Higher Mycorrhizal Colonization Research Articles

Arbuscular Mycorrhizal Fungi Mediate the Acclimation of Rice to Submergence

Flooding is a critical factor that limits the establishment of a symbiosis between rice and arbuscular mycorrhizal fungi (AMF) in wetland ecosystems. The distribution of carbon resources in roots and the acclimation strategies of rice to flooding stress in the presence of AMF are poorly understood. We conducted a root box experiment, employing nylon sheets or nylon meshes to create separate fungal chambers that either prevented or allowed the roots and any molecules to pass through. We found that the mycorrhizal colonization rate and the expression of genes OsD14L and OsCERK1, which are involved in fungal perception during symbiosis, both increased in mycorrhizal rice roots following intermittent flooding compared to continuous flooding. Furthermore, AMF inoculation affected root morphological traits, facilitating both shallower and deeper soil exploration. Increased submergence intensity led to carbohydrate deprivation in roots, while high mycorrhizal colonization increased soil oxygen consumption and decreased the neutral lipid concentration in roots. However, mycorrhizal inoculation increased the rice photosynthesis rate and facilitated acclimation to submergence by mediating the expression of the genes OsCIPK15 and OsSUB1A to enhance rice shoot elongation and the sugar concentration in roots as a result of reduced competition for carbon between rice and AMF under different flooding conditions.

Shifts of arbuscular mycorrhizal fungal functioning along a simulated nitrogen deposition gradient

AbstractThe deposition of atmospheric nitrogen can significantly boost the amount of nitrogen available in various ecosystems, potentially altering the mutualistic association between arbuscular mycorrhizal fungi (AMF) and their host plants. Nevertheless, the precise mechanisms and the degree to which externally induced nitrogen‐related changes in AMF functionality might impact Sorghum bicolor (L.) Moench, a plant known for its high mycorrhizal colonization, remains unclear. In this study, the mycorrhizal response affected by environmental N enrichment was addressed by conducting a glasshouse experiment, and four fertilization treatments (N1, N2, N3, and N4, 0, 15, 30, and 60 kg N hm−1 a−1, respectively) were used to simulate N deposition differences over the mycorrhizal response. The changes in mycorrhizal colonization and plant variables during different AMF and N fertilizer applications were investigated. When the gradient's nitrogen levels increased, the mycorrhizal growth response and mycorrhizal nitrogen response showed a pattern of first dropping and then increasing. N‐induced changes in the mycorrhizal response were associated with vesicular colonization, arbuscular colonization, and root‐length colonization. The variation in the mycorrhizal response over the N concentration gradient highlights the critical role of AMF in agroecosystems.

Tomato plant growth promotion and drought tolerance conferred by three arbuscular mycorrhizal fungi is mediated by lipid metabolism

Arbuscular mycorrhizal fungi (AMF) can promote plant growth and enhance plant drought tolerance with varying effect size among different fungal species. However, the linkage between the variation and the lipid metabolism, which is exclusively derived from plants, has been little explored thus far. Here, we established AM symbiosis between tomato (Solanum lycopersicum) plants and three AMF species (Rhizophagus intraradices, Funneliformis mosseae, Rhizophagus irregularis) under well watered (WW) or drought stressed (DS) conditions in pot experiment. The plant biomass, chlorophyll fluorescence Fv/Fm, shoot P content and mycorrhizal colonization were determined. Meanwhile, fatty acid (FA) profiles and relative expression of genes encoding for nutrition exchange (SlPT4, SlPT5, RAM2, STR/STR2) in roots were also monitored. DS significantly decreased plant biomass while AMF significantly increased it, with three fungal species varying in their growth promoting capacity and drought tolerance capacity. The growth promoting effect of R. irregularis was lower than those of R. intraradices and F. mosseae, and was associated with higher mycorrhizal colonization and more consumption of lipids. However, the drought tolerance capacity of R. irregularis was greater than those of R. intraradices and F. mosseae, and was associated with less decrease in mycorrhizal colonization and lipid content. We also found that AMF mediated plant drought tolerance via regulating both AM specific FAs and non-AM specific FAs in a complementary manner. These data suggest that lipid metabolism in AM plays a crucial role in plant drought tolerance mediated by AMF.

On farm inoculation of native arbuscular mycorrhizal fungi improves efficiency in increasing sugarcane productivity in the field

The objective of this study was to evaluate the effect of inoculation of native arbuscular mycorrhizal fungi (AMF) multiplied on farm in the productivity and quality of different cultivars of sugarcane (Saccharum ssp.) in field conditions by three ratoons. The experimental design was of randomized blocks, in factorial scheme 6 × 2: six cultivars (CTC 1, CTC 7, CTC 9, CTC 16, SP89-1115 and RB925345), with and without AMF inoculation, in three ratoons. The AMF species mix, used to compose the inoculant, were collected from the experimental area, multiplied in trap culture, and applied to the sugarcane planting line. To assess the effectiveness of establishing mycorrhizal symbiosis, root mycorrhizal colonization (MC), spore density (SD), and AMF diversity were quantified. Sugarcane productivity and quality were also obtained by quantifying of the vegetative and technological characteristics. With the inoculation and the increase of viable AMF propagules in the soil resulted in higher MC and SD. Acaulospora scrobiculata and Glomus sp. were the species with the highest frequency of occurrence. Sugarcane productivity and quality were also significantly higher in inoculated treatments, with average increases in the three ratoons of 20% in sugarcane productivity and 30% in sugar production. The increase in sugarcane productivity and quality after AMF inoculation is a positive indicator of the effectiveness this biotechnology has over the production of this commodity.

Effect of soil bacteriomes on mycorrhizal colonization by Rhizophagus irregularis—interactive effects on maize (Zea mays L.) growth under salt stress

In this study, we investigated the interactive effects of the arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis and soil bacteriomes on maize growth under salt stress (100 mM NaCl) and also the effect of salt and bacteriomes on the mycorrhizal infection levels. We found that soil bacteriomes directly promoted the growth of maize and indirectly enhanced maize biomass by increasing mycorrhizal colonization levels, irrespective of salt stress. Although R. irregularis by itself had no maize growth-promoting effect even at a high mycorrhizal colonization level in roots, its benefits to maize were reflected in other aspects, evidenced by the significantly increased rate of arbuscule formation (a proxy for a functional plant-AMF nutritional exchange) under salinity. A negative correlation between arbuscule colonization and root biomass suggested R. irregularis expands the role of maize roots. Besides, the positive correlation between the overall AMF colonization level and shoot biomass supported the tenet of a positive contribution of R. irregularis to maize growth. Our findings suggest that soil bacteriomes interactively work with R. irregularis, modulating the growth of maize by affecting the colonization of AMF in roots.

Effects of AMF on nutrient and stoichiometric characteristics in different organs of sunflower

In order to explore the effects of arbuscular mycorrhizal fungi (AMF) on growth and nutrient absorption for ornamental sunflowers, explain the related physiological mechanism, four species of AMF Acaulospora scrobiculata (AS), Diversispora spurca (DS), Funneliformis mosseae (FM) and Diversispora versiformis (DV) were selected, and inoculated into potted ornamental sunflower seedlings under greenhouse condition. Effects of AMF on growth, nutrient absorption and ion balance of ornamental sunflower were analyzed. Results showed that four different AMF could infect sunflower roots. In which, DS inoculation has the highest mycorrhizal colonization; whereas, the mycelial length of DV treatment in rhizosphere soil was significantly higher than the other three AMF treatments. Four kinds of AMF markedly decreased the fresh weight in roots and leaves, but significantly increase the fresh weight in flower discs. Furthermore, the four different AMF increased the nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) contents in roots, leaves and flower discs of sunflower in varying degrees, meanwhile reduced the N:P and N:K in root and the flower discs. In addition, the four different AMF significantly reduced the sodium ion (Na+) concentration but significantly increased K+/Na+, Ca2+/Na+ and P/Na+ in flower discs. The correlation analysis showed that there was a significant positive correlation between the mycorrhizal infection rate and the content of P or K in roots, or P, K, Ca in leaves, or N, K in flower discs in various organs of sunflower. In short, AMF could promote ornamental sunflower growth by ameliorating nutrient absorption and transport, adjusting the distribution of mineral elements in organs and the balance between ions, to enhance adaptability and ecological benefits.

Evaluation of commercial composts and potting mixes and their ability to support arbuscular mycorrhizal fungi with maize (Zea mays) as host plant.

The use of composts and potting mixes in food production systems is a promising way to counteract the effects of soil degradation and allows crop growth in soilless culture systems. Arbuscular mycorrhizal fungi (AMF) are a well-studied group of beneficial plant symbionts that have been shown to provide important ecosystem services. This study analysed the properties of nine commercial Australian potting mixes and composts and investigated whether they support colonization of maize plants with AMF in a plant growth bioassay. Physicochemical analyses showed highly variable properties between the substrates, with some extreme values that limited plant growth. DNA-based analysis revealed the presence of various plant pathogens, which was linked to inhibited plant growth in one substrate. Some substrates did not meet national quality standards, due to the concentrations of plant nutrients, heavy metals, or substrate maturity. Plant growth was mostly limited due to nitrogen immobilization, which required weekly fertilizer applications. Solid state 13C nuclear magnetic resonance spectroscopy gave insight into the decomposition state of the substrates. Plant roots in most substrates were well colonized with AMF (>60% root length), regardless of most substrate properties. Root colonization was negatively affected in only one substrate, likely due to ammonium toxicity. Results of this study show that not all commercial substrates adhered to national quality standards. Potting mixes and composts can support high mycorrhizal root colonization when plant growth is otherwise not limited.

Influence of Local Isolates of Arbuscular Mycorrhizal Fungi on Growth and Some Physiological Performance of Zea mays Grown in Calcareous Soil as Affected by Phosphorus Levels

Arbuscular mycorrhizal fungi (AMF) are among plant-symbiotic fungi with higher plant roots. The applicability of AMF poses a strategy to minimize the deleterious effect of abiotic stress to enhance plant tolerance. Phosphorus is an essential macronutrient for plants, can cause toxic effects at low levels. Our target was to determine the mitigation effect of local inoculum of AMF on growth and metabolic activity of Zea mays under phosphorus levels. Phosphorus deficiency disturbed physiological performance however, AMF mitigated negative effects by enhancing the dry weight significantly (P < 0.05), P content and alkaline phosphatase in calcareous soil amended with P concentrations (from 15 to 120 mg P kg-1 soil), compared with non-inoculated plant. The maximum H+-ATPase activity was 28.13 µmol Pi-1ngP-1min in leaves of Zea mays in AM- inoculated soil and amended with 60 mg P kg-1soil. AMF enhanced antioxidant enzyme activities, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) together with their substrates glutathione (GSH) and ascorbic acid (AA), with concurrent reduction of lipid peroxidation and hydrogen peroxide content. Highest mycorrhizal colonization (88%) recorded in maize grown in 60 mg P kg-1 soil. Established data on morphological characters revealed AMF local isolates belong to four native spores related to genus Glomus, Acaulospora, Scutellospora and Entrophospora. Analysis of the genetic material confirmed that spores were related to Glomus mosseae and Acaulospora spinose. These findings demonstrate that root colonization by local AMP inoculum could ameliorate the phosphorus deficiency in calcareous soils collected from Southwestern coast of Egypt

Fungos micorrízicos arbusculares influenciam o desempenho hortícola de cultivares de morangueiro

The inoculation of strawberry cultivars with arbuscular mycorrhizal fungi (AMF) is a profitable and viable biotechnological tool, with potential to improve the horticultural performance of plants. However, this biotechnology is lacking and unknown to producers. The aim of the research was to investigate whether strawberry cultivars in the absence and presence of inoculation with AMF differ in their horticultural performance. The treatments, delineated in a bifactorial scheme, were four strawberry cultivars in the absence and presence of two AMF-based inoculants. The experiment was designed in randomized blocks, with three replications. The root system of ‘Albion’ cultivar showed the highest mycorrhizal colonization. Claroideoglomus etunicatum showed greater capacity to infect plant roots. ‘Portola’ was the most productive cultivar and ‘Albion’ and ‘Aromas’ produced strawberries with the highest levels of total anthocyanins. It is concluded that the use of mycorrhizal biotechnology enhances the levels of total flavonoids in fruits of the ‘Albion’ cultivar inoculated with the fungal species C. etunicatum. The root system of ‘Albion’ cultivar has greater mycorrhizal colonization. The fungal species C. etunicatum is more effective in colonizing the roots of the plant host. It is suggested to use the ‘Portola’ cultivar to obtain higher fruit yields and the ‘Albion’ and ‘Aromas’ cultivars for producers who aim to obtain strawberries with higher levels of total anthocyanins. ‘Aromas’ is recommended for those seeking a dual purpose (production and quality).

Survival Rate, Chemical and Microbial Properties of Oak Seedlings Planted with or without Oak Forest Soils in a Black Locust Forest of a Dryland

Native tree species are frequently unable to effectively grow in non-native tree cultivation scenarios. In the Loess Plateau, China, it is difficult to find native oak (Quercus liaotungensis) seedlings in non-native black locust forests. Black locust is an arbuscular mycorrhizal (AM) tree, but oak is an ectomycorrhizal (ECM) tree. Plants highly depend on their symbiotic mycorrhizal fungi to take up water, nitrogen (N) and other nutrients. We hypothesized that black locust forests would not provide ECM inoculum to oak seedlings, limiting their water and nutrient uptake, which would be improved by ECM inoculum. Here, we (1) sowed seeds, with or without oak forest soils, (2) transplanted seedlings collected in oak forests, with or without oak forest soils, and (3) planted seedlings germinated in autoclaved or unautoclaved oak forest soils. We measured the survival and growth rate for all three experiments, along with chemical properties, and root ECM colonization. Oak seeds sowed with oak forest soils had higher mycorrhizal colonization, leaf N concentrations and survival rate, and lower root δ13C than the seeds sowed without oak forest soils. Planting with oak forest soils also increased the survival rate of the germinated seedlings, but not the transplanted seedlings. Overall, our study suggested that the use of oak forest soils in the black locust forest to improve the water and N uptake of oak seedlings by providing the ECM inoculum, resulting in a high survival rate. Our study also implies that the method of sowing seeds was effortless and effectively compared to transplanting wild/nursery seedlings.

The effect of nitrogen-modified lignite granules on mycorrhization and root and shoot growth of Secale cereale (winter rye) in a nutrient-deficient, sandy soil

ABSTRACT Organic soil amendments such as modified lignite and biostimulants like arbuscular mycorrhizal fungi (AMF) may have the potential to improve soil biological conditions of agricultural soils. The aim of the study was to test if nitrogen-modified lignite granules (NH) are beneficial for mycorrhization, root and shoot development compared to common mineral nitrogen (Nmin) in a nitrogen and phosphorus limited soil. A greenhouse experiment with Secale cereale L. was carried out using non-sterilized and sterilized sand substrate treated with NH, AMF or Nmin and AMF+NH and AMF+Nmin and was compared to an untreated substrate (control). 7.5 t ha−1 NH and 120 kg Nmin ha−1 led to a similar increase of AMF colonization compared to the control; however, Nmin had a more positive influence on biomass development. Significantly highest mycorrhizal colonization intensity was found for AMF+NH. The co-application of AMF+NH revealed that shoot and root development and shoot nutrient concentrations were significantly higher or were among the significantly highest values, when compared to the other treatments. AMF+NH may be a suitable soil amendment for nutrient-limited soils and may be more sustainable than Nmin due to a combined increase of nitrogen, AMF and carbon/humic acids in the soil that comes with the NH.

Salicylic acid affects mycorrhizal features, antioxidant enzyme activities and seed yield of linseed under water-deficit stress in open-field conditions.

The research aims were to study salicylic acid (SA) effects on mycorrhiza [hyphal width (HW), vesicle diameter (VD) and mycorrhizal colonization (MC)] and interaction between them on greenness index (GI), drought tolerance index (DTI), antioxidant enzymes activities, and seed yield of linseed under drought. A factorial experiment was conducted in an open-field place with mycorrhiza [non-inoculation, Funneliformis mosseae (FM), and Rhizoglomus intraradices (RI)], SA (250μM and non-SA), and irrigation levels [100%, 70%, and 40% field capacity (FC)] as treatments. Severe drought increased VD, MC, superoxide dismutase (SOD), ascorbate peroxidase (APX), and peroxidase activities while decreased GI, DTI, and yield. The RI-linseed had higher MC, GI, SOD, and glutathione reductase (GR) activities, but FM-linseed had greater VD and yield under drought. Inoculated linseed with both mycorrhiza showed a reduction in DTI and yield under SA than non-SA. In RI-linseed, SA increased GI, MC, HW, VD, catalase and GR, but decreased in FM-plants. Mycorrhiza (particularly RI) alleviated drought (40% FC)-caused negative effects onlinseed via the improvement of SOD, APX, and GI. Regardless of other treatments, SA had negative effects on HW and VD, but SA effects varied depending on mycorrhizal species so that SA increased HW, VD, and MC in RI. Due to the positive correlation between MC and HW, SA reduces FM colonization by reducing the HW of FM. Totally, SA along with RI species can mitigate the harmful effects of drought and improve tolerance via increasing MC, HW, VD, catalase, peroxidase, and GR activities.

Root growth phenology, anatomy, and morphology among root orders inVaccinium macrocarponAit.

Understanding the mechanisms controlling plant growth is essential in order to maintain and increase productivity in managed ecosystems. However, the lack of information on below-ground growth compared with above-ground growth limits our ability to adjust crop management practices under changing climate conditions. This study examines seasonal fine-root growth and its spatial distribution through the soil profile across the growing season, and the anatomical and morphological traits of roots according to their branching order in Vaccinium macrocarpon Ait. Root production followed a unimodal curve, with one marked flush of root growth starting at bloom, with a peak at the end of fruit maturation. Root vertical distribution concentrated in the upper 5 cm of soil depth, accounting for over 50% of new roots produced during the study. Root anatomy and morphology were related to root function, as the first three root orders had intact cortex and epidermis and high mycorrhizal colonization, indicative of absorptive function, while orders ranking fifth and higher had secondary development and the presence of a cambium cork layer, indicative of translocation. Our study highlights the importance of examining the timing of root growth and root traits by root order, and its implications for the timing of fertilization and other practices in managed ecosystems.

Crescimento de milho crioulo cultivado com fungos micorrízicos arbusculares

Os fungos micorrízicos arbusculares realizam simbiose com a maioria das espécies de plantas e podem influenciar no crescimento, na resistência à seca e também reduzir o consumo de fertilizantes minerais, a depender da interação com a planta hospedeira. O objetivo deste trabalho foi avaliar a colonização micorrízica e a sua interação no crescimento do milho crioulo. O delineamento experimental utilizado foi inteiramente casualizado composto por quatro tratamentos: controle (sem inoculante micorrízico) e três isolados micorrízicos arbusculares (UFLA351 - Rhizoglomus clarum, UFLA372 - Claroideoglomus etunicatum e UFLA401 - Acaulospora morrowiae) com cinco repetições. A colonização micorrízica do milho crioulo é arbuscular-vesicular com o emprego dos isolados UFLA351, UFLA372 e UFLA401. A alta taxa de colonização micorrízica do milho crioulo não garante incremento na biomassa, mas pode influenciar na emissão das inflorescências. O milho crioulo foi responsivo à inoculação do isolado UFLA372.

Ectomycorrhizal fungi drive positive phylogenetic plant-soil feedbacks in a regionally dominant tropical plant family.

While work in temperate forests suggests that there are consistent differences in plant-soil feedback (PSF) between plants with arbuscular and ectomycorrhizal associations, it is unclear whether these differences exist in tropical rainforests. We tested the effects of mycorrhizal type, phylogenetic relationships to overstory species, and soil fertility on the growth of tree seedlings in a tropical Bornean rainforest with a high diversity of both ectomycorrhizal and arbuscular mycorrhizal trees. We found that ectomycorrhizal tree seedlings had higher growth in soils conditioned by close relatives and that this was associated with higher mycorrhizal colonization. By contrast, arbuscular mycorrhizal tree seedlings generally grew more poorly in soils conditioned by close relatives. For ectomycorrhizal species, the phylogenetic trend was insensitive to soil fertility. For arbuscular mycorrhizal seedlings, however, the effect of growing in soils conditioned by close relatives became increasingly negative as soil fertility increased. Our results demonstrate consistent effects of mycorrhizal type on plant-soil feedbacks across forest biomes. The positive effects of ectomycorrhizal symbiosis may help explain biogeographic variation across tropical forests, such as familial dominance of the Dipterocarpaceae in southeast Asia. However, positive feedbacks also raise questions about the role of PSFs in maintaining tropical diversity.

Urochloa decumbens Has Higher Mycorrhizal Colonization in Degraded than in Pristine Areas in the Brazilian Cerrado

ABSTRACT Brazil has extensive degraded areas, where vegetation fails to establish due to harsh soil conditions. However, some invasive species such as Urochloa decumbens are successful pioneers in such areas, but the reasons deserve investigation. Mycorrhizal fungi are abundant in Cerrado soils, and their association with plants are beneficial for their establishment in natural and degraded areas. This study investigated whether arbuscular mycorrhizal colonization of native and exotic plants in the Cerrado differs between pristine and degraded areas. We collected 135 plants from four functional groups in 68 areas and determined the percentage of mycorrhizal colonization. The invasive grass Urochloa decumbens had significantly higher colonization rates in degraded than in native areas, and higher colonization than the native species. These results are important for soil management since Urochloa decumbens is widely used in early soil restoration efforts, and for nature conservation concerning the management of invasive plants in restoration areas.

Mycorrhizal features and leaf traits covary at the community level during primary succession

Abstract The mycorrhizal association between fungi and plants is thought to be an important component of the functional diversity of plant communities, although evidence is weak. We explored community-level changes to mycorrhizal features and leaf traits along a primary successional gradient on a sedimentation coast. We found that community weighted mean values of mycorrhizal features and leaf traits varied systematically along the successional series, representing a transition from communities dominated by more stress-tolerant plant species (less mycorrhizal colonization and lower specific leaf area) to less stress-tolerant plant species (higher mycorrhizal colonization and specific leaf area). Despite the co-variation in leaf traits and mycorrhizal features at the community level, only mycorrhizal features showed an increasing functional diversity with successional age. These results suggest that mycorrhizal fungi should not be forgotten in trait-based plant community ecology.

MICROBIAL INTERACTIONS IN THE DEVELOPMENT OF THE BIOMASS OF GLIRICIDIA

ABSTRACT The objective of this work was to evaluate the interaction of microorganisms and phosphorus dosages in the development of gliricidia. The experimental design was completely randomized with six treatments (control, native microbial inoculant, and four arbuscular mycorrhizal fungi isolates: UFLA05 - Gigaspora albida, UFLA351 - Rhizoglomus clarum, UFLA372 - Claroideoglomus etunicatum, and UFLA401 - Acaulospora morrowiae), with four replicates. The parameters evaluated were: height plant, the number of branches, shoot and root dry mass matter, root length and volume, leaf phosphorus, mycorrhizal colonization, the number of spores of the arbuscular mycorrhizal fungi, the number of nodules of nitrogen fixing bacteria, and the presence of endophytic dark septate fungi, after 95 days of inoculation. The high mycorrhizal colonization of gliricidia does not guarantee an increase in biomass, which depends on the interaction of the arbuscular mycorrhizal fungi, the endophytic dark septate fungi, the nitrogen fixing bacteria, and the endophytic bacteria. Gliricidia was responsive to the inoculation of the native microbiota, UFLA372 and UFLA401. Mycorrhizal colonization by UFLA401 was influenced by the presence of nitrogen fixing bacteria. Gliricidia was not responsive to the inoculation of UFLA05 and UFLA351. The presence of the endophytic dark septate fungi did not inhibit mycorrhization and the formation of nodules of nitrogen fixing bacteria in gliricidia.

Crescimento inicial e absorção de fósforo e nitrogênio de Enterolobium contortisiliquum inoculada com fungos micorrízicos arbusculares

Enterolobium contortisiliquum is a leguminous tree that associates by symbiosis with arbuscular mycorrhizal fungi (AMF) and can be used to recover degraded areas. Therefore, the aim of this work was to evaluate the effects of AMF inoculation, supply of phosphorus (P), and rate of nitrogen (N) and P absorption in E. contortisiliquum. The variables were analyzed into randomized blocks with factorial design 5 x 3, in which the factors were levels of P (0, 50, 100, 200, and 400 mg kg-1), and inoculation with AMF (Gigaspora margarita and native population in soil), or non-inoculation (control treatment), with four repetitions in each treatment. The highest mycorrhizal colonization (35%) occurred in seedlings inoculated with G. margarita. Plants inoculated with G. margarita and under P supply of 0 and 50 mg kg-1 exhibited increase in height of 19.5% and 7.4%, respectively, compared to the control treatment. P levels in aerial part of plants inoculated with G. margarita, under levels of 0, 50, 100 and 400 mg kg-1of P presented high increment of 198%, 108%, 181% and 106%, respectively, compared to the control. The control treatment, without any P supply, seedlings inoculated with G. margarita exhibited high colonization efficiency (34.89%) and high mycorrhizal dependence (25.53%).

Arbuscular Mycorrhizal Association Contributes to Cr Accumulation and Tolerance in Plants Growing on Cr Contaminated Soils

Arbuscular mycorrhizal (AM) fungi are well known root symbionts in heavy metal polluted soils. To assess AM fungal association and their contribution to the host plants naturally growing on a highly chromium (Cr) contaminated soil, the present study has been undertaken. The soil of the study site was contaminated with 32,562 ppm Cr coming from tannery industry. The study site was dominated by Cynodon dactylon (L.) Pers., Parthenium hysterophorus L., Croton bonplandianum Baill and Prosopis juliflora (Sw.) DC. High mycorrhizal colonization (31–83%) and low spore population (5–11 spores/g) was recorded. The diversity of AM fungi was very low because of stress caused by Cr. Only seven AM fungal isolates have been recovered. Funneliformis mosseae, Rhizophagus intraradices, Funneliformis geosporus and Glomus sinuosum have been recovered from two hosts, while, Rhizophagus fasciculatus, Glomus aggregatum and Acaulospora scrobiculata from single host only. Cr accumulation in the roots were analyzed through AAS and correlated with various mycorrhization parameters. The results of correlation through PCA showed that, various mycorrhization parameters were under strong influence of Cr accumulation in the roots. Furthermore, all the AM fungi showed certain adaptive features like compact sporocarp, thick spore wall, sloughing outermost wall layer and formation of water stable aggregates. Low species diversity, high mycorrhizal colonization, presence of adaptive features and strong correlation of mycorrhizal parameters with the Cr accumulation in the roots clearly indicated that, these AM fungi have contributed to the Cr accumulation and tolerance to the host plants in Cr sludge deposit.