Occurrence and richness of arbuscular mycorrizal fungi in vineyards with grapevine decline and dieback symptoms

ABSTRACT: This research identified arbuscular mycorrhizal fungi (AMF) in rhizosphere soil of grapevines with Grapevine Death and Decline symptoms (GDD) or asymptomatic healthy (H) plants, and characterized the relationship of AMF communities with soil chemical attributes. The AMF spore number ranged from 287 to 432 spores 50 cm-3 in soil with GDD plants, and from 357 to 464 spores 50 cm-3 in H plants, with no differences among vineyards or between GDD and H plants within each vineyard. We detected 42 species and 17 genera, and most taxa belonged to Acaulosporaceae or Glomeraceae. Claroideoglomus etunicatum, Funneliformis mosseae, and Archaeospora trappei were the most frequent species in all vineyards. Soil chemical attributes were not determinant for the occurrence of most fungal species; although, Entrophospora infrequens, Diversispora sp1 and Diversispora sp2 were associated with a vineyard having high soil copper. Vineyards harbor highly diverse AMF communities, which are determined by location.

Host-Specific Effects of Arbuscular Mycorrhizal Fungi on Two Caragana Species in Desert Grassland

Arbuscular mycorrhizal fungi (AMF), which form symbioses with most land plants, could benefit their hosts and potentially play important roles in revegetation of degraded lands. However, their application in revegetation of desert grasslands still faces challenges and uncertainties due to the unclear specificity of AMF-plant interactions. Here, Caragana korshinskii and Caragana microphylla were inoculated with either conspecific (home) or heterospecific (away) AM fungal communities from the rhizosphere of three common plant species (C. korshinskii, C. microphylla and Hedysarum laeve) in Kubuqi Desert, China. AMF communities of the inocula and their home and away effects on growth and nutrition status of two Caragana species were examined. Results showed that AMF communities of the three inocula from C. korshinskii, H. laeve and C. microphylla were significantly different, and were characterized by high abundance of Diversispora, Archaeospora, and Glomus, respectively. The shoot biomass, photosynthetic rate, foliar N and P contents of C. korshinskii only significantly increased under home AMF inoculation by 167.10%, 73.55%, 9.24%, and 23.87%, respectively. However, no significant effects of AMF on C. microphylla growth were found, regardless of home or away AMF. Positive correlations between C. korshinskii biomass and the abundance of AMF genus Diversispora were found. Our study showed strong home advantage of using native AMF community to enhance C. korshinskii growth in the desert and presented a potentially efficient way to use native AMF in restoration practices.

Arbuscular Mycorrhizae of Phormium Tenax in a restored New Zealand wetland across hydrological gradients

<p>New Zealand has lost over 90% of its former wetlands and many that remain are in a degraded state. Restoration projects are often impeded by the failure of native plants to establish back into non-native dominated communities. Phormium tenax is fast growing and acts a nurse plant in wetlands, accelerating the establishment of slower growing native woody species. The roles of below ground organisms are increasingly recognised as affecting plant community dynamics, and this study investigates the diversity of a group of pervasive organisms, the arbuscular mycorrhizal fungi (AMF), growing in symbiosis with Phormium tenax. Next generation sequencing was used to create two libraries to determine the sensitivity of coding and non-coding molecular markers when characterising the AMF community associated with Phormium tenax. AMF communities colonising individual plants were found to be diverse, and varied across restoration stages, but uncorrelated with soil moisture. The composition of of AMF communities changed seasonally and I observed more AMF hyphae and arbuscules in winter.</p>

Arbuscular Mycorrhizae of Phormium Tenax in a restored New Zealand wetland across hydrological gradients

<p>New Zealand has lost over 90% of its former wetlands and many that remain are in a degraded state. Restoration projects are often impeded by the failure of native plants to establish back into non-native dominated communities. Phormium tenax is fast growing and acts a nurse plant in wetlands, accelerating the establishment of slower growing native woody species. The roles of below ground organisms are increasingly recognised as affecting plant community dynamics, and this study investigates the diversity of a group of pervasive organisms, the arbuscular mycorrhizal fungi (AMF), growing in symbiosis with Phormium tenax. Next generation sequencing was used to create two libraries to determine the sensitivity of coding and non-coding molecular markers when characterising the AMF community associated with Phormium tenax. AMF communities colonising individual plants were found to be diverse, and varied across restoration stages, but uncorrelated with soil moisture. The composition of of AMF communities changed seasonally and I observed more AMF hyphae and arbuscules in winter.</p>

The role of genetic diversity and arbuscular mycorrhizal fungal diversity in population recovery of the semi-natural grassland plant species Succisa pratensis

Ecosystem restoration is as a critical tool to counteract the decline of biodiversity and recover vital ecosystem services. Restoration efforts, however, often fall short of meeting their goals. Although functionally important levels of biodiversity can significantly contribute to the outcome of ecosystem restoration, they are often overlooked. One such important facet of biodiversity is within-species genetic diversity, which is fundamental to population fitness and adaptation to environmental change. Also the diversity of arbuscular mycorrhizal fungi (AMF), obligate root symbionts that regulate nutrient and carbon cycles, potentially plays a vital role in mediating ecosystem restoration outcome. In this study, we investigated the relative contribution of intraspecific population genetic diversity, AMF diversity, and their interaction, to population recovery of Succisa pratensis, a key species of nutrient poor semi natural grasslands. We genotyped 180 individuals from 12 populations of S. pratensis and characterized AMF composition in their roots, using microsatellite markers and next generation amplicon sequencing, respectively. We also investigated whether the genetic makeup of the host plant species can structure the composition of root-inhabiting AMF communities. Our analysis revealed that population allelic richness was strongly positively correlated to relative population growth, whereas AMF richness and its interaction with population genetic diversity did not significantly contribute. The variation partitioning analysis showed that, after accounting for soil and spatial variables, the plant genetic makeup explained a small but significant part of the unique variation in AMF communities. Our results confirm that population genetic diversity can contribute to population recovery, highlighting the importance of within-species genetic diversity for the success of restoration. We could not find evidence, however, that population recovery benefits from the presence of more diverse AMF communities. Our analysis also showed that the genetic makeup of the host plant structured root-inhabiting AMF communities, suggesting that the plant genetic makeup may be linked to genes that control symbiosis development.

Native AMF Communities in an Italian Vineyard at Two Different Phenological Stages of Vitis vinifera

Arbuscular mycorrhizal fungi (AMF) are beneficial soil microorganisms that can establish symbiotic associations with Vitis vinifera roots, resulting in positive effects on grapevine performance, both in terms of water use efficiency, nutrient uptake, and replant success. Grapevine is an important perennial crop cultivated worldwide, especially in Mediterranean countries. In Italy, Piedmont is one of the regions with the longest winemaking tradition. In the present study, we characterized the AMF communities of the soil associated or not with the roots of V. vinifera cv. Pinot Noir cultivated in a vineyard subjected to conventional management using 454 Roche sequencing technology. Samplings were performed at two plant phenological stages (flowering and early fruit development). The AMF community was dominated by members of the family Glomeraceae, with a prevalence of the genus Glomus and the species Rhizophagus intraradices and Rhizophagus irregularis. On the contrary, the genus Archaeospora was the only one belonging to the family Archaeosporaceae. Since different AMF communities occur in the two considered soils, independently from the plant phenological stage, a probable role of V. vinifera in determining the AMF populations associated to its roots has been highlighted.

Contrasting Responses of Arbuscular Mycorrhizal Fungal Families to Simulated Climate Warming and Drying in A Semiarid Shrubland

We carried out a 4-year manipulative field experiment in a semiarid shrubland in Southeastern Spain to assess the impacts of experimental warming (W), rainfall reduction (RR) and their combination (W+RR) on the composition and diversity of arbuscular mycorrhizal fungal (AMF) communities in rhizosphere soil using singlemolecule real-time (SMRT) DNA sequencing. Across climate treatments, we encountered 109 AMF OTUs that were assigned to four families: Glomeraceae (93.94%), Gigasporaceae (2.19%), Claroideoglomeraceae (1.95%) and Diversisporaceae (1.92%). The AMF community composition and diversity indices at OTU level were unaffected by the climate manipulation treatments, except for a significant decrease in AMF richness in the W treatment relative to the control. In contrast, AMF family richness decreased significantly in all the climate manipulation treatments relative to the control treatment. Members of the Gigasporaceae and Diversisporaceae families appeared to be highly vulnerable to intensification of heat and drought stress, as their abundances decreased by 67% and 77% respectively, in the W+RR treatment relative to current ambient conditions. In contrast, the relative abundance and dominance of the Glomeraceae family within the AMF community increased significantly under the W+RR treatment, with Glomeraceae being indicator family for the W+RR treatment. The interaction between warming and rainfall reduction had a significant effect on AMF community structure at family level. These findings provide new insights into AM fungal community responses to climate warming and drying in dryland ecosystems.

Differential responses of arbuscular mycorrhizal fungal communities to long-term fertilization in the wheat rhizosphere and root endosphere

Arbuscular mycorrhizal fungi (AMF) provide essential nutrients to crops and are critically impacted by fertilization in agricultural ecosystems. Understanding shifts in AMF communities in and around crop roots under different fertilization regimes can provide important lessons for improving agricultural production and sustainability. Here, we compared the responses of AMF communities in the rhizosphere (RS) and root endosphere (ES) of wheat ( Triticum aestivum ) to different fertilization treatments: Non-fertilization (Control), mineral fertilization only (NPK), mineral fertilization plus wheat straw (NPKS), and mineral fertilization plus cow manure (NPKM). We employed high-throughput amplicon sequencing and investigated the diversity, community composition, and network structure of AMF communities to assess their responses to fertilization. Our results elucidated that AMF communities in the RS and ES respond differently to fertilization schemes. Long-term NPK application decreased the RS AMF alpha diversity significantly, whereas additional organic amendments (straw or manure) had no effect. Contrastingly, NPK fertilization increased the ES AMF alpha diversity significantly, while additional organic amendments decreased it significantly. The effect of different fertilization schemes on AMF network complexity in the RS and ES were similar to their effects on alpha diversity. Changes to AMF communities in the RS and ES correlated mainly with the pH and phosphorus level of the rhizosphere soil under long-term inorganic and organic fertilization regimes. We suggest that the AMF community in the roots should be given more consideration when studying the effects of fertilization regimes on AMF in agroecosystems. Importance Arbuscular mycorrhizal fungi are an integral component of rhizospheres, bridging the soil and plant systems and are highly sensitive to fertilization. However, surprisingly little is known about how the response differs between the roots and the surrounding soil. Decreasing arbuscular mycorrhizal fungal diversity under fertilization has been reported, implying a potential reduction in the mutualism between plants and arbuscular mycorrhizal fungi. However, we found opposing responses to long-term fertilization managements of arbuscular mycorrhizal fungi in the wheat roots and rhizosphere soil. These results suggested that changes in the arbuscular mycorrhizal fungal community in soils do not reflect those in the roots, highlighting that the root arbuscular mycorrhizal fungal community is pertinent to understand arbuscular mycorrhizal fungi and their crop hosts’ responses to anthropogenic influences.

Disentangling nematode and arbuscular mycorrhizal fungal community effect on the growth of range-expanding Centaurea stoebe in original and new range soil

Aims Numerous organisms show range expansions in response to current climate change. Differences in expansion rates, such as between plants and soil biota, may lead to altered interactions in the new compared to the original range. While plant-soil interactions influence plant performance and stress tolerance, the roles of specific soil organisms driving these responses remain unknown. Methods We manipulated the abundances of nematodes and arbuscular mycorrhizal fungi (AMF), collected from original and new range soils, and examined their effects on the biomass of range-expanding Centaurea stoebe and native Centaurea jacea. In the first approach, nematode and AMF communities were extracted from field soils, and inoculated to sterilized soil. In the second approach, the abundance of soil organisms in soil inocula was reduced by wet sieving; at first, plants were grown to condition the soil, and then plant-soil feedback was determined under ambient and drought conditions. Results The origin of soil communities did not influence the biomass production of range-expanding or native plant species, neither by addition nor by (partial) removal. However, after conditioning and under drought, range expanding C. stoebe produced more biomass with soil communities from the original range while C. jacea, native to both ranges, produced more biomass with new range soil communities. Conclusions We show that nematode and AMF communities from original and new range have similar effect on the growth of range expanding C. stoebe. Our results highlight that the effect of soil communities on plant growth increases after soil conditioning and under drought stress.