Mycorrhiza Effect on Maize P Uptake from Phosphate Rock and Superphosphate

Low available phosphorus (P) is a serious constraint for crop production in acidic tropical soils. Economical yields in these environments require application of large amounts of costly nitrogen (N) and P fertilizers. Although phosphate rock (PR) has been proposed as a less expensive P source, the slow P release to the soil limits its use for annual crops. The objective of this work was to examine the effect of inoculating a nonsterile acidic soil with vesicular arbuscular mycorrhizal (VAM) Gigaspora margarita on PR dissolution and P uptake by aluminum (Al)–tolerant maize inbreds. Three maize inbreds from CIMMYT, at Cali, Colombia, ranked as Al‐tolerant and one local breed ranked as Al‐susceptible were seeded in 4‐kg pots filled with a soil of pH 4.1 and 2.5 mg kg^?1 available P. Inoculants (Gigaspora margarita and indigenous VAM), P fertilizer (Riecito phosphate rock and triple superphosphate), and the four inbreds were arrainged in a factorial design (2 × 2 × 4) with four replications. Plants were harvested 35 days after seeding, and P was determined in shoots. Four 2.5‐cm‐diameter soil cores were obtained from each pot to determine root length (two cores), root colonization (one core), and available P (one core). The inoculation with Gigaspora margarita caused a reduction in root length but better root colonization, 55% increase in P uptake, and 27% increase in shoot growth. When PR was used as fertilizer, plant growth was reduced in both roots and shoots. However, when PR was used in the presence of Gigaspora margarita, inbreds had 13% longer roots and shoot growth was the same as shoots fertilized with triple superphosphate. Our data suggest that inbreds exhibit different abilities to acquire P from PR under the influence of Gigaspora margarita fungi.     

Use of specific phospholipid fatty acids for identifying and quantifying the external hyphae of the arbuscular mycorrhizal fungus Gigaspora rosea

The external hypha of arbuscular mycorrhizal (AM) fungi, extending from roots out into soil, is an important structure in the uptake of phosphate from the depletion zone around each root. In this paper, we analysed some phospholipid fatty acids (PLFAs) derived from external hyphae of four AM fungi (Glomus etunicatum, Glomus clarum, Gigaspora margarita and Gigaspora rosea) to find fatty acids which may be useful as specific markers for identifying and quantify the external hyphae of Gigaspora species. Leek (Allium porrum L.) seedlings inoculated with each AM fungus were grown in river sand. Sand samples were collected and four PLFAs (16:1ω5, 18:1ω9, 20:1ω9 and 20:4) in the sand were analysed. In addition, the hyphal biomass in the sand was determined by the direct microscopic method. PLFAs 18:1ω9 and 20:4 were found in all the AM-inoculated and non-inoculated sand samples. PLFA 16:1ω5 was detected in the sand inoculated with G. etunicatum, G. clarum and Gi. rosea. PLFA 20:1ω9 was detected only in the sand inoculated with Gi. rosea. PLFAs 16:1ω5 and 20:1ω9 were not found in the sand inoculated with Gi. margarita. The amount of PLFA 20:1ω9 was closely correlated with the amount of biomass of external hyphae of Gi. rosea (r=0.937, P<0.001), whereas no correlation was observed for PLFA 16:1ω5. The 20:1ω9 content of Gi. rosea was approximately 6.56 nmol mg⁻¹ hyphal biomass. We suggest that PLFA 20:1ω9 can be used as a specific marker for identifying and quantifying the external hyphae of Gi. rosea, at least in controlled experimental systems.     

Glycosidation of apigenin results in a loss of its activity on different growth parameters of arbuscular mycorrhizal fungi from the genus Glomus and Gigaspora

The effect of different concentrations (0.5, 2 and 8 μM) of apigenin and its glycosidated form 5,7,4′-hydroxy flavone glycoside on arbuscular mycorrhizal (AM) fungal spore germination, hyphal growth, hyphal branching, the formation of entry points and root colonization of Gigaspora. rosea, Gi. margarita, Glomus mosseae and G. intraradices was tested. The lowest apigenin concentration (0.5 μM) nearly doubled hyphal branching, the formation of entry points and root colonization of all four tested fungi, whereas higher concentrations (2 and 8 μM) nearly doubled the hyphal growth of Gi. margarita, G. mosseae and G. intraradices. In none of the treatments with the apigenin-glycoside any effect on AM fungi could be observed. Our data show that apigenin exhibits an AM fungal genus and even species activity and we provide strong evidence that glycosidation results in a loss of its activity towards AM fungi.     

Rhodotorulic acid enhances root colonization of tomato plants by arbuscular mycorrhizal (AM) fungi due to its stimulatory effect on the pre-symbiotic stages of the AM fungi

Exudates of Rhodotorula mucilaginosa, a yeast commonly found in the rhizosphere, increased hyphal length of the arbuscular mycorrhizal (AM) fungi Gigaspora rosea and Gigaspora margarita. Rhodotorulic acid (RA), a siderophore compound obtained from R. mucilaginosa exudates, increased hyphal length and branching. Thus, the increase in the number of entry points and the higher AM root colonization of tomato plants in the presence of RA can at least partially be explained by the positive effect of RA on the pre-symbiotic stages of the AM fungi.     

Effects of arbuscular mycorrhizal inoculation on the growth of Elsholtzia splendens and Zea mays and the activities of phosphatase and urease in a multi-metal-contaminated soil under unsterilized conditions

A pot culture experiment was carried out to study the effects of arbuscular mycorrhizal (AM) inoculation on the growth of Elsholtzia splendens and Zea mays and the activities of phosphatase and urease in a soil contaminated with Cu, Zn, Pb and Cd. Two AM fungal inocula, MI containing Glomus caledonium and MII containing Gigaspora margarita,Gigaspora decipens, Scutellospora gilmori, Acaulospora spp. and Glomus spp., were applied to the soil. The plants of E. splendens and Z. mays were harvested after 24 and 10 weeks of growth, respectively. Both plant species had a similar trend in mycorrhizal colonization rates, MI > MII > control. Shoot and root biomass of Z. mays was increased by MI, while not affected significantly by MII. Although both MI and MII increased plant dry weight of E. splendens, MII was more effective. Mycorrhizal dependency (MD) with MI and MII was 14.8 and 33.5, respectively for E. splendens, and 11.0 and 0.9, respectively for Z. mays. Both inocula increased the activities of phosphatase and urease in the soils of E. splendens and Z. mays, but MI was more effective than MII for urease, while MII more effective than MI for phosphatase. Although the mechanisms involved in these responses are not clear, AM fungal inoculum may be important and used for the phytoremediation of heavy metal contaminated soils, but both inoculum type and host species must be considered.     

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

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

Foliar application of zinc promotes cadmium absorption by increasing expression of cadmium transporter genes and activities of antioxidative enzymes in winter wheat

Cadmium (Cd) is a deleterious non-essential metal in plants.To elucidate the mechanisms by which zinc (Zn) application alleviates cadmium (Cd)toxicity in wheat,we characterized plant growth,antioxidant system,leaf cell ultrastructure,and Cd transporter gene expression in winter wheat under Cd exposure (50μmol L^-1Cd) with foliar Zn application in a hydroponic experiment.Results showed that Zn addition (Zn+Cd) or pretreatment (pre-Zn+Cd) at 2 g L^-1as Zn SO₄·7H_...     

Effect of Zn-tolerant bacterial strains on growth and Zn accumulation in Orychophragmus violaceus

Several Zn-tolerant bacterial strains were isolated from heavy-metal contaminated sludge, and their effects on root elongation, mobility, and accumulation of Zn in Orychophragmus violaceus were studied. The isolated strains included Bacillus subtilis, B. cereus, Flavobacterium sp. and Pseudomonas aeruginosa which were capable of stimulating root elongation in O. violaceus seedlings either in the presence or absence of Zn. The four bacterial strains significantly increased the concentration of water-extractable Zn compared with axenic soil. In addition, the four Zn-tolerant bacteria significantly increased the shoot biomass and Zn accumulation in O. violaceus compared to non-inoculated plants. The bacterial strains displayed different capacities to enhance plant Zn accumulation. Flavobacterium sp. was identified as the best candidate for enhancing Zn accumulation in plants, increasing Zn accumulation up to 1.21- and 1.19-fold in shoots and roots, respectively, compared to non-inoculated plants. It was indicated that Zn-tolerant bacteria played an important role in influencing the availability of water-soluble Zn in soil and Zn accumulation by plants. This study provides insight into the development of plant–microbe systems for phytoremediation.     

Molecular diversity of arbuscular mycorrhizal fungi associated with two dominant xerophytes in a valley-type savanna,southwest China

The diversity of arbuscular mycorrhizal fungi (AMF) colonizing the roots and rhizosphere soils of Heteropogon contortus and Dodonaea viscose growing in a valley-type savanna, southwest China, were analyzed by the large subunit ribosomal RNA genes (LSU). A total of 547 AMF sequences were screened for establishment of four clone libraries. Phylogenetic analysis revealed that the sequences clustered in at least 8 discrete sequence groups, all belonging to the genus Glomus. Among the Glomus spp., Glo 1 (GlGr A) and Glo 7 (GlGr B) were the most common in all root and soil samples of the two xerophytes, accounting for 42% and 33% of all screened clones, respectively. The ∫-LIBSHUFF analysis revealed that the composition of AMF communities associated with the two xerophytic hosts varied greatly both in roots and their rhizosphere soils.     

Physiological and molecular characterization of Fe acquisition by tomato plants from natural Fe complexes

The aim of this work is to evaluate the capability of tomato plants to use different Fe sources, such as Fe citrate, Fe phytosiderophores, and Fe complexed by a water-extractable humic substances (Fe-WEHS) also in relation to physiological and molecular adaptations induced by these complexes at the root level. Tomato plants acquired higher amounts of Fe from Fe-WEHS than from the other two sources and this phenomenon occurred only when the treatment lasted 24 h. The higher acquisition of Fe from Fe-WEHS than other sources depended on a reductive mechanism and on rhizosphere acidification and appeared to be due neither to a higher apoplastic loading nor to a higher resistance of WEHS to microbial degradation. Supply of the different Fe complexes to deficient plants induced a transient upregulation of Fe(III)-chelate reductase (LeFRO1) and Fe transporter genes, LeIRT1 and LeIRT2. In Fe-WEHS-fed plants, where a quicker and higher upregulation of these genes was evident, a coordination in the expression of LeFRO1, LeIRT1, and LeIRT2 genes occurred already after 1 h treatment when the amount of Fe acquired by the plants from the three sources was similar. Iron from Fe-WEHS could be efficiently acquired in a mixture of natural Fe complexes possibly occurring in the rhizosphere. This phenomenon is due to an altered expression of Fe uptake-related genes and to the root capacity to create favorable conditions for the micronutrient uptake into the rhizosphere.     

Improved zinc tolerance in Eucalyptus globulus inoculated with Glomus deserticola and Trametes versicolor or Coriolopsis rigida

The potential of interactions between saprophytic and arbuscular mycorrhizal (AM) fungi to improve Eucalyptus globulus grown in soil contaminated with Zn were investigated. The presence of 100 mg kg ⁻¹ Zn decreased the shoot and root dry weight of E. globulus colonized with Glomus deserticola less than in plants not colonized with AM. Zn also decreased the extent of root length colonization by AM and the AM fungus metabolic activity, measured as succinate dehydrogenase (SDH) activity of the fungal mycelium inside the E. globulus root. The saprophytic fungi Trametes versicolor and Coriolopsis rigida increased the shoot dry weight and the tolerance of E. globulus to Zn when these plants were AM-colonized. Both saprophytic fungi increased the percentage of AM root length colonization and elevated G. deserticola SDH activity in the presence of all Zn concentrations applied to the soil. In the presence of 500 and 1000 mg kg⁻¹ Zn, there were higher metal concentrations in roots and shoots of AM than in non-AM plants; furthermore, both saprophytic fungi increased Zn uptake by E. globulus colonized by G. deserticola. The higher root to shoot metal ratio observed in mycorrhizal E. globulus plants indicates that G. deserticola enhanced Zn uptake and accumulation in the root system, playing a filtering/sequestering role in the presence of Zn. However, saprophytic fungi did not increase the root to shoot Zn ratio in mycorrhizal E. globulus plants. The effect of the saprophytic fungi on the tolerance and the accumulation of Zn in E. globulus was mediated by its effect on the colonization and metabolic activity of the AM fungi.     

脱落酸通过影响生长素合成及分布抑制拟南芥主根伸长

脱落酸(ABA)在介导植物生长发育及逆境响应中发挥重要功能,但ABA抑制根伸长的机制尚不清楚。本文以拟南芥为材料,通过研究ABA对拟南芥根伸长的影响以及ABA受体突变体根发育表型的鉴定,探讨ABA抑制植物主根的机制。研究发现:ABA能够抑制主根生长及伸长,并且经典受体PYR1/PRL介导了ABA抑制根伸长的过程;ABA能够改变细胞周期蛋白CycB1;1::GUS表达模式,并影响根中生长素分布和响应。结果表明,ABA可能通过影响生长素在根部的分布和剂量,进而影响根尖分生区细胞分裂,从而抑制根伸长。     

Interaction between the soil yeast Rhodotorula mucilaginosa and the arbuscular mycorrhizal fungi Glomus mosseae and Gigaspora rosea

The effect of the soil yeast, Rhodotorula mucilaginosa LBA, on Glomus mosseae (BEG n°12) and Gigaspora rosea (BEG n°9) was studied in vitro and in greenhouse trials. Hyphal length of G. mosseae and G. rosea spores increased significantly in the presence of R. mucilaginosa. Exudates from R. mucilaginosa stimulated hyphal growth of G. mosseae and G. rosea spores. Increase in hyphal length of G. mosseae coincided with an increase in R. mucilaginosa exudates. No stimulation of G. rosea hyphal growth was detected when 0.3 and 0.5 ml per petri dish of yeast exudates was applied. Percentage root length colonization by G. mosseae in soybean (Glycine max L. Merill) and by G. rosea in red clover (Trifolium pratense L. cv. Huia) was increased only when the soil yeast was inoculated before G. mosseae or G. rosea was introduced. Beneficial effects of R. mucilaginosa on arbuscular mycorrhizal (AM) colonization were found when the soil yeast was inoculated either as a thin agar slice or as a volume of 5 and 10 ml of an aqueous solution. R. mucilaginosa exudates (20 ml per pots) applied to soil increased significantly the percentage of AM colonization of soybean and red clover.     

Effect of Bioaccumulation of Cs and Sr Natural Isotopes on Foliar Structure and Plant Spectral Reflectance of Indian Mustard (Brassica Juncea)

The objectives of this study are: (1) Evaluate the capacity of Indian mustard (Brassica juncea) for uptake and accumulation of Cs and Sr natural isotopes. (2) Identify foliar structural and other physiological changes (biomass, relative water content etc.) resulted from the accumulation of these two elements. (3) Monitor the Cs and Sr uptake and bioaccumulation process by spectral reflectance. Potted Indian mustard plants were exposed to different concentrations of Cs (50 and 600 ppm) and Sr (50 and 300 ppm) natural isotopes in solution form for 23 days. Bioaccumulation of Cs and Sr were found in the order of leaves > stems > roots for both Cs- and Sr-treated plants. The highest leaf and root Sr accumulations are observed to be 2,708, and 1,194 mg kg^?1, respectively; and the highest leaf and root Cs accumulations are 12,251, and 6,794 mg kg^?1, respectively. High translocation efficiency for both elements is documented by shoot/root concentration ratios greater than one. Biomass decreases were observed for plants treated with higher concentration of Cs or Sr. Cs accumulation affected the pigment concentration and internal structure of the leaf and the spectral characteristics of plants. Within the applied concentration range, Sr accumulation resulted in no significant changes in relative water content (RWC), leaf structural and spectral characteristics of mustard plants. Cs shoot concentration showed significant negative correlation with relative water content (RWC; r = ?0.88*) and normalized difference vegetative index (NDVI) value (r = ?0.68*) of plant shoots. The canopy spectral reflectance and NDVI analysis clearly revealed (p < 0.05) the stress caused by Cs accumulation.     

Diversity of 16S-rRNA and nifH genes derived from rhizosphere soil and roots of an endemic drought tolerant grass,Lasiurus sindicus

Lasiurus sindicus is a highly nutritive, drought tolerant, perennial grass, endemic to the Thar Desert of Rajasthan, India. In order to characterize the diversity of bacteria associated with roots of this grass that had survived severe drought stress, 16S-rRNA gene clone libraries were established from RT-PCR amplified products of the total RNA extracted from the washed roots and rhizosphere soil samples. Eight major bacterial taxa were identified in a total of 121 16S-rRNA gene clones. The majority of sequences belonged to Gram-positive bacteria, Actinobacteria being the most predominant ones, closely followed by Firmicutes. Most of the sequences showed similarity with sequences from cultivated bacteria or uncultivated environmental clones associated with arid, semi-arid environments, cold deserts and contaminated soils. PCR amplification of nifH genes using total DNA as template produced a total of 48 nifH clones from the rhizosphere soil and root samples and revealed a predominance of nifH sequences closely affiliated to Pseudomonas pseudoalcaligenes, isolated in a previous study from root samples of Lasiurus sindicus. Some nifH sequences showed close similarity to cultivated diazotrophs like Azospirillum brasilense, Rhizobium sp., and a variety of uncultured nitrogen fixing bacteria. Thus, this study provides us with evidence that L. sindicus harbors a diversity of bacteria with potential for nitrogen fixation.     

Mycorrhizal alleviation of acid soil stress in the sweet potato (Ipomoea batatas)

It is not known why sweet potato (Ipomoea batatas) cultivated in tropical regions tolerates acid soil. Here, we report the involvement of mycorrhizal symbiosis in this tolerance. Plants were grown in root-boxes filled with either acidic soil (pH 4.2) or the same soil amended with lime (pH 5.2) for 30 d in a growth chamber. In the inoculated treatments, the percentage of root length colonized by Gigaspora margarita was not affected by soil pH (23±9% at pH 4.2 vs. 30±12% at pH 5.2). The root and shoot dry weights of the non-mycorrhizal plants at pH 4.2 were 27 and 35%, respectively, of those at pH 5.2. The root and shoot dry weights of the mycorrhizal plants at pH 4.2 were 70 and 51% of those at pH 5.2. Growth promotion in mycorrhizal plants was significant only at pH 4.2 (2-fold increase in whole plant dry weight), but not at pH 5.2. As a result, no significant difference was detected in whole plant dry weight between the mycorrhizal plants at pH 4.2 and non-mycorrhizal plants at pH 5.2. The mycorrhizal plants at pH 4.2 showed reduced toxic symptoms of Mn (brown specks on mature leaves) and Al (poor root growth) compared to non-mycorrhizal ones, but tissue concentrations of P, K and Ca did not increase in mycorrhizal plants. We assume that the mycorrhizal colonization can reduce toxic effects of those elements while the exact mechanisms should be further investigated.     

Accumulation of specific flavonoids in soybean (Glycine max (L.) Merr.) as a function of the early tripartite symbiosis with arbuscular mycorrhizal fungi and Bradyrhizobium japonicum (Kirchner) Jordan

This study is the first report assessing the effect of soil inoculation on the signalling interaction of Bradyrhizobium japonicum, arbuscular mycorrhizal fungi (AMF) and soybean plants throughout the early stages of colonisation that lead to the tripartite symbiosis. In a study using soil disturbance to produce contrasting indigenous AMF treatments, the flavonoids daidzein, genistein and coumestrol were identified as possible signals for regulating the establishment of the tripartite symbiosis. However, it was unclear whether soil disturbance induced changes in flavonoid root accumulation other than through changing the potential for AMF colonization. In this study, soil treatments comprising all possible combinations of AMF and B. japonicum were established to test whether (1) modifications in root flavonoid accumulation depend on the potential for AMF colonization, and (2) synthesis and accumulation of flavonoids in the roots change over time as a function of the early plant-microbial interactions that lead to the tripartite symbiosis. The study was comprised of two phases. First, maize was grown over 3-week periods to promote the development of the AM fungus Glomus clarum. Second, the interaction between soybean, G. clarum and B. japonicum was evaluated at 6, 10, 14 and 40 days after plant emergence. Root colonization by G. clarum had a positive effect on nodulation 14 days after emergence, producing, 30% more nodules which were 40% heavier than those on roots solely inoculated with B. japonicum. The tripartite symbiosis resulted in 23% more N₂ being fixed than did the simpler symbiosis between soybean and B. japonicum. The presence of both symbionts changed accumulation of flavonoids in roots. Daidzein and coumestrol increased with plant growth. However, development of the tripartite symbiosis caused a decrease in coumestrol; accumulation of daidzein, the most abundant flavonoid, was reduced in the presence of AMF.     

Release of the recombinant Cry3Bb1 protein of Bt maize MON88017 into field soil and detection of effects on the diversity of rhizosphere bacteria

A three-year experimental field study with a genetically engineered Bt maize (event MON88017) and three conventionally bred cultivars was conducted to quantify the recombinant Cry3Bb1 protein released into soil and detect effects on the diversity of soil bacteria. Protein extraction and an enzyme-linked immunosorbent assay (ELISA) allowed a threshold detection of 0.01 ng Cry3Bb1 g^?1 soil. The maximum amount found in field plots with Bt maize was 1.0 ng Cry3Bb1 g^?1 rhizosphere soil. Average concentrations during the growing seasons varied between years from 0.07 to 0.29 ng g^?1. No accumulation of Cry3Bb1 in soil occurred over the three growing seasons. Four weeks after harvest, the major Cry3Bb1 reservoirs on the field were the remaining root stubbles, but their Cry3Bb1 concentration declined by 98.30–99.99% in the following seven months. During the three consecutive years of study there were never significant differences between the rhizosphere bacterial community structure of the Bt maize and the other cultivars, as detected by cultivation independent profiling of PCR-amplified 16S rRNA genes. The low concentrations of soil extractable Cry3Bb1, its degradation in decaying roots, and the lack of effects on rhizosphere bacteria give no indications of adverse effects of MON88017 cultivation on soil ecology.     

The Effect of Arbuscular Mycorrhizal Fungi Inoculation in Mitigating Salt Stress of Pea (Pisum Sativum L.)

ABSTRACT

Salinity is one of the major threats to an agriculture production system and limits crop growth and productivity. Arbuscular mycorrhizal fungi (AMF) form a mutualistic association with majority of land plants and play important role in stress tolerance. In the present study, effect of three mycorrhizal treatments, i.e., single-species AMF (Rhizoglomus intraradices), formulated AMF (Funneliformis mosseae and R. intraradices), and multispecies AMF (Rhizoglomus fasciculatum and Gigaspora sp.) along with control (nonmycorrhizal) on growth, yield performance, and metabolic changes in pea crop under salinity stress was examined in completely randomized design with four replications. The results revealed that AMF inoculation mitigated negative effects of salinity in pea due to higher nutrient uptake, accumulation of compatible osmolytes, and lower cellular leakage of electrolyte which in turn enhanced biomass production, chlorophyll synthesis, yield, and growth attributes. Overall, consortium-based application of R. fasciculatum and Gigaspora sp. was found most suitable approach to ameliorate the salt stress in pea crop and enhanced the yield by ~11%, 24%, and 54% than single-species, multispecies, and control treatments, respectively. The variation in results under different mycorrhizal treatment might be due to specific compatibility relationships that exist between symbionts.     

Occurrence of vesicular-arbuscular mycorrhizae with Amaranthaceae in soils of the Indian semi-arid region

Summary Some members of the family Amaranthaceae, which has mostly been reported as non-mycorrhizal, were examined for a symbiotic association with mycorrhizae in the semiarid and arid zones. Ten species belonging to five genera, Achyranthes, Aerva, Alternanthera, Amaranthus, and Celosia were examined, using 1.0-cm long root standards. Intercellular hyphae, vesicles and arbuscules were observed in the root cortex. The number of different types of spores in the rhizosphere soil of different plants ranged from one to three. The spores isolated represented nine species belonging to four genera, Glomus, Gigaspora, Sclerocystis, and Scutellospora. No correlation could be established between spore counts and either soil pH or soil moisture.