Susceptibility and effectiveness of vesicular-arbuscular mycorrhizae in wheat cultivars under different growing conditions

Summary Wheat cultivars assumed to be non-susceptible to vesicular-arbuscular (VA) mycorrhizae became colonized, and this effect persisted under different growth conditions. Colonization of all cultivars was similar regardless of the amount of inoculum and the time interval of inoculation. Different plant growth temperatures and the support given by the culture media, inoculation with different endophytes, and inoculation with sterilized and unsterilized spores affected VA colonization levels, although the level of colonization reached in cv. Champlein was similar to that reached in cv. 7-Cerros under each condition. VA mycorrhizal colonization was also affected by different plant growth conditions. After VA reinoculation, the plant dry weight of Castan and 7-Cerros increased, but not Negrillo and Champlein cultivars. VA mycorrhizae increased the shoot dry weight of 7-Cerros only, but not of Champlein, when grown at 35/24°C, and had no effect on the dry weight of either cultivar grown at 18/12°C and 42/24°C. Inoculation with Glomus mosseae increased the dry weight of the cultivars more than inoculation with G. fasciculatum or G. agregatum. The effect on the plant dry weight was greater in plants grown in soil than in sand/vermiculite pots. Inoculation with sterilized and unsterilized spores of G. mosseae, either in soil pots or in sand/vermiculite tubes, did not increase the plant dry weight. Our results indicate that there was no close relationship between the level of root colonization and the effect on plant growth. The effects of accompanying microorganisms in the VA inoculum on VA mycorrhizal symbiosis are discussed.     

Plant and soil responses to mycorrhizal fungi and rhizobacteria in nodulated or nitrate-fertilized peas (Pisum sativum L.)

Rhizosphere organisms affect plant development and soil stability. This study was conducted to determine the effects of a vesicular-arbuscular mycorrhizal (VAM) fungus [Glomus mosseae (Nicol. &>; Gerd.) Gerd. and Trappe] and a rhizobacterium (Bacillus sp.) on nitrate-fertilized or nodulated pea (Pisum sativum L.) plants and on the status of water-stable soil aggregates. The plants were grown in pots in a yellow clay-loam soil, and inoculated with the VAM fungus and the rhizobacterium, with one of the two, or with neither. The Bacillus sp. and G. mosseae did not affect shoot dry mass in nodulated plants. Under N fertilization, the VAM fungus enhanced plant growth, while the rhizobacterium inhibited shoot growth, VAM root colonization, and nodule formation, but enhanced the root:shoot and the seed:shoot ratios. The inhibition of shoot growth and of root colonization appeared to be related. The water stability and pH of the VAM soils were higher than those of the non-VAM soils. The rhizobacterium enhanced the water-stable aggregate status in the non-VAM soils only. Under both N-nutrition regimes, the soils had the greatest proportion of the water-stable aggregates when inoculated with both rhizo-organisms and the lowest when colonized by neither. The two rhizo-organisms affected both plants and soil, and these effects were modified by the source of N input through N₂ fixation or fertilization. Received: 5 April 1995     

VA菌根菌丝对紧实土壤中磷的吸收

本文采用三室隔网盆栽试验方法,选择三种土壤容重(1.3;1.6;1.8g/cm3)来模拟自然条件下不同紧实度对植物根系生长的抑制情况,探讨了接种VA菌根真菌Gmosseae对三叶草植株生长和对土壤磷吸收的影响。结果表明随着土壤容重的增加,三叶草根系生长受到抑制的程度随之加重。当土壤容重为1.8g/cm3时,根系基本不能生长,而菌丝却能在其中伸展并吸收养分。表现为1.8土壤容重的处理菌根植物的含磷量明显高于无菌根植物。而在低容重的处理中两者却没有显著差异。说明VA菌根真菌能缓解甚至消除土壤机械阻力对植物生长的胁迫。     

Effects of AM fungi and organic fertilizers on the reproduction of the nematode <Emphasis Type="Italic">Meloidogyne incognita</Emphasis> and on the growth and water loss of tomato

Glasshouse experiments were conducted to assess the influence of arbuscular mycorrhizal (AM) fungi (Glomus mosseae and Gigaspora margarita) and organic fertilizers (cow dung, horse dung, goat dung and poultry manure) alone and in combination on the reproduction of the nematode Meloidogyne incognita and on growth and water loss of tomato. Meloidogyne incognita decreased water loss of tomato from the first week onwards after inoculation. AM fungi increased water loss of both nematode-infected and uninfected plants. Glomus mosseae was better at improving growth of tomato and reducing galling and nematode multiplication than G. margarita, but the rate of water loss was similar with both fungi. Addition of organic fertilizers improved growth of tomato, but decreased the rate of water loss. There was less galling and nematode multiplication with poultry manure, which improved tomato growth more than goat dung, while cow dung was the least effective organic fertilizer. Greatest plant growth and least nematode reproduction were observed in plants inoculated with M. incognita along with G. mosseae and poultry manure.     

Mycorrhizae,biocides, and biocontrol. 4. Response of a mixed culture of arbuscular mycorrhizal fungi and host plant to three fungicides

The effects of three commonly used fungicides on the colonization and sporulation by a mixture of three arbuscular mycorrhizal (AM) fungi consisting of Glomus etunicatum (Becker & Gerd.), Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, and Gigaspora rosea (Nicol. & Schenck) in symbiosis with pea plants and the resulting response of the host-plant were examined. Benomyl, PCNB, and captan were applied as soil drenches at a rate of 20 mg active ingredient kg^-1 soil 2 weeks after transplanting pea seedlings in a silty clay-loam soil containing the mixed inocula of AM fungi (AM plants). Effects of fungicides were compared to untreated plants that were inoculated with fungi (AM control). The effect of mycorrhizal inoculation on plant growth was also examined by including nonmycorrhizal, non-fungicide-treated plants (non-AM control). Fungicides or inoculation with AM fungi had only a small effect on the final shoot weights of pea plants, but had greater effects on root length and seed yield. AM control plants had higher seed yields and lower root lengths than the corresponding non-AM plants, and the fungicide-treated AM plants had intermediate yields and root lengths. Seed N and P contents were likewise highest in AM control plants, lowest in non-AM plants, and intermediate in fungicide-treated AM plants. All three fungicides depressed the proportion (%) of root length colonized by AM fungi, but these differences did not translate to reductions in the total root length that was colonized, since roots were longer in the fungicide-treated AM plants. Pea plants apparently compensated for the reduction in AM-fungal metabolism due to fungicides by increasing root growth. Fungicides affected the population of the three fungi as determined by sporulation at the final harvest. Captan significantly reduced the number, relative abundance, and relative volume of G. rosea spores in the final population relative to the controls. The relative volume of G. etunicatum spores was greater in all the fungicide-treated soils, while G. mosseae relative volumes were only greater in the captan-treated soil. These findings show that fungicides can alter the species composition of an AM-fungal community. The results also show that AM fungi can increase seed yield without enhancing the vegetative shoot growth of host plants.     

Interactions between the arbuscular mycorrhizal fungus Glomus mosseae and plant growth-promoting fungi and their significance for enhancing plant growth and suppressing damping-off of cucumber (Cucumis sativus L.)

This study investigated the interactions between the arbuscular mycorrhizal fungus (AMF) Glomus mosseae and the plant growth-promoting fungi (PGPF) Penicillium simplicissimum GP17-2 and Trichoderma harzianum GT3-2 in relation to their colonization of roots and the rhizosphere of cucumber (Cucumis sativus L.), and their effect on plant growth and suppression of the damping-off pathogen Rhizoctonia solani. Combined inoculation of T. harzianum with G. mosseae increased the percentage of AMF root colonization, but the presence of P. simplicissimum had no significant effect on mycorrhizal formation. The existence of G. mosseae decreased the population development of T. harzianum in and/or around the roots, however, growth of P. simplicissimum was not affected. Both PGPF isolates were effective in increasing the plant shoot and root dry weight, G. mosseae, however, was not. Nevertheless, co-inoculation of G. mosseae with T. harzianum synergistically enhanced plant growth. A comparable additive effect on plant growth was not observed when P. simplicissimum was combined with G. mosseae. Treating plants with the PGPF either simultaneously with the pathogen or prior to pathogen infection suppressed damping-off disease. G. mosseae was significantly effective in reducing disease severity when inoculated prior to the pathogen but not when inoculated simultaneously with the pathogen. Interestingly, the levels of disease protection achieved by the single inoculation of P. simplicissimum, T. harzianum or G. mosseae were significantly increased by combined inoculation of each PGPF with G. mosseae.     

长期施肥黑土微生物区系及功能多样性的变化

Black soil （Mollisol） is one of the main soil types in northeastern China. Biolog and polymerase chain reactiondenaturing gradient gel electrophoresis （PCR-DGGE） methods were used to examine the influence of various fertilizer combinations on the structure and function of the bacterial community in a black soil collected from Harbin, Heilongjiang Province. Biolog results showed that substrate richness and catabolic diversity of the soil bacterial community were the greatest in the chemical fertilizer and chemical fertilizer＋manure treatments. The metabolic ability of the bacterial community in the manure treatment was similar to the control. DGGE fingerprinting indicated similarity in the distribution of most 16S rDNA bands among all treatments, suggesting that microorganisms with those bands were stable and not influenced by fertilization. However, chemical fertilizer increased the diversity of soil bacterial community. Principal com- ponent analysis of Biolog and DGGE data revealed that the structure and function of the bacterial community were similar in the control and manure treatments, suggesting that the application of manure increased the soil microbial population, but had no effect on the bacterial community structure. Catabolic function was similar in the chemical fertilizer and chemical fertilizer＋manure treatments, but the composition structure of the soil microbes differed between them. The use of chemical fertilizers could result in a decline in the catabolic activity of fast-growing or eutrophic bacteria.     

Effects of inoculation with Glomus mosseae, Azorhizobium caulinodans and rock phosphate on the growth of and nitrogen and phosphorus accumulation in Sesbania rostrata

A study was carried out to evaluate the influence of single or dual inoculation with Glomus mosseae and Azorhizobium caulinodans with and without rock phosphate on the growth of and N, P and K accumulation in Sesbania rostrata grown in sterilized soil. Height of plants inoculated with G. mosseae in combination with A. caulinadans and/or rock phosphate was significantly higher than that of uninoculated plants or plants inoculated with A. caulinodans alone before but not after 28 days. However, the oven-dry weight of shoots and roots from all treatments did not vary significantly. Generally, concentration and uptake of N and P but not K in shoots and roots of plants were improved by dual inoculation with G. mosseae and A. caulinodans plus or minus P. Mycorrhizal infection of roots was enhanced significantly by A. caulinodans. Received: 18 March 1996     

Nitrogen fixation and CO2 exchange in soybeans (Glycine max L.) inoculated with mixed cultures of different microorganisms

N₂ fixation, photosynthesis of whole plants and yield increases in soybeans inoculated with mixed cultures of Bradyrhizobium japonicum 110 and Pseudomonas fluorescens 20 or P. fluorescens 21 as well as Glomus mosseae were found in pot experiments in gray forest soil carried out in a growth chamber. The effects of pseudomonads and vesicular-arbuscular (VA) mycorrhizal fungus on these parameters were found to be the same. Dual inoculation of soybeans with mixed cultures of microorganisms stimulated nodulation, nitrogenase activity of nodules and enhanced the amount of biological nitrogen in plants as determined by the ¹⁵N dilution method in comparison to soybeans inoculated with nodule bacteria alone. An increased leaf area in dually infected soybeans was estimated to be the major factor increasing photosynthesis. P. fluorescens and G. mosseae stimulated plant growth, photosynthesis and nodulation probably due to the production of plant growth-promoting substances. Increasing phosphorus fertilizer rates within the range of 5–40 mg P 100 g^-1 1:1 (v/v) soil: sand in a greenhouse experiment led to a subsequent improvement in nodulation, and an enhancement of N₂ fixation and yield in soybeans dually inoculated with B. japonicum 110 and P. fluorescens 21. These indexes were considerably higher in P-treated plants inoculated with mixed bacterial culture than in plants inoculated with nodule bacteria alone.     

Enhancement of Lead Uptake by Fenugreek Using EDTA and Glomus mosseae

The influence of Glomus mosseae supplemented with ethylenediaminetetraacetic acid (EDTA) on lead (Pb) uptake by Fenugreek (Trigonella foenum-graecum) was studied under pot conditions in a 2?×?2?×?5 factorial design with two AM treatments (G. mosseae inoculated and uninoculated), two EDTA concentrations (without and with 2.5 mmol EDTA kg^?1), and five lead concentrations (0, 50, 100, 400, and 800 mg kg^?1). A negative interaction was found between increasing lead concentration and G. mosseae. The plant dry matter and chlorophyll content was enhanced by G. mosseae whereas G. mosseae with EDTA showed the greatest root and shoot phosphorus (P) content. Ethylenediaminetetraacetic acid significantly enhanced lead concentration in the plant; however, at the same time it resulted in a slight decrease in the dry matter. However, when EDTA was applied along with G. mosseae, the deleterious effect of EDTA was overcome by the G. mosseae by promoting mineral uptake and plant growth, and hence metal accumulation also increased.     

Protecting Cucumber from Fusarium Wilt with Arbuscular Mycorrhizal Fungi

A pot experiment was conducted to investigate the biocontrol effects of arbuscular mycorrhizal fungi (AMF) Glomus mosseae and Glomus versiforme on Fusarium oxysporum wilt disease of cucumber (Cucumis sativus L.). The results indicated that both AMF improved the growth of cucumber seedlings and reduced disease severity, but G. versiforme was more efficient. Compared with nonmycorrhizal plants infected by F. oxysporum, shoots and roots dry weights increased by 100% and 80% in G. versiforme–inoculated plants, and the qualities of seedlings were significantly improved; meanwhile, nitrogen, phosphorus, and potassium contents in shoots of G. versiforme–inoculated plants were significantly greater than those of G. mosseae–inoculated plants and nonmycorrhizal plants. Moreover, for mycorrhizal plants, soluble sugar and free proline contents in mycorrhizal roots were significantly greater than those of nonmycorrhizal treatment; however, malonaldehyde content in roots and the quantity of fungi in rhizosphere decreased when the plants were attacked by F. oxysporum.     

Effect of manganese on the resistance of tomato to Pseudocercospora fuligena

Black leaf mold caused by Pseudocercospora fuligena is an important fungal disease of tomato in Southeast Asia. The objective of this study was to evaluate the control of this disease using high manganese (Mn) applied to the root substrate and to evaluate the role of the leaf apoplast in plant response to fungal infection. In a nethouse experiment in Thailand, Mn above the optimum for plant growth but below toxicity increased resistance of tomato plants to black leaf mold. Enhanced resistance caused by Mn was also obtained when tomato plants were grown under controlled conditions in a mist chamber and artificially inoculated with the fungus. Manganese significantly increased plant peroxidases in the leaf apoplast. The highest peroxidase activity was measured when plants were inoculated with Pseudocercospora fuligena. Defense‐related proteins in the leaf apoplast increased when plants were inoculated with Pseudocercospora fuligena but not when treated with high Mn. It is concluded that Mn above the optimum level for plant growth can contribute to the control of Pseudocercospora fuligena in tomato. The Mn effect on disease resistance is associated with the activation of plant peroxidases in the leaf apoplast. A systemic response, possibly mediated by NADH peroxidase activity, also seems to trigger disease resistance in leaves with low Mn concentrations.     

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     

VA菌根对蚕豆吸收钼、磷营养的研究

在肥力较低的灰棕紫泥土上,研究了VA菌根(Glomus epigaeum)对蚕豆(Vicia faba)的钼、磷营养及其效应。盆裁试验结果表明,接种VA菌根不仅有利于植物对磷的吸收,而且还有利于钼的吸收。并能促进根系生长和根瘤形成,进而促进地上部分生长,植株健壮,抗赤斑病能力和抗衰老能力增强,从而使产量和品质等都优于未接种VA菌根处理的植株。其中以Mo+P+VA处理的植株最好,Mo+VA处理的植株次之.     

Inoculation withGlomus mosseae improves N2 fixation by field-grown soybeans

Summary A field study carried out in a sandy, relatively acid Senegalese soil with a low soluble P content (7 ppm) and low vesicular-arbuscular mycorrhizal (VAM) populations showed that soybean responded toGlomus mosseae inoculation when the soluble P level in the soil had been raised by the addition of 22 kg P ha^–1. In P-fertilized plots, N₂ fixation of soybean, assessed by the A value method, was 109 kg N₂ fixed hat when plants were inoculated withRhizobium alone and it reached 139 kg N₂ fixed ha^–1 when plants were dually inoculated withRhizobium andGlomus mosseae using an alginate bead inoculum. In addition to this N₂ fixation increase (+28%),Glomus mosseae inoculation significantly improved grain yield (+13%) and total N content of grains (+16%). This success was attributed mainly to the low infection potential of the native VAM populations in the experimental site. In treatments without solubleP or with rock phosphate, no effect of VAM inoculation was observed.     

The influence of use of different rates of mycorrhizal inoculum on root infection,plant growth,and phosphorus uptake

Abstract

Sorghum and leek plants were used as hosts in order to test the effectiveness and infectiveness of four mycorrhizal species on spore production, plant growth and phosphorus (P) uptake. When sorghum was used as a test plant, Glomus mosseae, Glomus etunicatum, and Glomus caledonium, respectively, gave the highest number of spores, while on leek, G. etunicatum, G. mosseae, and G. caledonium, respectively, resulted in higher spore production. Glomus intraradices produced the least amount of inoculum among the four species. Based on relative spore production and root infection, G. mosseae and G. etunicatum were determined to be the two best fungi as sources of inoculum for further use in the experiment. It is very important to know the minimum amount of inoculum in order to reach the maximum percentage of infection. Thus different amounts of inoculum were applied to determine optimum rates of inoculation. Sorghum and leek plants were infected with 0, 6, 12, 18, and 24 g G. mosseae and G. etunicatum of mycorrhizal inoculum per pot in a low P content and natural soil. As the inoculum rate increased, plant parameters and the percent of infection gradually increased with increasing rate to 18 g. Higher inoculum rates did not stimulate growth on infection percentage.     

The significant contribution of mycorrhizal fungi and earthworms to maize protection and phytoremediation in Cd-polluted soils

Mycorrhizal fungi and earthworms can individually or interactively influence plant growth and heavy metal uptake. The influence of earthworms and arbuscular mycorrhizal (AM) fungi either alone or in combination on maize (Zea mays L.) growth and cadmium (Cd) uptake was investigated in a calcareous soil artificially spiked with Cd. Soils were contaminated with Cd (10 and 20 mg Cd kg⁻¹), inoculated or un-inoculated with the epigeic earthworm Lumbricus rubellus and two AM fungal species (Rhizophagus irregularis and Funneliformis mosseae) for two months of growth under greenhouse conditions. Generally, earthworms alone increased both shoot P uptake and biomass but decreased shoot Cd concentration and root Cd uptake. AM fungi individually often increased total maize P uptake, declined shoot Cd concentration, and consequently produced higher total biomass. However, R. irregularis enhanced shoot Cd uptake at low Cd level and root Cd uptake at high Cd level. In plants inoculated with F. mosseae species, earthworms increased shoot biomass and Cd uptake, decreased root biomass and Cd uptake at all Cd levels, and increased shoot Cd concentration at low Cd level. In plants colonized by R. irregularis species, however, earthworm addition decreased maize biomass only at high Cd level and root Cd concentration and total maize Cd uptake at both Cd levels. Earthworm activity decreased Cd transfer from the soil to maize roots at low Cd level, but this was counterbalanced in the presence of F. mosseae. Mycorrhizal symbiosis significantly reduced the transfer of Cd from roots to shoots, independence of earthworm effect. Overall, it is concluded that L. rubellus and AM fungi, in particular F. mosseae isolate, improved maize tolerance to Cd toxicity both individually and interactively by increasing plant growth and P nutrition, and restricting Cd transfer to the aboveground biomass. Consequently, the single and interactive effects of the two soil organisms might potentially be important not only in protecting maize plants against Cd toxicity, but also in Cd phytostabilization in soils polluted by this highly toxic metal.     

Effects of benomyl on vesicular‐arbuscular mycorrhizal infection of red clover (Trifolium pratense L.) and consequences for phosphorus inflow.

The roots of red clover plants inoculated with the vesicular‐arbuscular mycorrhizal fungus Glomus clarus Nicolson & Schenck were treated with a drench of benomyl at a time when mycorrhizal infection was already well established. Benomyl halted further infection and reduced phosphorus inflow by one order of magnitude compared to untreated controls. The fungicide also decreased the rate of plant growth probably as a consequence of reduced phosphorus inflow.     

Efficacy,phytotoxicity and economics of different herbicides in aerobic rice

Abstract

Aerobic rice is a potential water-wise rice production system, but high weed infestation has threatened its sustainability, which demands an efficient and cost-effective weed management technique. Eight commercial herbicide products were applied singly or as tank-mix or in sequence to evaluate their efficacy, rice selectivity and cost-effectiveness in aerobic rice. The study was conducted under field conditions in Malaysia during 2010/2011 following a randomized complete block design. Most of the herbicide treatments provided excellent weed control, and produced much higher net benefit than weedy or weed-free check. None of the herbicides caused significant phytotoxicity to rice plants. Among the herbicide treatments, sequential application of Cyhalofop-butyl+Bensulfuron at early growth stage followed by Bentazon/MCPA at mid growth stage provided the highest weed control efficiency, productivity and net benefit. Application of Bispyribac-sodium at early growth stage followed by Bentazon/MCPA at mid growth stage performed very close to the above-mentioned treatments. Sequential application of Pretilachlor/safener just after seeding followed by Propanil/Thiobencarb at early growth stage also provided satisfactory results in terms of efficacy and economic return. Since manual weeding was not economic, herbicide rotation using the above chemicals may be recommended for effective weed management in aerobic rice.     

Interaction between AM fungi and a liquid organic amendment with respect to enhancement of the performance of the leguminous shrub Retama sphaerocarpa

This study examined the interactions between the inoculation with three arbuscular mycorrhizal fungi, namely, Glomus intraradices, Glomus deserticola and Glomus mosseae, and the addition of a liquid organic amendment at different rates (0, 50, 100 or 300 mg C of liquid amendment per kilogram soil) obtained by alkaline extraction of composted dry olive residue with respect to their effects on growth of Retama sphaerocarpa seedlings and on some microbiological and physical properties of soil. One year after planting, both mycorrhizal inoculation treatments and the addition of amendment had increased plant growth and dehydrogenase, urease and benzoyl argininamide hydrolysing activities. The inoculation with G. mosseae increased plant growth to a greater extent than the addition of the amendment (about 35% greater than plants grown in the amended soil and about 79% greater than control plants) and both treatments produced similar increases in soil aggregate stability (about 31% higher than control soil). The organic amendment produced a very significant decrease in the levels of microbial biomass C and a strong increase in soil dehydrogenase and urease activities, which were proportional to the amendment rate. Only the combined treatment involving the addition of a medium dose of amendment (100 mg C kg⁻¹ soil) and the mycorrhizal inoculation with G. intraradices or G. deserticola produced an additive effect on the plant growth with respect to the treatments applied individually (about 77% greater than plants grown in the amended soil and about 63% greater than inoculated plants).