mycorrhizal uptake of organic nitrogen

Mycorrhizal plants from a variety of ecosystems have the capacity to take up organic forms of nitrogen, yet the fraction of plant nitrogen demand met by organic N (ON) uptake remains unclear. ON uptake by mycorrhizal plants is a biochemical process that involves multiple steps, including breakdown and uptake of soil ON by mycorrhizal fungi, internal transformation of ON, and transfer of N to the host plant. We present hypothetical mechanisms controlling each of these steps and outline predictions for how these mechanisms structure patterns of ON uptake by mycorrhizal plants in ecosystems. Using a synthesis of published data, we found that uptake of amino acids by mycorrhizal fungi is related to the relative abundance, N content, and carbon structure of the amino acid. We hypothesize that the bond strength and structural diversity of soil ON controls the breakdown of polymeric ON by mycorrhizal fungi. In addition, the availability of carbon resources for the mycorrhizal fungus influences the capacity for mycorrhizal fungi to assimilate amino acids and produce extracellular enzymes that catalyze the breakdown of polymeric ON.     

Fertilizer-induced pathogenicity of mycorrhizal fungi to sweetgum seedlings

One isolate of Glomus clarus, two of G. etunicatus, and one of G. claroideum, obtained from plants growing on abandoned stripmine sites in Kentucky, and an isolate of G. fascicutatus known to stimulate growth of various woody plants, were evaluated for their influence on growth of sweetgum seedlings in a mixture of sand and stripmine soil. Soils were supplemented with various rates of a complete slow-release fertilizer. Throughout the growth period, G. fasciculatus, and most of the stripmine isolates, stimulated growth at low fertilizer rates. At higher fertilizer rates, including the level optimum for non-mycorrhizal plants, the stripmine isolates inhibited plant growth. After 14 weeks, plants inoculated with one of the four stripmine isolates overcame the early growth depression, and those inoculated with a second isolate appeared to be overcoming the growth depression. G. fasciculatus was not inhibitory at any fertilizer rate. Root colonization by all three isolates evaluated was inhibited by the highest fertilizer rate, but this effect was not related to growth inhibition of plants. The other two isolates colonized roots at an extremely low rate (< 1%). Sporulation of all the stripmine isolates, but not G. fasciculatus, was also inhibited by the highest fertilizer rate. The G. fasciculalus isolate used in this study may be atypical of mycorrhizal fungi occurring randomly in nature in its mutualistic or neutral effect on plants under a wide range of growth conditions.     

Surface phosphatase activity of mycorrhizal roots of beech

Mycorrhizal roots of beech possess active surface acid phosphatases catalysing hydrolysis of p-nitrophenyl phosphate, glucose-6-phosphate, β-glycerophosphate, inositol hexaphosphate, inositol triphosphate and inorganic pyrophosphate. The products of hydrolysis of inositol hexaphosphate include free inositol, orthophosphate and intermediate esters.These observations are discussed in relation to the utilization of complex phosphates by mycorrhizas in general and to their capacity to exploit marginal habitats.     

AM 真菌对蔬菜品质的影响

大田生产条件下试验研究丛枝菌根（Arbuscular mycorrhiza，AM）真菌4个高效菌种Glomus mosseae、Glo-mus versiforme、Gigaspora rosea 和Sclerocystis sinousa对西瓜、黄瓜、芋头和菜豆品质的影响结果表明，AM真菌能显著提高这些蔬菜维生素C、氨基酸、粗蛋白等营养成分含量，接种Glomus mosseae处理可分别增加菜豆维生素C含量25％、磷63％，芋头粗蛋白19％、氨基酸总量24％，黄瓜可溶性糖20％、磷26％、粗蛋白40％，西瓜可溶性固形物25％、维生素C32％。     

Limitations to using benomyl in evaluating mycorrhizal functioning

Arbuscular mycorrhizal (AM) grasses compete for nutrients with ectomycorrhizal (EM) pine in the southeastern United States. Our objective was to determine if benomyl could be used to selectively inhibit the function of AM and thereby reduce grass competition in the field. The effects of Benlate (active ingredient: benomyl) in the greenhouse and field were evaluated. No effect was observed on pine inoculated with Pisolithus tinctorius in the greenhouse. Colonized root length of benomyl-treated Zea mays L. plants inoculated with Glomus sp. in the greenhouse remained static over time and the response was not dose dependent at concentrations of 0, 20, 60 and 150kg benomyl ha^–1 equivalent. In contrast, colonization of nontreated plants increased over time. In the field, a minimal reduction of grass colonization was observed following four applications of benomyl ranging from 5 to 20kgha^–1. We conclude that benomyl can successfully inhibit development of AM fungi under controlled conditions in the greenhouse with no inhibitory effects on the EM fungus P. tinctorius; however, in the field several factors may interfere with the effect of benomyl on AM fungi. These factors include: (a) the presence of ground cover which obstructs penetration of the fungicide to the soil, (b) timing of application in relation to mycorrhizal development, and (c) the application method of benomyl, a soil drench being preferable to a foliar spray. Received: 30 September 1996     

Arbuscular mycorrhizal fungi influence tomato competition with bahiagrass

A strip-tillage production system for tomatoes (Lycopersicon esculentum Mill.) is impacted by nutrient competition from bahiagrass (Paspalum notatum Flügge). Tomato and bahiagrass differ in mycorrhizal responsiveness and our objective was to evaluate the influence of arbuscular mycorrhizal (AM) fungi on the competitive pressure of bahiagrass on growth of tomato. The first experiment evaluated the effect of bahiagrass competition, soil pasteurization, and AM fungal inoculation on tomato growth, P content, and root colonization in a low-P soil. Tomato grown alone was very responsive to mycorrhizal colonization - shoot dry mass of inoculated plants was up to 243% greater than that of noninoculated plants. Tomato grown with bahiagrass had reduced root and shoot growth across all treatments compared with tomato grown alone, but there was an increase in shoot mass following AM fungal inoculation across both pasteurized and nonpasteurized treatments resulting in a >50% increase in shoot dry mass of tomato compared to noninoculated controls. A second experiment was conducted to test bahiagrass competition, soil pasteurization, AM fungal inoculation, and P amendment on tomato growth in a moderate-P soil. With bahiagrass competition and no P addition, inoculation increased root mass by 115% and shoot mass by 133% in pasteurized soil; however, with the application of 32 mg P kg^-1 the trend was reversed and inoculated plants were smaller than noninoculated controls. We conclude that the role of mycorrhizae in plant competition for nutrients is markedly impacted by soil nutrient status and reduced P application may allow tomatoes to take advantage of their inherent responsiveness to mycorrhizae in a low to moderate soil-P environment.     

Global diversity and distribution of arbuscular mycorrhizal fungi

Arbuscular mycorrhizal (AM) fungi form associations with most land plants and can control carbon, nitrogen, and phosphorus cycling between above- and belowground components of ecosystems. Current estimates of AM fungal distributions are mainly inferred from the individual distributions of plant biomes, and climatic factors. However, dispersal limitation, local environmental conditions,and interactions among AM fungal taxa may also determine local diversity and global distributions. We assessed the relative importance of these potential controls by collecting 14,961 DNA sequences from 111 published studies and testing for relationships between AM fungal community composition and geography, environment, and plant biomes. Our results indicated that the global species richness of AM fungi was up to six times higher than previously estimated, largely owing to high beta diversity among sampling sites. Geographic distance, soil temperature and moisture, and plant community type were each significantly related to AM fungal community structure, but explained only a small amount of the observed variance. AM fungal species also tended to be phylogenetically clustered within sites, further suggesting that habitat filtering or dispersal limitation is a driver of AM fungal community assembly. Therefore, predicted shifts in climate and plant species distributions under global change may alter AM fungal communities.     

Vesicular-arbuscular mycorrhizal associations with barley on sewage-amended plots

Barley plants grown on field plots amended with sewage from two sources were examined for vesicular-arbuscular (VAM) infection. Three treatments (control. 8.2 tonnes sludge ha⁻¹ and 32.9 ha⁻¹) were applied annually for 8 yr with no additions during years 9 and 10. A barley crop was grown on the site during each of the 10 yr of the study. Percent VAM infection on barley roots showed no effect of nonindustrial sludge application. The urban-industrial sludge treatments, however, produced a 6-fold drop in infection rate. Little correlation was found between percent VAM infection and available soil P content. Zn concentration in the soil were found to be negatively correlated with VAM infection. This study suggests that there are factors within sludge, in addition to P, that affect mycorrhizal occurrence 2 yr after the last application of sludge to soil.     

VA菌根对土壤酸度的耐性

A 45－day greenhouse experiment was carried out to determine effect of vesicular-arbuscular（VA）my-corrhizal fungi on colonization rate,plant height,plant growth,hyphae lenth,total Al in the plants,ex-changeable Al in the soil and soil pH by comparison at soil pH 3.5,4.5 and 6.0 Plant mung bean(Phaseolus radiatus L.)and crotalaria(Crotalaria muronata Desv.) were grown with and without VA mycorrhizal fungi in pots with red soil,Ten VA mycorrhizal fungi strains were tested,including Glomus epigaeum(No.90001),Glomus caledonium(No.90036),Glomus mosseae(No.90107),Acaulospora soo.(No.34),Scutellopora het-erogama(No.36),Scutellospora calopsora(No.37),Glomus manihotis(No.38).Gigaspora spp.(No.47),Glomus manihotis(No.49),and Acaulospora spp.(No.53).Being the most tolerant to acidity,strain 34 and strain 38 showed quicker and higher-rated colnization without lagging,three to four times more in number of nodules,two to four times more in plant dry weighy,30% to 60% more in hyphae length,lower soil exchaneable Al,and higher soil pH than without VA mycorrhizal fungi(CK).Other strains also could improve plant growth and enhance plant tolerance to acidity,but their effects were not marked.This indicated that VA mycorrhizal fungi differed in the tolerance to soil acidity and so did their inoculation effects.In the experiment,acidic soil could be remedied by inoculation of promising VA mycorrhizal fungi tolerant of acidity.     

The identification of vesicular-arbuscular mycorrhizal fungi using immunofluorescence

An antiserum was produced to a species of Gigaspora using cell wall antigen from hyphae collected from germinating spores. Using this antiserum in the fluorescent antibody (FA) technique, vesicular-arbuscular mycorrhizal (VAM) fungi could easily be distinguished from non-endogonaceous fungi. Differentiation among different VAM fungi, though not clear cut, was possible, and specificity was improved by absorption of the serum with hyphae of Acaulospora laevis. Variations in staining reactions between different fungi suggest that wall structure interferes with the expression of the FA test.     

Response of nitrogen-transforming microorganisms to arbuscular mycorrhizal fungi

 We studied fluctuations in the numbers of autotrophic ammonium oxidizers, ammonifying microorganisms and denitrifying microorganisms in pot cultures of mycorrhizal and non-mycorrhizal maize. The populations were enumerated after 0, 15, 30, 45 and 60 days of plant growth. Two arbuscular mycorrhizal (AM) fungi belonging to different Glomus species were investigated. Pot cultures with AM-infected maize had significant quantitative and qualitative changes in the root-associated population of N-transforming bacteria compared with the non-mycorrhizal controls. The occurrence of autotrophic ammonium oxidizers in pot cultures of the AM fungi Glomus mosseae and G. fasciculatum was significantly higher than in non-mycorrhizal cultures throughout maize growth. The occurrence of these bacteria was delayed by 15 days in non-mycorrhizal as opposed to Glomus-colonized soil. Ammonifying and denitrifying bacterial populations were significantly decreased in the pot cultures of AM plants compared with the control. The distribution patterns of the physiological groups of bacteria tested were similar for both AM treatments but different from that of the non-mycorrhizal controls. Activity measurements expressed on a per cell basis showed changes with respect to the form of N in the mycorrhizal soil. G. fasciculatum was more active than G. mosseae during the earlier stages of plant growth. Received: 8 July 1997     

Dual plant host effects on two arbuscular mycorrhizal fungi

Mycorrhizal fungi may simultaneously associate with multiple plant hosts, and the implications of this for the fungi involved are not well understood. To address this question, two arbuscular mycorrhizal fungi (AMF), Glomus clairoideum (a treatment referred to as “Glo”) and Scutellospora fulgida (a treatment referred to as “Scut”), were grown separately in pots that each consisted of two plant compartments separated by a root-free-compartment (RFC). Fungi within each two-plant-compartment pot were exposed to either two individuals of indiangrass (Sorghastrum nutans), two individuals of big bluestem (Andropogon gerardii), or one of each. A non-inoculated treatment (“Non”) was included to help gauge the potential influence of greenhouse contaminant fungi, cross-contamination, or any misidentification of non-AMF hyphae. The two host species had additive effects on the growth of AM hyphae in plant compartments of Scut, Glo, and Non pots, and in the RFCs of Scut pots. In Glo RFCs, however, they were antagonistic in their effects. Synergism between hosts in Non RFCs suggested that any potential contaminants or misidentification could not explain this result. Underyielding was not seen in shoot weight, root weight, or root length in dual host pots, and also therefore could not explain the result. Hyphal growth in the Scut treatment was evenly distributed between the RFC and plant compartments (or marginally skewed toward the RFC), while hyphal growth in the Glo treatment was skewed toward plant compartments (nearer roots). However, hyphal lengths were more highly correlated across plant compartments within a common pot in the Glo treatment, suggesting that this AMF bridged the RFC to experience the entire two-host pot as a single environment to a greater extent than Scut did. These AMF differed in how they responded to both the species composition of the two-host environment and its spatial structure; potential implications for mycorrhizal community dynamics are discussed.