Acaulospora Laevis Gerd Research Articles

Potential Role of Arbuscular Mycorrhizal Fungi and Pseudomonas fluorescens on Growth, Physiological Parameters, and Yield of Capsicum frutescens L.

ABSTRACTLimited land resources affect production of Hot Pepper (Capsicum frutescens L.). Strategies to increase production of hot pepper include use of chemical fertilizers, pesticides, and insecticides, but these can negatively impact the soil. Methods must be derived to improve nutrient uptake while reducing synthetic chemical inputs. Soil microbes including, arbuscular mycorrhizal (AM) fungi, represent a link between plants and soil mineral nutrients. The investigation was carried out to determine the ability of AM fungi [Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe and Acaulospora laevis Gerd. & Trappe] applied alone and in combination with the bacterium Pseudomonas fluorescens to affect growth, biochemical attributes and yield of hot pepper. All treatments enhanced C. frutescens growth, physiological parameters, and yield over the untreated control. Inoculation with G. mosseae (G) + A. laevis (A) + P. fluorescens (P), followed by G + A inoculation produced the best growth response, AM colonization, phosphorus uptake, and biochemical responses due to a positive interaction among rhizospheric microorganisms. Soil amended with G. mosseae + A. laevis + P. fluorescens at transplanting increased production of high-quality hot pepper and reduced fertilizer required.

Role of arbuscular mycorrhiza fungi on tolerance to salinity of the tree legume Albizia lebbeck (L.) inoculated by Rhizobium

Myrica esculenta (Myricaceae) and Syzygium cumini(Myrtaceae), the Indian traditional fruits The effect of different level of salinity on growth, nodulation and Nitrogen fixation of single and dual inoculated tree legumes which help arbascular mycorrhizal fungi (AMF) Acaulospora laevis Gerd. and Trappe with Rhizobium bacteria in the presence of different levels of salinity (concentration of NaCl) conducted in earthen pots in a completely randomized block design with three replications resulted in effective plant growth, shoot and root biomasses, nodulation and N2 fixation. The effect of different levels of salinity (concentration of NaCl) on growth, nodulation and N2 fixation of single (Rhizobium or AMF alone) and dual inoculated (Rhizobium + AMF ) tree legume has a pot culture experiment using The parameter growth , nodulation, nitrogen fixation and % AMF colonization of roots were considerable influenced with the increase in salt concentration from 0.5 % to 4.0 % NaCl. It was observed that the mycorrhizal tree legume (inoculated with the most preferred AMF Acaulospora laevis) performed better in the increasing levels of salinity in comparison to non-mycorrhozal ones. These investigations suggested a protective role play by AMF in providing resistance to the tree legume against injurious effects of salinity. Inoculation of efficient strain of AMF (Acaulospora laevis) during the course of study, prevented the injurious effects of salinity in the test plants due to enhanced water and sustainable nutrient uptake thereby promoting growth, nodulation and biogeochemical N2 cycle (fixation of nitrogen) of the tree legume under investigation.

Biological Amendments on Growth, Nutritional Quality, and Yield of Celery

Soil nutrients can decrease during organic production of celery (Apium graveolens L.) transplants. Arbuscular mycorrhizal fungi (AMF) are known to promote plant nutrition and growth. Hence, a study was carried out to determine the potential of AMF [Funneliformis mosseae (Nicol. and Gerd.) Walker and Schüβler and Acaulospora laevis Gerd. and Trappe], used alone or in combination with the bacterium Pseudomonas fluorescens and/or the nonmycorrhizal fungus Trichoderma viride Pers. on celery in a greenhouse. The objective was to select an efficient AMF, or other growth-promoting microbes, for soil inoculation to improve establishment and growth of celery transplants. Inoculation with a combination of F. mosseae + P. fluorescens produced increased root length and fresh and dry weights, and the best plant height was obtained when all of the bioinoculants were used together. Mycorrhizal root colonization increased when P. fluorescens was used and the combination of F. mosseae + P. fluorescens produced the most colonization. Inoculation with F. mosseae + P. fluorescens increased shoot and root P content and root N content and increased celery yield by increasing leafstalk length. Higher photosynthetic rate, chlorophyll content, and shoot N content occurred when F. mosseae + A. laevis + P. fluorescens was used, with improved numbers of leafstalks, leaf area, and basal disc diameter. Soil amended with F. mosseae + P. fluorescens and F. mosseae + A. laevis + P. fluorescens at transplanting stage increased production of high-quality celery stalks with better nutrition and reduced fertilizer application.

Interactions between Azotobacter, Pseudomonas and Arbuscular Mycorrhizal Fungi on Two Varieties of Sesamum indicum L.

AbstractEarthen pot experiments were conducted in a randomized block design with three replications to evaluate the effects of sesame varieties, DS 1 and E 8 on a single inoculation of Glomus fasciculatum (Thax. sensu Gerd.) Gerd. and Trappe and Acaulospora laevis Gerd. & Trappe respectively, dual inoculation of arbuscular mycorrhizal fungi (AMF) with Azotobacter chroococcum (Ac) or Pseudomonas fluorescens (Pf) and a triple inoculation of AMF, A. chroococcum and P. fluorescens. The results revealed that inoculation of AMF + Ac + Pf to DS 1 and E 8 varieties stimulated increased AMF colonization, plant growth, i.e. shoot, root length, fresh and dry weight of shoot and root, phosphorus uptake and number of capsules significantly over the dual and single inoculation treatments. The association of bacteria and AMF provides evidence that bacteria are involved in the beneficial effects to AMF on sesame varieties.

A change in the concentration of NaCl in soil alters the rate of hyphal extension of some arbuscular mycorrhizal fungi

This study investigated the effect of a rapid change in the concentration of the soil solution on hyphal growth from germinated spores of three arbuscular mycorrhizal fungi: isolates of Acaulospora laevis Gerd. & Trappe, Gigaspora decipiens Hall & Abbott, and Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders. Spores of either G. decipiens or S. calospora were incubated between millipore filters buried in sand that had been watered to field capacity with solutions of 0, 150, or 300 mmol/L NaCl. After 11 d, the intact pairs of filters were recovered, left undisturbed, or transferred into and further incubated in soil watered with one of the three solutions. Spores of A. laevis were incubated between filters in sand without NaCl and after 20 d were either left undisturbed or transferred to soil with 0, 50, 150, or 300 mmol/L NaCl in the soil solution for a further 11 d. The filter sandwiches were stained and opened, and determinations of spore germination, number of auxiliary cells, and length of hyphae on each were made. For G. decipiens and S. calospora, the effect of NaCl on hyphal growth was reversible. Hyphae from spores germinated in sand with 300 mmol/L NaCl showed markedly increased growth when transferred to a less saline environment. Hyphae from spores germinated in nonsaline sand continued to grow, but at a slower rate, when transferred to a saline environment. Hyphae of A. laevis continued to elongate after transfer to soil with 50 mmol/L NaCl but not 150 or 300 mmol/L NaCl. Morphological differences were observed between hyphae of G. decipiens grown in a highly saline as compared with a nonsaline substrate.Key words: soil salinity, arbuscular mycorrhizas, species and genera of arbuscular mycorrhizal fungi, hyphae.

Infectivity of arbuscular mycorrhizal fungi after wetting and drying.

In a mediterranean environment, a hot and dry summer is followed by a cool and rainy winter, the growing season. Arbuscular mycorrhizal (AM) fungi survive in dry soil in the summer and are able to colonize newly emerged plants in winter. However, late summer and autumn rains are frequently followed by periods of drought, resulting in the wetting and drying of the soil before the onset of regular winter rains. The results of three experiments investigating the effect of wetting and drying of soil on the subsequent infectivity of different AM fungi and their individual propagules are presented. In a first experiment, pot-culture inoculum of Acaulospora laevis Gerd. & Trappe, Glomus invermaium Hall, or fine endophytes, each containing a mixture of propagule forms, was mixed into pots of steam-sterilized soil with low phosphorus content. Pots were treated with a wetting and drying cycle where the soil was watered to field capacity for three consecutive days and then left to dry to a water content of less than 1.5% g g-1 . Infectivity was assessed in a subsequent growth cycle planted with clover. In a second experiment, the infectivity of spores of A. laevis, Glomus monosporum Gerd. & Trappe or Scutellospora calospora (Nicol & Gerd.) Walkers & Sanders, and of dried mycorrhizal root fragments of G. invermaium or S. calospora was assessed after a wetting and drying cycle in which the soil was watered to field capacity for seven consecutive days before drying. In a third experiment, the infectivity of the extraradical hyphae of G. invermaium after wetting and drying was assessed. AM fungi and their individual propagules responded differently to wetting and drying. The infectivity of pot-culture inoculum of A. laevis, G. invermaium and fine endophytes was increased, decreased and unaffected, respectively, by wetting and drying. The infectivity of spores of A. laevis and G. monosporum was increased by wetting and drying but the infectivity of spores of 5. calospora was not affected. Infectivity of mycorrhizal root fragments of G. invermaium and S. calospora was decreased and increased, respectively, by wetting and drying. Finally, the infectivity of the extraradical hyphae of G. invermaium was eliminated by a wetting and drying cycle. These results indicate that the development and function of mycorrhizas after late summer and early autumn rains may be limited by the occurrence and predominance of propagules of different AM fungi.

Localization of β (1-3) glucan in walls of the endomycorrhizal fungi Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe and Acaulospora laevis Gerd. & Trappe during colonization of host roots.

Previous studies showed that cell walls of endomycorrhizal fungi belonging to the Acaulosporaceae and Glomaceae contain β (1-3) glucan polymers as well as chitin. Indirect immunolabelling with monoclonal and polyclonal antibodies has been used to investigate the distribution of these structural polysaccharides in cell walls of Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe and Acaulospora laevis Gerd. & Trappe as they interact with pea and tobacco roots, respectively. The (l-3) glucans were detected in the walls of external hyphae, and of hyphal coils and intercellular hyphae developing in outer root tissues. The glucan component was alkali-insoluble but treatment with chitinase resulted in solubilization of most of the β(1-3) glucans from the fungal wall. A decrease in immunolabelling was associated with thinning out of the hyphal wall as the fungi colonized deeper in the host root, and β(1-3) glucans could not be detected in walls of intercellular hyphae or arbuscules in the parenchyma cortical tissue. The molecular configuration of cell walls of G. mosseae and A. laevis is discussed in relation to fungal morphogenesis and the symbiotic state in endomycorrhiza.

The survival of infective hyphae of vesicular–arbuscular mycorrhizal fungi in dry soil: an interaction with sporulation

SUMMARYContrary to previous evidence, the hyphae of a vesicular–arbuscular (VA) mycorrhizal fungus, Acaulospora laevis Gerd. and Trappe, did not remain infective in soil for a length of time, and at a level of dryness, equivalent to that occurring in seasonally‐dry field soils. A possible interaction between the survival of hyphae and the timing of sporulation was therefore examined in a second experiment. We tested the hypothesis that hyphae of A. laevis and Scutellospora calospora (Nicolson and Gerdemann) Walker and Sanders, will only remain infective in dry soil if sporulation has not commenced. The capacity of the hyphae of A. laevis to remain infective, in undisturbed soil that had been allowed to dry, depended on the stage of the life cycle reached at the time of the onset of drying. If sporulation had commenced, then infectivity quickly declined as the soil dried. In contrast, infective hyphae of S. calospora survived for at least 11 wk, regardless of the timing of the commencement of drying of the soil in relation to sporulation. Quantifying entry points was an important measure for assessing the survival of infective hyphae, complementing the measure of total mycorrhiza formation by the test plants.

The effect of long-term applications of phosphorus fertilizer on populations of vesicular-arbuscular mycorrhizal fungi in pastures

We assessed whether 6-year-old applications of phosphorus (P) fertilizer to a previously unfertilized field site resulted in the selection of populations of vesicular-arbuscular (VA) mycorrhizal fungi that were more 'tolerant' of added P than the original VA mycorrhizal population at the site. In 1977, four rates of P (0, 49, 97 and 200 kg P/ha) were applied to a field site at Mt Barker, Western Australia. In 1983, either no P or a rate of P sufficient for maximum plant growth (352 kg P/ha) was applied to each of these plots and the formation of spores and colonization of roots by VA mycorrhizal fungi were examined in the following 3 years. Residual P from fertilizers applied in 1977 increased both the percentage of root length colonized and the length of root colonized by VA mycorrhizal fungi in 1983, 1984 and 1985. Colonization by 'medium hyphae' Glomus spp., Acaulospora laevis Gerd. and Trappe and fine endophyte increased in response to the 1977 applications of P. By contrast, colonization by Scutellospora calospora (Nicol. and Gerd.) Walker and Sanders decreased with the 1977 applications of P. Application of an adequate rate of P to the field plots in 1983 generally decreased the development of VA mycorrhizal infection in plots, to a greater extent where larger rates of P had previously been applied in 1977. We attributed this effect to higher initial levels of mycorrhizal colonization in the plots which received larger rates of P in 1977. The 1977 applications of P are unlikely to have resulted in the selection of strains of VA mycorrhizal fungi that are less tolerant of added P than the strains present in the unfertilized plots. There was a common relationship between VA mycorrhizal colonization and the residual value of the P applications which provided indirect evidence that there was no change in the P-tolerance of the indigenous VA mycorrhizal population in response to P applied in 1977. Interpretation of the effects of the 1977 and 1983 applications of P on VA mycorrhizal colonization was compounded by the effects these applications of P had on the botanical composition of the pasture and also on the inoculum potential in each plot. Spores of A. laevis and S. calospora were recovered from each field plot. The number of spores of A. laevis increased in response to P applied in 1977 and generally decreased in response to P applied in 1983. These effects could be directly related to the effects the 1977 and 1983 applications of P had on the length of root colonized by A. laevis in the preceding growing season.

Hyphae of a vesicular—arbuscular mycorrhizal fungus maintain infectivity in dry soil, except when the soil is disturbed

SUMMARYWe examined the hypothesis that hyphae of a VA mycorrhizal fungus in dry soil remain infective, but that the infectivity decreases if the soil is disturbed. We used split‐pots, and sealed cylinders of nylon mesh, to create volumes of dry soil which contained hyphae of Acaulospora laevis Gerd. and Trappe that were attached, outside the mesh, to roots of living plants of Acacia satigna. (Labill.) H. Wendl. After the soil was dried in situ, the hyphae were detached from the roots without soil disturbance, or the soil containing the hyphae was disturbed. The infectivity of the hyphae after these treatments was then compared with that of intact hyphae.External hyphae of A. laevis remained highly infective in soil in which the matric potential had reached −21 MPa. Hyphae detached from the original host plant roots were equally infective. However, disturbance of the dry soil containing the external hyphae severely reduced the infectivity of the hyphae. After fluorescent staining, fungal structures with fluorescing nuclei were readily visible both within, and attached to, roots of A. Saligna which had no fluorescing nuclei.

Factors Controlling the Distribution of Vesicular-Arbuscular Mycorrhizal Fungi in Relation to Soil pH

(1) The successful commercial application of vesicular-arbuscular (VA) mycorrhizal fungi depends on understanding which factors restrict their distribution. The aim of this study was to identify the particular soil properties which caused distinct populations of VA mycorrhizal fungi to occur at two adjacent sites in a semi-arid, Mediterranean environment in Western Australia. (2) From a series of experiments it was concluded that, when inoculated into the soil in which they did not occur naturally (i) the fungi infected fewer roots and produced fewer spores than in their soil of origin, and (ii) fewer spores of the dominant fungi (Site I: Acaulospora laevis Gerd. & Trappe; Site II: Glomus sp. (WUM 2) and Glomus sp. (WUM 3) germinated, and they produced shorter germ tubes than in their soil of origin. (3) From two subsequent experiments studying the effect of adjusting the pH of either the soil or an extracted soil solution used as germinating media, it was concluded that soil pH is likely to be important in limiting the distribution of A. laevis and Glomus sp. (WUM 3).

FORMATION OF EXTERNAL HYPHAE IN SOIL BY FOUR SPECIES OF VESICULAR‐ARBUSCULAR MYCORRHIZAL FUNGI

SummaryThe ability of several species of vesicular–arbuscular (VA) mycorrhizal fungi to form hyphae in soil was compared in two glasshouse experiments. We measured the length of hyphae in soil and related this to the length of infected root. Species of VA mycorrhizal fungi differed in the length of external hyphae produced per cm of infected root. Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe produced less external hyphae per cm infected root than did Gigaspora calospora (Nicol. and Gerd.) Gerd. at all harvest times and when inoculum was either placed in a band below the seed or mixed throughout the soil. Glomus tenue (Greenall) Hall and Acaulospora laevis Gerd. and Trappe both produced similar lengths of external hyphae per cm infected root to that formed by G. calospora.Differences among isolates of VA mycorrhizal fungi in the distribution of hyphae in soil may be as important as differences in the length of external hyphae when selecting fungi that are effective at increasing nutrient uptake.

Ecological interaction of little bluestem and vesicular–arbuscular mycorrhizal fungi

The percentage of vesicular–arbuscular mycorrhizal (VAM) colonization of little bluestem (Schizachyrium scoparium) (Michx.) Nash.) and VAM spore populations in the rhizosphere of little bluestem from four prairie areas in Illinois were studied. At Goose Lake Prairie, a significant positive correlation (r = 0.77, p < 0.01) was found between soil moisture and density of VAM spores, but soil moisture and percent VAM colonization were not significantly correlated at any of its sites. Percentage of VAM colonization tended to be higher at study areas where little bluestem was a dominant species. However, spore numbers and abundance of little bluestem tended to be inversely related. Colonization decreased from May to July at all areas and this trend frequently continued into September. Month of sample collection had no significant effect on spore numbers except at Reavis Hill Prairie. The endophyte isolated at all areas was Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. & Trappe. Other species, such as Gigaspora heterogama (Nicol. & Gerd.) Gerd. & Trappe and Acaulospora laevis Gerd. & Trappe, were more restricted in their distribution.

Endogonaceae from Quebec soils

Spores of the Endogonaceae, isolated from soils in the vicinity of Macdonald College, P.Q., included those of the following species: Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, G. macrocarpus var. geosporus (Nicol. & Gerd.) Gerd. & Trappe, G. caledonius (Nicol. & Gerd.) Gerd. & Trappe, and Acaulospora laevis Gerd. & Trappe. Sporocarps of Sclerocystis rubiformis Gerd. & Trappe were also found.The ectocarpic spore population was lowest in May or June. It increased in late summer, reaching a peak in September or October.