Arbuscular mycorrhizal fungi and Trichoderma viride mediated Fusarium wilt control in tomato

The biocontrol potential of two arbuscular mycorrhizal fungi (AMF) (Funneliformis mosseae and Acaulospora laevis) and Trichoderma viride was assessed against tomato wilt caused by Fusarium oxysporum Schlecht. f. sp. lycopersici under pot condition. All the bioagent showed appreciable results in increasing plant growth. Combined inoculation of F. mosseae, A. laevis and T. viride showed maximum increases in plant height, shoot fresh weight, root dry weight, number of leaves and number of branches per plant while dual inoculation of F. mosseae and T. viride increased rest of the growth parameters like shoot dry weight, root fresh weight, root length and leaf area. AM colonisation and spore number was found highest in single inoculation of AMF, which decreases with the addition of T. viride. But, this decrease has no effect on biocontrol efficiency of bioagents. Photosynthesis, chlorophyll content and nutrient content were markedly decreased by pathogen infection. Bioagent application overcomes this effect and a remarkable increase in the plant phosphorus and nitrogen content was recorded. Among both the AMF, F. mosseae proved to be more effective strain compared to A. laevis for tomato. Maximum reduction in disease incidence and severity was recorded in combined inoculation of F. mosseae, A. laevis and T. viride. Whereas control plants without any bioagent showed maximum occurrence of disease. The findings of this study concludes that soil inoculation with F. mosseae along with root inoculation with conidial suspension of T. viride before transplantation offered better survival and resistance to tomato seedlings against Fusarium wilt.     

Impact of two fluorescent pseudomonads and an arbuscular mycorrhizal fungus on tomato plant growth,root architecture and P acquisition

The ability of fluorescent pseudomonads and arbuscular mycorrhizal fungi (AMF) to promote plant growth is well documented but knowledge of the impact of pseudomonad-mycorrhiza mixed inocula on root architecture is scanty. In the present work, growth and root architecture of tomato plants (Lycopersicon esculentum Mill. cv. Guadalete), inoculated or not with Pseudomonas fluorescens 92rk and P190r and/or the AMF Glomus mosseae BEG12, were evaluated by measuring shoot and root fresh weight and by analysing morphometric parameters of the root system. The influence of the microorganisms on phosphorus (P) acquisition was assayed as total P accumulated in leaves of plants inoculated or not with the three microorganisms. The two bacterial strains and the AMF, alone or in combination, promoted plant growth. P. fluorescens 92rk and G. mosseae BEG12 when co-inoculated had a synergistic effect on root fresh weight. Moreover, co-inoculation of the three microorganisms synergistically increased plant growth compared with singly inoculated plants. Both the fluorescent pseudomonads and the myco-symbiont, depending on the inoculum combination, strongly affected root architecture. P. fluorescens 92rk increased mycorrhizal colonization, suggesting that this strain is a mycorrhization helper bacterium. Finally, the bacterial strains and the AMF, alone or in combination, improved plant mineral nutrition by increasing leaf P content. These results support the potential use of fluorescent pseudomonads and AMF as mixed inoculants for tomato and suggest that improved tomato growth could be related to the increase in P acquisition.     

Contributions of arbuscular mycorrhizal fungi to growth,photosynthesis, root morphology and ionic balance of citrus seedlings under salt stress

A pot study was conducted to determine the effects of arbuscular mycorrhizal (AM) fungi (Glomus mosseae and Paraglomus occultum) and salt (NaCl) stress on growth, photosynthesis, root morphology and ionic balance of citrus (Citrus tangerine Hort. ex Tanaka) seedlings. Eighty-five-day-old seedlings were exposed to 100 mM NaCl for 60 days to induce salt stress. Mycorrhizal colonization of citrus seedlings was not affected by salinity when associated with P. occultum, but significantly decreased when with G. mosseae. Compared with the non-mycorrhizal controls, mycorrhizal seedlings generally had greater plant height, stem diameter, shoot, root and total plant biomass, photosynthetic rate, transpiration rate and stomatal conductance under the 0 and 100 mM NaCl stresses. Root length, root projected area and root surface area were also higher in the mycorrhizal than in the non-mycorrhizal seedlings, but higher root volume in seedlings with G. mosseae. Leaf Na⁺ concentrations were significantly decreased, but leaf K⁺ and Mg²⁺ concentrations and the K⁺/Na⁺ ratio were increased when seedlings with both G. mosseae and P. occultum. Under the salt stress, Na⁺ concentrations were increased but K⁺ concentrations decreased in the mycorrhizal seedlings. Under the salt stress, Ca²⁺ concentrations were increased in the seedlings with P. occultum or without AM fungi (AMF), but decreased with G. mosseae. Ratios of both Ca²⁺/Na⁺ and Mg²⁺/Na⁺ were also increased in seedlings with G. mosseae under the non-salinity stress, while only the Mg²⁺/Na⁺ ratio was increased in seedlings with P. occultum under the salt stress. Our results suggested that salt tolerance of citrus seedlings could be enhanced by associated AMF with better plant growth, root morphology, photosynthesis and ionic balance.     

The differential behavior of arbuscular mycorrhizal fungi in interaction with Astragalus sinicus L. under salt stress

Three arbuscular mycorrhizal (AM) fungi (Glomus mosseae, Glomus claroideum, and Glomus intraradices) were compared for their root colonizing ability and activity in the root of Astragalus sinicus L. under salt-stressed soil conditions. Mycorrhizal formation, activity of fungal succinate dehydrogenase, and alkaline phosphatase, as well as plant biomass, were evaluated after 7 weeks of plant growth. Increasing the concentration of NaCl in soil generally decreased the dry weight of shoots and roots. Inoculation with AM fungi significantly alleviated inhibitory effect of salt stress. G. intraradices was the most efficient AM fungus compared with the other two fungi in terms of root colonization and enzyme activity. Nested PCR revealed that in root system of plants inoculated with a mix of the three AM fungi and grown under salt stress, the majority of mycorrhizal root fragments were colonized by one or two AM fungi, and some roots were colonized by all the three. Compared to inoculation alone, the frequency of G. mosseae in roots increased in the presence of the other two fungal species and highest level of NaCl, suggesting a synergistic interaction between these fungi under salt stress.     

Effect of arbuscular mycorrhizal fungi and Pseudomonas fluorescens on root-rot and wilt,growth and yield of Coleus forskohlii

Root-rot and wilt caused by Fusarium chlamydosporum affects the cultivation of Coleus forskohlii, a medicinal plant grown for its roots, which contain a pharmaceutically important compound called forskolin. In this study, management of this disease under low and high inoculum levels was assessed with four arbuscular mycorrhizal (AM) fungi and a strain of Pseudomonas fluorescens. The AM fungus Glomus fasciculatum and P. fluorescens were the most effective treatments that reduced the severity of root-rot and wilt of C. forskohlii by 56–65% and 61–66%, respectively, under lower and higher levels of pathogen F. chlamydosporum. G. fasciculatum increased the dry shoot and root weight by 108–241% and 92–204%, respectively, while in plants treated with P. fluorescens, an increase of 97–223% and 97–172% in dry shoot and root weight, respectively, was observed. Although P. fluorescens was effective, it gave higher root yields only under lower inoculum level of the pathogen. G. fasciculatum performed equally well under both lower and higher inoculum levels. Increase in yields with both the biocontrol agents was accompanied by increase in P uptake (230–303%) and in K uptake (270–335%). The forskolin content of the roots was significantly increased (14–21%) by G. fasciculatum, P. fluorescens or G. mosseae under lower inoculum level of pathogen.     

Increased Growth and Yield of Hydroponically Grown Greenhouse Tomato Plants Inoculated with Arbuscular Mycorrhizal Fungi and Fusarium oxysporum f. sp. radicis-lycopersici

The arbuscular mycorrhizal fungi Glomus monosporum, G. vesiculiferum, G. deserticola, G. intraradices, G. mosseae, and two unidentified species were tested to determine their effect on plant growth and fruit production of tomato (Lycopersicon esculentum Mill.) cv. Trust inoculated with Fusarium oxysporum f. sp. radicis-lycopersici (FORL) under near-commercial greenhouse conditions. Inoculation with G. monosporum and G. mosseae significantly increased fruit yield and fruit number of tomato plants grown hydroponically in sawdust. Plant height and plant dry weight increased significantly when inoculated with G. monosporum and G. mosseae. Further, plants inoculated with G. monosporum and G. mosseae showed significantly lower FORL root infection than the untreated control plants.     

Enhanced growth and nutrition of micropropagated Ficus benjamina to Glomus mosseae co-inoculated with Trichoderma harzianum and Bacillus coagulans

A greenhouse investigation was conducted to study the influence of the arbuscular mycorrhizal (AM) fungus Glomus mosseae and the plant growth-promoting rhizomicroorganisms (PGPRs) Bacillus coagulans and Trichoderma harzianum on the growth and nutrition of micropropagated Ficus benjamina plantlets. The AM fungus was inoculated either singly or in combination with the PGPRs. Plants showed maximum plant height, biomass, P content, mycorrhizal root colonization, spore numbers and populations of T. harzianum and B. coagulans in root zone soil when all the three organisms were inoculated together. Thus, when G. mosseae co-inoculated with PGPRs enhances growth and nutrition of Ficus benjamina. T. harzianum and B. coagulans are thus designated as mycorrhizal helper organisms.     

Effect of <Emphasis Type="Italic">Glomus</Emphasis> species on physiology and biochemistry of <Emphasis Type="Italic">Catharanthus roseus</Emphasis>

The present study on efficacy of different Glomus species, an arbuscular mycorrhizal (AM) fungus (G. aggregatum, G. fasciculatum, G. mosseae, G. intraradices) on various growth parameters such as biomass, macro and micronutrients, chlorophyll, protein, cytokinin and alkaloid content and phosphatase activity of pink flowered Catharanthus roseus plants showed that all Glomus species except G. intraradices enhanced the chlorophyll, protein, crude alkaloid, phosphorus, sulphur, manganese and copper contents of C. roseus plants along with phosphatase activity significantly over uninoculated plants. However only G. mosseae and G. fasciculatum exhibited superior symbiotic relationship with the plant. G. mosseae was found to be the best for increasing the crude alkaloid content (8.19%) in leaf and also in increasing the quantity of important alkaloids vincristine and vinblastine.     

Expression studies of plant genes differentially expressed in leaf and root tissues of tomato colonised by the arbuscular mycorrhizal fungus Glomus mosseae

Arbuscular mycorrhizal (AM) fungi are a multifaceted group of mutualistic symbionts that are common to terrestrial ecosystems. The interaction between AM fungi and plant roots is of environmental and agronomic importance. Understanding the molecular changes within the host plant upon AM fungal colonisation is a pre-requisite to a greater understanding of the mechanisms underlying the interaction. Differential mRNA display was conducted on leaf tissue of tomato plants colonised and non-colonised by the AM fungus Glomus mosseae and five putative differentially regulated cDNAs were identified. All cDNAs isolated shared high sequence similarity to known plant genes. Differential screening was initially used to establish whether the cDNAs were differentially expressed. Semi-quantitative RT-PCR was used to establish gene expression patterns for all five clones within leaf and root tissue of mycorrhizal and non-mycorrhizal colonised tomato plants. Differential regulation was observed for all five cDNAs. Down-regulation within the leaf tissue of mycorrhizal plants was observed for 4 out of the 5 cDNAs with an up-regulation observed only for one. Tissue specific regulation was observed for several cDNAs, with down-regulation observed in mycorrhizal leaf tissue and up-regulation observed within mycorrhizal root tissue as compared to non-mycorrhizal tissue.     

Bacterial effects on arbuscular mycorrhizal fungi and mycorrhiza development as influenced by the bacteria, fungi, and host plant

Bacterial strains from mycorrhizal roots (three belonging to Comamonadaceae and one to Oxalobacteraceae) and from non-mycorrhizal roots (two belonging to Comamonadaceae) of Medicago truncatula and two reference strains (Collimonas fungivorans Ter331 and Pseudomonas fluorescens C7R12) were tested for their effect on the in vitro saprophytic growth of Glomus mosseae BEG12 and on its colonization of M. truncatula roots. Only the Oxalobacteraceae strain, isolated from barrel medic mycorrhizal roots, and the reference strain P. fluorescens C7R12 promoted both the saprophytic growth and root colonization of G. mosseae BEG12, indicating that they acted as mycorrhiza helper bacteria. Greatest effects were achieved by P. fluorescens C7R12 and its influence on the saprophytic growth of G. mosseae was compared to that on Gigaspora rosea BEG9 to determine if the bacterial stimulation was fungal specific. This fungal specificity, together with plant specificity, was finally evaluated by comparing bacterial effects on arbuscular mycorrhizal symbiosis when each of the fungal species was inoculated to two different plant species (M. truncatula and Lycopersicon esculentum). The results obtained showed that promotion of saprophytic growth by P. fluorescens C7R12 was expressed in vitro towards G. mosseae but not towards G. rosea. Bacterial promotion of mycorhization was also expressed towards G. mosseae, but not G. rosea, in roots of M. truncatula and L. esculentum. Taken together, results indicated that enhancement of arbuscular mycorrhiza development was only induced by a limited number of bacteria, promotion by the most efficient bacterial strain being fungal and not plant specific.     

Influence of two legume species on hyphal production and activity of two arbuscular mycorrhizal fungi

 Two arbuscular mycorrhizal (AM) fungi (Glomus mosseae and G. intraradices) were compared for abundance of intraradical and soil-borne hyphae in association with Astragalus sinicum, a small-seeded, and Glycine max, a large-seeded legume. A. sinicum was more responsive than G. max to mycorrhizal formation, especially at early growth stages. Biomass allocation was greater in roots than shoots for mycorrhizal A. sinicum, while the opposite was true for G. max. Hyphal development in root and soil compartments was estimated by trypan blue staining and after staining for succinate dehydrogenase (SDH) or alkaline phosphatase (ALP) activity. Total fungal abundance increased steadily in roots and soil with time to a maximum 8 weeks after planting. SDH- and ALP-active AM hyphae increased in roots during plant growth but decreased in soil at later harvests. Mycorrhizal root mass in A. sinicum and G. max increased about 14-fold and 2.5-fold, respectively, but total length of soil hyphae produced per plant differed little, so that the pattern of AM soil to root abundance of the two fungi varied considerably with the host plant. Accepted: 23 July 1997     

Effects of arbuscular mycorrhizal fungi on the growth,nutrient uptake and glycyrrhizin production of licorice (<Emphasis Type="Italic">Glycyrrhiza uralensis</Emphasis> Fisch)

The growth of licorice in arid areas faces nutritional and environmental stresses. Arbuscular mycorrhizal (AM) fungi have been shown to increase the abilities of plants to develop. However, little is known regarding the role of AM fungi in licorice (Glycyrrhiza uralensis) growth. In the present study, by inoculation with two AM fungi, Glomus mosseae (Nicolson & Gerdemann) Gerd. & Trappe and Glomus veriforme (P. Karst.), the effects on licorice growth in sand were examined by measuring plant height, number of leaves, shoot and root fresh weight, and by analyzing morphological parameters of the root system in sand. The influence of the two microorganisms on the accumulation of mineral nutritions and bioactive components in licorice were also investigated. The results showed that mycorrhyzae were of the Arum-type and their colonization frequency (F %), colonization intensity (M %) and colonization intensity (m %) of AM fungi inoculation were found to be 80.0–84.6%, 49.4–60.0% and 58.4–71.9%, respectively. The inoculation significantly improved plant growth during early and late growth stages in comparison with the control. Moreover, inoculation of G. mosseae and G. versiforme, alone or in combination, improved plant phosphorus acquisition in the leaf over non-inoculation plants. In addition, mycorrhiza formation enhanced the glycyrrhizin concentration in roots, but resulted in a considerable reduction of the root oxidase activity. The results indicate that the inoculation with AM fungi could be a useful approach to increase the licorice pharmic quality.     

Influences of Arbuscular Mycorrhizal Fungus Glomus mosseae on Growth and Nutrition of Lentil Irrigated with Arsenic Contaminated Water

Arsenic (As) contamination of irrigation water represents a major constraint to Bangladesh agriculture. While arbuscular mycorrhizal (AM) fungi have their most significant effect on P uptake, they have also been shown to alleviate metal toxicity to the host plant. This study examined the effects of As and inoculation with an AM fungus, Glomus mosseae, on lentil (Lens culinaris L. cv. Titore). Plants were grown with and without AM inoculum for 9 weeks in a sand and terra green mixture 50:50 v/v and watered with five levels of As (0, 1, 2, 5, 10 mg As L⁻¹ arsenate). Inoculum of Rhizobium leguminosarum b.v. Viceae strain 3841 was applied to all plants. Plants were fed with modified Hoagland solution (1/10 N of a full-strength solution and without P). Plant height, leaf number, pod number, plant biomass and shoot and root P concentration/offtake increased significantly due to mycorrhizal infection. Plant height, leaf/ pod number, plant biomass, root length, shoot P concentration/offtake, root P offtake and mycorrhizal infection decreased significantly with increasing As concentration. However, mycorrhizal inoculation reduced As concentration in roots and shoots. This study shows that growing lentil with compatible AM inoculum can minimise As toxicity and increase growth and P uptake.     

Arbuscular mycorrhizal fungi can alter some root characters and physiological status in trifoliate orange (<Emphasis Type="Italic">Poncirus trifoliata</Emphasis> L. Raf.) seedlings

Citrus plants strongly depend on mycorrhizal symbiosis because of less or no root hairs, but few reports have studied if their root traits and physiological status could be altered by different arbuscular mycorrhizal fungi (AMF). In a pot experiment we evaluated the effects of three AMF species, Glomus mosseae, G. versiforme and Paraglomus occultum on the root traits and physiological variables of the trifoliate orange (Poncirus trifoliata L. Raf.) seedlings. Root mycorrhizal colonization was 58–76% after 180 days of inoculation. AMF association significantly increased plant height, stem diameter, leaf number per plant, shoot and root biomass. Mycorrhizal seedlings also had higher total root length, total root projected area, total root surface area and total root volume but thinner root diameter. Among the three AMFs, greater positive effects on aboveground growth generally ranked as G. mosseae > P. occultum > G. versiforme, whilst on root traits as G. mosseae ≈ P. occultum > G. versiforme. Compared to the non-mycorrhizal seedlings, contents of chlorophyll, leaf glucose and sucrose, root soluble protein were significantly increased in the mycorrhizal seedlings. In contrast, root glucose and sucrose, leaf soluble protein, and activity of peroxidase (POD) in both leaves and roots were significantly decreased in the mycorrhizal seedlings. It suggested that the improvement of root traits could be dependent on AMF species and be related to the AMF-induced alteration of carbohydrates and POD.     

Effects of Common Mycorrhizal Network on Plant Carbohydrates and Soil Properties in Trifoliate Orange–White Clover Association

Common mycorrhizal network (CMN) allows nutrients and signals to pass between two or more plants. In this study, trifoliate orange (Poncirus trifoliata) and white clover (Trifolium repens) were planted in a two-compartmented rootbox, separated by a 37–μm nylon mesh and then inoculated with an arbuscular mycorrhizal fungus (AMF), Diversispora spurca. Inoculation with D. spurca resulted in formation of a CMN between trifoliate orange and white clover, whilst the best AM colonization occurred in the donor trifoliate orange–receptor white clover association. In the trifoliate orange–white clover association, the mycorrhizal colonization of receptor plant by extraradical hyphae originated from the donor plant significantly increased shoot and root fresh weight and chlorophyll concentration of the receptor plant. Enzymatic activity of soil β-glucoside hydrolase, protease, acid and neutral phosphatase, water-stable aggregate percentage at 2–4 and 0.5–1 mm size, and mean weight diameter in the rhizosphere of the receptor plant also increased. The hyphae of CMN released more easily-extractable glomalin-related soil protein and total glomalin-related soil protein into the receptor rhizosphere, which represented a significantly positive correlation with aggregate stability. AMF inoculation exhibited diverse changes in leaf and root sucrose concentration in the donor plant, and AM colonization by CMN conferred a significant increase of root glucose in the receptor plant. These results suggested that CMN formed in the trifoliate orange–white clover association, and root AM colonization by CMN promoted plant growth, root glucose accumulation, and rhizospheric soil properties in the receptor plant.     

Mycorrhizal Networks Interacting with Litter Improves Nutrients and Growth for One Plant through the Vary of N/P Ratio under Karst Soil

Arbuscular mycorrhizae (AM) fungi affect nutrient uptake for host plants, while it is unclear how AM fungi interacting with soil litter affect plant growth and nutrient utilization through mycorrhizal networks in karst soil of deficient nutrients beyond the rhizosphere. An experiment was conducted in a microcosm composed of a planting compartment for Cinnamomum camphora seedlings with or without Glomus mosseae fungus (M⁺ vs. M⁻ ) and an adjacent litter compartment containing or not containing additional litter material of Arthraxon hispidus (L⁺ vs. L⁻ ), where the compartments are connected either by nylon mesh of 20 μm or 0.45 μm which either allow available mycorrhizal networks within the litter compartment or prevent mycelium entering into the litter compartment (N⁺ vs. N⁻ ). Plant biomass and nutrients were measured. The results showed that the addition of litter changed the symbiotic process in mycorrhizal colonization, spore, and hyphal density, which when in association with the host plant then affected the biomass, and accumulations of N (nitrogen) and P (phosphorus) in the individual plant as well as root, stem, and leaf respectively. AM fungi increased N and P accumulations and N/P ratio in individual plants and plant tissues. A decrease of the N/P ratio of the individual plant was observed when AM fungus interacted significantly with litter through mycorrhizal networks in the litter compartment. The results indicate that the C. camphora seedlings benefited from litter in nutrient utilization of N and P through the vary of N/P ratio when accessing mycorrhizal networks. These findings suggest that mycorrhizal networks interacting with litter improve growth and nutrients of N and P for plants through the vary of N/P ratio in order to alleviate nutrient limitation under karst soil.     

Growth and gas exchange responses of Hevea brasiliensis seedlings to inoculation with Glomus mosseae

 The beneficial effect of arbuscular mycorrhizal (AM) fungi on plant growth is well known, but the physiological processes involved are still discussed. The purpose of this study was to determine if Glomus mosseae affects the growth of Hevea brasiliensis seedlings and, if it is the case, if it could be associated with variations in leaf CO₂ and H₂O gas exchange. H. brasiliensis rubber trees were grown for 9 months in a medium containing either propagules of G. mosseae or sterilized inoculum. Plant size, root collar diameter and leaf area, as well as net CO₂ assimilation, stomatal conductance (g_s) and water-use efficiency of photosynthesis were evaluated during the first 5 stages of growth. At stage 2, a growth depression occurred in the mycorrhizal seedlings coincident with the first AM infections. Then, at stage 5, Glomus mosseae-inoculated plants had moderate colonization (47% of root length) and were taller than control plants with a larger root collar diameter and an enhanced leaf organogenesis. This enhanced growth was accompanied by increased photosynthesis, transpiration, and stomatal conductance. After 9 months, dry weights of shoots and roots of inoculated plants were greater than those of controls by 27 and 17%, respectively. Received: 10 May 1997 / Accepted: 9 September 1997     

RETRACTED ARTICLE: Influence of arbuscular mycorrhizal fungi and copper on growth, accumulation of osmolyte, mineral nutrition and antioxidant enzyme activity of pepper (Capsicum annuum L.)

The effect of arbuscular mycorrhizal (AM) fungi inoculation on pepper (Capsicum annuum L. cv. Zhongjiao 105) plant growth and on some physiological parameters in response to increasing soil Cu concentrations was studied. Treatments consisted of inoculation or not with Glomus mosseae and the addition of Cu to soil at the concentrations of 0 (control), 2 (low), 4 (medium), and 8 (high) mM CuSO₄. AM fungal inoculation decreased Cu concentrations in plant organs and promoted biomass yields as well as the contents of chlorophyll, soluble sugar, total protein, and the concentrations of P, K, Ca, and Mg. Plants grown in high Cu concentration exhibited a Cu-induced proline accumulation and also an increase in total free amino acid contents; however, both were lower in mycorrhizal pepper. Cu-induced oxidative stress by increasing lipid peroxidation rates and the activity of superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase, and AM symbiosis enhanced these antioxidant enzyme activities and decreased oxidative damage to lipids. In conclusion G. mosseae was able to maintain an efficient symbiosis with pepper plants in contaminated Cu soils, improving plant growth under these conditions, which is likely to be due to reduced Cu accumulation in plant tissues, reduced oxidative stress and damage to lipids, or enhanced antioxidant capacity.     

Mycorrhizal inoculation in neem (Azadirachta indica) enhances azadirachtin content in seed kernels

In view of the high mycorrhizal dependency of neem trees (Azadirachta indica), an experiment was conducted to study if Arbuscular Mycorrhizal (AM) inoculation can enhance the azadirachtin content in seed kernels of trees grown in the field. Azadirachtin is an important active ingredient in neem seed kernels based on which a large biopesticide industry has emerged in India and few countries in Europe and the USA. Inoculation of neem seedlings in the nursery with Glomus fasciculatum and Glomus mosseae resulted in increased height, dry weight, root colonization and phosphorus (P) content. In a separate experiment, field-grown neem plants inoculated in the nursery and during transplantation with Glomus fasciculatum were evaluated after 5 years. No significant differences were found in the tree height, girth at breast height (GBH) and fruit yield but oil percentage, total triterpenoids and azadirachtin content in kernels increased significantly as a result of AM inoculation. A similar enhancement in azadirachtin was noted with P application. These results open up possibilities of producing quality neem seed with high bioactive ingredients through AM inoculation.     

Phytate utilization of maize mediated by different nitrogen forms in a plant–arbuscular mycorrhizal fungus–phosphate-solubilizing bacterium system

A pot experiment was conducted to investigate the organic phosphorus (P) (phytate) utilization of Zea mays L. with different nitrogen (N) forms (NH₄⁺ and NO₃^?) when both arbuscular mycorrhizal (AM) fungus (Funelliformis mosseae) and phosphate-solubilizing bacterium (PSB, Pseudomonas alcaligenes) are present. The soil was supplied with either KNO₃ or (NH₄)₂SO₄ (200 mg kg^?1 N) with or without phytin (75 mg P kg^?1). Results showed that the application of NH₄⁺ to the soil in a plant–AM fungus–PSB system decreased rhizosphere pH and increased phosphatase activity. It also enhanced the mineralization rate of phytin, which resulted in the release of more inorganic P. The application of NO₃^? promoted mycorrhizal colonization and hyphal length density in the soil. The inorganic P in the hyphosphere decreased, but more P was transferred to the plant through the mycorrhizal hyphae. Hence, in addition, the application of the two different N forms did not significantly alter the content of plant P. The plant supplied with different N fertilizers acquired P through different mechanisms associated with other microbes. NH₄⁺ application promoted phytin mineralization by decreasing soil pH, whereas NO₃^? application increased inorganic P uptake by strengthening the mycorrhizal pathway.