Three new records of Arbuscular Mycorrhizal Fungi (Glomeromycota) from Mexico: Acaulospora tuberculata, Glomus crenatum, and Racocetra crispa

We conducted field and culture experiments to study the effects of arbuscular mycorrhizal (AM) fungi on the establishment of the alien plant Oenothera laciniata (Onagraceae) in a coastal sand dune in Japan. We examined the distribution of plants, AM fungal colonization of their roots, and fungal spore density in the soil of a coastal sand dune at Keinomatsubara, Hyogo Prefecture, western Japan. Of the nine dominant plant species at the study site, six species, including O. laciniata, were heavily colonized by AM fungi. The spore density tended to decrease from inland toward the shoreline, but there were no significant relationships between the level of AM fungal colonization and spore density. Seedlings of O. laciniata inoculated with AM fungi, as well as uninoculated seedlings, were transplanted to the study site. No significant difference in survival rates was detected between the two groups of seedlings. We also examined the effects of AM infection and nutrient (N and P) application on plant growth in a pot culture experiment. The results suggested that the growth of O. laciniata was limited mainly by N availability and that AM mycorrhizae had little effect on the establishment of the plant on the coastal sand dune.

Effects of sand dune, desert and field arbuscular mycorrhizae on lettuce (Lactuca sativa, L.) growth in a natural saline soil

Mycorrhizal fungi (mycobionts) form a ubiquitous mutualistic symbiotic association with the roots of higher plants (phytobionts) in coastal sand dunes worldwide. These obligate biotrophs perform vital functions in the survival, establishment and growth of plants by playing an active role in nutrient cycling. As such they serve as a crucial link between plants, fungi and soil at the soil–root interface (Rillig and Allen 1999). Mycorrhizas occur in a wide variety of habitats and ecosystems including aquatic habitats, cold or hot deserts, temperate and tropical coastal dunes, tropical rainforests, saline soils, volcanic tephra soils, prairies and coral substrates (Klironomos and Kendrick 1993). Simon et al. (1993) sequenced ribosomal DNA genes from 12 species of arbuscular mycorrhizal (AM) fungi and confirmed that mycorrhizas (fungal roots) fall into three families. He estimated that they originated about 353–462 million years ago and were instrumental in facilitating the colonization of ancient plants on land. Further evidence was provided by Remy et al. (1994) who discovered arbuscules in an early Devonian land plant, Aglaophyton major, and concluded that mycorrhizal fungi were already established on land > 400 million years ago. Thus the nutrient transfer mechanism of AM fungi was already in existence before the origin of roots. Plant roots probably evolved from rhizomes and AM fungi served as an important evolutionary step in the acquisition of water and mineral nutrients (Brundrett 2002). Over evolutionary time the divergence among these fungi has accompanied the radiation of land plants, and about 200 species of AM fungi have been recognized (Klironomos and Kendrick 1993) that exist in association with about 300 000 plant species in 90% of families (Smith and Read 1997), indicating that AM fungi are capable of colonizing many host species. Approximately 150 of the described mycorrhizal species may occur in sand dunes (Koske et al. 2004). Most host–fungus associations are beneficial to both the plant and the fungus and are thus regarded as mutualistic (++); however, the widespread use of the term mutualism (mutual benefit) for mycorrhizal interactions has been questioned because all associations are not beneficial to both the plant and fungus (Brundrett 2004).

Drought become the foremost abiotic stress limiting plant growth and leading to crop-yield loss. This study was aimed to evaluate the effect of native arbuscular mycorrhizal (AM) and cellulolytic fungi (CF) on the growth, yield, mycorrhizal colonization, and the phosphorous (P) and proline contents of maize under drought. This study was conducted using a 3 x 3 factorial arranged in randomized complete block design with three replications The treatments were inoculation of native AM fungi (no AM fungi, Acaulospora tuberculata, and Gigaspora cf. gigantea) and native celluloltic fungi (no CF, Talaromyces pinophilus strain MR107 and Talaromyces pinophilus isolate OK3SP103P) evaluated under 50% field capacity (FC). Our results clearly indicated that increasing plant height, plant diameter, mycorrhizal colonization, and P content and decreasing proline content were affected either by native AM or cellulolytic fungi, but dry weight of 100-grain was only increased by native cellulolytic fungi. Combined inoculation of native AM and cellulolytic fungi improved P content and mycorrhizal colonization. Gi. cf. gigantea and T. pinophilus strain MR107 were more potential native inoculants to eliminate negative effect of water stress on maize.

Fresh knowledge for an old relationship: new discoveries in molecular mycorrhizal research.

The diversity and community structure of arbuscular mycorrhizal fungi (AMF) associated with coconut (Cocos nucifera) roots was evaluated by next generation sequencing (NGS) using partial sequences of the 18S rDNA gene and by spore isolation and morphological identification from rhizosphere soil. Root samples from six different Green Dwarf coconut plantations and from one organic plantation surrounded by tropical dry forest along the coastal sand dunes in Yucatan, Mexico, were collected during the rainy and dry seasons. In total, 14 root samples were sequenced with the Illumina MiSeq platform. Additionally, soil samples from the dry season were collected to identify AMF glomerospores. Based on a 95-97% similarity, a total of 36 virtual taxa (VT) belonging to nine genera were identified including one new genus-like clade. Glomus was the most abundant genus, both in number of VT and sequences. The comparison of dry and rainy season samples revealed differences in the richness and composition of AMF communities colonizing coconut roots. Our study shows that the main AMF genera associated with coconut tree roots in all samples were Glomus, Sclerocystis, Rhizophagus, Redeckera, and Diversispora. Based on glomerospore morphology, 22 morphospecies were recorded among which 14 were identified to species. Sclerocystis sinuosa, Sclerocystis rubiformis, Glomus microaggregatum, and Acaulospora scrobiculata were dominant in field rhizosphere samples. This is the first assessment of the composition of AMF communities colonizing coconut roots in rainy and dry seasons. It is of importance for selection of AMF species to investigate for their potential application in sustainable agriculture of coconut.

Greenhouse inoculation of psammophilic plant species with arbuscular mycorrhizal fungi to improve survival and early growth

Many of the disturbance‐sensitive, late successional plant species in grasslands respond to arbuscular mycorrhizal (AM) fungi more positively via growth and establishment than plants that readily establish in disturbed areas (i.e. early successional species). Inoculation with AM fungi can therefore aid the establishment of late successional species in disturbed areas. If the differential benefit of AM fungi to late versus early successional plants is context‐dependent, however, this advantage could be diminished in high phosphorus (P) post‐agricultural soils or in future climates with altered precipitation. In this greenhouse experiment, we tested if late successional plant species are less plastic in their reliance on AM fungi than early successional plants by growing 17 plant species of different successional status (9 early and 8 late successional) in full factorial combinations of inoculated or uninoculated with AM fungi, with ambient or high P levels, and with low or high levels of water. AM fungi positively affected the biomass of the 17 grassland plant species, but across all environments, late successional plant species generally responded more positively to AM fungi than early successional plants species. AM fungal growth promotion and change in below‐ground biomass allocation was generally diminished with P fertilizer across all plant species, and while there was significant variation among plant species in the sensitivity of AM fungal responsiveness to P fertilization, this differential sensitivity was not predicted by plant successional status. The role of AM fungi in plant growth promotion was not generally altered by variation in watering, however late successional plant species allocated a greater proportion of their biomass below‐ground in response to AM fungi in low versus high water conditions. Synthesis. Overall greater responsiveness to arbuscular mycorrhizal (AM) fungi by late successional species is consistent with an important role of AM fungi in plant succession, even while AM fungi are less impactful overall in high P soils. However, the increase in responsiveness of below‐ground allocation of late successional species to AM fungi in low water conditions suggests that successional dynamics may be more dependent on AM fungi in future climates that feature greater propensity for drought.

The present study was aimed at comparing the number of arbuscular mycorrhizal fungi (AMF) propagules found in soil from a mature tropical forest and that found in an abandoned cornfield in Noh-Bec Quintana Roo, Mexico, during three seasons. Agricultural practices can dramatically reduce the availability and viability of AMF propagules, and in this way delay the regeneration of tropical forests in abandoned agricultural areas. In addition, rainfall seasonality, which characterizes deciduous tropical forests, may strongly influence AMF propagules density. To compare AMF propagule numbers between sites and seasons (summer rainy, winter rainy and dry season), a "most probable number" (MPN) bioassay was conducted under greenhouse conditions employing Sorgum vulgare L. as host plant. Results showed an average value of 3.5 ± 0.41 propagules in 50 ml of soil for the mature forest while the abandoned cornfield had 15.4 ± 5.03 propagules in 50 ml of soil. Likelihood analysis showed no statistical differences in MPN of propagules between seasons within each site, or between sites, except for the summer rainy season for which soil from the abandoned cornfield had eight times as many propagules compared to soil from the mature forest site for this season. Propagules of arbuscular mycorrhizal fungi remained viable throughout the sampling seasons at both sites. Abandoned areas resulting from traditional slash and burn agriculture practices involving maize did not show a lower number of AMF propagules, which should allow the establishment of mycotrophic plants thus maintaining the AMF inoculum potential in these soils.

Lead (Pb) contamination in soil presents a major threat to plant health and ecosystem integrity, particularly in urban areas with ornamental plants. Arbuscular mycorrhizal fungi (AMF) mitigates heavy metal toxicity, but comparative data across ornamental species are limited. This study investigated Rhizophagus irregularis effects on Pb uptake and physiological traits in ornamental cabbage (Brassica oleracea) and gladiolus (Gladiolus grandiflorus) under five Pb levels (0–200 mg Pb/kg soil) in a greenhouse using a factorial experimental design. Results showed that AMF reduced Pb translocation from roots to shoots in both species. At 200 mg/kg Pb, root Pb concentrations decreased from 67.8 ± 3.2 mg/kg to 54.6 ± 2.9 mg/kg in ornamental cabbage, and from 63.2 ± 3.0 mg/kg to 51.7 ± 2.8 mg/kg in gladiolus due to AMF inoculation. Chlorophyll content and shoot biomass also declined less severely in AMF-treated plants. Notably, gladiolus plants exhibited higher AMF colonization (70.2% at 0 mg/kg Pb) and maintained greater stability in growth and chlorophyll content than ornamental cabbage, indicating a species-specific variation in symbiotic efficiency and Pb stress tolerance. These results highlight species-specific benefits of AMF under Pb stress and underscore the potential of integrating diverse ornamental and crop species in phytoremediation strategies based on their symbiotic compatibility.

Dune vegetation is essential for the formation and preservation of sand dunes and the protection of the coast line. Coastal sand dunes are harsh environments where arbuscular mycorrhizal fungi (AMF) play an important role in promoting plant establishment and growth. We present a study of the diversity of AMF associated with A. arenaria ssp. arundinacea in two locations of the Portuguese coast under a Mediterranean climate. These two locations were selected to compare a well-preserved dune system from a protected area with a degraded dune system from a public beach. AMF diversity was assessed mainly by cloning and sequencing of a fragment of the ribosomal SSU using the primer NS31 and AM1. Most of the 89 AMF clones obtained from the rhizosphere and roots of A. arenaria belonged to the genus Glomus, the largest clade within the Glomeromycota. Higher AMF diversity was found in the least disturbed site, in which spores of Scutellospora persica, Glomus constrictum and Glomus globiferum were found in the rhizosphere of A. arenaria.

Plant-driven genome selection of arbuscular mycorrhizal fungi.

Mycorrhizal fungi form the most important mutualistic symbioses on earth with plants. The most prevalent type of mycorrhizal fungi are the arbuscular mycorrhizal (AM) fungi. Much research has shown that the development of AM fungi is correlated with plant secondary metabolism. AM fungi can directly or indirectly affect plant secondary metabolic processes. Secondary metabolites are classified into 3 groups, terpenoids, phenolics and alkaloids. In this paper, we summarize the effects of AM fungi on the 3 groups of secondary metabolites. The relationship between terpenoids and AM fungi have been well studied, and some research has explored interactive mechanisms at the molecular level. Blumenin was first isolated and identified from mycorrhizal cereals, and its biosynthesis has been proven via the Glyceraldehyde 3_phosphate/ pyruvate pathway (MEP) by an isotopic labeling method. Since then, the accumulation of blumenin induced by AM fungi and differences in blumenin levels among different kinds of AM fungi have been observed. Studies on 1_deoxy_D_xylulose_5_phosphate synthase (DXS) and 1_deoxy_D_xylulose_5_phosphate reductoisomerase (DXR), two key enzymes in the biosynthesis of carotenoid metabolism via the MEP pathway, have found to increase the transcription of DXS and DXR in plants with AM fungi. Moreover it was temporarily and spatially correlated with the accumulation of apocarotenoids. Subsequently, two genes were identified: TC78589 encoding DXS2 which is highly expressed in roots inoculated with AM fungi, and TC77051 encoding mevalonate disphosphate decarboxylase, which is catalysed in the synthesis of terpenoids in the mevalonate pathway. Although both genes separately encode enzymes in different pathways, an enhancement of carotenoid biosynthesis has been observed. The interaction between phenolic compounds (such as phytoalexin, wall_bound phenol, flavonoids, isoflavonoids and their derivatives) and AM fungi also has been investigated intensively. It has been shown that some flavonoids stimulated the spore germination and hyphal growth of AM fungi, and the contents of flavonoids increased before the infection of AM fungi. Therefore some investigators hypothesized that flavonoids were a signal compound during the formation of AM fungi. Afterward, increased levels of flavonoids were found after the formation of AM fungi which was related to specific species of AM fungi. In addition, some experiments have indicated that the activity of peroxidase (POD), phenylalanine ammonia_lyase (PAL) and polyphenol oxidase (PPO) were significantly enhanced in AM plants. In phenylpropamoid metabolism, there are two different signaling pathways in the accumulation of secondary metabolites induced by the mycorrhizal fungus: one is through the induction of PAL and chalcone synthase (CHS), and the other is through the suppression of isoflavone reductase (IFR).Although little research seldom has examined the relationship between alkaloids and AM fungi, a recent study has shown that the formation of AM is beneficial to the accumulation of alkaloids. This study also showed the species specificity in AM affected biosynthesis of alkaloids.

Coastal sand dunes in South Korea were listed 133 first in 2001 by the Ministry of Environment, and from 2007 to 2009, the National Institute of Environmental Research listed 199. Listed from the prior research, we delimitated 207 coastal sand dune boundaries. Past and present coastal dune boundaries were presumed by aerial photos took in 2014 and during the 1940s to 1960s at the National Geographic Information Institute. Then, we modified the boundary of coastal sand dunes by conducting a field survey. We categorized 189 listed up and 19 history management coastal sand dunes based on the characteristics of coastal sand dunes. Coastal sand dunes in South Korea were located in each district: 58 in Jellanam-do, 42 in Chungcheongnam-do, 30 in Gangwon-do, 14 in Jeju, 12 in Gyeongsangbuk-do, seven in Jeonbuk-do, and two coastal sand dunes in Gyeonggi-do and Gyeongsangnam-do. The change in the area of coastal sand dunes between the past and present 36.5% of coastal sand dunes were decreased because of agricultural and commercial use. Coastal sand dunes could be changed by high-pressure development. Our data were valuable for temporal and spatial usage and change of coastal sand dunes.

This study was conducted to provide the coastal sand dunes flora of vascular plants in Chungcheong to Jeolla region based national coastal dune natural environment survey from 2018 to 2019. In the study area, a total 631 taxa, consisting of 119 family, 372 genera, 566 species, 8 subspecies, 50 varieties, and 7 forma, were found. Among them, there were 95 taxa with 23 family, 66 genera, 99 species and 5 varieties as alien species. The number of alien species ranged from 7 to 45 on each coastal sand dune. The largest number was recorded in Sinjimyeongsa dune, while the lowest was in Namujeon dune. Moreover, ecosystem disturbing species had mainly existed on Sinhap dune. Japanese hop (Humulus japonicus) were distributed most widely on 17 coastal sand dune, and bur cucumber (Sicyos angulatus) was only found on Sinhap dune. The spatial status of flora of coastal sand dune in our data can be basic ecological information for the conservation and management of the coastal dune plant species diversity.