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The survival and productivity of potato plantlets transplanted from in vitro to commercial hydroponic minituber culture are crucial. Mycorrhizal fungi are an efficient tool to enhance potato nutrient uptake, survival, and productivity under these conditions. This study aimed to assess the effect of mycorrhizal fungi on improving the yield of minitubers and nutrient uptake in potatoes transferred from the in vitro environment to the greenhouse. This study was conducted in a greenhouse in Hamadan province, I.R. Iran, in 2013. The experimental design was factorial, including treatments with and without inoculation with the mycorrhizal fungus Rhizophagus irregularis and varying phosphorus (P) concentrations in Hoagland's solution (100%, 75%, 50%, and 25% of its maximum content, i.e. 0.965, 0.482, 0.241, and 0.12 mM H2PO4-) with three replications on potato plantlets transferred from in vitro to pots. The results indicated that the highest colonization percentage was achieved with 25% P and inoculation. The highest number of minitubers (8.9), total minituber weight per plant (53.2 grams), plant height (54.6 cm), minituber (0.38%) and leaf (0.363%) P content, minituber (33 mg/kg) and leaf (65 mg/kg) manganese (Mn) content, and minituber (38 mg/kg) and leaf (65 mg/kg) zinc (Zn) content were obtained with inoculation and 75% P of Hoagland nutrient solution, which was statistically comparable to the inoculation with 100% P treatment. In summary, inoculating potato plantlets with mycorrhiza can enhance minituber yield and nutrient uptake and potentially replace approximately 50% of the P requirement in hydroponic solutions. [ABSTRACT FROM AUTHOR]

The coming century in agriculture will be marked by increasing exposure of crops to abiotic stress and disease due to climate change. The plant traits with the strongest potential to mitigate these stresses are complex, and are increasingly recognized to involve interaction with the microbiome. Through symbiosis with soil fungi, plants form arbuscular mycorrhizae (AM) that can alleviate nutrient, water, and temperature stress, and can confer pathogen resistance and increased yield. The portfolio of advantages offered by AM overlaps with the benefits of agriculturally useful plant traits that have been the subject of decades of intensive biotechnological efforts, such as C4 photosynthesis and rhizobial nitrogen fixation. In this article we illustrate the prospective benefits of genetic engineering to produce AM in nonmycorrhizal plants and modify AM in already-mycorrhizal crops. We highlight recent advances which have clarified the key genetic and metabolic components of AM symbiosis, and show that many of these components are involved in other plant biological processes and have already been subject to extensive genetic engineering in nonsymbiotic contexts. We provide a theoretical research roadmap to accomplish engineering of AM into the nonmycorrhizal model Arabidopsis including specific molecular genetic approaches. We conclude that AM is potentially more tractable than other complex plant traits, and that a concerted research initiative for biotechnological manipulation of AM could fill unique needs for agricultural resilience. Finally, we note that engineering of AM provides a potential back door into manipulation of other essential plant traits, including carbon storage, and beneficial microbiome assembly. [ABSTRACT FROM AUTHOR]

Root colonization by arbuscular mycorrhizal (AM) fungi has traditionally been analyzed by microscopy. However, this method is time consuming and it is often difficult to distinguish between AM and non-AM fungi. In this study, we analyzed the fatty acid profiles in soybean roots colonized by AM fungi to determine if specific fatty acids derived from AM fungi can be used as markers for the intensity of the AM fungal colonization. The wild-type Enrei and hypernodulating Kanto100 soybean cultivars were inoculated with an AM fungus (Gigaspora rosea) alone or with Bradyrhizobium diazoefficiens, which nodulates soybean roots. Fatty acids 20:1ω9, 20:4ω6, and 20:5ω3 were specifically detected in the lateral roots of AM fungus-inoculated and dual-inoculated soybean plants. In the second lateral roots, the percentage of AM-specific fatty acids (i.e., 20:1ω9, 20:4ω6, and 20:5ω3) derived from AM fungi was closely correlated with the intensity of the AM fungal colonization. We propose that the AM-specific fatty acids represent useful markers for estimating the degree of AM fungal colonization. The percentage of AM-specific fatty acids was more than twofold higher in the second lateral roots than in the first lateral roots. Thus, the degree of AM fungal colonization is probably twofold higher in the second lateral roots than in the first lateral roots. [ABSTRACT FROM AUTHOR]

Phosphorus (P) behavior and its efficiency in mycorrhizal plants are of great importance. The objective was to evaluate the behavior of soil labeled P absorbed by different mycorrhizal wheat genotypes subjected to saline water. Three wheat genotypes including cultivar Kavir, the local cultivar Roshan, and the mutated line Tabasi T-65-7-1 were inoculated with different species of arbuscular mycorrhiza (AM) includingGlomus etunicatum, G. mosseae, andG. intraradices. Plants were irrigated using saline water (electrical conductivity of 13.87 dS m−1). The experiment was a factorial with 12 treatments and three replications under greenhouse conditions. Wheat genotypes and AM species significantly affected plant dry weight, specific activity, and total plant activity (P = 0.01). A maximum of 1.49-fold increase in specific activity or P uptake per gram of plant dry matter and 3.53-fold increase in plant activity or plant total P uptake resulted byG. etunicatumas compared with control. [ABSTRACT FROM AUTHOR]

Diverse forms of microorganisms present in the soil and near the roots of plants, which play a vital role in numerous physiological processes, have attracted the attention of scientists. The dynamic microbial associations may be saprophytic, pathogenic, or symbiotic. The most widespread symbiosis of plants is the mycorrhizal association between root-inhabiting fungi and the feeder roots of plants. The present study was conducted to study the effects of arbuscular mycorrhizal fungi on mineral nutrition ofVigna unguiculataandAbelmoschus esculentus. The experiment comprised of uninoculated seedlings and seedlings inoculated withGlomus mosseae. The chlorophyll a, chlorophyll b, total chlorophyll, carotenoid, protein, nitrate, nitrogen, and phosphorus content showed an increase in vesicular arbuscular mycorrhiza fungus-treated seedlings compared to non-mycorrhizal plants. The total soluble sugars and soluble starch content in leaves of all selected plant species in the present study showed a decrease in mycorrhizal seedlings compared to non-mycorrhizal seedlings. [ABSTRACT FROM PUBLISHER]

Recent research on arbuscular mycorrhizas has demonstrated that AM fungi play a significant role in plant phosphorus (P) uptake, regardless of whether the plant responds positively to colonization in terms of growth or P content. Here we focus particularly on implications of this finding for consideration of the balance between organic carbon (C) use by the fungi and P delivery (i.e. the C-P trade between the syrnbionts). Positive growth responses to arbuscular mycorrhizal (AM) colonization are attributed frequently to increased P uptake via the fungus, which results in relief of P deficiency and increased growth. Zero AM responses, compared with non-mycorrhizal (NM) plants, have conventionally been attributed to failure of the fungi to deliver P to the plants. Negative responses, combined with excessive C use, have been attributed to this failure. The fungi were viewed as parasites. Demonstration that the AM pathway of P uptake operates in such plants indicates that direct P uptake by the roots is reduced and that the fungi are not parasites but mutualists because they deliver P as well as using C. We suggest that poor plant growth is the result of P deficiency because AM fungi lower the amount of P taken up directly by roots but the AM uptake of P does compensate for the reduction. The implications of interplay between direct root uptake and AM fungal uptake of P also include increased tolerance of AM plants to toxins such as arsenate and increased success when competing with NM plants. Finally we discuss the new information on C-P trade in the context of control of the symbiosis by the fungus or the plant, including new information (from NM plants) on sugar transport and on the role of sucrose in the signaling network involved in responses of plants to P deprivation. [ABSTRACT FROM AUTHOR]

Two experiments were designed to investigate the effects of soil disturbance and organic P (Naphytate and lecithin) on mycorrhiza formation and symbiotic efficiency of AMF associated with maize in greenhouse. The results showed that P forms did not affect the root colonization of BEG167 and Glomus versifome (G.v) with maize. G.v produced more extraradical fungal biomass than BEG167 when KH2PO4 and lecithin were applied. The treatments with lecithin and KH2PO4 had higher maize biomass than those supplied with Na-phytate. BEG167 and G.v differed in maize biomass contribution when Na-phytate was applied. Soil disturbance reduced significantly root colonization, and significantly or slightly decreased shoot biomass and P uptake of maize colonized by BEG141. However, mycorrhiza development and symbiotic efficiency of G.v were not influenced by soil disturbance. On cellulose acetate membrane, numerous regeneration hyphae with anastomosis structure and dichotomous structure were observed. The results suggested that rapid recovery of extraradical hyphae of AMF might compensate the P contribution loss caused by soil disturbance and buffer the decrease of propagule reserve in soil ecosystem. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizae (AM) engage in the most common underground symbiosis that occurs with plants. More than 80% of the higher plants have the ability to form arbuscular mycorrhizal associations. Plants exchange carbohydrates and lipids for nutrients, especially phosphates from AM. Five billion tons of carbon are transferred from plants to fungi via AM each year, worldwide. The fungus in AM symbiosis forms hyphae outside the plant, which provide a connection between the soil and inner part of plant. Phosphorus is transported from the soil solution across the membrane of the hyphae, moves to the arbuscule, unloads from the fungal arbuscule at the arbuscule-cortical interface and is then taken up by the plant cortical cell. AM, in turn, derive carbon from the host plant in the form of hexose/sucrose, which is taken up at the interface and is converted to trehalose and glycogen, typical fungal carbohydrates. This review discusses the transfer of phosphate from soil to plant via AM and the carbon flux and metabolism in AM fungi. [ABSTRACT FROM AUTHOR]

Plant species in the subfamily Monotropoideae are mycoheterotrophs; they obtain fixed carbon from photosynthetic plants via a shared mycorrhizal network. Previous findings show mycoheterotrophic plants exhibit a high level of specificity to their mycorrhizal fungi. In this study we explore the association of mycorrhizal fungi and Monotropa uniflora (Monotropoideae: Ericaceae) in eastern North America. We collected M. uniflora roots and nearby basidiomycete sporocarps from four sites within a 100 km² area in eastern Massachusetts. We analyzed DNA sequences of the internal transcribed spacer region (ITS) from the fungal nuclear ribosomal gene to assess the genetic diversity of fungi associating with M. uniflora roots. In this analysis we included 20 ITS sequences from Russula sporocarps collected nearby, 44 sequences of Russula or Lactarius species from GenBank and 12 GenBank sequences of fungi isolated from M. uniflora roots in previous studies. We found that all 56 sampled M. uniflora mycorrhizal fungi were members of the Russulaceae, confirming previous research. The analysis showed that most of the diversity of mycorrhizal fungi spreads across the genus Russula. ITS sequences of the mycorrhizal fungi consisted of 20 different phylotypes: 18 of the genus Russula and two of Lactarius, based on GenBank searches. Of the sampled plants, 57% associated with only three of the 20 mycorrhizal fungi detected in roots, and of the 25 sporocarp phylotypes collected three, were associated with M. uniflora. Furthermore the results indicate that the number of different fungal phylotypes associating with M. uniflora of eastern North America is higher than that of western North America but patterns of fungal species abundance might be similar between mycorrhizae from the two locations. [ABSTRACT FROM AUTHOR]

Investigations were carried out with grape cv. Perlette to assess the influence of arbuscular mycorrhiza (AM) on breaking bud dormancy, and hastening flowering, berry set and berry ripening. Eighteen year old vines of Perlette, having uniform vigour and growth, planted at 2.5 × 2.5 m and trained on a telephone system, were inoculated with three strains of AM namely Glomus mossae, Glomus deserticola and Gigaspora calospora, when the root system was active in February. Treatments with FYM and inorganic NPK were maintained as checks. The grapevines inoculated with Glomus deserticola took significantly fewer days for bud sprouting, inflorescence emergence, 50% flowering, berry set and ripening compared with all other treatments. The observations are discussed in relation to observed changes in the soil pH and leaf nutrient status. Hastening of bud sprouting, flowering, berry set and ripening in AM treated plants helped in harvesting the fruits before the onset of rains and reduced the damage due to monsoons. It is suggested that AM strain Glomus deserticola can potentially be included in the fertilizer management practice as an alternative to chemical fertilizers for providing the plant nutrient requirement. [ABSTRACT FROM AUTHOR]

Mycorrhizal symbiosis is generally advantageous for plants in nutrient-poor soils, but this advantage may be low in arcto-alpine conditions. While the relative coverage of nonmycorrhizal plant species has been found to increase along an altitudinal gradient, the within-species patterns of mycorrhizal colonization in arctic and alpine plants are not well known, and different results have been obtained in relation to altitude. We investigated arbuscular mycorrhizal (AM) and dark-septate endophytic (DSE) root colonization in six subarctic herbaceous plants Ranunculus glacialis L., Saxifraga aizoides L., Sibbaldia procumbens L., Solidago virgaurea L., Trientalis europaea L., and Viola biflora L. along an altitudinal gradient (0-1400 m a.s.l.) at Mt. Paras, North Norway. We did not find any consistent decline in the different types of fungus colonization along the entire gradient. There was no statistically significant shift in coarse AM or DSE colonization with altitude. However, fine endophyte type AM colonization showed a statistically significant, positive relationship with altitude. These results suggest that root colonization of any particular mycorrhizal species may yield different gradient patterns with altitude than the relative coverages of mycorrhizal and nonmycorrhizal plant taxa. Because of its positive association with altitude, fine endophyte colonization may have a specific role in the nutrition of arctic and alpine plants. [ABSTRACT FROM AUTHOR]