Mycorrhizal dependency of banana (Musa acuminata,AAA group) cultivar

Seven banana cultivars (Musa acuminata, AAA group) were inoculated with two species of vesicular arbuscular mycorrhizal (VAM) fungi (Glomus mosseae and Glomus macrocarpum) in a greenhouse experiment. Inoculated plants had generally greater shoot dry weight and shoot phosphorus concentrations compared to the noninoculated plants. A great variation in dependency on mycorrhizal colonization was observed among the banana cultivars. Cv. Williams showed the highest relative mycorrhizal dependency (RMD) and cv. Poyo the lowest. For all the cultivars studied, inoculation with G. macrocarpum resulted in the highest RMD values. Both root dry weight and root hair length or density of the noninoculated plants were inverserly correlated with the RMD values of cultivars.     

Compatibility and Coselection of Vesicular-Arbuscular Mycorrhizal Fungi and Rhizobia for Tropical Legumes

Abstract

The effect of dual inoculation on three local cultivars (Miss Kelly, Portland Red, Round Red) of red kidney bean (Phaseolus vulgaris, L.) with four strains of Rhizobium phaseoli (B36, B17, T2, and CIAT652) and three species of vesicular-arbuscular mycorrhizal (VAM) fungi (Glomus pallidum, Glomus aggregatum, and Sclerocystis microcarpa) was examined in sterilized and nonsterilized soil. Symbiotic efficiency (improved plant growth response and enhanced nitrogen (N) and phosphorus (P) nutrition) was dependent on the particular combination of Rhizobium strain, VAM fungus, and cultivar of kidney bean. Whereas rhizobial strains B36 and B17 paired with G. pallidum or G. aggregatum showed increased growth response of cv. Miss Kelly and Portland Red, rhizobial strain T2 paired with any of the three VAM fungi was the best compatible pairing for the cv. Round Red. It is suggested that even though dual inoculation significantly improves the growth response of the bean, the best pairings of VAM fungus and rhizobia for legumes is a question to be carefully examined.     

Influence of temperature on colonization of spring barleys by vesicular arbuscular mycorrhizal fungi

The effects of three soil temperatures on growth of spring barleys (Hordeum vulgare L.) and on their root colonization by vesicular arbuscular mycorrhizal (VAM) fungi from agricultural soils in Montana (USA) or Syria at different inoculum concentrations were tested in soil incubators in the greenhouse. The number of mycorrhizal plants as well as the proportion and intensity of roots colonized increased with higher soil temperatures. VAM fungi from Montana, primarily Glomus macrocarpum, were cold tolerant at 11°C while those from Syria, primarily G. hoi, were heat tolerant at 26°C. Inoculum potential of Montana VAM fungi was higher than Syrian VAM fungi in cool soils. Harmal, selected from Syrian barley land races, had the highest colonization by mycorrhizal fungi of the cultivars tested.Journal Series Paper: J-2532 Montana Agricultural Experiment Station.     

Soil color and surface residue effects on seedling light environment

Three leafless pea cultivars (JI 1198, BS 142 and BS 4) with the same phenotype and similar patterns of development, were tested in a sterilized low-phosphate soil for their response to phosphate fertilizer and to vesicular-arbuscular mycorrhizal (VAM) infection by threeGlomus species. Cultivar JI 1198 was very responsive to phosphate but not to inoculation withGlomus mosseae, Glomus caledonium orGlomus epigaeum. Phosphate and VAM treatments increased growth of cultivar BS 142 but were ineffective with cultivar BS 4. Fungal infectivity could not be related with endophyte effectiveness at stimulating plant growth, although the percentage of root length infected by each one of the threeGlomus species did not vary between cultivars. Genetic differences among plant cultivars can thus markedly affect the symbiosis between the host root and VAM fungi; this suggests that potential host-endophyte combinations need to be evaluated before being tested in the field.     

Interaction of vascular plants and vesicular-arbuscular mycorrhizal fungi across a soil moisture-nutrient gradient

Summary Abundance and distribution of vascular plants and vesicular-arbuscular mycorrhizal (VAM) fungi across a soil moisture-nutrient gradient were studied at a single site. Vegetation on the site varied from a dry mesic paririe dominated by little bluestem (Schizachyrium scoparium) to emergent aquatic vegetation dominated by cattail (Typha latifolia) and water smartweed (Polygonum hydropiperoides). Plant cover, VAM spore abundance, plant species richness, and number of VAM fungi represented as spores, had significant positive correlations with each other and with percent organic matter. The plant and VAM spore variables had significant negative correlations with soil pH and available Ca, Mg, P and gravimetric soil moisture. Using stepwise multiple regression, Ca was found to be the best predictor of spore abundance. Test for association between plant species and VAM fungal spores indicated that the spores of Glomus caledonium are associated with plants from dry, nutrient poor sites and spores of gigaspora gigantea are positively associated with plants occurring on the wet, relatively nutrient rich sites. Glomus fasciculatum was the most abundant and widely distributed VAM fungus and it had more positive associations with endophyte hosts than the other VAM fungi. We found no relationship between beta niche breadth of plant species and the presence or absence of mycorrhizal infection. However, our data suggest that some plant species may vary with respect to their infection status depending upon soil moisture conditions that may fluctuate seasonally or annually to favor or hinder VAM associations.     

Establishment of Vesicular-Arbuscular Mycorrhizal Fungi and Other Microorganisms on a Beach Replenishment Site in Florida

Beach replenishment is a widely used method of controlling coastal erosion. To reduce erosional losses from wind, beach grasses are often planted on the replenishment sands. However, there is little information on the microbial populations in this material that may affect plant establishment and growth. The objectives of this research were to document changes in the populations of vesicular-arbuscular mycorrhizal (VAM) fungi and other soil microorganisms in replenishment materials and to determine whether roots of transplanted beach grasses become colonized by beneficial microbes. The study was conducted over a 2-year period on a replenishment project in northeastern Florida. Three sampling locations were established at 1-km intervals along the beach. Each location consisted of three plots: an established dune, replenishment sand planted with Uniola paniculata and Panicum sp., and replenishment sand left unplanted. Fungal and bacterial populations increased rapidly in the rhizosphere of beach grasses in the planted plots. However, no bacteria were recovered that could fix significant amounts of N₂. The VAM fungi established slowly on the transplanted grasses. Even after two growing seasons, levels of root colonization and sporulation were significantly below those found in the established dune. There was a shift in the dominant VAM fungi found in the planted zone with respect to those in the established dunes. The most abundant species recovered from the established dunes were Glomus deserticola, followed by Acaulospora scrobiculata and Scutellospora weresubiae. The VAM fungi that colonized the planted zone most rapidly were Glomus globiferum, followed by G. deserticola and Glomus aggregatum.     

Vesicular-arbuscular mycorrhizal fungi,particularly Glomus tenue,in Venezuelan bromeliad epiphytes

The mycorrhizal status of water-impounding tank bromeliad epiphytes from three locales differing in altitude and moisture regime within Venezuelan cloud forest was examined. Species of vesicular-arbuscular mycorrhizal (VAM) fungi found in arboreal soils were compared to VAM fungi found in terrestrial soils. Sixteen of the 19 epiphytes examined for the presence of VAM fungi had roots with infection stages; 14 of these specimens showed growth of the fine endophyte Glomus tenue. Fine endophyte was the only VAM fungus found associated with epiphytes in the driest locale studied, while coarse VAM fungi (Gigaspora and Scutellospora spp.) were found at sampling locales receiving more moisture. Root infection was usually composed of intercellular hyphae and peletons; few arbuscules were observed. However, abundant extracellular hyphae were often observed tangled about roots in arboreal soil. It is concluded that epiphytic bromeliads probably benefit, at least periodically, from VAM fungi scavenging for sporadically available nutrients in arboreal soils. Glomus tenue may be particularly important as a colonizing VAM fungus in drier sites of Venezuelan cloud forest. The species composition of VAM fungi in arboreal soils was different to that of terrestrial soils sampled directly under epiphytic bromeliad perches, suggesting that VAM fungi species associated with bromeliads are dispersed to their hosts by vagile animal vectors.     

The Glycine–Glomus–Rhizobium symbiosis. IV. Interactions between the mycorrhizal and nitrogen-fixing endophytes

Abstract Soybean (Glycine max (L.) Men) plants were grown under controlled conditions in an experiment designed as a 4 × 4 factorial. The factors were N or P nutrition, with different strains of Rhizobium japonicum or N-fertilization as levels of the first factor and different species of vesicular-arbuscular mycorrhizal (VAM) fungi or P fertilization as levels of the other. Organisms used were R. japonicum strains USDA 110, USDA 136, and 61A118, and the VAM fungi Glomus versiforme (Karst.) Berch, Glomus fasciculatum (Thaxt. sensu Gerd.) Gerd. and Trappe, and Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe. There were 16 treatments: nine Rhizobium + Glomus combinations, three Rhizobium + V and three Glomus+ N combinations, and one non-symbiotic set of plants supplied with N + P. The tripartite symbioses were evaluated by analysis of variance against the Rhizobium + P and Glomus + N comparison treatments for effects on root and leaf dry mass, root N and P content, nodule mass and activity, and VAM colinization. Significant to highly significant main effects and interactions were found in virtually all evaluations due to both Rhizobium strain and VAM–fungal species. We conclude that different endophyte isolates affect not only the host plant, but also the development and function of their co-endophytes. These findings establish the existence of inter-endophyte compatibility, an important consideration when selecting or engineering for desirable endophyte traits.     

New acidic chitinase isoforms induced in tobacco roots by vesicular-arbuscular mycorrhizal fungi

Summary Chitinase activities have been compared in tobacco roots (Nicotiana tabacum cv. Xanthi nc) infected by the pathogenic fungus Chalara elegans or three species of vesicular arbuscular mycorrhizal (VAM) fungi: Glomus versiforme, G. intraradix and G. fasciculatum, using native polyacrylamide gel electrophoresis (PAGE). All previously known acidic chitinase isoforms were stimulated in roots by the pathogenic fungus and by the VAM fungi, while two new acidic chitinase isoforms were specifically induced in response to the endomycorrhizal association. After separation in sodium dodecyl sulphate polyacrylamide denaturing gels (SDS-PAGE) under non-reducing conditions, the estimated apparent molecular mass for these additional acidic chitinase isoforms from VAM-colonized samples was 33 kDa, compared to 30 kDa for the main activity stimulated in C. elegans-infected root extracts.     

Effect of vesicular-arbuscular mycorrhizal fungi and ofagrobacterium radiobacter on maize growth

An influence of dual inoculation with the rhizosphere bacteriumAgrobacterium radiobacter, and the VAM fungi,Glomus mosseae andGlomus sp., on maize growth and mycorrhizal infection was observed. Separate inoculations of bacteria or fungi showed significant positive effects on the shoot biomass production of pot-cultured plants only at the last of three consecutive harvests. Plant biomass production was enhanced substantially after a dual inoculation with bacteria and fungi. Synergistic interaction of fungal and bacterial inoculation and growth stimulation was evident at all three harvests compared to uninoculated plants and also compared to plants inoculated with fungi or bacteria only. The dual inoculation increased the shoot biomass of plants by approximately 30% as compared with control. No significant differences were found in mycorrhizal infection between plants uninoculated and inoculated with bacteria.Agrobacterium radiobacter seems to be compatible with mycorrhizal symbiosis and can act a synergistic partner of some VAM fungi.     

Dynamics of vesicular-arbuscular mycorrhizae during old field succession

Summary The species composition of vesicular-arbuscular mycorrhizal (VAM) fungal communities changed during secondary succession of abandoned fields based on a field to forest chronosequence. Twenty-five VAM fungal species were identified. Seven species were clearly early successional and five species were clearly late successional. The total number of VAM fungal species did not increase with successional time, but diversity as measured by the Shannon-Wiener index tended to increase, primarily because the community became more even as a single species, Glomus aggregatum, became less dominant in the older sites. Diversity of the VAM fungal community was positively correlated with soil C and N. The density of VAM fungi, as measured by infectivity and total spore count, first increased with time since abandonment and then decreased in the late successional forest sites. Within 12 abandoned fields, VAM fungal density increased with increasing soil pH, H₂O soluble soil C, and root biomass, but was inversely related to extractable soil P and percent cover of non-host plant species. The lower abundance of VAM fungi in the forest sites compared with the field sites agrees with the findings of other workers and corresponds with a shift in the dominant vegetation from herbaceous VAM hosts to woody ectomycorrhizal hosts.     

Effect of soil liming and vesicular-arbuscular-mycorrhizal inoculation on the growth and micronutrient content of the teff plant

In a greenhouse experiment involving an acid soil teff [Eragrostis tef (Zucc.) Trotter] plants failed to grow unless the soil was limed or inoculated with either of two vesicular-arbuscular-mycorrhizal (VAM) fungi,Glomus mosseae orGlomus macrocarpum. Plant growth increased by liming and to a lesser extent by VAM fungal inoculation. Liming also enhanced root colonization by VAM fungi. Shoot micronutrient content generally increased as a result of inoculation, and decreased by increased lime applications.     

Effects of VA mycorrhiza on the growth of cacao seedlings under nursery conditions in Venezuela

The effects of vesicular-arbuscular mycorrhizae inoculation on the growth of cacao seedlings (Theobroma cacao var. Ocumare 60) grown for 5 months in a nursery were studied. The effects of introduced VAM fungi (Glomus occultum, Acaulospora appendicula, Glomus manihotis, Acaulospora morrowae and Scutellospora pellucida) in soils treated with copper oxychloride or methyl bromide, were compared with the indigenous VAM and with their respective non-inoculated controls.Cacao seedlings responded well to indigenous VAM fungi, which included Scutellospora calospora as the dominant species, inducing increases significant in height, dry weight and foliar uptake of P, Cu and Zn in relation to the sterile control. G. occultum and A. appendicula increased the height of cacao seedlings but to an extent not yet statistically significant through the duration of the experiment. S. pellucida and A. appendicula doubled the phosphorus uptake of cacao seedlings. The methyl bromide sterilization induced the lowest Cu and Zn uptake in the cacao seedlings but this effect was ameliorated with VAM inoculation. Manifest deficiency symptoms were not observed in the treatments.Copper oxychloride treatment depressed growth to the same level as the sterile control although its residual effects did not kill VAM. It could change the competitive relations among the VAM species and in this case seemed to affect adversely the more efficient native fungi.The influence of the presence and long permanence of large cotyledons in cacao on the results obtained is discussed.     

Stimulation of Growth and Nutrient Uptake by VAM Fungi in Brassica Oleracea Var. Capitata

Cabbage (Brassica oleracea, var. capitata, cv. Hercules) seedlings were inoculated with vesicular-arbuscular mycorrhizal (VAM) fungi Glomus fasciculatum, G. aggregatum, and G. mosseae. Differential efficiency in mycorrhizal colonization and the specificity of fungal symbiont to stimulate the growth and nutrient uptake of the host were observed. In addition, there was an increase in phenol, protein, reducing sugar contents, and peroxidase activity in the VAM inoculated seedlings. Since these compounds are known to confer resistance against fungal pathogens, the use of VAM as a biological control agent to protect cabbage against several root diseases is suggested.     

Responses of barley,pea, and maize to inoculation with different vesicular-arbuscular mycorrhizal fungi in irradiated soil

Summary The efficiency of different VAM fungi was investigated by inoculating barley, pea, and maize with different VAM fungi in irradiated soil in pots buried in the field. VAM frequency, growth and nutrient uptake were measured. In barleyGlomus epigaeus (CA) andG. macrocarpus (CA) were the most efficient out of 11 tested species and increased yield of grain by 24% and 21%, though they were not significant according to oneway analysis of variance. In pea, yield of grain was significantly increased from 46% to 104% (mean=68%) by 7 out of 10 tested species and by 105% by application of P fertilizer. The most efficient species wereG. epigaeus (CA),G. mosseae (GB), andG. etunicatus (CA). In maizeG. mosseae (GB) andG. caledonius (DK) increased total yield significantly by 59% and 47% in one experiment and in another experiment yield of cob was increased by 68% byG. mosseae (GB), 72% byG. caledonius (DK), and by 153% by application of P fertilizer. This experiment demonstrated that responsiveness to inoculation by VAM fungi differed among plant species, and that efficiency of different VAM fungi differed.     

Utility of phyllosphere N2-fixing micro-organisms in the improvement of crop growth

Summary The beneficial effect of spraying some highly active phyllosphere N₂-fixing microorganisms on high and low yielding cultivars of rice plants as compared with that of urea applied at different doses are described. The dry weight, N-content, 1000 grain weight, and yield were remarkably increased in all cases with the application of phyllosphere microorganisms. The performance of two isolates KUP₄ and KUPBR₂ with IR-8 and IR-26 rice, was better than that of 52 kg urea-N per hectare. IR-579 rice leaves in association with some phyllosphere bacteria reduced acetylene at the rate of 664–816 nmoles/g leaf/h. In IR-26 rice the effect of application of bacterial suspension at three phases of plant growth corresponded very well with that of urea application in three split doses under identical conditions. Recommended fertilizer rates produced the same yield as the half dose plus bacterial spray in the cultivars Pankaj and Rupsail. Fertilizer application in Pankaj and Rupsail rice reduced nitrogenase activity and the beneficial effects of phyllosphere N₂-fixation was reduced by 40–55%.     

Hyphal contribution to water uptake in mycorrhizal plants as affected by the fungal species and water status

Vesicular-arbuscular mycorrhizae may increase resistance of plants to drought by a number of mechanisms, such as increased root hydraulic conductivity, stomatal regulation, hyphal water uptake and osmotic adjustment. However, a substantial contribution of vesicular-arbuscular mycorrhizal (VAM) hyphae to water uptake has not been demonstrated unequivocally. The objective of this investigation was to examine the contribution of hyphae from two VAM fungi to water uptake and transport by the host plant. Lettuce (Lactuca sativa L.) plants were grown in a container divided by a screen into two compartments. One was occupied by roots, the other only by VAM hyphae, which the screen permitted to pass. Roots were colonized by the VAM fungi Glomus deserticola or Glomus fasciculatum, or were left uninoculated but P-supplemented. Water was supplied to the hyphal compartment at a distance of 10 cm from the screen (root). CO₂ exchange rate, water-use efficiency, transpiration, stomatal conductance and photosynthetic phosphorus-use efficiency of VAM or P-amended control plants were evaluated at three levels of water application in the hyphal compartment. Results indicate that much of the water was taken up by the hyphae in VAM plants. VAM plants, which had access to the hyphal compartment, had higher water and nutrient contents. G. deserticola functioned efficiently under water limitation and mycelium from G. fasciculatum-colonized plants was very sensitive to water in the medium. This discrepancy in VAM behaviour reflects the various abilities of each fungus according to soil water levels. Different abilities of specific mycelia were also expressed in terms of nutritional and leaf gas-exchange parameters. G. fasciculatum caused a significant increase in net photosynthesis and rate of water use efficiency compared to G. deserticola and P-fertilized plants. In contrast, the G. deserticola treatment was the most efficient affecting N, P and K nutrition, leaf conductance and transpiration. Since no differences in the intra- and extra-radical hyphal extension of the two endophytes were found, the results demonstrate that mycorrhizal hyphae can take up water and that there are considerable variations in both the behaviour of these two VAM fungi and in the mechanisms involved in their effects on plant water relations.     

Effect of aromatic plant species on vesicular-arbuscular mycorrhizal establishment in Pistacia terebinthus

The inoculation of Pistacia terebinthus with vesicular-arbuscular mycorrhizal (VAM) fungi and the spread of the infection were studied using a mixed cropping system, under glasshouse conditions, with Salvia officinalis, Lavandula officinalis and Thymus vulgaris colonized by Glomus mosseae as an inoculation method. This method was compared with soil inoculum placed under the seed or distributed evenly in the soil. Indirect inoculation with all the aromatic plants tested significantly increased VAM root colonization of P. terebinthus compared with the use of soil inoculum, although the effect on plant growth was different for each one of the aromatic species used as inoculum source. Inoculation with L. officinalis and T. vulgaris were the best treatments resulting in high VAM colonization and growth enhancement of P. terebinthus.     

Arbuscular mycorrhizal fungi and their effects on growth of different cultivars of <i>Capsicum annuum</i> L.

We studied the changes in the number of leaves, roots and height on three cultivars of Capsicum anuumm (Jalapeño, Serrano and De árbol) after inoculation with Glomus intraradices FS18 and Glomus Zac-19. Results indicated that Glomus intraradices FS18 produced greater effects on height (6.12 and 5.63 cm) and number of leaves (10.66 and 5.84) in the cultivars “Jalapeño” and “De árbol”, respectively. On the other hand, Glomus zac-19 stimulated the number of leaves and roots in “Serrano” pepper (6.17 leaves and 15.31 roots) and “Arbol” (6.52 leaves and 26.32 roots). Our results demonstrate the capacity of Glomus intraradices FS18 and Glomus Zac-19 of stimulating seedling growth on the three cultivars of Capsicum annuum L. This demonstrates the potential for using arbuscular mycorrhizal fungi in the production of plants of agronomic interest.     

Characteristic responses of three tropical legumes to the inoculation of two species of VAM fungi in Andosol soils with different fertilities

The growth and mineral nutrition responses were evaluated of three tropical legumes, cowpea (Vigna unguiculata L. cv Kuromame), pigeonpea [Cajanus cajan L. (Millsp.) cv ICPL 86009] and groundnut (Arachis hypogaea cv Nakateyutaka) inoculated with two different species of VAM fungi, Glomus sp. (Glomus etunicatum-like species) and Gigaspora margarita, and grown in Andosols with different fertilities [Bray II-P: topsoil (72 ppm), subsoil (<0.1 ppm)]. Percent fungal root colonization was high in cowpea and groundnut but relatively low in pigeonpea in both soil types. Despite the low rate of root infection, significant growth responses were produced, especially in the inoculated pigeonpea plant. In all legumes, shoot dry matter production was favoured by the inoculations. Increases in shoot biomass due to mycorrhizae were greater in the subsoil than in the topsoil. Mycorrhization raised shoot concentrations of P and Ca (in cowpea and groundnut) and P and K (in pigeonpea) in the topsoil. Whereas the P concentration in shoots in the subsoil was not positively affected by VAM fungi, particularly in cowpea and pigeonpea, the concentration of K in such plants was significantly increased by VAM treatment. The results also showed that mycorrhizal enhancement of shoot micronutrient concentrations was very rare in all plants, with negative effects observed in certain cases. Cu concentration, in particular, was not affected by VAM formation in any of the plants, and Mn and Fe in pigeonpea and groundnut, respectively, remained the same whether plants were mycorrhizal or not. In both soils the three legumes responded to Glomus sp. better than to Gigaspora margarita, and the effects of the VAM fungi on each of the crops relative to the controls were greater in the subsoil than in the topsoil. However, shoot growth of groundnut was not affected as much as cowpea and pigeonpea by the type of soil used. In spite of the relatively low infection of its root, pigeonpea was generally the most responsive of the three legume species in terms of mycorrhizal/nonmycorrhizal ratios.