Response of pineapple to mycorrhizal inoculation and fosetyl‐Al treatment

Abstract

A pot experiment was conducted in the greenhouse to determine the influence of vesicular‐arbuscular mycorrhizal (VAM) inoculation on growth of pineapple (Ananas comosus, cv.’Smooth Cayenne') and its interaction with fosetyl‐Al in a Wahiawa soil (Tropeptic Eutrustox) at soil solution P levels of 0.003, 0.02 and 0.2 mg/L. Pineapple crowns were dipped in a solution of fosetyl‐Al before planting. Inoculation of soil with the fungus Glomus aggregatum (Schenck & Smith emend. Koske) significantly increased VAM colonization of pineapple roots at soil solution P levels of 0.003 and 0.02 mg/L. VAM inoculation also increased mycorrhizal effectiveness measured six weeks after planting. At harvest, pineapple grown in the inoculated soil at the lowest P level had significantly higher D‐leaf P concentration and plant fresh weight than that grown in the uninoculated soil. Fosetyl‐Al appears to have no significant effect on VAM‐pineapple interaction.     

Boron fertilization,vesicular‐arbuscular mycorrhizal colonization and growth of citrus jambhiri lush

The role of boron (B) fertilization in the vesicular‐arbuscular mycorrhizal (VAM) colonization and growth of container‐grown Citrus seedlings was evaluated. Citrus jambhiri Lush, seedlings inoculated with Glomus fasciculatum, Glomus etunicatum or non‐inoculated were grown in a sandy loam soil for sixteen weeks. Seedlings were fertilized with 25 ug/ml B applied to the foliage as a mist, to the soil as a solution, or to both the foliage and the soil. Boron applied to the foliage or to the soil significantly increased root exudation of reducing sugars and amino acids two weeks after seedling germination. Subsequently, foliar fertilization with B significantly increased VAH colonization of seedlings relative to the controls. Plants inoculated with G. fasciculatum were larger and had greater VAM development than those inoculated with G. etunicatum. The growth of the noninoculated seedlings was not enhanced by B fertilization. The superior VAH colonization and growth of inoculated seedlings fertilized with B suggests that B stimulates the efficacy of plant fungi symbiosis.     

Are the rates of photosynthesis stimulated by the carbon sink strength of rhizobial and arbuscular mycorrhizal symbioses?

Rhizobial and arbuscular mycorrhizal (AM) symbioses each may consume 4-16% of recently photosynthetically-fixed carbon to maintain their growth, activity and reserves. Rhizobia and AM fungi improve plant photosynthesis through N and P acquisition, but increased nutrient uptake by these symbionts does not fully explain observed increases in the rate of photosynthesis of symbiotic plants. In this paper, we test the hypothesis that carbon sink strength of rhizobial and AM symbioses stimulates the rates of photosynthesis. Nutrient-independent effects of rhizobial and AM symbioses result in direct compensation of C costs at the source. We calculated the response ratios of photosynthesis and nutrient mass fraction in the leaves of legumes inoculated with rhizobial and/or AM fungi relative to non-inoculated plants in a number of published studies. On average, photosynthetic rates were significantly increased by 28 and 14% due to rhizobial and AM symbioses, respectively, and 51% due to dual symbiosis. The leaf P mass fraction was increased significantly by 13% due to rhizobial symbioses. Although the increases were not significant, AM symbioses increased leaf P mass fraction by 6% and dual symbioses by 41%. The leaf N mass fraction was not significantly affected by any of the rhizobial, AM and dual symbioses. The rate of photosynthesis increased substantially more than the C costs of the rhizobial and AM symbioses. The inoculation of legumes with rhizobia and/or AM fungi, which resulted in sink stimulation of photosynthesis, improved the photosynthetic nutrient use efficiency and the proportion of seed yield in relation to the total plant biomass (harvest index). Sink stimulation represent an adaptation mechanism that allows legumes to take advantage of nutrient supply from their microsymbionts without compromising the total amount of photosynthates available for plant growth.     

Nutrient uptake in mycorrhizal plants – role of earthworms

Both arbuscular mycorrhizal fungi (AMF) and earthworms often coexist in agriculture ecosystems, but very little is known on the interactions between them. A two-compartment air gap-incorporating device was used to investigate the effects of three species of earthworm (epigeic Eisenia foetida, endogeic Aporrectodea trapezoide, and anecic Pheretima guillelmi) on AMF (Glomus intraradices) under the exclusion of plant roots, and then on maize (Zea mays L.) performance and nutrients uptake. Results showed a strong correlation between hyphal length density and subsequent plant growth and nutrient uptake. Earthworms improved soil nutrients availability in hyphal compartment (HC): E. foetida improved the concentration of soil inorganic N, A. trapezoide changed the concentration of available phosphate in the soil, and P. guillelmi changed the soil's physical properties. We found some indications that different species of earthworm and AMF might interact within the soil. Earthworms and AMF mainly acting on different nutrients create distinct niches for plants. The feeding and burrowing activities did not significantly destroy hyphal length density and made negative affect on plant performance.     

Acid phosphatase activity and vesicular‐arbuscular mycorrhizal infection associated with roots of four wheat cultivars

Acid phosphatase activity and vesicular‐arbuscular mycorrhizal (VAM) infection associated with four spring wheat genotype roots were investigated. Plants were grown in a typic low P volcanic soil with and without P‐fertilizer addition and harvested at 21, 42, 63, 84 and 96 days. Results show that phosphatase activity, expresed as ug p‐nitrophenol released per g dry root, decreased from 21 to 96 days in all cultivars. Conversely, trends of VAM infection were similar in all genotypes being higher in P added plants at 63 days after sown. This opposite effects may be viewed as alternative and/or complementary adaptations for P‐uptake by plants growing in low nutrient situations. It was concluded that one of the ways of P‐alleviation in wheat growing in our volcanic soils might be the search of genotypes having high biochemical and/or biological root activities.     

Inoculation of pines with mycorrhizal fungi in natural soils—II.: Effects of density and time of application of inoculum and phosphorus amendment on seedling yield

Addition of superphosphate at 40 kgP/ha greatly increased yield in seedlings of Pinus radiata D. Don, and P. elliottii Little and Dorman on two soils lacking fungi capable of forming mycorrhizas with Pinus. P could be partially replaced by increasing inoculum density or avoiding delay in inoculation. Chlamydospores were less effective than basidiospores as inoculum, and there were highly significant differences in yield produced by different fungal species at high inoculum densities and in the presence of added P. These effects are discussed with respect to the intensity of mycorrhizal infection and postulated differences in sensitivity to microbial competition and antagonism.     

Relative effectiveness of phosphorus on narrow‐leaf and broadleaf birdsfoot trefoil growth and the effect of added phosphorus on vesicular arbuscular mycorrhizal infection

The relative effectiveness of phosphorus (P) applications on growth and the effect of added P on the extent of infection of roots of narrowleaf birsfoot trefoil (Lotus tenuis) and of broadleaf birdsfoot trefoil (Lotus corniculatus) by an indigenous VAM fungi (Glomus sp.) was studied on a P‐deficient soil (Typic Natraquoll). In terms of rate of increase of shoot growth per unit of added P, broadleaf was more efficient than narrowleaf birsdfoot trefoil but they did not differ in the relative effectiveness of P for growth. For the two Lotus species, when increasing the level of added P there was an initial increase in the percentage of root length infected, and then with further additions, there was a consistent decrease of the infection. For narrowleaf, the maximum percentage of root length infected was when plants reached 11% of their maximum shoot growth. Whereas for broafleaf, the maximum percentage of root infected was when plants reached the 66% of their maximum shoot growth. Despite differences in both, the shape of the response curve of shoot growth to P and the extent of infection between Lotus species, they did not differ in their ability to utilize the P that had reacted with the soil for a period of time.     

Vesicular-arbuscular mycorrhizal infection of “host” and “non-host” plants: Effect on the growth responses of the plants and competition between them

The effect of host plant infection on the mycorrhizal response of non-host plants was examined in a double pot system. The absence of nutrient transfer from a mature host (sorghum) to a young-non-host (cabbage) indicates the inability of the atypical infection of non-host plants to take up nutrients. However, nutrient transfer between mature and young sorghum plants, possibly through mycelial connections, was observed. The direction of this nutrient transfer seemed to depend on the nutrient status of the nurse plant. Because the nurse plants were grown in P-deficient soil, mature sorghum competed with young sorghum plants. Sorghum infected with vesicular-arbuscular (VA) mycorrhiza was better equipped than non-infected sorghum to compete with young cabbage for soil nutrients.     

Effects of vesicular arbuscular mycorrhizal inoculation on growth and phosphorus nutrition of barley in natural or methyl bromide‐treated soil

The growth and phosphorus (P) nutrition of barley (Hordeum vulgare L.) in a soil, methyl bromide fumigated or untreated and supplied with or without mycorrhizal inoculum, was studied in pots placed under a field environment. Inoculation significantly raised the overall levels of vesicular arbuscular mycorrhizal (VAM) infection. The relative increase was significantly greater in sterile than nonsterile soil. Soil sterilization produced significantly higher dry matter throughout the experiment. Inoculation resulted in a significant growth depression earlier in the season which could not be offset by the following mycorrhizal enhancement in P absorption rates. The primary reasons for this yield depression were most probably the root density and available P status of the soil which might have been over the threshold limit for positive mycorrhizal yield response in barley. In this experiment, the result of inoculation could be regarded beneficial considering 17 and 30% higher P concentrations in grain and straw, respectively, but detrimental with respect to 20% loss in grain plus straw yield.     

Diversity of arbuscular mycorrhizal fungi associated with the rhizosphere of tea growing in ‘natural’ and ‘cultivated’ ecosites

The colonization and diversity of arbuscular mycorrhizal fungi (AMF) associated with the rhizosphere of tea [Camellia sinensis (L.) O. Kuntze] growing under ‘natural’ as well as ‘cultivated’ conditions in the Kumaun region of Uttaranchal Himalaya (India), during the periods of active growth and dormancy were investigated. Root and rhizosphere soil samples, collected from both the ecosites (natural and cultivated), were monitored for root colonization. While the percent root colonization was quite high (77.66 ± 4.40 and 86.40 ± 3.02%, in the natural and cultivated tea, respectively) during the period of active growth in both the ecosites, relatively higher colonization (97.33 ± 0.78 and 98.13 ± 0.80%, in the natural and cultivated tea, respectively) was recorded during the period of dormancy. The rhizosphere of cultivated tea bushes was found to be dominated by Glomus morhpotypes (88.89% of the total isolates) along with three morphotypes of Acaulospora; occurrence of 35 morphotypes belonging to four genera viz. Acaulospora (11.43%), Gigaspora (11.43%), Glomus (68.57%) and Scutellospora (8.57%) was recorded in the rhizosphere of tea plants from the natural ecosite. A total of 51 AMF morphotypes were detected. Shannon–Weaver index of diversity was higher (1.80 ± 0.13 and 2.05 ± 0.10 during periods of active growth and dormancy, respectively) at the species level for the natural ecosite over its counterparts from the cultivated ecosite. Values for the diversity indices of natural and cultivated ecosites did not show much variation in the period of dormancy. These data suggest that collectively, various cultural practices negatively affect AMF diversity at the genus level in tea plantations of the colder regions.     

Inoculation of pines with mycorrhizal fungi in natural soils—III: Effect of soil fumigation on rate of infection and response to inoculum density

Pinus radiata seedlings were inoculated with basidiospores of Rhizopogon roseolas and Suillus granulatus, and with chlamylospores of two unidentified but highly effective mycorrhizal fungi in undisturbed cores of natural soil fumigated with methyl bromide. Fumigation stimulated mycorrhizal infection rate and enhanced the response of seedlings to increasing concentrations of both inoculum types, but the effect of chlamydospore inoculum was more favoured by fumigation than that of basidio-spores. Chlamydospore inocula appear more sensitive to competitive and antagonistic soil microorganisms than basidiospores. Soil fumigation appears a necessary adjunct to the use of chlamydospores as inoculants in nurseries and is discussed in relation to nursery culture of pines.     

Genotypic variation in vesicular‐arbuscular mycorrhizal dependence of the pejibaye palm

Two experiments were undertaken to determine the degree of mycorrhizal dependency of pejibaye (Bactris gasipaes, Palmae) seedling progenies from two Amazonian (Pampa Hermosa; Putumayo) and one Central American (Guatuso) land races. Plants were grown in subsurface samples of either an Oxisol (the Amazonian progenies) or an Ultisol, with or without inoculation with the vesicular‐arbuscular mycorrhizae fungus (VAMF) Glomus aggregatum, at three concentrations of soil solution phosphorous (P). VAMF inoculation enhanced leaf phosphorus (P) concentration and dry matter accumulation at the intermediate soil P concentration in all progenies. Dry matter accumulation was enhanced by 17%, 54%, and 64% in the Pampa Hermosa, Putumayo, and Guatuso progenies, respectively. They are therefore classified as being marginally (Pampa Hermosa) or highly dependent. This infra‐specific genetic variation with respect to mycorrhizal dependency merits further study for possible exploitation in plant improvement for sustainable agriculture.     

The sensitivity of three vesicular‐arbuscular mycorrhizal species to simulated erosion

Abstract

A greenhouse experiment was conducted to determine the effectiveness of three vesicular‐arbuscular mycorrhizal (VAM) species in an Oxisol subjected to simulated erosion using Leucaena leucocephala as an indicator host. The extent of colonization of leucaena roots increased significantly due to VAM inoculation of the eroded and uneroded soils. The highest level of VAM colonization was observed when leucaena was grown in association with Glomus aggregatum. followed by G. mosseae and G. etunicatum. Increased infection associated with inoculation of the eroded soil did not result in enhanced mycorrhizal effectiveness. Inoculation of the uneroded soil, however, led to significant improvement in root colonization as well as in symbiotic effectiveness. Suppression in expression of mycorrhizal effectiveness in the eroded soil appears to be a result of nutrient deficiency. The results suggest the importance of restoring lost nutrients before differences in VAM species could be effectively exploited for a successful establishment of a mycorrhizal plants in eroded soils.     

Effects of benomyl on vesicular‐arbuscular mycorrhizal infection of red clover (Trifolium pratense L.) and consequences for phosphorus inflow.

The roots of red clover plants inoculated with the vesicular‐arbuscular mycorrhizal fungus Glomus clarus Nicolson & Schenck were treated with a drench of benomyl at a time when mycorrhizal infection was already well established. Benomyl halted further infection and reduced phosphorus inflow by one order of magnitude compared to untreated controls. The fungicide also decreased the rate of plant growth probably as a consequence of reduced phosphorus inflow.     

Stable isotope labelling of earthworms can help deciphering belowground–aboveground interactions involving earthworms,mycorrhizal fungi,plants and aphids

Functional relationships between belowground detritivores and/or symbionts and aboveground primary producers and their herbivores are not well studied. In a factorial greenhouse experiment we studied interactions between earthworms (addition/no addition of Lumbricus terrestris; Clitellata: Lumbricidae) and arbuscular-mycorrhizal fungi (AMF; with/without inoculation of Glomus mosseae; Glomerales: Glomeraceae) on the leguminous herb Trifolium repens (Fabales: Fabaceae) and associated plant aphids (Aphis gossypii, A. craccivora; Hemiptera: Aphidoidea). In order to be able to trace organismic interactions, earthworms were dual-labelled with stable isotopes (¹⁵N-ammonium nitrate and ¹³C-glucose). We specifically wanted to investigate whether (i) isotopic signals can be traced from the labelled earthworms via surface castings, plant roots and leaves to plant aphids and (ii) these compartments differ in their incorporation of stable isotopes. Our results show that the tested organismic compartments differed significantly in their ¹⁵N isotope enrichments measured seven days after the introduction of earthworms. ¹⁵N isotope incorporation was highest in casts followed by earthworm tissue, roots and leaves, with lowest ¹⁵N signature in aphids. The ¹³C signal in roots, leaves and aphids was similar across all treatments and is for this reason not recommendable for tracing short-term interactions over multitrophic levels. AMF symbiosis affected stable isotope incorporation differently in different subsystems: the ¹⁵N isotope signature was higher below ground (in roots) but lower above ground (leaves and aphids) in AMF-inoculated mesocosms compared to AMF-free mesocosms (significant subsystem × AMF interaction). Aphid infestation was unaffected by AMF and/or earthworms. Generally, these results demonstrate that plants utilize nutrients excreted by earthworms and incorporate these nutrients into their roots, leaf tissue and phloem sap from where aphids suck. Hence, these results show that earthworms and plant aphids are functionally interlinked. Further, ¹⁵N-labelling earthworms may represent a promising tool to investigate nutrient uptake by plants and consequences for belowground-aboveground multitrophic interactions.     

Effects of epigeic earthworm (Eisenia fetida) and arbuscular mycorrhizal fungus (Glomus intraradices) on enzyme activities of a sterilized soil–sand mixture and nutrient uptake by maize

A pot experiment was conducted to investigate the effect of epigeic earthworm (Eisenia fetida) and arbuscular mycorrhizal (AM) fungi (Glomus intraradices) on soil enzyme activities and nutrient uptake by maize, which was grown on a mixture of sterilized soil and sand. Maize plants were grown in pots inoculated or not inoculated with AMF, treated or not treated with earthworms. Wheat straw was added as a feed source for earthworms. Mycorrhizal colonization of maize was markedly increased in AM fungi inoculated pots and further increased by addition of epigeic earthworms. AM fungi and epigeic earthworms increased maize shoot and root biomass, respectively. Soil acid phosphatase activity was increased by both earthworms and mycorrhiza, while urease and cellulase activities were only affected by earthworms. Inoculation with AM fungi significantly (p?<?0.001) increased the activity of soil acid phosphatase but decreased soil available phosphorus (P) and potassium (K) concentrations at harvest. Addition of earthworms alone significantly (p?<?0.05) increased soil ammonium-N content, but decreased soil available P and K contents. AM fungi increased maize shoot weight and root P content, while earthworms improved N, P, and K contents in shoots. AM fungi and earthworm interactively increased maize shoot and root biomass through their regulation of soil enzyme activities and on the content of available soil N, P, and K.     

Host–pathogen interaction of maize (Zea mays L.) and Aspergillus niger as influenced by arbuscular mycorrhizal fungi (Glomus deserticola)

This study was carried out to investigate the interaction of maize and Aspergillus niger as influenced by arbuscular mycorrhizal fungi (AMF). Three quality protein maize (QPM) genotypes (ILE1-OB, ART-98-SW5-OB and ART-98-SW6-OB) and two market accessions (Ilishan and Shagamu) were evaluated in a pot experiment conducted under natural environment conditions at the Research and Teaching Farm of Babcock University, Ogun State, Nigeria. AMF (Glomus deserticola) in mixtures of soil and root fragments was inoculated at the rate of 15 g per plant, while maize was artificially infected with A. niger (15 cfu ml^?1) in each designated pots. The coefficient of emergence (COV), percentage emergence (% E) and disease severity were determined using standard methods. Generally, plants treated with AMF only produced the highest cumulative cob yield (18 g), followed by plants treated with AMF and A. niger (15 g) and then control (12 g), while the least was recorded for only A. niger-treated plants (4 g).     

Agronomic bio-fortification and quality enhancement in okra–pea cropping system through arbuscular mycorrhizal fungi at varying phosphorus and irrigation regimes in Himalayan acid alfisol

A field experimentation was conducted during 2009-2011 at CSK Himachal Pradesh Agricultural University, Palampur, India characterized with wet-temperate climate and acid Alfisol soil having medium available phosphorus content. The study aimed at bio-fortification and quality enhancement of okra (Abelmoschus esculentus)–pea (Pisum sativum) cropping system through arbuscular mycorrhizal fungi (AMF) (Glomus mosseae) at varying inorganic phosphorus (50, 75, and 100% soil-test-based recommended P dose) and irrigation regimes (40 and 80% available water capacity) in a Himalayan acid Alfisol. The results revealed that AMF and inorganic P significantly enhanced the concentrations and uptake of various primary [nitrogen (N), phosphorus (P), and potassium (K)]; secondary [calcium (Ca)]; and micronutrients [iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), boron (B), and molybdenum (Mo)] in okra and pea crops. However, effects of varying irrigation regimes were found to be nominal. In okra, AMF inoculation considerably enhanced N, P, K, B, and Mo uptake by 5, 19, 3, 4, and 15%, respectively, over their non-AMF counterparts. Likewise in pea, a higher amount of N (10%), P (26%), K (7%), Fe (7%), Cu (38%), Zn (20%), Mn (4%), B (7%), and Mo (13%) uptake was registered through AMF inoculation over their non-AMF counterparts. Application of soil-test-based P dose from 50% to 100% P also resulted in significant and consistent improvement in N, P, K, B, and Mo uptake both in okra and pea and in Zn, Cu, Mn, and Fe uptake in pea crop. Magnitude of increase in Ca content was to the tune of 13 and 4%, respectively, in okra fruits and pea pods following AMF inoculation, whereas crude protein content enhanced by 4% each in both the crops. Overall, the current study demonstrates the important role of AMF in nutrient enrichment and quality enhancement of okra and pea crops in acid Alfisol, besides considerable reduction in investment on chemical fertilizers. Results of current study suggest that AMF use in Himalayan production systems is of tremendous significance to harvest nutritionally-rich farm produce for Himalayan communities suffering from malnutrition especially anemia and Zn deficiency, and equally to resource-poor Himalayan farmers who ill-afford expensive external inputs.     

Effects of iron nutritional status and time of day on concentrations of phytosiderophores and nico‐tianamine in different root and shoot zones of barley

The diurnal pattern in concentrations of phytosiderophores (PS) and its precursor nicotianamine (NA) was studied in different root and shoot zones of iron (Fe)‐sufficient and Fe‐deficient barley (Hordeum vulgare L. cv. Europa) grown in nutrient solution. Roots were separated into apical (0–3 cm) and basal zones (>3 cm) and shoots into young (3 cm basal zones of youngest two leaves) and old (remaining zones of youngest two leaves and oldest leaf) parts. The main PS in barley was identified as epi‐hydroxymugineic acid (epi‐HMA). Regardless of the sampling zone and time of day, epi‐HMA concentrations were several times higher in Fe‐deficient than in Fe‐sufficient plants and several times higher in the roots than in the shoots. In roots and shoots, epi‐HMA concentrations were always higher in the younger compared with the older zones. In both root zones of Fe‐deficient plants, an inverse diurnal rhythm occurred in epi‐HMA concentrations and in its release by the roots. In contrast, such a rhythm was absent in roots of Fe‐sufficient plants and in the shoots regardless of the Fe nutritional status. Nicotianamine concentrations in roots were not affected by the Fe nutritional status in apical zones but slightly enhanced under Fe deficiency in basal zones. In contrast to roots, NA concentrations in both shoot parts were lower in Fe‐deficient than in Fe‐sufficient plants. Regardless of the Fe nutritional status in roots and shoots, NA concentrations were higher in young than in old parts and no consistent diurnal variations were observed. The results suggest that PS are also synthesized in the shoot, although at much lower rates than in roots. As with roots, PS synthesis in the shoot is enhanced under Fe deficiency and is mainly localized in young growing tissue. The distinct diurnal rhythm in PS release in roots is apparently not regulated by variation in the rate of PS synthesis during the day.