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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]

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]

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]