Mycorrhizal Inoculation Treatments Research Articles

Entrophospora etunicata: A mycorrhizal biostimulant with the potential to enhance the production of bioactive health-promoting compounds in leaves of Capsicum chinense seedlings

Arbuscular mycorrhizal fungi (AMF) are known to benefit pepper species, but there are no reports of such efficiency in Capsicum chinense, one of the most valuable commercial plant species. Therefore, this study aimed to select an efficient mycorrhizal biostimulant to increase the production of secondary compounds and the antioxidant activity in C. chinense leaves. The experiment was conducted in a greenhouse with four mycorrhizal inoculation treatments (control without AMF, seedlings inoculated with Entrophospora etunicata, Acaulospora longula, and Gigaspora albida). After 120 days, agronomic growth parameters, production of primary and secondary metabolites, and foliar antioxidant activity were evaluated. Capsicum chinense seedlings inoculated with E. etunicata had increases in growth parameters ranging from 27 to 133% compared to the non-inoculated control, depending on the variable considered. Pepper seedlings associated with E. etunicata produced 77%, 147%, 140%, and 136% more soluble carbohydrates, total proanthocyanidins, total phenols, and total saponins, respectively, compared to those not inoculated. Such benefits were also reported for total proteins and total foliar flavonoids. On the other hand, this AMF was ineffective in enhancing the accumulation of alkaloids. It is concluded that E. etunicata is an alternative for improving the production of C. chinense seedlings and enhancing the anabolism of health-promoting bioactive compounds in the phytomass to be offered to the herbal medicine industry. This is the first report on the potential of mycorrhizal inoculation to optimize secondary anabolism in C. chinense leaves.

Effects of arbuscular mycorrhizal fungus inoculation on the growth and nitrogen metabolism of Catalpa bungei C.A.Mey. under different nitrogen levels.

Evidence suggests that arbuscular mycorrhizal fungi (AMF) may promote the growth of woody plants. However, the effects of AMF on nitrogen (N) metabolism in plants, especially trees, and its regulatory mechanism are rarely reported. Here, the effects of AMF inoculation on the growth and N nutrition status of Catalpa bungei under different N levels were reported. Three N levels (low, medium, high) and two mycorrhizal inoculation treatments (inoculation with Rhizophagus intraradices or not) were used with factorial design. The results showed that medium N could significantly improve the physiological metabolism and growth of C. bungei seedlings. However, when N was excessive, growth was significantly inhibited whether inoculated AMF or not. Compared with non-inoculated treatments, AMF inoculation could promote the absorption of N and P, improve photosynthesis under low to medium N levels, thus promoting the growth of seedlings. AMF changed the biomass allocation in seedlings by reducing the stem mass ratio and root/shoot ratio, and increasing the leaf mass ratio. At medium N levels, compared with non-inoculated treatment, AMF inoculation could significantly promote root growth by changing root hormone levels and improving root architecture and root activity. Under N addition, AMF inoculation could improve the absorption and assimilation of N by regulating the expression of key enzyme genes of N metabolism and nitrate transporter genes (NRT2.4, NRT2.5, NRT2.7) in roots, and enhancing the activities of the key enzyme of N metabolism. This study may provide a reference for the application of AMF in the cultivation and afforestation technology of C. bungei in Northwest China.

The yield of maize-soybean intercropping on Mycorrhizal inoculation treatment and plant nutrition provision in suboptimal land North Lombok, Indonesia

Mycorrhizal inoculation and plant nutrition have an important role in increasing the yield of maize-soybean intercropping in suboptimal land. The experimental design used was a factorial randomized block design with two factors, the first factor was AMF inoculation which consisted of two levels, namely M0 = without AMF inoculation and M1 = with AMF inoculation, and the second factor was plant nutrition treatment. with four levels, namely U0 = without the addition of nutrients, U1 = with the addition of 100% dose of inorganic fertilizer (maize = urea 300 kg ha-1 and Phonska 200 kg ha-1, soybean = 60 kg ha-1 Urea and 120 kg ha-1 Phonska), U2 = with the addition of 100% dose of cattle manure and U3 = with the addition of 50% dose of cattle manure (6 t ha-1) plus 50% dose of inorganic fertilizer (maize = urea 150 kg ha-1 and Phonska 100 kg ha-1, soybean= 30 kg ha-1 Urea and 60 kg ha-1 Phonska). The results showed that AMF inoculation treatment and application of 50% inorganic fertilizer plus 50% organic fertilizer gave the highest yield with maize grain weight of 4.3 tons ha-1 and soybean grain weight of 0.5 tons ha-1.

Effectiveness of mycorrhizae on growth and production of orange sweet potato at various watering level

Sweet potato is a food crop that is widely cultivated during the dry season in rice fields. Increasing sweet potato production can be done by inoculating mycorrhizae which play a role in increasing plant resistance to drought. This research was conducted to analyse the effectiveness of mycorrhizae to increase the growth and production of sweet potatoes cultivated in paddy fields with different levels of watering. Sweet potato planting began in April-July 2020 in rainfed paddy fields located in Tandem Hilir I Village, Deli Serdang Regency. The research design used was a randomized block design with 2 factors namely mycorrhizal inoculation (0 g/plant inoculum, 20 g/plant inoculum) and watering level (watered once in 10 days for 1 month, watered once in 10 days for 2 months, watered once in 10 days for 3 months, and watered once in 10 days for 4 months). The results showed that mycorrhizal inoculation treatment at a dose of 20 g/plant significantly affected the length increase of sweet potato plants. All parameters observed were not affected by the treatment watering level. The best interaction is the combination of treatment with 20 g of mycorrhizal inoculum/plant and watered once in 10 days for 3 months.

Effects of Arbuscular Mycorrhizal Fungi on Growth and Physiological Performance of Catalpa bungei C.A.Mey. under Drought Stress

Catalpa bungei C.A.Mey. is a common ornamental timber species. Its survival and growth are greatly affected by water scarcity in arid and semi-arid areas of Northwest China. Evidence suggests arbuscular mycorrhizal fungus (AMF) may improve plant drought resistance. However, there is limited information on the systematic effects of AMF on drought resistance in C. bungei seedlings. Here, a pot experiment was used to explore the effects of inoculation with the AMF Rhizophagus intraradices on the growth and physiological performance of C. bungei under different water treatment conditions. Three water levels and two mycorrhizal inoculation treatments were used with factorial design. The results showed that drought stress noticeably affected the growth and physiological performance of C. bungei seedlings. However, inoculation with R. intraradices significantly ameliorated the growth, and alleviated the effects of drought stress. The growth parameters of AMF-inoculated seedlings significantly increased regardless of water status. AMF changed the biomass allocation in seedlings by reducing the root mass ratio (RMR) and root/shoot ratio. AMF-inoculated seedlings displayed higher gas exchange parameters, photosynthetic pigment concentrations, specific leaf area (SLA), but lower specific leaf weight (SLW), regardless of water status. AMF alleviated drought-induced oxidative stress by attenuating the excess generation of reactive oxygen species (ROS), especially H2O2 and O2−, in leaves. Inoculation with AMF under drought stress also dramatically augmented indole-3-acetic acid (IAA) and gibberellins (GA3) levels and the IAA/abscisic acid (ABA) and GA3/ABA ratios, but reduced ABA and zeatin (ZT) levels in leaves. AMF symbiosis improved root morphology and promoted the absorption of nitrogen (N) and phosphorus (P) in seedlings. We conclude that inoculation with R. intraradices is potentially useful for afforestation and cultivation of C. bungei in Northwest China. Furthermore, AMF improved soil structure by increasing the glomalin-related soil protein (GRSP) contents and the proportion of macro-aggregates (0.25–0.5 mm) in the rhizosphere soil.

Reduced P fertilization improves Fe and Zn uptake in potato when inoculated with AMF in P, Fe and Zn deficient soil

Mycorrhiza fungi can use as an efficient resource to increase the efficiency of potato nutrients use, especially phosphorus (P) and nitrogen (N) to achieve sustainable production and protecting the environment and human health. This experiment conducted to study the interaction of P levels and mycorrhiza fungi on absorption of elements and qualitative and quantitative yields of potato under field conditions. Factors including inoculation of mycorrhiza fungi (Rhizophagus irregularis and Glomus mosseae and non-inoculation) and the amount of P (0, 28, 57, 86 and 115 Kg ha−1 P according to H2PO−4, equivalent 0, 25, 50, 75 and 100 percent of P recommended, respectively), with three replications in years 2015 and 2016 at Agriculture and Natural Resource Research Center of Hamadan. The results showed that the maximum of P in tubers (0.351%) and leaves (0.364%), Zn in tuber (24.4 ppm) and leaves (43.9 ppm) and tuber dry matter percentage (24.1%) achieved under inoculation with Rhizophagus irregularis and using of 75% of recommended Phosphorus. Maximum tubers number per plant (7.2) obtained in inoculation with G. mosseae and using of 100% recommended P. Highest tubers weight per plant (898 g) and tuber yield (47.9 ton ha−1) were achieved under inoculation with G. mosseae and using of 75% of recommended P. Both species of mycorrhiza at all levels of P did not show significant difference. The P 75% and 100% under mycorrhizal inoculation treatment did not show significant difference. Highest nitrate percentage in tuber dry matter (136 ppm) and lowest amount of all traits were under non-inoculation along with no application of P. Inoculation treatment with mycorrhizal fungi significantly increased the average weight of tuber compared to non-inoculated treatment. Generally, the use of mycorrhizal fungi at low levels of P was more efficient on all studied traits compared to high levels of P. Given that, there was no significant difference between 75% and 100% P under inoculation with two species of mycorrhiza, provided this conclusion that applying mycorrhizal fungi can reduce agricultural phosphorus consumption without significant decrease in yield.

The Interaction of Arbuscular Mycorrhizal Fungi and Phosphorus Inputs on Selenium Uptake by Alfalfa (Medicago sativa L.) and Selenium Fraction Transformation in Soil.

Selenium (Se) is a beneficial element to plants and an essential element to humans. Colonization by arbuscular mycorrhizal fungi (AMF) and supply of phosphorus (P) fertilizer may affect the bioavailability of Se in soils and the absorption of Se by plants. To investigate the interaction between AMF and P fertilizer on the transformation of soil Se fractions and the availability of Se in the rhizosphere of alfalfa, we conducted a pot experiment to grow alfalfa in a loessial soil with three P levels (0, 5, and 20 mg kg-1) and two mycorrhizal inoculation treatments (without mycorrhizal inoculation [−AMF] and with mycorrhizal inoculation [+AMF]), and the interaction between the two factors was estimated with two-way ANOVA. The soil in all pots was supplied with Se (Na2SeO3) at 1 mg kg-1. In our results, shoot Se concentration decreased, but plant Se content increased significantly as P level increased and had a significant positive correlation with AMF colonization rate. The amount of total carboxylates in the rhizosphere was strongly affected by AMF. The amounts of rhizosphere carboxylates and alkaline phosphatase activity in the +AMF and 0P treatments were significantly higher than those in other treatments. The concentration of exchangeable-Se in rhizosphere soil had a positive correlation with carboxylates. We speculated that rhizosphere carboxylates promoted the transformation of stable Se (iron oxide-bound Se) into available Se forms, i.e. exchangeable Se and soluble Se. Colonization by AMF and low P availability stimulated alfalfa roots to release more carboxylates and alkaline phosphatase. AMF and P fertilizer affected the transformation of soil Se fractions in the rhizosphere of alfalfa.

Plant biostimulants (Funneliformis mosseae and humic substances) rather than chemical fertilizer improved biochemical responses in peppermint.

Plant biostimulants such as arbuscular mycorrhizal (AM) fungi and humic substances (HS) can be used as an appropriate alternative to chemical fertilizers, as regards to environmental problems of chemicals. The effects of Funneliformis mosseae as an AM fungus, HS (foliar spray and topdressing application), and chemical fertilizer (NK), separately or interacting, on biochemical responses in Mentha piperita L. plants were investigated under field conditions. Results revealed that the mentioned three factors appear as valid practicable method for improving growth and metabolites of peppermints cultivated in the field even when root colonization of AM fungus does not achieve high rates. The triple interaction between mycorrhizal inoculation, HS application (especially foliar spray), and NK fertilizer treatment induced the maximum accumulation of photosynthetic pigments, starch, soluble sugars, total proteins, proline, total phenolics, and the antioxidants in leaves. However, positive effects of F. mosseae and HS were more than those of the chemical fertilizer. We propose that F. mosseae and foliar spray of HS, particularly in combination can be used as suitable plant biostimulants in peppermint plants under field conditions, which in turn will improve soil health and reduce environmental problems.

Qualitative response of roselle to planting methods, humic acid application, mycorrhizal inoculation and irrigation management

ABSTRACTCrop management is an important factor affecting the quality of medicinal plants. Therefore, objectives of our investigation on roselle (Hibiscus sabdariffa L.) were: 1) To identify an appropriate planting method in semi-arid regions and 2) to study crop production under water-deficit conditions using eco-friendly techniques. We specifically investigated the effects of planting methods (direct sowing vs. transplanting) (experiment 1, in a randomized complete-block design), as well as effects of water regimes [irrigation after pan evaporation of 100 mm (normal irrigation) and 200 mm (deficit irrigation)], humic acid application (0 and 4 kg ha −1) and mycorrhizal inoculation (Glomus versiforme, Glomus intraradices, and control) (experiment 2, in a split-split-plot layout) on certain qualitative indices of roselle. The amounts of total soluble solids (TSS), anthocyanin content, and maturity index for direct seeding were, respectively, 17%, 15%, and 33% higher than those for transplanting, whereas vitamin C content and total acidity for transplanting treatment were, respectively, 17% and 20% more than those for direct sowing. According to data obtained from the average of the three mycorrhizal treatments, normal irrigation combined with humic acid application increased total acidity (0.88 mg.100 g−1), anthocyanins (67.1 mg.l−1), and vitamin C content (2177 mg.100 g−1) over the control (deficit irrigation and no humic acid application, which had lower acidity (0.53 mg.100 g−1), anthocyanins (38.8 mg.l−1), and vitamin C content (1882 mg.100 g−1). Total phenol and anthocyanins content under mycorrhizal inoculation were relatively higher than under control treatment at both levels of irrigation. G. intraradices produced the largest amount of vitamin C (2353 mg.100 g−1) under deficit irrigation. On average, no-inoculation treatment had higher TSS, pH, and total acidity than any mycorrhizal inoculation treatment. Humic acid application and mycorrhizal inoculation, especially using G. intraradices, showed the highest values of anthocyanins (56.9 mg.l−1) and vitamin C (2309 mg.100 g−1) content. Overall, normal irrigation, combined with humic acid application and mycorrhizal inoculation, partially improved the quality indices of roselle.

Enhanced transfer of biologically fixed N from faba bean to intercropped wheat through mycorrhizal symbiosis

In Morocco, the use of seed legumes is limited because significant water deficits and the low availability of soil phosphorus (P) limit nitrogen fixation. However, little is known about the ability of faba bean-rhizobium symbiosis to fix nitrogen in P-deficient soils and to transfer fixed nitrogen (N) to intercropped wheat. Arbuscular mycorrhizal fungi (AM) and their extraradical hyphae networks play an important role in the facilitation process by promoting interconnectivity and the transfer of nutrients, such as N and P, between associated plants. The aim of this study was to analyse the impact of AM inoculation on N2 fixation and the transfer of fixed N from faba bean to intercropped wheat. Germinated faba bean and wheat seeds were transferred into 1–l pots filled with a P-deficient soil that was collected from the Haouz valley near Marrakech (Morocco). Plants from the two species were grown in pots in either pure or mixed stands under greenhouse conditions, and each cropping system was subjected to three mycorrhizal inoculation treatments with a non-inoculated (AM0) and two concentrations of Rhizophagus irregularis inoculants containing 1000 (AM1) or 2000 (AM2) spores pot−1. The 15N isotope dilution method was used to determine the amount and proportion of atmospheric N fixed by faba bean (Ndfa%) and the fixed N that was transferred to wheat. Mycorrhizal inoculation had a significantly positive effect on the shoot dry weights and total shoot N in faba bean, but not in wheat. The cropping system had no significant effect on the plant growth and total shoot N in both faba bean and wheat. The Ndfa percentage was very high in all of the treatments, varying from 86 to 91%. The total N fixed by faba bean was 27% significantly higher in the AM2 treatment compared with the AM1 and AM0 treatments for both cropping systems combined. The estimated proportions of fixed N that were transferred from faba bean to wheat were far higher in AM1 (50%) and AM2 (32%) treatments than in AM0 (15%) treatment as well as for the total transferred fixed N. As corroborated by a parallel observation of root mycorrhizal colonization, these results suggest that the development of mycorrhizal networks stimulates the transfer of fixed N from faba bean to wheat, which could significantly contribute to the facilitation process under intercropping conditions.

Effects of plant growth-promoting rhizobacterium (PGPR) and arbuscular mycorrhizal fungus (AMF) on antioxidant enzyme activities in salt-stressed bean (phaseolus vulgaris l.)

Abstract Plant Growth-Promoting Rhizobacterium (PGPR) represents a wide variety of soil bacteria that, when grown in association with a host plant, result in stimulation of growth of their host. The aim of this study was to investigate the influence of inoculation with a PGPR, Pseudomonas fluorescence, alone or in combination with an arbuscular mycorrhizal fungus, Glomus mosseae (Nicol. & Gerd.), on antioxidant enzyme activities (catalase (CAT) and peroxidase (POX)), phosphatase activity, solutes accumulation, growth and minerals nutrient uptake in shoots of bean (Phaseolus vulgaris L.) affected by three levels of salt stress. Salinity decreased bean growth, regardless of the biological treatment and the salt stress level. The plants inoculated with P. fluorescence had significantly greater shoot biomass than the control plants at all salinity levels, whereas the mycorrhizal inoculation treatments were only effective in increasing shoot biomass at a low salinity level. The plants inoculated with P. fluorescence presented higher concentrations of shoots’ K+ and lower concentrations of shoots’ Na+ under high salt conditions. Salt stress increased shoots’ proline concentration, particularly in plants inoculated with the PGPR. Increasing salinity stress raised significantly the antioxidant enzyme activities, including those of total POX and CAT, of bean shoots compared with their corresponding nonstressed plants. The PGPR strain induced a higher increase in these antioxidant enzymes in response to severe salinity. Inoculation with selected PGPR could serve as a useful tool for alleviating salinity stress in salt-sensitive plants.

Sustainable production of fennel (Foeniculum vulgare Mill.) by seed inoculation with mycorrhizae strains under drought stress conditions

In order to study effect of seed inoculation with Mycorrhiza strains on yield of fennel under drought stress conditions a factorial field experiment was carried out at the Research Station of Islamic Azad University, Tabriz Branch, Iran, during 2011-2012 on Fennel (Foeniculum vulgare Mill.) cv. Malayer. Studied factors were irrigation intervals (70mm, 100mm and 130mm evaporation from pan class A) and Mycorrhizae strains (Glomus interadics and G. mosseae). There was a field with non-inoculation with Mycorrhizae as control plot. Mean comparisons revealed that the lowest green cover percentage of fennel (0.13%) could be obtained from noninoculated seeds, but the highest one from those seeds inoculated with G. mosseae. Appearance of leaf senescence symptoms in fennel plants happened earlier when seeds were sown without inoculation. But appearance of these symptoms delayed nearly 5 days. Lower number of secondary branches (8.2 branches) observed in normally irrigated treatment (70mm evaporation from pan). Plants under sever water deficit produced higher seed yield than 100mm evaporation level. Seeds inoculated with G. interadics strain produced higher seed yield (75.25 g m-2) than non-inoculated seeds (55.04 g m-2). Essential oil percentage of fennel seeds only affected by mycorrhizal inoculation treatment, and those seeds inoculated with G. interadics was in a better condition. The stepwise regression analysis verified that the green cover percentage and secondary branches had a marked increasing effect (R2=0.71) on the seed yield of fennel. The present study concluded that seed inoculation with mycorrhizae strains can play a major role in improvement of seed yield in fennel under water deficit conditions.

Growth, root colonization and nutrient status of Helianthemum sessiliflorum Desf. inoculated with a desert truffle Terfezia boudieri Chatin

This study aims to investigate the effects of inoculation using Terfezia boudieri Chatin ascospores (ectomycorrhizal fungus) on growth, root colonization and nutrient status of Helianthemum sessiliflorum Desf. seedlings grown in pots on two-soil types (gypseous and sandy loam). Mycorrhizal seedlings had significantly increased their height and leaf number compared to non-mycorrhizal ones. Regardless of mycorrhizal inoculation treatments, the plants growing on gypseous soil showed higher growth as compared to sandy loam one. It appears that inoculation with T. boudieri changed root morphology, increasing branching of first-order lateral roots of H. sessiliflorum seedlings. The highest root mycorrhizal colonization was recorded in inoculated seedlings on sandy loam soil (89%) when compared to gypseous one (52%). N, P and K concentrations in mycorrhizal seedlings were significantly improved by fungal inoculation. It can be concluded that inoculation of H. sessiliflorum with T. boudieri increased growth attributes and improved plant nutritional status.

Induction of antioxidant enzymes is involved in the greater effectiveness of a PGPR versus AM fungi with respect to increasing the tolerance of lettuce to severe salt stress

This study investigated the influence of inoculation with a plant growth-promoting rhizobacterium, Pseudomonas mendocina Palleroni, alone or in combination with an arbuscular mycorrhizal (AM) fungus, Glomus intraradices (Schenk & Smith) or Glomus mosseae (Nicol & Gerd.) Gerd. & Trappe, on antioxidant enzyme activities (catalase and total peroxidase), phosphatase activity, solute accumulation, growth and mineral nutrient uptake in leaves of Lactuca sativa L. cv. Tafalla affected by three different levels of salt stress. Salinity decreased lettuce growth, regardless of the biological treatment and of the salt stress level. The plants inoculated with P. mendocina had significantly greater shoot biomass than the control plants at both salinity levels, whereas the mycorrhizal inoculation treatments only were effective in increasing shoot biomass at the medium salinity level. At the highest salinity level, the water content was greater in leaves of plants treated with P. mendocina or G. mosseae. At the medium salinity level, G. intraradices- or G. mosseae-colonised plants showed the highest concentrations of foliar P. The P. mendocina- and G. mosseae-colonised plants presented higher concentrations of foliar K and lower concentrations of foliar Na under high salt conditions. Salt stress decreased sugar accumulation and increased foliar proline concentration, particularly in plants inoculated with the PGPR. Increasing salinity stress raised significantly the antioxidant enzyme activities, including those of total peroxidase and catalase, of lettuce leaves compared to their respective non-stressed controls. The PGPR strain induced a higher increase in these antioxidant enzymes in response to severe salinity. Inoculation with selected PGPR could serve as a useful tool for alleviating salinity stress in salt-sensitive plants.

Changes in biological activity of a degraded Mediterranean soil after using microbially-treated dry olive cake as a biosolid amendment and arbuscular mycorrhizal fungi

A field experiment was carried out to assess the effect of a combined treatment involving addition of Aspergillus niger-treated dry olive cake (DryOC) in the presence of rock phosphate, plus pre-transplant inoculation of seedlings with the arbuscular mycorrhizal (AM) fungi Glomus intraradices, Glomus deserticola or Glomus mosseae, on the establishment of Dorycnium pentaphyllum L., in a degraded semiarid Mediterranean area. Associated changes in soil labile C fractions, enzyme activities and aggregate stability were also observed. One year after planting, the combined treatment of fermented DryOC addition and inoculation with AM fungi, particularly with G. mosseae (on average 328% greater than control plants), had the strongest effect on the shoot biomass of D. pentaphyllum. Only the fermented DryOC addition increased assimilable P, total N and aggregate stability, the greatest increase being in the soil available P content (about four-fold higher than in the non-amended soil). Both the addition of fermented DryOC and the mycorrhizal inoculation treatments significantly increased enzyme activities of rhizosphere soil (dehydrogenase, protease-BAA, acid phosphatase and β-glucosidase). The microbially-treated DryOC proved to be an effective amendment for improving the soil quality which, in turn, enhanced the success of revegetation with mycorrhizal D. pentaphyllum seedlings.

Impact of DOM from composted “alperujo” on soil structure, AM fungi, microbial activity and growth of Medicago sativa

Water-soluble extracts from compost may represent an alternative nutrient and organic matter source for crop production under drip irrigation. Dissolved organic matter (DOM), extracted from composted "alperujo", the main by-product from the Spanish olive oil industry, was applied to soil alone or in combination with either Glomus intraradices Schenck and Smith or a mixture of G. intraradices, Glomus deserticola (Trappe, Bloss. and Menge) and Glomus mosseae (Nicol and Gerd.) Gerd. and Trappe. Response measurements included mycorrhizal colonisation, nutrient uptake and growth of Medicago sativa and microbiological and physical properties in the rhizosphere. Dissolved organic matter was added to soil at concentrations of 0, 50, 100 or 300mgCkg(-1) substrate. During the four months of the experiment, the plants were harvested three times. Both mycorrhizal inoculation treatments significantly increased soil aggregate stability. Only the mycorrhizal inoculations increased microbial biomass C and protease and phosphatase activities and decreased water-soluble C, particularly the mixture of arbuscular mycorrhizal fungi. At the third harvest, the greatest increase in growth of M. sativa was observed in the inoculated plants with shoot biomass being 38% greater than for plants grown in the soil amended with the highest dose of DOM and 57% greater than for control plants. The addition of DOM was not sufficient to restore soil structure and microbial activity and did not affect the mycorrhizal development of introduced populations of arbuscular mycorrhizal fungi, but, depending on the dose, its fertiliser efficiency for improving plant growth was apparent.

Interaction between AM fungi and a liquid organic amendment with respect to enhancement of the performance of the leguminous shrub Retama sphaerocarpa

This study examined the interactions between the inoculation with three arbuscular mycorrhizal fungi, namely, Glomus intraradices, Glomus deserticola and Glomus mosseae, and the addition of a liquid organic amendment at different rates (0, 50, 100 or 300 mg C of liquid amendment per kilogram soil) obtained by alkaline extraction of composted dry olive residue with respect to their effects on growth of Retama sphaerocarpa seedlings and on some microbiological and physical properties of soil. One year after planting, both mycorrhizal inoculation treatments and the addition of amendment had increased plant growth and dehydrogenase, urease and benzoyl argininamide hydrolysing activities. The inoculation with G. mosseae increased plant growth to a greater extent than the addition of the amendment (about 35% greater than plants grown in the amended soil and about 79% greater than control plants) and both treatments produced similar increases in soil aggregate stability (about 31% higher than control soil). The organic amendment produced a very significant decrease in the levels of microbial biomass C and a strong increase in soil dehydrogenase and urease activities, which were proportional to the amendment rate. Only the combined treatment involving the addition of a medium dose of amendment (100 mg C kg−1 soil) and the mycorrhizal inoculation with G. intraradices or G. deserticola produced an additive effect on the plant growth with respect to the treatments applied individually (about 77% greater than plants grown in the amended soil and about 63% greater than inoculated plants).

Formation of stable aggregates in rhizosphere soil of Juniperus oxycedrus: Effect of AM fungi and organic amendments

The effects of mycorrhizal inoculation, with an arbuscular mycorrhizal (AM) fungus ( Glomus intraradices Schenck and Smith) or with a mixture of three AM fungi ( G. intraradices, G. deserticola (Trappe, Bloss. and Menge) and G. mosseae (Nicol and Gerd.) Gerd. and Trappe), and addition of composted sewage sludge or Aspergillus niger-treated dry olive cake (DOC) residue on aggregate stabilisation of the rhizosphere soil of Juniperus oxycedrus were studied. The influence of such structural improvements on the establishment of J. oxycedrus was evaluated. Six months after planting, the inoculation with the mixture of three AM fungi and the combination of G. intraradices with both organic amendments had significantly enhanced the structural stability. Water soluble C and carbohydrates values were increased only with the addition of composted sewage sludge or fermented DOC. The addition of both organic amendments, particularly fermented DOC, decreased significantly the dehydrogenase, urease, protease and β-glucosidase activities. Rhizosphere soil from the inoculation treatments had higher dehydrogenase and β-glucosidase activities than control soil. Both the organic amendments addition and the mycorrhizal inoculation treatments increased significantly shoot biomass in J. oxycedrus. AM inoculation treatments were more effective with respect to increasing shoot biomass than the addition of organic amendments alone, and there were no significant differences between the two mycorrhization treatments (on average, about 53% higher with respect to control plants and about 18% higher with respect to plants grown in the amended soil).

Involvement of antioxidant enzyme and nitrate reductase activities during water stress and recovery of mycorrhizal Myrtus communis and Phillyrea angustifolia plants

In a greenhouse experiment, we studied the effect of inoculation with an arbuscular mycorrhizal (AM) fungus ( Glomus intraradices Schenck and Smith) or with a mixture of three AM fungi ( G. intraradices Schenck and Smith, Glomus deserticola (Trappe, Bloss. and Menge) and Glomus mosseae (Nicol and Gerd.) Gerd. and Trappe) on root and shoot nitrate reductase (NR, EC 1.6.6.1.) activity, mycorrhizal colonisation, plant growth, nutrient uptake and superoxide dismutase (SOD) and peroxidase (POX) activities in shoots of Myrtus communis and Phillyrea angustifolia seedlings after well-watered, drought and recovery periods. The mycorrhizal inoculation treatments increased significantly the growth and foliar nutrients (N and P) of both species independent of the water regime. Drought reduced NR activity in roots of both species and in shoots of M. communis, although both species inoculated with the mixture of AM fungi reached values higher than non-inoculated plants and plants inoculated with G. intraradices. The mycorrhizal inoculation treatments decreased significantly POX and SOD activities in shoots of both species. POX and SOD activities in inoculated P. angustifolia seedlings hardly varied during the drought and recovery periods. SOD activity was enhanced by drought in non-AM plants of both species and in inoculated M. communis, but to a lesser extent than in control plants.

AM fungi inoculation and addition of microbially‐treated dry olive cake‐enhanced afforestation of a desertified Mediterranean site

AbstractA field experiment was carried out to compare the effectiveness of inoculation with three arbuscular mycorrhizal (AM) fungi, namely Glomus intraradices Schenck & Smith, Glomus deserticola (Trappe, Bloss. & Menge) and Glomus mosseae (Nicol & Gerd.) Gerd. & Trappe, and the addition of Aspergillus niger‐treated dry olive cake (DOC) in the presence of rock phosphate, in increasing root nitrate reductase (NR) and acid phosphatase activities, mycorrhizal colonization, plant growth and nutrient uptake in Dorycnium pentaphyllum L. seedlings afforested in a semiarid degraded soil. Three months after planting, both the addition of fermented DOC and the mycorrhizal inoculation treatments had increased root NR activity significantly, particularly the inoculation with G. deserticola (by 75 per cent with respect to non‐inoculated plants), but they had no effect on root acid phosphatase. Mycorrhizal inoculation treatments with G. deserticola or G. mosseae on their own were even more effective than the addition of fermented DOC alone in improving the growth and (NPK) foliar nutrients of D. pentaphyllum plants. The combined treatment involving the application of microbially‐treated agrowastes and mycorrhizal inoculation with AM fungi, particularly with G. mosseae, can be proposed as a successful revegetation strategy for D. pentaphyllum in P‐deficient soils under semiarid Mediterranean conditions. Copyright © 2004 John Wiley & Sons, Ltd.