Vesicular-arbuscular Mycorrhizal Inoculation Research Articles

Influence of Inorganic Phosphorus, VAM Fungi, and Irrigation Regimes on Crop Productivity and Phosphorus Transformations in Okra (Abelmoschus esculentus L.)–Pea (Pisum sativum L.) Cropping System in an Acid Alfisol

The present investigation was carried out at CSK Himachal Pradesh Agricultural University, Palampur, India, during 2009–2011 to economize inorganic phosphorus (P) and water needs of an okra (Abelmoschus esculentus)–pea (Pisum sativum) cropping system through vesicular arbuscular mycorrhizal (VAM) fungi (Glomus mosseae) in a Himalayan acid Alfisol. The field experiment was replicated three times in a randomized block design comprising 14 treatments consisting of 12 treatment combinations of two VAM levels [0 and 12 kg ha−1], three phosphorus levels [50, 75, and 100% of recommended soil-test-based nitrogen (N)–P–potassium (K)], and two irrigation regimes [40 and 80% of available water-holding capacity of field soil (AWC)], in addition to one treatment with “generalized recommended NPK dose with generalized recommended irrigations (GRD)” and one treatment based on “farmers’ practice of plant nutrition and irrigation management in the region.” This article presents crop productivity and P dynamics studies during the second crop cycle of okra–pea sequence (2010–2011) and statuses of different P fractions in the soil after the second pea crop harvest during 2010–2011. Crop productivity and P uptake data in okra–pea sequence indicated that application of VAM + 75% P dose at either of two irrigation regimes did not differ significantly than GRD treatment and VAM + 100% P dose. It suggests an economy of about 25% inorganic P dose through VAM fungi. The treatments imbedded with VAM inoculation enhanced the P uptake in okra–pea system, on an average by 21% over the GRD and non-VAM-inoculated counterparts. Further, integrated application of P, VAM, and irrigation regimes evaluated in okra–pea sequence for 2 years led to greater status of water-soluble P (21%), sodium bicarbonate (NaHCO3)–inorganic phosphorus (Pi) (11%), sodium hydroxide (NaOH)–Pi (9%), hydrochloric acid (HCl)–extractable–P (20%) over non-VAM-inoculated counterparts and low status of organic P (NaHCO3-Po and NaOH-Po), all of which appreciably contributed to available P supply to plants in the present study in an acid Alfisol. The correlation coefficient reveals that contribution of inorganic P forms is highly correlated to crop productivity and total P uptake in okra and pea crops besides soil available P in the present study. Overall, it is concluded that VAM inoculation in okra–pea cropping system significantly enhanced the P availability to plants by way of enriching the labile-P pool such as water-soluble P and P loosely bound to aluminium (Al-P) and iron (Fe-P) on adsorption complexes and by P mineralization from organic matter in an Himalayan acid Alfisol.

Effect of Vesicular Arbuscular–Mycorrhizal Fungi and Phosphorus Application through Soil-Test Crop Response Precision Model on Crop Productivity, Nutrient Dynamics, and Soil Fertility in Soybean–Wheat–Soybean Crop Sequence in an Acidic Alfisol

A field experiment was conducted in a phosphorus (P)–deficient acidic alfisol of the northwestern Himalayas using three vesicular arbuscular mycorrhizal (VAM) cultures: a local culture developed by CSK Himachal Pradesh Agricultural University, Palampur (Glomus mosseae), VAM culture from Indian Agricultural Research Institute (IARI), New Delhi (Glomus mosseae), and a culture from the Centre for Mycorrhizal Research, The Energy Research Institute (TERI), New Delhi (Glomus intraradices). These were applied alone or in combination with 25 to 75% of recommended P2O5 and recommended nitrogen (N) and potassium (K) based on soil-test crop response (STCR) precision model with an absolute control, farmers’ practice, and 100% of recommended P2O5 dose based on the STCR model. The results revealed that sole application of either of the three VAM cultures have produced 2.68 to 9.81% and 25.06 to 28.62% greater grain yield than the control in soybean and wheat crops, respectively. Besides greater straw yield, NPK uptake as well as soil nutrient buildup increased. Increase in P fertilization from 25 to 75% of recommended P2O5 dose coupled with VAM inoculation with either of the three VAM cultures resulted in consistent and significant improvement in crop productivity (grain and straw yields), NPK uptake, and improved soil nutrient status, though significantly greatest magnitude was obtained with sole application of 100% of the recommended P2O5 dose. The targeted grain yields of soybean (25 q ha−1) and wheat (30 q ha−1) were achievable with 75% of recommended P2O5 dose along with mycorrhizal biofertilizers, thereby indicating that application of efficient VAM fungi with 75% of recommended P2O5 dose can economize the STCR precision model fertilizer P dose by about 25% without impairing crop yield targets or soil fertility in a soybean-based cropping system in an acidic alfisol.

Influence of Vesicular Arbuscular Mycorrhizal Fungi and Applied Phosphorus on Root Colonization in Wheat and Plant Nutrient Dynamics in a Phosphorus-Deficient Acid Alfisol of Western Himalayas

Vesicular arbuscular mycorrhizal (VAM) fungi symbiosis confers benefits directly to the host plant's growth and yield through acquisition of phosphorus and other macro- and micronutrients, especially from phosphorus (P)–deficient acidic soils. The inoculation of three VAM cultures [viz., local culture (Glomus mosseae), VAM culture from Indian Agricultural Research Institute (IARI), New Delhi (Glomus mosseae), and a culture from the Centre for Mycorrhizal Research, Energy Research Institute (TERI), New Delhi (Glomus intraradices)] along with P fertilization in wheat in a P-deficient acidic alfisol improved the root colonization by 16–24% while grain and straw yields increased by 12.6–15.7% and 13.4–15.4%, respectively, over the control. Uptake of nitrogen (N), P, potassium (K), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) was also improved with VAM inoculation over control, but the magnitude of uptake was significantly greater only in the cases of P, Fe, Zn, and Cu. Inoculation of wheat with three VAM cultures in combination with increasing inorganic P application from 50% to 75% of the recommended P2O5 dose to wheat through the targeted yield concept following the soil-test crop response (STCR) precision model resulted in consistent and significant improvement in grain and straw yield, macronutrient (NPK) uptake, and micronutrient (Fe, Mn, Zn, Cu) uptake in wheat though root colonization did not improve at P2O5 doses beyond 50% of the recommended dose. The VAM cultures alone or in combination with increasing P levels from 50% to 75% P2O5 dose resulted in reduction of diethylenetriaminepentaacetic acid (DTPA)–extractable micronutrient (Fe, Mn, Zn, Cu) contents in P-deficient acidic soil over the control and initial fertility status, although micronutrient contents were relatively greater in VAM-supplied plots alone or in combination with 50% to 75% P2O5 dose over sole application of 100% P2O5 dose, thereby indicating the positive role of VAM in nutrient mobilization and nutrient dynamics in the soil–plant system. There was significant improvement in available N and P status in soil with VAM inoculation coupled with increasing P levels upto 75% P2O5 dose, although the greatest P buildup was obtained with sole application of 100% P2O5 dose. The TERI VAM culture (Glomus intraradices) showed its superiority over the other two cultures (Glomus mosseae) in terms of crop yield and nutrient uptake in wheat though the differences were nonsignificant among the VAM cultures alone or at each P level. Overall, it was inferred that use of VA-mycorrhizal fungi is beneficial under low soil P or in low input (nutrient)–intensive agroecosystems.

Effects of solarization and vesicular arbuscular mycorrhizal fungus (VAM) on phytopthora blight (Phytophthora capsici leonian) and yield in pepper

In this work, effects of soil solarization and vesicular arbuscular mycorrhizal (VAM) fungus, Glomus intraradices on diseases caused by Phytophthora capsici Leonian in pepper plants and crop yields were studied. At the end of the growth season, 82.5% mortality of plants and 47.7% of yield loss caused by P. capsici were obtained in control plots. At the beginning of the vegetative period, plant mortality caused by P. capsici in solarized plots was less than that in non-solarized plots, but it was higher at the end of the experiments. The total crop yield, however, increased to 20.9% by solarization. At the beginning of the growth season, anthocyanin production, early flowering and fruit settings were observed in the seedlings inoculated with VAM. Plant mortality caused by P. capsici was inhibited by 69.4% in plants inoculated with VAM fungus, but this rate decreased to 14.9% at the end of the experiment. On the other hand, total yield increased to 40.4% in plots infested with P. capsici, but treated with VAM. The total yield increased to 49.9% in pathogen free solarized + VAM inoculated grown plants plots in comparison to pathogen free non-solarized + non-VAM inoculated grown plants plots. This increase was 42.8% in solarized + VAM inoculated grown plants plots, which were infested with P. capsici. Total yield was 22.7% in solarized + VAM inoculated grown plants plots without P. capsici in comparison to non-solarized plots + non-VAM inoculated grown plants plots but infected with P. capsici. The yield loss caused by P. capsiciin pepper was decreased by means of long-term effect of soil solarization with artificially VAM inoculation. Key words: Soil solarization, vesicular arbuscular mycorrhizal, Glomus intraradices, Phytophthora capsici, yield, phytopthora blight, pepper.

The relationships between relative water content, chlorophyll synthesis and yield performance of yam (Dioscorea rotundata) as affected by soil amendments and mycorrhizal inoculation

The response of yam to inoculation with two species of vesicular-arbuscular mycorrhizal (VAM), Glomus mosseae and Glomus etunicatum and applications of fertilizer, and manure was investigated. Field experiment was conducted at the research farm of Botany and Microbiology Department, University of Ibadan, Nigeria. The treatments were arranged in a factorial randomized complete block design. There were four levels of VAM inoculation. The yam plants were either inoculated with a VAM fungus or not. Manure and NPK fertilizer were also applied as treatments. Each of the VAM was either combined with manure or NPK fertilizer. Chlorophyll synthesis, relative water content (RWC) and dry matter accumulation were investigated. The results showed that there was enhanced chlorophyll content in yam inoculated with the VAM with G. mosseae being more effective when combined with manure. RWC and yield of yam were also significantly influenced by the treatments. RWC was found to affect the chlorophyll production when water became limited. Chlorophyll content was also found to have effect on yam productivity. Combinations of mycorrhizae with the soil amendments are highly promising for sustainable yam production in degraded soils.

Mycorrhization of coriander (Coriandrum sativum L) to enhance the concentration and quality of essential oil

AbstractThe effect of association of two vesicular arbuscular mycorrhizal (VAM) fungi, Glomus macrocarpum and G fasciculatum, on the concentration and composition of essential oil in coriander (Coriandrum sativum) was studied. VAM inoculation increased the essential oil concentration in fruits by as much as 43%. Although significant variation in effectiveness of the two fungal species was observed, the quality of essential oil was significantly enhanced on mycorrhization. GC characterisation of essential oil showed increased concentration of geraniol and linalool in plants inoculated with G macrocarpum and G fasciculatum respectively.© 2002 Society of Chemical Industry

Effect of the vesicular–arbuscular mycorrhizal (VAM) fungus Glomus fasciculatum on the essential oil yield related characters and nutrient acquisition in the crops of different cultivars of menthol mint ( Mentha arvensis) under field conditions

The effects of inoculation with vesicular–arbuscular mycorrhizal (VAM) fungus Glomus fasciculatum on the root colonization, growth, essential oil yield and nutrient acquisition of three cultivars of menthol mint ( Mentha arvensis); Kalka, Shivalik and Gomti, were studied under field conditions. The VAM inoculation significantly increased the root colonization, plant height, fresh herbage and dry matter yield, oil content and oil yield as compared to non-inoculated cultivars. The effect of VAM inoculation on the root colonization, growth and yield of mint was more pronounced with the cv Shivalik than the cvs Kalka and Gomati, indicating Shivalik as a highly mycorrhizal dependent genotype. VAM inoculation significantly increased the uptake of N, P and K by shoot tissues of mint, but most markedly increased the uptake of P. The VAM-inoculated mint plants depleted the available N, P and K in the rhizosphere soil as compared to non-inoculated control plants, however the extent of nutrient depletion was greater for P than N and K. We conclude that the VAM inoculation could significantly increase the root colonization, growth, essential oil yield and nutrient acquisition of mint for obtaining economic production under field conditions.

Preinoculation of lettuce and onion with VA mycorrhizal fungi reduces deleterious effects of soil salinity

The hypothesis that inoculation of transplants with vesicular-arbuscular mycorrhizal (VAM) fungi before planting into saline soils alleviates salt effects on growth and yield was tested on lettuce (Lactuca sativa L.) and onion (Allium cepa L.). A second hypothesis was that fungi isolated from saline soil are more effective in counteracting salt effects than those from nonsaline soil. VAM fungi from high- and low-salt soils were trap-cultured, their propagules quantified and adjusted to a like number, and added to a pasteurized soil mix in which seedlings were grown for 3–4 weeks. Once the seedlings were colonized by VAM fungi, they were transplanted into salinized (NaCl) soil. Preinoculated lettuce transplants grown for 11 weeks in the saline soils had greater shoot mass compared with nonVAM plants at all salt levels [2 (control), 4, 8 and 12 dS m−1] tested. Leaves of VAM lettuce at the highest salt level were significantly greener (more chlorophyll) than those of the nonVAM lettuce. NonVAM onions were stunted due to P deficiency in the soil, but inoculation with VAM fungi alleviated P deficiency and salinity effects; VAM onions were significantly larger at all salt levels than nonVAM onions. In a separate experiment, addition of P to salinized soil reduced the salt stress effect on nonVAM onions but to a lesser extent than by VAM inoculation. VAM fungi from the saline soil were not more effective in reducing growth inhibition by salt than those from the nonsaline site. Colonization of roots and length of soil hyphae produced by the VAM fungi decreased with increasing soil salt concentration. Results indicate that preinoculation of transplants with VAM fungi can help alleviate deleterious effects of saline soils on crop yield.

Effects of vesicular–arbuscular mycorrhizal inoculation on the yield and phosphorus uptake of field-grown barley

In a field experiment on barley, the effects of soil application of phosphorus fertilizer and inoculum of Glomus mosseae on the mycorrhizal colonization of roots, crop yield and P uptake were evaluated in a natural or methyl bromide fumigated soil. Soil fumigation raised the amount of available nitrogen (NH 4–N+NO 3–N) in the soil by 13 mg kg −1. Although both soils were equalized for the N status by adding N fertilizer to non-fumigated soil, fumigated soil gave higher crop yield. The applied P increased the dry matter yield significantly but suppressed mycorrhizal infection. An overall small increase of 3% in total P uptake and a decrease of up to 2% in grain and straw yield were observed as a result of inoculation, which were statistically non-significant at P<0.05. These trends in results were most likely due to the status of available soil P higher than the threshold limit for a positive mycorrhizal growth response.

Influence of Inoculation with Vesicular-Arbuscular Mycorrhizae on Posttransplant Growth of Prairie Forb Seedlings

The objectives of this study were to compare the growth of prairie forb seedlings inoculated with vesicular-arbuscular mycorrhizal (VAM) fungi to noninoculated seedlings transplanted to a highway right-of-way and to evaluate the effect of different VAM fungal species or combinations on posttransplant seedling growth. Four species of prairie forbs: pale-purple coneflower (Echinacea pallida Nutt.), prairie blazingstar (Liatris pycnostachya Michx.), prairie phlox (Phlox pilosa L.), and gray-headed coneflower [Ratibida pinnata (Venten.) Barnh.], were grown in greenhouse mix and inoculated with Gigaspora margarita Becker and Hall, or Glomus interadicies Schenk and Smith, or with a native Indiana prairie soil inoculum, or with a mix of all three. They were transplanted to a highway site in June, 1994. Only gray-headed coneflower exhibited a positive growth response to VAM inoculation. Inoculation of gray-headed coneflower with G. margarita produced the largest growth response by the end of the experiment.

Effects of vesicular arbuscular mycorrhizal inoculation on growth and phosphorus nutrition of barley in natural or methyl bromide‐treated soil

The growth and phosphorus (P) nutrition of barley (Hordeum vulgare L.) in a soil, methyl bromide fumigated or untreated and supplied with or without mycorrhizal inoculum, was studied in pots placed under a field environment. Inoculation significantly raised the overall levels of vesicular arbuscular mycorrhizal (VAM) infection. The relative increase was significantly greater in sterile than nonsterile soil. Soil sterilization produced significantly higher dry matter throughout the experiment. Inoculation resulted in a significant growth depression earlier in the season which could not be offset by the following mycorrhizal enhancement in P absorption rates. The primary reasons for this yield depression were most probably the root density and available P status of the soil which might have been over the threshold limit for positive mycorrhizal yield response in barley. In this experiment, the result of inoculation could be regarded beneficial considering 17 and 30% higher P concentrations in grain and straw, respectively, but detrimental with respect to 20% loss in grain plus straw yield.

Effect of Glomus etunicatum inoculation on aluminum, phosphorus, calcium, and magnesium uptake of two barley genotypes with different aluminum tolerance

This study was conducted to evaluate the effect of vesicular‐arbuscular mycorrhizal (VAM) fungus Glomus etunicatum on growth, absorption, and distribution of calcium (Ca), magnesium (Mg), phosphorus (P), and aluminum (Al) in one Al‐tolerant and one Al‐sensitive barley cultivar. The plants were grown in sand daily irrigated with nutrient solution containing 0 or 600 μM Al at pH 4.8. Significant interaction (P=0.05) among variety, mycorrhiza, and aluminum (VxMxAl) were noted for both shoot and root dry matter (DM); shoot concentration and content of Al, P, Ca, and Mg; root concentration of Al, P, and Mg; and root content of Al, P, Ca, and Mg. With VAM inoculation: i) root colonization degree was about 50% in all treatment, ii) shoot DM yield increased between 30 and 70%, iii) Al concentration and content decrease down to a half both in shoots and roots of sensitive barley, iv) Ca concentration in shoots of sensitive barley showed a high increase at 600 μM Al, and v) P concentration and content in shoots of both varieties increased significantly.

Effects of phosphorus application and vesicular arbuscular mycorrhizal inoculation on the growth and phosphorus nutrition of maize

The growth and nutrition of maize (Zea mays L.) grown with and without the soil application of phosphorus (P) fertilizer and/or mycorrhizal inoculum was studied in pots placed under field environments. Inoculation enhanced the growth of maize significantly (up to 81.8%) during the early stages but response gradually disappeared during the later stages of growth. Addition of phosphate increased plant growth, but suppressed mycorrhizal infection. In the first half of the season, the stimulation in plant growth was related to higher rates of P uptake by the inoculated plants, but later a decline of growth in these treatments was most probably due to fungal parasitism as a result of high root densities.

Effects of vesicular-arbuscular mycorrhizal inoculation at different soil P availabilities on growth and nutrient uptake of in vitro propagated coffee ( Coffea arabica L. ) plants

In a pot experiment, the growth and the nutrient status of in vitro propagated coffee (Coffea arabica L.) microcuttings were investigated for 5 months following vesicular-arbuscular mycorrhizal (VAM) inoculation with either Acaulospora melleae or Glomus clarum at four soil P availabilities. Control plants remained P-deficient even at the highest soil P availability while mycorrhizal plants were P-sufficient at all soil P availabilities. Growth of control plants was only improved at the highest soil P availability. In P-deficient soil, neither of the two VAM species improved plant growth. Plant growth increased by 50% following inoculation with either A. melleae or G. clarum when P availability went from deficient to low. No further plant growth improvement was induced by either VAM species at intermediate and high soil P levels. Nevertheless, growth of plants inoculated with G. clarum was still significantly greater than that of non-mycorrhizal plants at the highest soil P availability. Root colonization by G. clarum increased with increasing soil P availability while root colonization by A. mellea decreased with soil P level increasing above low P availability. Soil P availability also affected Zn nutrition through its influence on VAM symbiosis. With increasing soil P availability, foliar Zn status increased with G. clarum or decreased with A. mellea in parallel to root colonization by VAM. This study demonstrates the beneficial effects of VAM inoculation on in vitro propagated Arabica coffee microcuttings, as shown previously for seedlings. This study also demonstrates differences in tolerance to soil P availability between VAM species, most likely resulting from their differing abilities to enhance coffee foliar P status.

GROWTH, ROOT ALTERATION, AND NUTRIENT UPTAKE OF NEEM TREE (Azadirachta indicaA. Juss) SEEDLINGS IN RESPONSE TO VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGI AND PHOSPHORUS NUTRITION

SUMMARY Growth and nutrient uptake of neem tree (Azadirachta indica A. Juss) seedlings were studied in response to vesicular-arbuscular mycorrhizal (VAM) fungi Glomus intraradices Schenck and Smith, and 2 levels of phosphorus (P). Extensive VAM colonization in neem roots occurred at both P levels: 0.65 and 1.30 mM P. Growth of VAM plants at both P levels was similar, while growth of noncolonized (Non-VAM) plants increased with increasing P supply. At the low P level, VAM plants had greater leaf area, shoot, root and leaf dry weight, and a greater root: shoot ratio than Non-VAM plants. Low P, VAM plants had a greater leaf area and root dry weight and a comparable leaf and shoot dry weight and root: shoot ratio, when compared with high P, Non-VAM plants. VAM inoculation also altered dry mass partitioning to root systems resulting in greater root length and dry weight of suberized roots in VAM plants. The length of nonsuberized roots increased with increasing P supply regardless of VAM inoculation. VAM inocu...

Wheat Responses to Vesicular‐Arbuscular Mycorrhizal Fungal Inoculation of Soils from Eroded Toposequence

AbstractLow fertility of eroded soils is often attributed to the loss of topsoil, an important source of nutrients for microorganisms and plants. Vesicular‐arbuscular mycorrhizal (VAM) fungi are known to improve nutrient uptake by plants from infertile soil. The objective of this study was to determine whether wheat (Triticum aestivum L.) responses to VAM fungal inoculation differ among eroded and noneroded soils from the same toposequence. Spring wheat plants were grown under growth chamber conditions in soils collected from three landscape positions of a typical toposequence in eastern Washington, with and without VAM fungal inoculation. Noninoculated soils exhibited 13 to 26% VAM root colonization, while inoculation increased VAM colonization up to 49 to 55% by 5 wk after planting. The VAM fungal inoculation of eroded soils increased shoot dry weight and tiller number, advanced the leaf stage, and increased root length compared with the noninoculated controls. Shoot concentrations of P and Zn were increased by VAM inoculation. In contrast, shoot concentrations of Cu and Mn were unchanged, while Fe was decreased. While VAM fungal inoculation also increased P, Zn, and Cu concentrations in water‐stressed plants, Mn and Fe concentrations decreased. No responses to VAM fungal inoculation were observed in soil from a noneroded toeslope, although VAM colonization was similar to that observed in the eroded soils. These results indicate the potential role of VAM fungi for improving dryland wheat productivity on eroded soils.

Plant Growth Stage for Geranium Inoculation with Vesicular–Arbuscular Mycorrhizal (VAM) Fungi

The most appropriate time for VAM inoculation has been assumed to be the early stages of plant growth, and this study aimed to investigate the impact of VAM inoculation at the seedling and at the 10-week geranium plant stage. Seeds were planted in propagation plug trays (200) filled with four different seed-germinating substrates: half were inoculated with Glomus intraradices while the other half were noninoculated controls. Two types of media received inoculum or not (control); they consisted of sphagnum peat with perlite in one case and vermiculite in the other. After 10 weeks growth, the root systems were checked for colonization, and height, weight, and leaf number were registered. The subsequent growth was carried out in 4-inch azalea pots with the appropriate medium. The pre-in-oculated plants were transferred in Mycori-Mix, and the controls were transferred in Pro-Mix. All plants received mild liquid fertilization at each irrigation time (20N–2P–20K). The number of cuttings and flowers were monitored 6 weeks after beginning of pot growth. The pots were displayed in a complete factorial block with six replicates per treatment, and 10 plants were used for each experimental unit. Significant differences did occur between plants initiated in the different germinating substrates; when pre-inoculated, 12.5 cuttings and 7 flowers were recorded in comparison to 9.8 and 3.9, respectively, for controls. These results reflect the importance of introducing VAM at the earliest growth stage.

Effect of three vesicular‐arbuscular mycorrhizae species and phosphorus on reproductive and vegetative growth of three strawberry cultivars1

Abstract A study was undertaken to evaluate the yield, fruit size, and vegetative growth of three strawberry cultivars inoculated with three vesicular‐arbuscular mycorrhizal (VAM) species at three phosphorus (P) fertility levels. Vesicular‐arbuscular mycorrhiza inoculation and P fertility had no effect on inflorescence or flower number, total yield, fruit weight, or crown number. Higher levels of P did not increased total dry shoot weight, total fresh shoot, weight leaf area, total dry root weight, and leaf number in the present of VAM. However, the cultivars responded differently to VAM inoculation. Vesicular‐ arbuscular mycorrhiza inoculation in combination with P at all levels increased total dry and fresh shoot weight, leaf area, and leaf number compared to application of P alone. The results indicated that it may be possible to increase strawberry stolon production by inoculating the strawberry plants with VAM, a technique which might be useful in nurseries to produce certified strawberry plants.

The effect of vesicular-arbuscular mycorrhizal inoculation on nutrient uptake and yield of alley-cropped cassava in a degraded Alfisol of southwestern Nigeria

Leaf and root (tuber) nutrient uptake patterns of cassava (Manihot esculenta Crantz) alley-cropped with gliricidia (Gliricidia sepium), leucaena (Leucaena leucocephala), and senna [(Senna (syn. Cassia) siamea] as influenced by vesicular-arbuscular mycorrhizal (VAM) inoculation in a degraded Alfisol were investigated in consecutive years. The cassava plants were mulched with fresh prunings of each hedgerow tree species at 2-month intervals in the second and third years of alley cropping. While VAM inoculation significantly influenced the root uptake of nutrients, the leaf uptake was not affected except for the uptake of P. In most cases, there was no difference in the nutrient concentration between inoculated and uninoculated plants, either in the leaf or in the root, indicating that the productivity of cassava was regulated by the amount of nutrients the roots could absorb. In spite of similar total soil N in all inoculated and uninoculated alley-cropped cassava plots and similar exchange-able soil K contents in inoculated and uninoculated alley-cropped cassava plots with leucaena and senna, greater uptake of N, P, and K and greater concentrations of K were observed in roots of inoculated alley-cropped cassava with gliricidia and leucaena than with senna. These results indicated that greater mineralization and availability of nutrients to cassava roots from prunings of nodulating gliricidia and leucaena than from non-nodulating senna may be important, particularly with efficient VAM inoculation, in these alley-cropping systems. Also, for similar nutrients in the inoculated and uninoculated cassava soils alley-cropped with each hedgerow species, VAM inoculation significantly enhanced cassava root dry weights, indicating that an effective VAM fungus can be an agent of greater nutrient uptake in a competitive environment.

Humid tropical leguminous tree and pasture grass responsiveness to vesicular-arbuscular mycorrhizal infection

Phosphorus is the major nutrient limiting plant growth in a Costa Rican silvopastoral system located on an acid, high P-retaining, volcanic soil. We investigated plant responsiveness to vesicular-arbuscular mycorrhizal (VAM) inoculation using the leguminous tree species Erythrina berteroana Urban, and the two dominant grass species Paspalum conjugatum Berg and Homolepsis aturensis Chase of this silvopastoral system. We grew grass seedlings in the greenhouse for 15 weeks in a methyl bromide-sterilized study soil to which either mixed-species VAM inoculum (Theobroma cacao feeder roots) or autoclave-sterilized cacao roots (non-inoculated control) were added. E. berteroana was grown from both seedlings and vegetative stakes (40 cm long) for 30 and 19 weeks, respectively. Upon harvest, we measured above and below ground biomass, N and P content, root∶shoot ratio, legume nodulation, and VAM infection levels. The total above-ground and root biomass of mycorrhizae-inoculated P. conjugatum seedlings were 2.5 and 2.8 times greater than those of noninoculated seedlings. In contrast, VAM-inoculated seedlings of H. aturensis produced 8.4 and 5.9 times more total above-ground and root mass than noninoculated seedlings. Mycorrhizae-inoculated E. berteroana seedlings produced 10.6 times greater shoot biomass for inoculated versus noninoculated seedlings, while E. berteroana vegetative stakes exhibited a negative growth response to VAM inoculation (an approximately 16% decrease in shoot biomass for VAM-inoculated cuttings). The difference in responsiveness between Erythrina growth forms is hypothesized to reflect the cost-benefit relationship between plant host and fungal symbiont for energy and nutrient reserves.