Uptake of Arsenic by Maize Inoculated with Three Different Arbuscular Mycorrhizal Fungi

Effects of inoculation with three different arbuscular mycorrhizal (AM) fungi (Glomus etunicatum, Glomus constrictum, and Glomus mosseae) on arsenic (As) accumulation by maize were investigated by using soil spiked with As at rates of 0, 25, 50, and 100 mg kg^?1. The root colonization rates by the three fungi were significantly different (G. mosseae > G. etunicatum > G. constrictum) and decreased markedly with increasing As concentration in the soil. Inoculation with G. etunicatum or G. mosseae increased maize biomass and phosphorus (P) accumulation (G. mosseae > G. etunicatum) and reduced As accumulation in shoots (G. mosseae ≈ G. etunicatum), whereas inoculation with G. constrictum had little effect on these parameters. Inoculation with G. mosseae produced greater biomass and P uptake and less shoot As accumulation, and therefore it may be a promising approach to reduce As translocation from contaminated soils to plants.     

The Effect of Different Compost Compositions on Arbuscular Mycorrhizal Colonization and Nutrients Concentration of Leek (allium Porrum L.) Plant

ABSTRACT

Plant residue material produced compost is an organic fertilizer source and it is commonly used for soil amendments. Also in order to reduce the amount of chemical fertilizers need mycorrhizal inoculation can be used as an agricultural strategy. Thus, the aim of the research is to examine the effect of several residue materials produced compost and mycorrhizae fungi with two growth media on leek plant growth, nutrient uptake, and mycorrhizae spores’ production.

Eight different row organic materials and animal manures were used as compost production during 8 months. Leek (Allium porrum L.) plants were inoculated with Funneliformis mosseae and Claroideoglomus etunicatum with a level of 1000-spore per pot. The leek plant was analyzed for determination of nutrient concentration, root colonization, spore production, and shoot/root dry weight.

The composts were made from domestic waste, animal manure (bovine animal), animal manure (ovine animal), and different plant materials were determined to be the most suitable compost material for plant growth and mycorrhizal spore production compared to the rest of compost material. Mycorrhizal inoculation significantly increased leek plant growth and nutrient uptake especially phosphorus (P), potassium (K), copper (Cu) and zinc (Zn). Plants grown in 5:3:2 (volume/volume) growth media was responded better to the mycorrhizal inoculation than grown in 1:1:1 (v/v) growth media. Funneliformis mosseae inoculated plants have higher plant growth and nutrient uptake than that of Claroideoglomus etunicatum inoculation.     

32P Isotope to Determine the Efficiency of Mycorrhizal Wheat Symbiosis Subjected to Saline Water

Phosphorus (P) behavior and its efficiency in mycorrhizal plants are of great importance. The objective was to evaluate the behavior of soil labeled P absorbed by different mycorrhizal wheat genotypes subjected to saline water. Three wheat genotypes including cultivar Kavir, the local cultivar Roshan, and the mutated line Tabasi T-65-7-1 were inoculated with different species of arbuscular mycorrhiza (AM) including Glomus etunicatum, G. mosseae, and G. intraradices. Plants were irrigated using saline water (electrical conductivity of 13.87 dS m^?1). The experiment was a factorial with 12 treatments and three replications under greenhouse conditions. Wheat genotypes and AM species significantly affected plant dry weight, specific activity, and total plant activity (P?=?0.01). A maximum of 1.49-fold increase in specific activity or P uptake per gram of plant dry matter and 3.53-fold increase in plant activity or plant total P uptake resulted by G. etunicatum as compared with control.     

水分胁迫及VA菌根接种对绿豆生长的影响

本文采用土培试验研究了水分胁迫下接种VA菌根真菌Glomusmosseae,G .sp .和G .caledonium对绿豆生长及代谢活动的影响。结果表明 ,水分胁迫严重抑制了植株的生长 ,但对VA菌根真菌的侵染能力影响不大。接种VA菌根真菌不仅有利于植株对土壤中磷和氮的吸收 ,而且明显改善了植株的水分状况 ,降低了植株叶片的脯氨酸含量 ,提高了接种株叶片的光合效率 ,显著增加了植株干物质量 ,增强了绿豆的抗旱性或耐旱性。 3种真菌中 ,以Glomusmosseae的接种效果最好。     

Effect of arbuscular mycorrhizal colonization of four species of glomus on physiological responses of maize

This greenhouse study aimed to analyze the impact of arbuscular mycorrhizal (AM) fungal associations on maize (Zea mays L. hybrid Pioneer 3905) in order to compare their functional compatibility and efficiency. The AM fungus species used for this study were Glomus aggregatum, G. etunicatum, G. mosseae, and G. versiforme. Shoot and leaf masses, chlorophyll, soluble protein, total and reducing sugar, carbon (C), and nitrogen (N) concentrations, and glutamine synthetase (GS) activity in the maize leaves were analyzed. The root colonization ranged from 26% to 72% depending on the AM fungus species. Leaf mass was significantly higher when maize plants were colonized with G. etunicatum in comparison to the non‐AM control. The mycorrhizal effect on dry leaf mass ranged from 15.9% to 23.9% depending on the AM species. However, the total shoot mass did not differ significantly among the treatments. The mycorrhizal treatment had a marginally significant effect on the chlorophyll concentrations in maize leaves. The protein concentration was the highest in the plants colonized with G. etunicatum and the N percentage was significantly higher in the leaves of plants colonized by G. versiforme or G. aggregatum than those with G. mosseae. However, the AM colonization did not significantly alter the GS activity among the treatments. The highest sugar concentrations were detected in the leaves of plants colonized by G. versiforme. The sugar concentrations as well as the C percentage were lower in the leaves of plants colonized by G. etunicatum compared to the other mycorrhizal treatments but the values were comparable to the non‐AM control. Our overall results suggest that the expression of the mycorrhizal potential in the maize host plants varies among AM fungal species.     

丛枝菌根真菌对西藏高原固沙植物吸磷效率的影响

采用盆栽方法,就外源菌种、土著菌种(含混合菌种)对固沙植物白草(Pennisetum.flaccidum)生长和吸磷效率的影响进行了研究。结果表明,白草具有较高的菌根依赖性(平均达166.4%);不同AM真菌(或真菌组合)对白草根系均具显著的侵染效应。随菌根侵染率的提高,植株生物量、吸磷量均呈显著增加(相关系数分别为0.7465*、0.6000*);菌根菌丝对白草吸收土壤磷素的贡献十分明显,各接种处理菌根菌丝对植物吸收土壤磷素的贡献量、贡献率分别在3.2～11.6.mg/pot和61.5%～85.3%之间;接种菌根处理植株吸磷量呈Glomus.intraradicesG.mosseae+G.etunicatum+G.intraradices+Scutellospora.erythropaG.mosseae(外源菌种)G.mosseae+G.intraradices+Scutellospora.calosporaG.mosseae-I(土著菌种)G.etunicatum的趋势。此外,不同AM真菌对寄主植物地上部、根部生物量和吸磷量的影响程度明显不同,一般呈地上部根系的趋势,但寄主植物根系的生长速率相对较快;土著菌种中,多菌混合接种对寄主植物的侵染效应明显高于单一接种。     

Various Mycorrhizal Fungi Enhance Dry Weights,P and Zn Uptake of Four Pistacia Species

Pistacia is a common wild plant in the Southeast Anatolia part of Turkey. The experiment was planned to screen and select the most suitable arbuscular mycorrhizae (AM) for enhancing Pistacia species seedling growth by improving phosphorus (P) and zinc (Zn) uptake. This study was carried out under greenhouse condition at the Department of Soil Science, Çukurova University, Adana, Turkey. Two genotypes from each of P. vera (cvs ‘Siirt’ and ‘Kirmizi’), P. eurycarpa, P. atlantica, and P. terebinthus species were tested with ten different mycorrhizal species. Plants were grown in a growth medium with a mixture of sand, soil and compost with 6:3:1 ratio, respectively. Seedling plants were harvested after eight months and transplanted to pots. There were significant differences between Pistacia species in growth, nutrient uptake and the percentage of mycorrhizal infection. Also mycorrhizal species were different in terms of enhancing plant growth and nutrient uptake. The results were that Siirt, Genotype 08, 11, 13, and 14 gave a high response to the mycorrhizal inoculation and Glomus clarium gave the best improvements in growth and nutrition, resulting in greater plant biomass and Zn and P uptake. Following this, G. etunicatum, G. intraradices, G. caledonium, and G. mosseae species were effective species. In general, G. mosseae and G. fasciculatum mycorrhizae enhanced plant growth; G. clarium was the most efficient species in terms of P and Zn uptake.

It has been concluded that these mycorrhizae species significantly enhance the Pistacia plant growth and nutrient uptake. Also using AM fungi in the pistachio nursery should be taken into consideration for better seedling production. Further work needs to be done to determine how much inoculum is needed for sufficient inoculation and how the mycorrhizal seedlings can be adapted under field conditions especially under drought and high calcareous marginal soil conditions.     

发酵牛粪对苏丹草根系丛枝菌根（AM）真菌侵染及磷吸收效率的影响

通过温室盆栽试验,研究接种苏格兰球囊霉(Glomus caledonium)条件下添加不同比例发酵牛粪(0.33%、0.50%和1.00%)对苏丹草(Sorghum sudanense)根系丛枝菌根(AM)真菌侵染率、土壤孢子密度、植株生物量与根冠比及根系磷(P)吸收效率的影响。结果发现,与对照相比,接种AM真菌处理植株地上部生物量趋于下降、根冠比显著提高(p<0.05),在此基础上添加0.33%或0.50%发酵牛粪处理土壤孢子密度、植株根系生物量和AM真菌侵染率均趋于升高,根冠比没有明显变化,根系P吸收效率显著提高(p<0.05);添加1.00%发酵牛粪显著提高土壤孢子密度、植株生物量和根系AM真菌侵染率(p<0.05),根冠比与仅接种AM真菌处理相同,根系P吸收效率则达到仅接种AM真菌处理的1.83倍。结果表明,添加1.00%发酵牛粪对苏格兰球囊霉扩繁及其宿主植物P吸收均具有突出促进作用。     

Mycorrhizae, biocides, and biocontrol 3. Effects of three different fungicides on developmental stages of three AM fungi

The effects of biocide use on nontarget organisms, such as arbuscular mycorrhizal (AM) fungi, are of interest to agriculture, since inhibition of beneficial organisms may counteract benefits derived from pest and disease control. Benomyl, pentachloronitrobenzene (PCNB) and captan were tested for their effects on the germination and early hyphal growth of the AM fungiGlomus etunicatum (Becker & Gerd.),Glomus mosseae (Nicol. & Gerd.). Gerd. and Trappe andGigaspora rosea (Nicol & Schenck) in a silty-clay loam soil placed in petri plates. Application of fungicides at 20 mg active ingredient (a.i) kg^–1 soil inhibited spore germination by all three AM-fungal isolates incubated on unsterilized soil for 2 weeks. However, fungicides applied at 10 mg a.i. kg^–1 soil had variable effects on AM-fungal isolates. Fungicide effects on germination and hyphal growth of G.etunicatum were modified by soil pasteurization and CO₂ concentration in petri plates and also by placing spores below the soil surface followed by fungicide drenches. Effects of fungicides on mycorrhiza formation and sporulation of AM fungi, and the resulting host-plant response, were evaluated in the same soil in associated pea (Pisum sativum L.) plants. Fungicides applied at 20 mg a.i. kg^–1 soil did not affect the root length colonized byG. etunicatum, but both benomyl and PCNB reduced sporulation by this fungus. Benomyl and PCNB reduced the root length colonized byG. rosea at 48 and 82 days after transplanting. PCNB also reducedG. mosseae-colonized root length at 48 and 82 days, but benomyl only affected root length colonized byG. mosseae at the earlier time point. Only PCNB reduced sporulation byG. mosseae, consistent with its effect on root length colonized by this fungus. captan reduced the root length colonized by G. rosea at 48 days, but not at 82 days, and reduced colonization byG. mosseae at 82 days, but not at 48 days. Captan did not affect sporulation by any of the fungi.G. rosea spore production was highly variable, but benomyl appeared to reduce sporulation by this fungus. Overall,G. etunicatum was the most tolerant to fungicides in association with pea plants in this soil, andG. rosea the most sensitive. Benomyl and PCNB were overall more toxic to these fungi than captan. Interactions of AM fungi and fungicides were highly variable and biological responses depended on fungus-fungicide combinations and on environmental conditions.     

EXPLOITATION OF PHOSPHORUS PATCHES WITH DIFFERENT PHOSPHORUS ENRICHMENT BY THREE ARBUSCULAR MYCORRHIZAL FUNGI

The effect of three arbuscular mycorrhizal (AM) fungi on phosphorus (P) nutrient activation and acquisition by maize from spatially heterogeneous sand was investigated using dual-mesh packages enriched with different P concentrations and compared with non-mycorrhizal cotrols. As would be expected the AM fungi significantly enhanced leaf photosynthetic rate and the biomass and P concentrations in shoots and roots. All three fungi (Glomus intraradices, Glomus mosseae and Glomus etunicatum) displayed the capacity to dissolve inorganic P and promoted P nutrient availability in the packages (P patches). G. etunicatum showed the largest effect comparing with Glomus intraradices and Glomus mosseae, particularly in packages with high concentrations of P. Possible mechanisms involved include the acidification of the P patches by the AM fungi, promotion of the dissolution of the P, and more marked effects of the three fungal isolates with increasing enrichment of P in the patches. Inoculation with G. etunicatum resulted in greater acidification compared to the other two fungi. We conclude that AM fungi can promote P availability by acidifying the soil and consequently exploiting the P in nutrient patches and by facilitating the growth and development of the host plants.     

Interactive effects of co-inoculation of Bradyrhizobium japonicum strains and mycorrhiza species on soybean growth and nutrient contents in plant

The main objective of this study was to investigate the effects of co-inoculation with different strains of Bradyrhizobium japonicum (i.e. Helinitro, Rizoking, and Nitragin) and arbuscular mycorrhizal fungi (AMF) species (i.e. Glomus fasciculatum, Glomus versiforme, Glomus intraradices, Glomus mosseae, and Glomus etunicatum) on soybean growth, fungal root colonization, and nutrient uptake of nitrogen (N), phosphorus (P), zinc (Zn), iron (Fe), and copper (Cu). Co-inoculation with various AMF species and rhizobia significantly (p<0.01) increased the soybean biomass production as compared to the non-inoculated controls. Furthermore, AMF colonization of roots of soybean plants increased by 79, 70.1, 67, 63, 57.5, and 50.1% in the presence of G. fasciculatum (GF), G. versiforme (GV), G. intraradices (GI), G. mosseae (GM), and G. etunicatum (GE), and Gmix (a mixed culture of fungi), respectively. Higher nutrient contents were observed in plants co-inoculated with Helinitro and GF. More insight into these results will enable optimization of the effective use of AM fungi in combination with their bacterial partners as a tool for increasing soybean yields in Iran; however, its general analytical framework could be applied to other parts of the world.     

Mycorrhizae, biocides, and biocontrol 3. Effects of three different fungicides on developmental stages of three AM fungi

The effects of biocide use on nontarget organisms, such as arbuscular mycorrhizal (AM) fungi, are of interest to agriculture, since inhibition of beneficial organisms may counteract benefits derived from pest and disease control. Benomyl, pentachloronitrobenzene (PCNB) and captan were tested for their effects on the germination and early hyphal growth of the AM fungiGlomus etunicatum (Becker & Gerd.),Glomus mosseae (Nicol. & Gerd.). Gerd. and Trappe andGigaspora rosea (Nicol & Schenck) in a silty-clay loam soil placed in petri plates. Application of fungicides at 20 mg active ingredient (a.i) kg^?1 soil inhibited spore germination by all three AM-fungal isolates incubated on unsterilized soil for 2 weeks. However, fungicides applied at 10 mg a.i. kg^?1 soil had variable effects on AM-fungal isolates. Fungicide effects on germination and hyphal growth of G.etunicatum were modified by soil pasteurization and CO₂ concentration in petri plates and also by placing spores below the soil surface followed by fungicide drenches. Effects of fungicides on mycorrhiza formation and sporulation of AM fungi, and the resulting host-plant response, were evaluated in the same soil in associated pea (Pisum sativum L.) plants. Fungicides applied at 20 mg a.i. kg^?1 soil did not affect the root length colonized byG. etunicatum, but both benomyl and PCNB reduced sporulation by this fungus. Benomyl and PCNB reduced the root length colonized byG. rosea at 48 and 82 days after transplanting. PCNB also reducedG. mosseae-colonized root length at 48 and 82 days, but benomyl only affected root length colonized byG. mosseae at the earlier time point. Only PCNB reduced sporulation byG. mosseae, consistent with its effect on root length colonized by this fungus. captan reduced the root length colonized by G. rosea at 48 days, but not at 82 days, and reduced colonization byG. mosseae at 82 days, but not at 48 days. Captan did not affect sporulation by any of the fungi.G. rosea spore production was highly variable, but benomyl appeared to reduce sporulation by this fungus. Overall,G. etunicatum was the most tolerant to fungicides in association with pea plants in this soil, andG. rosea the most sensitive. Benomyl and PCNB were overall more toxic to these fungi than captan. Interactions of AM fungi and fungicides were highly variable and biological responses depended on fungus-fungicide combinations and on environmental conditions.     

Mineral Uptake of Mycorrhizal Wheat (Triticum aestivum L.) under Salinity Stress

The hypothesis was that arbuscular mycorrhizal (AM) fungi are able to alleviate salt stress on plant growth by enhancing and adjusting mineral uptake. The objectives were to determine (1) the effects of soil salinity on mineral uptake by different wheat genotypes and (2) the effectiveness of different mycorrhizal treatments on the mineral uptake of different wheat (Triticum aestivum L.) genotypes under salinity. Wheat seeds of Chamran and Line 9 genotypes were inoculated with different species of AM fungi including Glomus mosseae, G. intraradices, and G. etunicatum and their mixture at planting using 100 g inoculum. Pots were treated with the salinity levels of 4, 8, and 12 dS/m before stemming. Different arbuscular mycorrhizal treatments, especially the mixture treatment, increased wheat mineral uptake for both genotypes. Although Line 9 genotype resulted in greater nutrient uptake under salinity stress, Chamran was more effective on adjusting sodium (Na⁺) and chloride (Cl^?) uptake under salt stress.     

RESPONSE OF MAIZE GENOTYPES TO SEVERAL MYCORRHIZAL INOCULUMS IN TERMS OF PLANT GROWTH,NUTRIENT UPTAKE AND SPORE PRODUCTION

A greenhouse experiment was conducted at the University of Çukurova, Rhisosphere Lab, Adana, Turkey, on a growth medium to assess the impact of several selected mycorrhiza including indigenous AMF-maize hybrid combinations on spore production, plant growth and nutrient uptake. In the experiment, six maize (Zea mays L.) (Luce, Vero, Darva, Pegasso, P.3394, and P.32K61) genotypes were used. Control, Glomus mossea, G. caledonium, G. etunicatum, G. clarium, G. macrocarpum, G. fasciculatum, G. intraradices, Dr. Kinkon (Japanese species), indigenous mycorrhizae (Balcal? series) and cocktail mycorrhizae species spores were used. The growth of maize genotypes was found to depend on the mycorrhizal species. For shoot and root dry weight production G. intraradices is one of the most efficient mycorrhiza species on average on all maize genotypes. Genotypes P.3394 and P.32K61 produced the highest shoot and root dry weight as well. Pagasso and Darva genotypes compared to the other genotypes have high root colonization percentages. On average G. clarium inoculated plants also have high percentages of root colonization. It has been found that the P.32K61 genotype has a high phosphorus (P)% content and Pagasso genotypes have higher zinc (Zn) content uptake than other genotypes. G. clarium inoculated maize genotype plant tissues have high P% and Zn content. G. intraradices is also efficient for P and Zn uptake. Mycorrhizal dependent maize genotypes showed variability in P efficiency from inefficient to efficient genotypes.     

Screening of Arbuscular Mycorrhizal Fungi for Symbiotic Efficiency with Sweet Potato

A greenhouse study was conducted to study the efficiency of 14 isolates of arbuscular mycorrhizal (AM) fungi isolated from a local agricultural soil on the productivity of sweet potato (Ipomoea batatas). The different AM fungi enhanced the biomass and nutritional status of sweet potato seedlings to different extents. The genus Glomus was more effective than Acaulospora or Scutellospora. Efficiency also varied among isolates of Glomus irrespective of individual host plant or location of origin. Intraspecific differences were sometimes greater than interspecific differences. Benefits deriving from fungal isolates were positively correlated with the root-colonization rate and the abundance of extraradical propagules of the AM fungi. Taking plant yield parameters, nutritional status of the plants, and fungal attributes into consideration, GEGM (Glomus etunicatum together with Glomus mosseae) and GE6 (Glomus etunicatum) were the most effective AM symbionts for sweet potato under the experimental conditions.     

Impact of Mycorrhizae Formation on the Phosphorus and Heavy-Metal Uptake of Alfalfa

Three pot experiments were set up to determine how efficiently mycorrhizal fungi affect the uptake, translocation, and distribution of labeled phosphorus (³²P), phosphorus (P), and heavy metals in alfalfa (Medicago sativa L.). In experiments 1 and 2, the efficiencies of different arbuscular mycorrhizal fungi (AMF) species including Glomus mosseae, G. etunicatum, G. intraradices and a mixed strain (G. mosseae, Gigaspora hartiga, and G. fasciculatum) on uptake, translocation, and distribution of ³²P and P in alfalfa were investigated, respectively. In a third experiment, the efficiency of G. mosseae on uptake and distribution of heavy metals [cadmium (Cd), cobalt (Co), lead (Pb), and combinations] was tested. Results of experiments 1 and 2 suggest that G. mosseae was the most effective at increasing the uptake of ³²P and P. Experiment 3 result showed that in the triple-metal-contaminated soil, inoculated plants had greater Co (32.56 mg kg^?1) and Pb (289.50 mg kg^?1) concentration and G. mosseae enhanced the translocation of heavy metals to shoot. Hence, mycorrhizal alfalfa in symbiosis with G. mosseae can be used for remediation of heavy metals polluted soils with high efficiency.     

Arbuscular mycorrhizal fungi associated with wild forage plants in typical steppe of eastern Inner Mongolia

A preliminary investigation was conducted on the arbuscular mycorrhizal (AM) status of the dominant and common wild forage plants in typical steppe of eastern Inner Mongolia, a major semi-arid grassland region in China. Fifty-four wild forage plant species were collected and examined, and 27 of these were colonized by AM fungi. Some plants belonging to families that are presumed to lack mycorrhizas (Cyperaceae, Caryophyllaceae and Chenopodiaceae) were also found to be mycorrhizal. Higher proportions of arbuscular mycorrhizal plants were found in perennial (56.1%) and monocotyledonous (64.7%) forage species. However, neither percentage of root length colonized nor spore density varied significantly between the two life forms or cotyledon types. Twenty-seven species belonging to 7 genera of AM fungi were identified in total according to the morphological characteristics of the spores from field soil and trap cultures, and the results indicate that Glomus was the dominant AM genus and Glomus geosporum (Nicolson & Gerdemann) Walker and Glomus mosseae (Nicolson & Gerdemann) Gerdemann & Trappe were the dominant species in field soil and trap cultures, respectively. Glomus intraradices Schenck & Smith, Glomus etunicatum Becher & Gerdemann, Glomus claroideum Schenk & Smith emend Walker & Vestberg, Glomus clarum Nicolson & Schenck and Scutellospora callospora (Nicolson & Gerdemann) Walker & Sanders also occurred with high frequencies.     

The sensitivity of three vesicular‐arbuscular mycorrhizal species to simulated erosion

Abstract

A greenhouse experiment was conducted to determine the effectiveness of three vesicular‐arbuscular mycorrhizal (VAM) species in an Oxisol subjected to simulated erosion using Leucaena leucocephala as an indicator host. The extent of colonization of leucaena roots increased significantly due to VAM inoculation of the eroded and uneroded soils. The highest level of VAM colonization was observed when leucaena was grown in association with Glomus aggregatum. followed by G. mosseae and G. etunicatum. Increased infection associated with inoculation of the eroded soil did not result in enhanced mycorrhizal effectiveness. Inoculation of the uneroded soil, however, led to significant improvement in root colonization as well as in symbiotic effectiveness. Suppression in expression of mycorrhizal effectiveness in the eroded soil appears to be a result of nutrient deficiency. The results suggest the importance of restoring lost nutrients before differences in VAM species could be effectively exploited for a successful establishment of a mycorrhizal plants in eroded soils.     

Interaction between Alternaria alternata or Fusarium equiseti and Glomus mosseae and its effects on plant growth

The effect of inoculation with the saprophytic fungi Alternaria alternata or Fusarium equiseti on maize (Zea mays) and lettuce (Lactuca sativa) with or without arbuscular mycorrhizal (AM) colonization by Glomus mosseae was studied in a greenhouse trial. Plant dry weights of non-AM-inoculated maize and lettuce were unaffected by the presence of A. alternata and F. equiseti. In contrast, A. alternata and F. equiseti decreased plant dry weights and mycorrhization when inoculated to the rhizosphere before G. mosseae. The saprophytic fungi inoculated 2 weeks after G. mosseae did not affect the percentage of root length colonized by the AM endophyte, but did affect its metabolic activity assessed as succinate dehydrogenase activity. Although F. equiseti inoculated at the same time as G. mosseae did not affect mycorrhization of maize roots, its effect on AM colonization of lettuce roots was similar to that with A. alternata. In the rhizosphere of both plants, the population of saprophytic fungi decreased significantly, but was not affected by the presence of G. mosseae. Our results suggest that there may have been a direct effect of the saprophytic fungi on the mycorrhizal fungi in the extramatrical phase of the latter, and when the AM fungus was established in the root the AM fungus was less affected by the saprophytic fungi. Received: 16 January 1996     

Spore production by the vesicular-arbuscular mycorrhizal fungus Glomus monosporum as related to host species,root colonization and plant growth enhancement

Summary The vesicular-arbuscular mycorrhizal fungus Glomus monosporum was inoculated on grapevine (Vitis vinifera), red clover (Trifolium pratense), meadow grass (Poa pratensis) and onion (Allium cepa) as hosts in two experiments carried out in different environments. Grapevine and clover showed the largest growth response and spore production. Mycorrhizal infection was lowest in meadow grass. Very poor correlations were observed, on an overall basis, between spore production and per cent root infection or infected root length. Spore production per unit infected root length for each host species was a comparatively stable parameter; it was largest for grapevine and smallest for meadow grass in both experiments. Sporulation was positively correlated with growth enhancement by mycorrhizal plants, and growth increments per unit infected root followed the same trend as spore numbers per unit infected root, i.e. largest for grapevine and lowest for meadow-grass. It is concluded that the ability of G. monosporum to produce spores and to enhance plant growth per unit infected root length depends on the host plant species.