AM Fungi Endow Greater Plant Biomass and Soil Nutrients under Interspecific Competition Rather Than Nutrient Releases for Litter

Plant competition affects belowground ecological processes, such as litter decomposition and nutrient release. Arbuscular mycorrhizal (AM) fungi play an essential role in plant growth and litter decomposition potentially. However, how plant competition affects the nutrient release of litter through AM fungi remains unclear especially for juvenile plants. In this study, a competitive potting experiment was conducted using juvenile seedlings of Broussonetia papyrifera and Carpinus pubescens from a karst habitat, including the intraspecific and interspecific competition treatments. The seedlings were inoculated by AM fungus or not inoculated, and the litter mixtures of B. papyrifera and C. pubescens were added into the soil or not added. The results were as follows: Litter addition significantly increased the root mycorrhizal colonization of two species in intraspecific competition. AM fungus significantly increased the biomass of B. papyrifera seedings and nitrogen release and decreased nitrogen concentration and N/P ratio of litter and further improved the total nitrogen and N/P ratio of soil under litter. The interspecific competition interacting with AM fungus was beneficial to the biomass accumulation of B. papyrifera and improvement of soil nutrients under litter. However, intraspecific competition significantly promoted nutrient releases via AM fungus. In conclusion, we suggest that AM fungi endow greater plant biomass and soil nutrients through interspecific competition, while intraspecific competition prefers to release the nutrients of litter.

Arbuscular Mycorrhizal Colonization Increased Above-Belowground Feedback of Maize In a Degraded Coal Mining Area Soil By Increasing The Photosynthetic Carbon Assimilation And Allocation of Mazie

A three-compartment culture system was used to study the mechanism by which the AM fungus Funneliformis mosseae influences host plant growth and soil organic carbon (SOC) content in a coal mining area. A 13CO2 pulse tracing technique traced the allocation of maize photosynthetic C in shoots, roots, AM fungus and soil to detect C accumulation and allocation in mycorrhizal (inoculated with Funneliformis mosseae) and non-mycorrhizal treatments.AM fungal inoculation significantly increased the 13C concentration and content in both above- and below-ground plant parts. Mycorrhizal inoculation significantly enhanced the anti-aging ability by increasing soluble sugars and catalase activity (CAT) in maize leaves while reducing foliar malondialdehyde content (MDA) and leaf temperature to promote plant growth. AM fungi also increased P uptake to promote maize growth. Soil organic carbon (SOC), glomalin, microbial biomass carbon (MBC) and nitrogen (MBN) contents increased significantly after inoculation. A mutually beneficial system was established involving maize, the AM fungus and the microbiome, and the AM fungus became an important regulator of C flux between the above- and below-ground parts of the system. Inoculation with the AM fungus promoted plant growth, C fixation and allocation belowground to enhance soil quality. The positive above-belowground feedback appeared to be established.

Arbuscular Mycorrhizal Fungi in Agriculture

Arbuscular mycorrhizal (AM) fungi are biotrophic symbionts forming close relationships with an estimated 80% of terrestrial plants suitable as their host. Via an established AM fungal–host relationship, soil-bound nutrients are made available to the host plant through root cortical arbuscules as the site of exchange. At these sites, photosynthetic carbohydrates are provided to the AM fungus—carbohydrates that cannot be produced by the fungus. AM fungal–host symbiosis is very sensitive to soil disturbance, for example, agricultural tillage practices can damage and reduce AM fungal abilities to interact with a host and provide plant growth-promoting properties.

Effect of Oil Cakes and Bio-agents Each Alone and in Combination for Management of Root Knot Nematode (Meloidogyne incognita) in Green Gram

A pot experiment was carried out in the net house of Department of Nematology, OUAT, Bhubaneswar, Odisha, India during June to August, 2017 on the application of oilcakes (mustard cake and neem cake) and bio-agents (Trichoderma viride, Glomus fasciculatum, Rhizobium leguminosarum) each alone and in combination for the management of root knot nematode (Meloidogyne incognita) in green gram. Result of the experiment indicated that soil application of mustard or neem cake @ 50 g m-2 with AM fungus (Glomus fasciculatum) @ 5 g m-² and seed treatment of Rhizobium @ 25 g kg-1 of green gram seed declined the root knot nematode population, number of galls plant-1, number of eggmass plant-1and root knot index with corresponding increase of plant growth parameters and chlorophyll content in green gram plant as compared to other treatments and untreated check. But integration of mustard cake @ 50 g m-2 at 2 weeks prior to sowing with AM fungus @ 5 g m-2 at 10 days before sowing and seed treatment of Rhizobium @ 25 g kg-1 green gram seed exhibited the lowest M. incognita population 200 cc soil-1 (153.33 J2), number of galls plant-1 (7.0), number of eggmass plant-1 (2.0) and root knot index (2.0) reflecting enhancement of plant growth parameters, number of pods (206.67%), number of nodules (691.17%) over untreated check. This integrated management module also recorded maximum increase in the availability of NPK content in soil and chlorophyll content as compared to other treatments.

Target of rapamycin, PvTOR, is a key regulator of arbuscule development during mycorrhizal symbiosis in Phaseolus

Target of rapamycin (TOR) is a conserved central growth regulator in eukaryotes that has a key role in maintaining cellular nutrient and energy status. Arbuscular mycorrhizal (AM) fungi are mutualistic symbionts that assist the plant in increasing nutrient absorption from the rhizosphere. However, the role of legume TOR in AM fungal symbiosis development has not been investigated. In this study, we examined the function of legume TOR in the development and formation of AM fungal symbiosis. RNA-interference-mediated knockdown of TOR transcripts in common bean (Phaseolus vulgaris) hairy roots notably suppressed AM fungus-induced lateral root formation by altering the expression of root meristem regulatory genes, i.e., UPB1, RGFs, and sulfur assimilation and S-phase genes. Mycorrhized PvTOR-knockdown roots had significantly more extraradical hyphae and hyphopodia than the control (empty vector) roots. Strong promoter activity of PvTOR was observed at the site of hyphal penetration and colonization. Colonization along the root length was affected in mycorrhized PvTOR-knockdown roots and the arbuscules were stunted. Furthermore, the expression of genes induced by AM symbiosis such as SWEET1, VPY, VAMP713, and STR was repressed under mycorrhized conditions in PvTOR-knockdown roots. Based on these observations, we conclude that PvTOR is a key player in regulating arbuscule development during AM symbiosis in P. vulgaris. These results provide insight into legume TOR as a potential regulatory factor influencing the symbiotic associations of P. vulgaris and other legumes.

Different Arbuscular Mycorrhizal Fungi Cocolonizing on a Single Plant Root System Recruit Distinct Microbiomes

<p>Plant roots are usually colonized by various arbuscular mycorrhizal (AM) fungal species, which vary in morphological, physiological, and genetic traits. This colonization constitutes the mycorrhizal nutrient uptake pathway (MP) and supplements the pathway through roots. Simultaneously, the extraradical hyphae of each AM fungus is associated with a community of bacteria. However, whether the community structure and function of the microbiome on the extraradical hyphae differ between AM fungal species remains unknown. In order to understand the community structure and the predicted functions of the microbiome associated with different AM fungal species, a splitroot compartmented rhizobox cultivation system, which allowed us to inoculate two AM fungal species separately in two root compartments, was used. We inoculated two separate AM fungal species combinations, (i) F<em>unneliformis mosseae</em> and <em>Gigaspora margarita</em> and (ii) <em>Rhizophagus intraradices </em>and <em>G. margarita</em>, on a single root system of cotton. The hyphal exudate-fed, active microbiome was measured by combining <sup>13</sup>C-DNA stable isotope probing with MiSeq sequencing. We found that different AM fungal species, which were simultaneously colonizing a single root system, hosted active microbiomes that were distinct from one another. Moreover, the predicted potential functions of the different microbiomes were distinct. We conclude that the arbuscular mycorrhizal fungal component of the system is responsible for the recruitment of distinct microbiomes in the hyphosphere. We found that arbuscular mycorrhizal fungi cocolonizing on single plant roots recruit their own specific microbiomes, which should be considered in evaluating plant microbiome form and function. Our findings demonstrate the importance of understanding trophic interactions in order to gain insight into the plant-AM fungus-bacterium symbiosis</p>

Interaction Effect of Soilless Media and Organic Amendments for Eco-Friendly Root-Knot Nematode Management in Brinjal and Tomato Nursery

Brinjal and tomato are the most important transplanted vegetable crops of the Solanaceae family. The successful cultivation of these crops is vital for meeting the nutritional dietary requirement of India’s population and earning foreign exchange for the country by exporting vegetables to foreign countries. However, there are several abiotic and biotic impediments in the cultivation of these crops. Among biotic impediments , plant-parasitic nematodes have become one of the critical factor adversely affecting the cultivation of these vegetables. In general, Meloidogyne spp. (root-knot nematode) is the most common, widespread and economically damaging plant parasitic nematode species in tomato and brinjal crop. In addition to the damage caused by root – knot nematode, it stimulates the entry of soil-borne pathogens leading to development of the disease complex. The present study was undertaken to study the interaction effect of soil & soilless growing media viz. cocopeat and vermicompost along with organic amendments i.e., Trichoderma, AM fungus, and Cabbage residue incorporated individually as well as in different combinations for eco-friendly root-knot nematode management in brinjal and tomato nursery. The results indicated that treatment C-8 (Cocopeat + Trichoderma + AM fungus + Cabbage residues) recorded the superior germination count, germination percentage, days to 50% germination, root length, shoot length, fresh weight, root weight, shoot weight and root: shoot ratio. It is pertinent to mention that the soilless media, along with various organic amendments, were found to be superior for all the root and shoot attributes as compared to the conventional soil media for growing healthy nursery of tomato and brinjal in root knot nematode infested geographies. Our findings provide an effective and sustainable method of growing healthy plant nursery in nematode infested regions.

Regulation of development of arbuscular-mycorrhizal symbiosis by alternative splicing in garden pea (Pisum sativum L.)

836 differentially expressed genes were detected in the roots of P. sativum in response to inoculation with AM fungus. 126 genes showing differential splicing were also detected.

Effect of the AM Fungus Sieverdingia tortuosa on Common Vetch Responses to an Anthracnose Pathogen

Colletotrichum lentis Damm causes anthracnose in Vicia sativa L, otherwise known as common vetch. It was first reported in China in 2019. This study evaluates the effects of the arbuscular mycorrhizal (AM) fungus Sieverdingia tortuosa (N.C. Schenck & G.S. Sm.) Błaszk., Niezgoda, & B.T. Goto on growth and disease severity in common vetch. Our main finding is that the AM fungus increased root biomass and reduced anthracnose severity of common vetch. Responses correlated with defense, such as chitinase activity, polyphenol oxidase (PPO) activity, the concentrations of jasmonic acid and proline, and the expression of resistance-related genes (e.g., upregulated “signal transduction,” “MAPK signaling pathway,” “chitinase activity,” “response to stress,” and the KEGG pathways “phenylpropanoid biosynthesis,” “MAPK signaling pathways,” and “plant-pathogen interactions”), were also affected These findings provide insight into the mechanism by which this AM fungus regulates the defense response of common vetch to C. lentis.

Different Arbuscular Mycorrhizal Fungi Cocolonizing on a Single Plant Root System Recruit Distinct Microbiomes

ABSTRACTPlant roots are usually colonized by various arbuscular mycorrhizal (AM) fungal species, which vary in morphological, physiological, and genetic traits. This colonization constitutes the mycorrhizal nutrient uptake pathway (MP) and supplements the pathway through roots. Simultaneously, the extraradical hyphae of each AM fungus is associated with a community of bacteria. However, whether the community structure and function of the microbiome on the extraradical hyphae differ between AM fungal species remains unknown. In order to understand the community structure and the predicted functions of the microbiome associated with different AM fungal species, a split-root compartmented rhizobox cultivation system, which allowed us to inoculate two AM fungal species separately in two root compartments, was used. We inoculated two separate AM fungal species combinations, (i) Funneliformis mosseae and Gigaspora margarita and (ii) Rhizophagus intraradices and G. margarita, on a single root system of cotton. The hyphal exudate-fed, active microbiome was measured by combining 13C-DNA stable isotope probing with MiSeq sequencing. We found that different AM fungal species, which were simultaneously colonizing a single root system, hosted active microbiomes that were distinct from one another. Moreover, the predicted potential functions of the different microbiomes were distinct. We conclude that the arbuscular mycorrhizal fungal component of the system is responsible for the recruitment of distinct microbiomes in the hyphosphere. The potential significance of the predicted functions of the microbial ecosystem services is discussed.IMPORTANCE Arbuscular mycorrhizal (AM) fungi form tight symbiotic relationships with the majority of terrestrial plants and play critical roles in plant P acquisition, adding a further dimension of complexity. The plant-AM fungus-bacterium system is considered a continuum, with the bacteria colonizing not only the plant roots, but also the associated mycorrhizal hyphal network, known as the hyphosphere microbiome. Plant roots are usually colonized by different AM fungal species which form an independent phosphorus uptake pathway from the root pathway, i.e., the mycorrhizal pathway. The community structure and function of the hyphosphere microbiome of different AM species are completely unknown. In this novel study, we found that arbuscular mycorrhizal fungi cocolonizing on single plant roots recruit their own specific microbiomes, which should be considered in evaluating plant microbiome form and function. Our findings demonstrate the importance of understanding trophic interactions in order to gain insight into the plant-AM fungus-bacterium symbiosis.