Use of nutrient: phosphorus ratios to evaluate the effects of vesicular arbuscular mycorrhiza on nutrient uptake in unsterilized soils

Summary Red clover was grown in soil previously treated with P at various rates, and growth, nutrient uptake, nutrient uptake in relation to phosphorus values, and levels of vesicular-arbuscular mycorrhizal (VAM) infection were determined. The soil was a silty clay loam and Glomus lacteum was the only fungus colonizing the plant roots. An examination of the effects of various rates of P application and of VAM colonization on nutrient (P, K, Ca, Mg, Mn, Fe, and Zn) uptake showed that the Mg : P ratio significantly increased and the Mn : P ratio significantly decreased with increasing VAM infection. It is concluded that in the Trifolium pratense-Glomus lacteum symbiosis, mycorrhizae improve Mg uptake and depress Mn uptake.     

Fitting plants to soil through mycorrhizal fungi: Mycorrhiza effects on plant growth and soil organic matter

Summary Vesicular-arbuscular mycorrhizal (VAM) fungi affect diverse aspects of plant form and function. Since mycorrhiza-mediated changes in host-plant responses to root colonization by different VAM fungi vary widely, it is important to assess each endophyte for each specific effect it can elicit from its host as part of the screening process for effectiveness. Three species of VAM fungi and a mixture of species were compared with non-VAM controls for their effects on soil organic matter contents and on nutrition and morphology in two varieties (native and hybrid) of corn (Zea mays L.) and one of sunflower (Helianthus annuus L.) in P-sufficient and N-deficient soil in pot cultures. Differences in soil organic matter due to the fungal applications were highly significant with all host plants. Native corn responded more to VAM colonization than the hybrid did; differences in treatments were significant in leaf area, plant biomass, and root: shoot ratio in the former, but not in the latter. Responses in the sunflower were similar to those in the native corn. Significant VAM treatment-related differences in shoot N and P contents were not reflected in shoot biomass, which was invariant. Correlations between plant or soil parameters and the intensity of VAM colonization were found only in soil organic matter with the native corn, in specific leaf area in the hybrid corn, and in plant biomass in the sunflower. The presence of the different endophytes and not the intensity of colonization apparently elicited different host responses.     

The effect of vesicular-arbuscular mycorrhizae in decreasing Ca acquisition by alfalfa plants in calcareous soils

Summary The legume Medicago sativa L. was grown in three calcareous soils supplied with increasing amounts of soluble phosphate, or a vesicular-arbuscular mycorrhizal (VAM) inoculum. The three test soils had high concentrations of extractable Ca. Analyses of dry-matter production and of the concentrations and content of the nutrients N, P, K, Ca, and Mg in plant tissues showed that, for each soil, a particular level of P application was able to match the VAM effects on N, P, and K levels. The Ca concentration and content in the VAM inoculated plants were, however, significantly lower than those in the P-supplied non-mycorrhizal treatments that matched the VAM effects. The N:P and the K:P ratios were about the same for mycorrhizal and non-mycorrhizal P-supplied control plants in all the three soils, but VAM inoculation lowered the Ca:P ratio in all soils. The mycorrhizae decreased Mg uptake in one of the soils, where non-mycorrhizal plants had high Mg concentrations in tissues. It is concluded that VAM depress the excessive acquisition of Ca by plants in calcareous soils.     

The influence of inorganic nutrient fertilization on the growth,nutrient composition and vesicular-arbuscular mycorrhizal colonization of pretransplant rice (Oryza sativa L.) plants

Summary The effects of P, N and Ca+Mg fertilization on biomass production, leaf area, root length, vesiculararbuscular mycorrhizal (VAM) colonization, and shoot and root nutrient concentrations of pretransplant rice (Oryza sativa L.) plants were investigated. Mycorrhizal plants generally had a higher biomass and P, N, K, Ca, Mn, Fe, Cu, Na, B, Zn, Al, Mg, and S shoot-tissue nutrient concentrations than non-mycorrhizal plants. Although mycorrhizal plants always had higher root-tissue nutrient concentrations than non-mycorrhizal plants, they were not significantly different, except for Mn. N fertilization stimulated colonization of the root system (colonized root length), and increased biomass production and nutrient concentrations of mycorrhizal plants. Biomass increases due to N were larger when the plants were not fertilized with additional P. P fertilization reduced the colonized root length and biomass production of mycorrhizal plants. The base treatment (Ca+Mg) did not significantly affect biomass production but increased the colonized root length. These results stress the importance of evaluating the VAM rice symbiosis under various fertilization regimes. The results of this study suggest that pretransplant mycorrhizal rice plants may have a potential for better field establishment than non-mycorrhizal plants.     

Effect of fertilizer and endomycorrhizal inoculum on growth and nutrient uptake of cocoa (Theobroma cacao L.) seedlings

Summary A greenhouse experiment was carried out to evaluate the influence of vesicular-arbuscular mycorrhiza (VAM) on growth and nutrient uptake of cocoa seedlings treated with five levels of palm oil mill effluent, in an unsterilized Oxisol and an Ultisol, either with or without addition of the VAM fungus Scutellospora calospora (Nicol. & Gred.) Walker and Sanders. Inoculation with the VAM fungi significantly increased nutrient uptake and plant growth in both soils. The dry matter yield, and the tissue N and K concentration in the plant tops increased significantly with increasing levels of palm oil mill effluent applied to both the Oxisol and the Ultisol. The maximum tissue P concentration, however, was obtained from plants grown in the Ultisol that was given 50.0 g palm oil mill effluent per kg while the maximum P recovery of 26% was obtained from plants given only 16.7 g effluent per kg. Overall, the percentage of P recovery decreased with the addition of increasing levels of palm oil mill effluent. In the Oxisol, the tissue P concentration increased with the addition of increasing levels of palm oil mill effluent, but the maximum recovery of P was recorded from plants given only 0.3 g effluent per kg. The percentage P recovery decreased with subsequent additions of the effluent.     

Effects of ammonium and nitrate on the growth of vesicular-arbuscular mycorrhizalErythrina poeppigiana O.I. Cook seedlings

Erythrina poeppigiana, a woody tropical plant, was inoculated with vesicular-arbuscular mycorrhizal (VAM) fungiGlomus etunicatum Becker and Gerdeman,G. mosseae Nicol. and Gerd. Gerdeman and Trappe, orG. intraradices Schenk and Smith. Growth, N uptake, and nutrition were evaluated in VAM-inoculated plants and controls fertilized with two levels (3 or 6 mM) of either NH _inf4 ^sup+ -N or NO _inf3 ^sup- -N. The response by the mycorrhizal plants to N fertilization, according to N source and/or level differed significantly from that of the control plants. In general, the growth of the mycorrhizal plants was similar to that of the non-mycorrhizal plants when N was provided as NH _inf4 ^sup+ . When the N source was NO _inf3 ^sup- the control plants grew significantly less than the VAM plants. Inoculation with VAM fungi gave yield increases of 255 and 268% forG. etunicatum-colonized plants, 201 and 164% forG. mosseae-colonized plants and 286 and 218% forG. intraradices-colonized plants fertilized with 3 and 6 mM NO _inf3 ^sup- -N, respectively. The increased growth and acquisition of nutrients by plants fertilized with NO _inf3 ^sup- -N and inoculated with VAM shows that VAM mycelium has a capacity for NO _inf3 ^sup- absorption. The results also showed thatE. poeppigiana seedlings preferred NH _inf4 ^sup+ as an N source.G. etunicatum was the most effective endophyte, not only increasing N, P, Ca, Mg, and Zn uptake in the presence of NO _inf3 ^sup- fertilizer but also P and Mg in the presence of NH _inf4 ^sup+ applications. From these results we conclude that VAM symbiosis affects N metabolism inE. poeppigiana plants and that this species can overcome limitations on the use of NO _inf3 ^sup- -N by the mediation of VAM fungi.     

Inoculation response in kidney beans (Phaseolus vulgaris,L.) to vesicular-arbuscular mycorrhizal fungi and rhizobia in non-sterilized soil

The effect of dual inoculation on three local cultivars (Miss Kelly, Portland Red, Round Red) of red kidney beans (Phaseolus vulgaris, L.) with four strains of Rhizobium leguminosarum bv. phaseoli and three species of vesicular-arbuscular mycorrhizal (VAM) fungi was examined in a clay loam soil. Rhizobial strains B 17 and B 36, each paired with Glomus pallidum or G. aggregatum, were the most effective pairings for cv. Miss Kelly. Inoculation of Miss Kelly with any of these pairings significantly (P=0.05) increased growth, number of nodules, nodule dry weight, mycorrhizal colonization, and shoot N and P content than other pairings. The growth response by cv. Portland Red was significantly improved by pairings of B 36 or B 17 with any of the three VAM fungi. For both cultivars (Miss Kelly and Portland Red), CIAT 652 or T 2 paired with VAM fungi did not give a positive growth response. In contrast, for cv Round Red the T 2 rhizobial strain in combination with any of the three VAM fungi showed a significant (P=0.05) growth improvement in all parameters. Our results suggest that while dual inoculation of VAM fungi and rhizobia significantly improves the growth response by red kidney beans, the best pairings of VAM fungus and rhizobia for each cultivar need to be carefully selected.     

Dual inoculation of pretransplant stage Oryza sativa L. plants with indigenous vesicular-arbuscular mycorrhizal fungi and fluorescent Pseudomonas spp.

Summary This study examined the response of rice (Oryza sativa L.) plants at the pretransplant/nursery stage to inoculation with vesicular-arbuscular mycorrhizal (VAM) fungi and fluorescent Pseudomonas spp., singly or in combination. The VAM fungi and fluorescent Pseudomonas spp. were isolated from the rhizosphere of rice plants. In the plants grown in soil inoculated with fluorescent Pseudomonas spp. alone, I found increases in shoot growth, and in root length and fine roots, and decreases in root growth, and P and N concentrations. In contrast, in the plants colonized by VAM fungi alone, the results were the reverse of those of the pseudomonad treatment. Dual inoculation of soil with VAM fungi and fluorescent Pseudomonas spp. yielded plants with the highest biomass and nutrient acquisition. In contrast, the plants of the control treatment had the lowest biomass and nutrient levels. The dual-inoculated plants had intermediate root and specific root lengths. The precentages of mycorrhizal colonization and colonized root lengths were significantly lower in the dual-inoculated treatment than the VAM fungal treatment. Inoculation of plants with fluorescent Pseudomonas spp. suppressed VAM fungal colonization and apparently reduced photosynthate loss to the mycorrhizal associates, which led to greater biomass and nutrient levels in dual-inoculated plants compared with plants inoculated with VAM fungi alone. Dual inoculation of seedlings with fluorescent Pseudomonas spp. and VAM fungi may be preferable to inoculation with VAM alone and may contribute to the successful establishment of these plants in the field.     

Synergistic effects of vesicular-arbuscular mycorrhizal fungi and diazotrophic bacteria on nutrition and growth of sweet potato (Ipomoea batatas)

Summary Sweet potatoes were micropropagated and then transplanted from axnic conditions to fumigated soil in pots in the greenhouse. Spores of Glomus clarum were obtained from Brachiaria decumbens or from sweet potatoes grown in soil infected with this fungus and with an enrichment culture of Acetobacter diazotrophicus. Three experiments were carried out to measure the beneficial effects of vesicular-arbuscular mycorrhizal (VAM) fungi-diazotroph interactions on growth, nutrition, and infection of sweet potato by A. diazotrophicus and other diazotrophs obtained from sweet potato roots. In two of these experiments the soils had been mixed with ¹⁵N-containing organic matter. The greatest effects of mycorrhizal inoculation were observed with co-inoculation of A. diazotrophicus and/or mixed cultures of diazotrophs containing A. diazotrophicus and Klebsiella sp. The tuber production was dependent on mycorrhization, and total N and P accumulation were increased when diazotrophs and G. clarum were applied together with VAM fungal spores. A. diazotrophicus infected aerial plant parts only when inoculated together with VAM fungi or when present within G. clarum spores. More pronounced effects on root colonization and intraradical sporulation of G. clarum were observed when A. diazotrophicus was co-inoculated. In non-fumigated soil, dual inoculation effects, however, were of lower magnitude. ¹⁵N analysis of the aerial parts and roots and tubers at the early growth stage (70 days) showed no statistical differences between treatments except for the VAM+Klebsiella sp. treatment. This indicates that the effects of A. diazotrophicus and other diazotrophs on sweet potato growth were caused by enhanced mycorrhization and, consequently, a more efficient assimilation of nutrients from the soil than by N₂ fixation. The possible interactions between these effects are discussed.     

Interactions of Glomus clarum with Acetobacter diazotrophicus in infection of sweet potato (Ipomoea batatas), sugarcane (Saccharum spp.), and sweet sorghum (Sorghum vulgare)

Summary Spores of the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus clarum obtained from sweet potatoes grown in soil inoculated with this fungus and with an enrichment culture of Acetobacter diazotrophicus contained A. diazotrophicus and several other bacteria, including a diazotrophic Klebsiella sp. Inoculation of micropropagated sweet potatoes with G. clarum and A. diazotrophicus enhanced spore formation in soil compared to VAM inoculation alone. Plants inoculated with VAM spores containing the bacteria showed additional increases in the number of spores formed within roots. A. diazotrophicus infected aerial plant parts only when inoculated together with VAM or when present within VAM spores. Micropropagated sugarcane seedlings inoculated with the same VAM spores containing the diazotrophs also contained much higher numbers of A. diazotrophicus in aerial parts than seedlings inoculated in vitro with the bacteria alone. When grown in non-sterile soil, the sugarcane seedlings again showed the greatest infection of aerial parts after inoculation with VAM spores containing the diazotrophs. This treatment also increased VAM colonization and the numbers of spores formed within roots. Similar effects were observed in sweet sorghum except that the aerial plant parts were not infected by A. diazotrophicus.     

SUGARCANE NUTRITIONAL DIAGNOSIS WITH DRIS NORMS ESTABLISHED IN BRAZIL,SOUTH AFRICA,AND THE UNITED STATES

ABSTRACT

The Diagnosis and Recommendation Integrated System (DRIS) approach evaluates plant nutritional status. The Diagnosis and Recommendation Integrated System is based on a comparison of crop nutrient ratios with optimum values from a high-yielding group (DRIS norms). Several researchers affirm that once DRIS norms based on foliar composition have been developed for a given crop, they are universal and applicable to that particular crop grown at any place and at any stage of its development. But different diagnoses with DRIS norms established for the same crop but under different growth conditions have been found. The objectives of this study were (i) to evaluate the confidence intervals of three DRIS norms of sugarcane crop, (ii) to compare sugarcane nutritional diagnosis with three DRIS norms, and (iii) to evaluate the universal use of DRIS norms in sugarcane crop. Sugarcane DRIS norms were tested. Means for nitrogen (N)/phosphorus (P), N/calcium (Ca), N/copper (Cu), manganese (Mn)/N, N/zinc (Zn), Ca/P, Cu/P, Mn/P, Zn/P, potassium (K)/Ca, K/Cu, Mn/K, Zn/K, Mn/Ca, Zn/Ca, Cu/magnesium (Mg), Mn/Mg, Zn/Mg, Mn/Cu, Zn/Cu, and Zn/Mn of these three DRIS norms were significantly different (?p<0.05). The sugarcane nutritional diagnosis derived from norms published in the literature was different. These three DRIS norms were not universally applicable to the sugarcane crop. Therefore, in the absence of DRIS norms locally calibrated, norms developed under one set of conditions only should be applied to another if the nutrient concentrations of high-yielding plants from these different set of conditions are similar.     

Effect of nitrogen and salinity levels in the nutrient solution on the DRIS diagnosis of greenhouse tomato

Abstract

Norms for the Diagnosis and Recommendation Integrated system (DRIS) developed for greenhouse tomato (Lycopersicon esculentum L.) were evaluated experimentally by varying the N concentration (115, 243, and 443 mg N L^‐1 ) or the salinity level (1.4, 2.5, and 3.7 dS m^‐1 ) of the nutrient solution. Foliar samples were taken at different intervals during the season for total N, P, K, Ca and Mg analysis. The nutrient imbalance index (NII) was calculated by summing up DRIS indexes irrespective of sign. A dry matter index (DM) was included in the modified DRIS (M‐DRIS) approach as a separator between excessive or deficient nutrients. Yield of marketable fruit that accumulated over a 8 week harvest period was quadratically related to N fertilization: 115, 243, and 443 mg N L^‐1 produced 2.9, 3.3, and 2.3 kg per plant respectively. Larger than critical NII values, 82 days after transplanting, were associated with excess of N, and Mg, and Ca deficiencies. Contrary to the DRIS and M‐DRIS approaches, the critical nutrient range approach (CNR) did not indicate any N excess. In the salinity experiment, marketable yield decreased linearly with salinity: 1.4, 2.5, and 3.7 dS m^‐1 produced 3.3, 2.9, and 2.3 kg per plant, respectively. Increasing salinity caused an increase in the NII at all sampling periods. However, Nil's were always smaller than the critical NII and were inconsistent with the low yields obtained. Thus, NII was considered a poor indicator of the salt effect.     

Effects of mes [2(n‐morpholino)‐ethanesulfonic acid] and ph on mineral nutrient uptake by mycor‐rhizal and nonmycorrhizal maize

Mycorrhizal (+VAM) and nonmycorrhizal (‐VAM) maize (Zea mays L.) plants were grown in sand culture in a greenhouse to determine effects of MES [2(N‐morpholino)‐ethanesulfonic acid] (2.0 mM) and pH (4.0, 5.0, 6.0, and 7.0) on mineral nutrient uptake. Plants were inoculated with the vesicular‐arbuscular mycorrhizal (VAM) isolate Glomus intraradices UT143. Shoot and root dry matter yields were lower in plants grown with MES (+MES) than without MES (‐MES), and decreased as pH increased. Shoot concentrations of N, Ca, Mg, Mn, and Zn were generally higher in +MES than in ‐MES plants, and nutrient contents of most nutrients were generally higher in + MES than in ‐MES plants. Concentrations of N, Ca, Mg, and Mn increased and P, S, and Fe decreased, while contents of all measured nutrients except Mn and Zn decreased as pH increased. Concentrations of Mn, Fe, Zn, and Cu were higher in +VAM than in ‐VAM plants, and contents of P and Ca were higher in ‐VAM than in +VAM plants and Zn content was higher in +VAM than in ‐VAM plants. MES had marked effects on mineral nutrient uptake which should be considered when MES is used to control pH of nutrient solutions for growth of maize.     

Mycorrhizal and common root-rot infection,and nutrient accumulation in barley grown on breton loam using N from biological fixation or fertilizer

Summary This paper presents soil biological data from a study on the functioning of three soil-plant systems on a Gray Luvisol in Cryoboreal Subhumid central Alberta. The systems were (1) an agroecological 8-year rotation, (2) a continuous grain system, both established in 1981, and (3) a classical Breton 5-year rotation established in 1930. The objectives were to (1) determine whether changes in vesicular-arbuscular mycorrhizae (VAM) populations occurred in soil under these cropping systems, (2) discover whether these cropping systems and/or VAM infection influenced the incidence of common root rot (Bipolaris sorokiniana), and (3) use nutrient translocation indices to test the hypothesis that soil quality influences non-specific physiological conditions in barley (Hordeum vulgare L.). VAM fungal propagules in soil samples and VAM infection under controlled conditions were significantly affected by the cropping system. VAM infection accounted for more than 85% of the variability in grain yield, plant biomass yield, and plant uptake of K, S, Ca, Fe, and Zn under controlled conditions. Backward-elimination regression analyses showed that under these conditions of high available P, plant P uptake was governed by the quantity of extractable P in the soil (r ²=0.82); the VAM infection contributed practically nothing when combined with available P (R ²=0.84). Neither VAM infection nor the cropping system were related to the B. sorokiniana infection in the barley. The growth of B. sorokiniana was equal, and its sporulation superior, when grown on residues of the non-host fababean (Vicia faba L.), compared with growth on residues of barley. Higher translocation of plant nutrients to the grain in the agroecological compared with the continuous grain treatments suggested that VAM and/or the soil history affected plant physiology, possible through hormonal effects. Superior barley yields in the agroecological compared with the continuous grain treatments were partly due to increased VAM colonization, greater nutrient accumulation and translocation to the grain, but not to a reduced disease incidence. These results demonstrate the benefits of a holistic systems approach while studying biological interactions involving plants and groups of soil microorganisms.(ICRISAT journal article number 1161)     

Infection of valuable broadleaf hardwood trees by Glomus mosseae: growth and mineral nutrition

In the past century, the excessive exploitation of the environment by human beings has resulted in the depletion of valuable broadleaf hardwood trees in Italian forests, creating a need for re-forestation. The aim of this research was to verify whether a vescicular-arbuscular mycorrhizal (VAM) fungus is able to colonise the root of valuable hardwood trees and to evaluate the impact of the VAM fungus on growth and macroelement nutrition of its plant hosts.Four species of valuable broadleaf hardwood trees, Prunus avium L., Fraxinus excelsior L., Acer pseudoplatanus L., and Juglans nigra L., were inoculated with Glomus mosseae, a VAM fungus, and cultivated in a greenhouse. Infection after inoculation and root colonization by the fungus, tree growth, and macro-element nutrition were evaluated two-years after inoculation. G. mosseae formed mycorrhizae on all plants. However, different morphological aspects - predominantly the formation of Arum type arbuscles in P. avium and F. excelsior - were observed. A general improvement of macro-element nutrition from species to species characterised an enhanced growth of mycorrhizal plants. Therefore, it is plausible that the association of VAMs with these broadleaf trees, could overcome the difficulties encountered in the transplanting and the slow growth typical of these tree species.Although numerous articles have reported the beneficial effects of ectomycorrhizal fungi on trees, there is a sparse literature on the association of VAM with tree species. Therefore, this study contributes to the understanding of the role of the symbiosis between valuable broadleaf trees and VAM fungi in macroelement nutrition.     

DIAGNOSIS AND RECOMMENDATION INTEGRATED SYSTEM (DRIS) FOR EVALUATING NUTRIENT STATUS OF COTTON (GOSSIPIUM HIRSUTUM)

Diagnosis and Recommendation Integrated System (DRIS) approach was employed to monitor the nutrient status of cotton (Gossipium hirsutum) in southwestern districts of Punjab, North-West India. DRIS norms for macro, secondary and micro nutrients in cotton plant are developed. Considering these DRIS norms, the most limiting nutrient for cotton plant in the region is identified along with the order in which the other nutrients become limiting. The DRIS approach indicated that 11, 3, 8, 5, 2, 4, 2, 3, 6 and 2 percent of the total cotton leaf samples collected were low in nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu), respectively. Leaf tissues of cotton plant were also found to contain high to excessive content of N, P, K, Ca, Mg, S, Fe, Mn Zn and Cu in 11, 7, 15, 19, 25, 18, 66, 33, 9 and 25 percent samples, respectively. DRIS derived sufficiency concentration ranges obtained from survey of cotton fields in this region were 2.22 to 5.20% N, 0.20 to 0.47% P, 1.05 to 2.14% K, 1.66 to 2.86% Ca, 0.34 to 0.57% Mg, 0.65 to 1.11% S, 106 to 172 mg kg^?1 Fe, 35 to 68 mg kg^?1 Mn, 18 to 33 mg kg^?1 Zn, and 5 to 8 mg kg^?1 Cu. The results elucidate that DRIS technique can be used for macro, secondary and micro nutrients indexing of cotton crop irrespective of its cultivar.     

Influence of varied soil microbial and inorganic nutrient conditions on the growth and vesicular-arbuscular mycorrhizal colonization of little bluestem [Schizachyrium scoparium (Michx.) Nash]

Summary A difference in biomass production between plants grown in autoclaved soil and non-autoclaved soil under N and base (Ca + Mg) treatments was probably caused by soil microbes other than vesicular-arbuscular mycorrhizal fungi. The plants were grown for 70 days in autoclaved soil, autoclaved soil with a vesicular-arbuscular mycorrhizal-free filtrate of non-autoclaved soil added, and non-autoclaved soil. The plants in each substrate received additional N, P, or Ca + Mg (base treatment) weekly. Control plants received no additional nutrients. The plant response to various substrates was a function of nutrient treatment. Colonization of roots by vesicular-arbuscular mycorrhizal fungi in non-autoclaved soil was lowest with the N and P treatments. There were significant negative correlations between vesicular-arbuscular mycorrhizal colonization and all plant growth variates. For all nutrient treatments, there were no differences in total biomass between plants grown in non-autoclaved soil and in the autoclaved-plus-filtrate substrate.     

Effects of excess manganese on mineral uptake in mycorrhizal sorghum

Associations between vesicular‐arbuscular mycorrhizal (VAM) fungi and manganese (Mn) nutrition/toxicity are not clear. This study was conducted to determine the effects of excess levels of Mn on mineral nutrient uptake in shoots and roots of mycorrhizal (+VAM) and non‐mycorrhizal (‐VAM) sorghum [Sorghum bicolor (L) Moench, cv. NB9040]. Plants colonized with and without two VAM isolates [Glomus intraradices UT143–2 (UT1 43) and Gl. etunicatum UT316A‐2 (UT316)] were grown in sand irrigated with nutrient solution at pH 4.8 containing 0, 270, 540, and 1080 μM of added Mn (as manganese chloride) above the basal solution (18 μM). Shoot and root dry matter followed the sequence of UT316 > UT143 > ‐VAM, and shoots had greater differences than roots. Shoot and root concentrations and contents of Mn, phosphorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), and copper (Cu were determined. The +VAM plants generally had higher mineral nutrient concentrations and contents than ‐VAM plants, although ‐VAM plants had higher concentrations and contents of some minerals than +VAM plants at some Mn levels. Plants colonized with UT143 had higher concentrations of shoot P, Ca, Zn, and Cu and higher root Mg, Zn, and Cu than UT316 colonized plants, while UT316 colonized plants had higher shoot and root K concentrations than UT143 colonized plants. These results showed that VAM isolates differ in enhancement of mineral nutrient uptake by sorghum.     

Effects of excess aluminum on mineral uptake in mycorrhizal sorghum

Soil acidity is often associated with toxic aluminum (Al), and mineral uptake usually decreases in plants grown with excess Al. This study was conducted to evaluate the effects of Al (0, 35, 70, and 105 μM) on Al, phsophorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn,) and copper (Cu) uptake in shoots and roots of sorghum [Sorghum bicolor (L.) Moench, cv. SC283] colonized with the vesicular‐arbuscular mycorrhizal (VAM) fungi isolates Glomus intraradices UT143–2 (UT143) and Glomus etunicatum UT316A‐2 (UT316) and grown in sand (pH 4.8). Mycorrhizal (+VAM) plants had higher shoot and root dry matter (DM) than nonmycorrhizal (‐VAM) plants. The VAM treatment had significant effects on shoot concentrations of P, K, Ca, Fe, Mn, and Zn; shoot contents of P, S, K, Ca, Mg, Fe, Mn, Zn, and Cu; root concentrations of P, S, K, Ca, Mn, Zn, and Cu; and root contents of Al, P, S, K, Ca, Mg, Fe, Mn, Zn, and Cu. The VAM effects on nutrient concentrations and contents and DM generally followed the sequence of UT316 > UT143 > ‐VAM. The VAM isolate UT143 particularly enhanced Zn uptake, and both VAM isolates enhanced uptake of P and Cu in shoots and roots, and various other nutrients in shoots or roots.     

Growth response of field-grown Siratro (Macroptilium atropurpureum Urb.) and Aeschynomene american L. to inoculation with selected vesicular-arbuscular mycorrhizal fungi

Summary The effect of inoculation with a selected isolate of Glomus etunicatum Becker and Gerdemann and one of G. intraradices Schenck and Smith on the growth and nutrient content of Macroptilium atropurpureum Urb. cv. Siratro and Aeschynomene americana L., at applied P levels of 10, 30, 60, and 120 kg ha^-1, was studied under field conditions. At all P levels and for all harvests, the shoot dry mass of Siratro and A. americana were greater for the plants inoculated with the vesicular-arbuscular mycorrhizal (VAM) fungi than the control plants. Differences between the VAM fungus-inoculated and the control plants were most marked between 30 and 90 kg ha^-1 of applied P and diminished at 120 kg ha^-1. At the first harvest of Siratro, the plants inoculated with G. etunicatum had a greater shoot dry mass than those inoculated with G. intraradices, for all levels of applied P. However, for subsequent harvest of Siratro and for the one harvest of A. americana the response of shoot dry mass to the two VAM fungi was equivocal. Fungal inoculation gave at least a 30% saving in the amount of P fertilizer required (40 kg ha^-1) for the maximum yield. The plants inoculated with VAM fungi had a greater tissue concentration and total content of P and N than the control plants at low and intermediate levels of applied P. The percentage of root colonized by VAM fungi for the inoculated plants of the two legumes increased linearly with P additions up to 60 kg ha^-1. The conclusion is that under amended (limed and fertilized) soil conditions, inoculation with selected VAM fungi can improve the establishement and growth of forage legumes in fields that contain ineffective populations of native VAM fungi.