Vermiculite as a culture substrate greatly improves the viability of frozen cultures of ectomycorrhizal basidiomycetes.

We assessed a new cryopreservation protocol that uses vermiculite as a culture substrate, called the vermiculite protocol (VP), by assessing the viability, recovery time of hyphae after revival, and colony diameter of cryosensitive ectomycorrhizal basidiomycete strains after storage for 2 weeks or 1 year in a vapour-phase liquid nitrogen tank. Twelve difficult-to-preserve strains of nine species (Amanita citrina, A. pantherina, A. rubescens, A. spissa, Kobayasia nipponica, Lactarius akahatsu, L. hatsudake, Sarcodon aspratus, and Tricholoma flavovirens) that did not achieve good revival after cryopreservation with our previous Homolka's perlite protocol and modified perlite protocol (MPP) experiments were used to assess the new methodology. Vermiculite and liquid medium were put into a cryotube and inoculated with an agar plug containing mycelia. The cryotube was cultured for various incubation times. After adequate mycelial growth, a mixture of cryoprotectants (5% dimethyl sulfoxide and 10% trehalose [5D10T] or 5% glycerol and 10% trehalose [5G10T]) was placed into the cryotube. The cryotube was frozen in a freezing container in a -80 °C freezer and then stored in vapour-phase liquid nitrogen. In the recovery test, 10 of 12 strains showed 100% revival after 2 weeks of storage in the 5G10T cryoprotectant, and all 12 strains showed 100% revival after 2 weeks of storage in the 5D10T cryoprotectant. Furthermore, all strains were viable after 1 year of storage in a vapour-phase liquid nitrogen tank. Thus, the VP is applicable to a wide range of ectomycorrhizal basidiomycete cultures, including highly cryosensitive strains.

Polyunsaturated fatty acids-enriched lipid from reduced sugar alcohol mannitol by marine yeast Rhodosporidiobolus fluvialis Y2.

Brown macroalgae is a promising marine biomass for the production of bioethanol and biodiesel fuels. Here we investigate the biochemical processes used by marine oleaginous yeast for assimilating the major carbohydrate found in brown macroalgae. Briefly, yeast Rhodosporidiobolus fluvialis strain Y2 was isolated from seawater and grown in minimal medium containing reduced sugar alcohol mannitol as the sole carbon source with a salinity comparable to seawater. Conditions limiting nitrogen were used to facilitate lipid synthesis. R. fluvialis Y2 yielded 55.1% (w/w) and 39.1% (w/w) of lipids, per dry cell weight, from mannitol in the absence and presence of salinity, respectively. Furthermore, mannitol, as a sugar source, led to an increase in the composition of polyunsaturated fatty acids, linoleic acid (C18:2) and linolenic acid (C18:3), compared to glucose. This suggests that oxidation of mannitol leads to the activation of NADH-dependent fatty acid desaturases in R. fluvialis Y2. Such fatty acid composition may contribute to the cold-flow properties of biodiesel fuels. Our results identified a salt-tolerant oleaginous yeast species with unique metabolic traits, demonstrating a key role as a decomposer in the global carbon cycle through marine ecosystems. This is the first study on mannitol-induced synthesis of lipids enriched with polyunsaturated fatty acids by marine yeast.

Bovistol B, bovistol D and strossmayerin: Sesquiterpene metabolites from the culture filtrate of the basidiomycete Coprinopsis strossmayeri.

Basidiomycete fungi are a rich source of natural products with a diverse array of potentially exploitable bioactivities. Two dimeric sesquiterpenes, bovistol B (1) and D (2), and one monomeric sesquiterpene, strossmayerin (7), were isolated from the culture filtrate of the basidiomycete fungus Coprinopsis strossmayeri. The structures were determined through a combination of MS and 1D/2D NMR spectroscopic techniques. Likely monomeric precursors, identified on the basis of HRMS analysis, allow a plausible biosynthetic pathway to be proposed for the biosynthesis of 1 and 2, involving the dimerisation of the monomer through a hetero-Diels-Alder mechanism. A gene cluster, including a putative sesquiterpene 1-11 cyclase, was identified through phylogenetic and RNA-seq analysis, and is proposed to be responsible for the biosynthesis of 1 and 2.

Combined Effect of Light and Nutrients on the Micromorphology of the White rot Fungus Cerrena Unicolor.

Light influences developmental pathways in fungi. Recent transcriptomic and biochemical analyses have demonstrated that light influences the metabolism of a white-rot basidiomycete Cerrena unicolor. However, the expression profile of genes involved in the growth and development, or micromorphological observations of the mycelium in response to variable lighting and culturing media, have not performed. We aim to reveal the effect of light and nutrients on C. unicolor growth and a potential relationship between the culture medium and lighting conditions on fungus micromorphological structures. Confocal laser scanning microscopy and scanning electron microscopy were employed for morphological observations of C. unicolor mycelium cultivated in red, blue, green, and white light and darkness on mineral and sawdust media. A comprehensive analysis of C. unicolor differentially expressed genes (DEGs) was employed to find global changes in the expression profiles of genes putatively involved in light-dependent morphogenesis. Both light and nutrients influenced C. unicolor growth and development. Considerable differences in the micromorphology of the mycelia were found, which were partially reflected in the functional groups of DEGs observed in the fungus transcriptomes. A complex cross-interaction of nutritional and environmental signals on C. unicolor growth and morphology was suggested. The results are a promising starting point for further investigations of fungus photobiology.

Oxalate oxidase from Abortiporus biennis - protein localisation and gene sequence analysis.

We have described for the first time the localisation of oxalate oxidase (OXO, EC 1.2.3.4) in Abortiporus biennis cells, using histochemical and immunochemical methods coupled with transmission electron microscopy. Rabbit anti-oxalate oxidase immunoglobulins with anti-rabbit secondary antibody conjugated with 10-nm gold particles were used. Moreover, the formation of electron dense precipitation of reaction of diaminobenzidine (DAB) with horseradish peroxidase (HRP) for histochemical localisation of the enzyme was found. OXO was localised close to the membranous structures of the cell membranes, in membranous vesicles located close to the outer cell membrane, and vacuolar membranes surrounding vacuoles. The positive immunoreaction to OXO was also intense in cell wall areas. Moreover, we proved that gene coding for OXO was expressed in the same cultures. Corresponding mRNA was isolated, full length cDNA was synthesized, cloned and sequenced. Two copies of cupin domains were found in the sequence of amino-acids conserved domain coding for the cupin enzyme. Comparison of the genomic DNA and cDNA sequences has revealed the presence of seventeen introns in the gene. The isoelectric point of the protein was estimated at pH 4.5 and several possible N-glycosylation sites were predicted.

Nitrogen deprivation elicits dimorphism, capsule biosynthesis and autophagy in Papiliotrema laurentii strain RY1.

Stress response due to the lack of essential nutrient(s) for an organism has been a focal point of several scientific investigations. The present study investigates the cellular adaptations behind the ability of Papiliotrema laurentii strain RY1 to perpetuate without added nitrogen and propagate robustly in growth- limiting amount of nitrogen. We executed phenotypic (using scanning electron microscopy, differential interference contrast microscopy and transmission electron microscopy), microbiological and computational analyses to show multiple responses of dimorphism, capsule formation and autophagy as a survival strategy by the yeast upon nitrogen starvation. The roles of phosphomannose isomerase, phosphomannomutase and several autophagy-related transcripts aiding in such a response have been discussed.

Russula swatica: A new species of Russula based on molecular, light microscopy, and scanning electron microscopy analyses from Swat Valley of Khyber Pakhtunkhwa province of Pakistan.

Himalayan range of Pakistan is one of the diversity rich hotspots of the world. Many areas are yet to be explored here to discover new species of organisms including fungi. During present research, Swat District of Pakistan was explored for fungal diversity. One new species of mushroom Russula swatica (Russulales) is described from Himalayan range of Pakistan and analyzed by light microscopy and scanning electron microscopy as well as by molecular markers. A comprehensive description, photographs, and comparisons with morphologically similar and phylogenetically related species are provided. Conclusions of its phylogenetic relationships within the genus are provided based on the sequence of the nuclear internal transcribed spacer region.

Shedding Light on Penetration of Cereal Host Stomata by Wheat Stem Rust Using Improved Methodology.

Asexual urediniospore infection of primary cereal hosts by Puccinia graminis f. sp. tritici (Pgt), the wheat stem rust pathogen, was considered biphasic. The first phase, spore germination and appressoria formation, requires a dark period and moisture. The second phase, host entry by the penetration peg originating from the appressoria formed over the guard cells, was thought to require light to induce natural stomata opening. Previous studies concluded that inhibition of colonization by the dark was due to lack of penetration through closed stomata. A sensitive WGA-Alexa Fluor 488 fungal staining, surface creation and biovolume analysis method was developed enabling visualization and quantification of fungal growth in planta at early infection stages surpassing visualization barriers using previous methods. The improved method was used to investigate infection processes of Pgt during stomata penetration and colonization in barley and wheat showing that penetration is light independent. Based on the visual growth and fungal biovolume analysis it was concluded that the differences in pathogen growth dynamics in both resistant and susceptible genotypes was due to light induced pathogen growth after penetration into the substomatal space. Thus, light induced plant or pathogen cues triggers pathogen growth in-planta post penetration.

ZnO-based nanofungicides: Synthesis, characterization and their effect on the coffee fungi Mycena citricolor and Colletotrichum sp.

In this work we compare the antifungal capacity of zinc oxide nanoparticles (ZnO-NPs) synthesized by a chemical route and a ZnO-based nanobiohybrid obtained by green synthesis in an extract of garlic (Allium sativum). To find out the characteristics of the materials synthesized, X-ray diffraction (XRD), IR spectroscopy and absorption in UV-Vis were used, as well as both scanning (SEM) and transmission (TEM) electron microscopy. The results showed that the samples obtained were of nanometric size (<100 nm), with a predominance of the wurtzite crystal phase of ZnO and little crystallization of the nanobiohybrids. Their antifungal capacity on two pathogenic fungi of coffee, Mycena citricolor (Berk and Curt) and Colletotrichum sp. was also evaluated. Both nanomaterials showed an efficient antifungal capacity, particularly the nanobiohybrids, with ~97% inhibition in growth of M. citricolor, and ~93% for Colletotrichum sp. The microstructural study with high resolution optical (HROM) and ultra-structural microscopy (using TEM) carried out on the fungi treated with the synthesized nanomaterials showed a strong nanofungicidal effect on the vegetative and reproductive structures and fungal cell wall, respectively. The inhibition of the growth of the fungi and micro and ultra-structural affectations were explained considering that the size of the nanomaterials allows them to pass easily through the cell membranes. This indicates that they can be absorbed easily by the fungi tested here, causing cellular dysfunction. Nanofungicide effects are also attributable to the unique properties of nanomaterials, such as the high surface-to-bulk ratio of atoms and their surface physicochemical characteristics that could directly or indirectly produce reactive oxygen species (ROS), which affect the proteins of the cell wall.

FGB1 and WSC3 are in planta-induced ß-glucan-binding fungal lectins with different functions.

In the root endophyte Serendipita indica, several lectin-like members of the expanded multigene family of WSC proteins are transcriptionally induced in planta and are potentially involved in ß-glucan remodeling at the fungal cell wall. Using biochemical and cytological approaches we show that one of these lectins, SiWSC3 with three WSC domains, is an integral fungal cell wall component that binds to long-chain ß1-3-glucan but has no affinity for shorter ß1-3- or ß1-6-linked glucose oligomers. Comparative analysis with the previously identified ß-glucan-binding lectin SiFGB1 demonstrated that whereas SiWSC3 does not require ß1-6-linked glucose for efficient binding to branched ß1-3-glucan, SiFGB1 does. In contrast to SiFGB1, the multivalent SiWSC3 lectin can efficiently agglutinate fungal cells and is additionally induced during fungus-fungus confrontation, suggesting different functions for these two ß-glucan-binding lectins. Our results highlight the importance of the ß-glucan cell wall component in plant-fungus interactions and the potential of ß-glucan-binding lectins as specific detection tools for fungi in vivo.

Identification of Wheat Yellow Rust Using Optimal Three-Band Spectral Indices in Different Growth Stages.

Yellow rust, a widely known destructive wheat disease, affects wheat quality and causes large economic losses in wheat production. Hyperspectral remote sensing has shown potential for the detection of plant disease. This study aimed to analyze the spectral reflectance of the wheat canopy in the range of 350⁻1000 nm and to develop optimal spectral indices to detect yellow rust disease in wheat at different growth stages. The sensitive wavebands of healthy and infected wheat were located in the range 460⁻720 nm in the early-mid growth stage (from booting to anthesis), and in the ranges 568⁻709 nm and 725⁻1000 nm in the mid-late growth stage (from filling to milky ripeness), respectively. All possible three-band combinations over these sensitive wavebands were calculated as the forms of PRI (Photochemical Reflectance Index) and ARI (Anthocyanin Reflectance Index) at different growth stages and assessed to determine whether they could be used for estimating the severity of yellow rust disease. The optimal spectral index for estimating wheat infected by yellow rust disease was PRI (570, 525, 705) during the early-mid growth stage with R² of 0.669, and ARI (860, 790, 750) during the mid-late growth stage with R² of 0.888. Comparison of the proposed spectral indices with previously reported vegetation indices were able to satisfactorily discriminate wheat yellow rust. The classification accuracy for PRI (570, 525, 705) was 80.6% and the kappa coefficient was 0.61 in early-mid growth stage, and the classification accuracy for ARI (860, 790, 750) was 91.9% and the kappa coefficient was 0.75 in mid-late growth stage. The classification accuracy of the two indices reached 84.1% and 93.2% in the early-mid and mid-late growth stages in the validated dataset, respectively. We conclude that the three-band spectral indices PRI (570, 525, 705) and ARI (860, 790, 750) are optimal for monitoring yellow rust infection in these two growth stages, respectively. Our method is expected to provide a technical basis for wheat disease detection and prevention in the early-mid growth stage, and the estimation of yield losses in the mid-late growth stage.

Ultrastructural studies and molecular characterization of root-associated fungi, of Crepidium acuminatum (D.Don) Szlach.: a threatened and medicinally important taxon.

Crepidium acuminatum (Orchidaceae) is a threatened medicinal orchid that grows under shady and moist forest floor where light remains for a very short period of time. Mycorrhizal association is known to be essential for seed germination and seedling establishment in amajority of orchids. Identification of fungi that form mycorrhizae with orchids is of crucial importance for orchid conservation. We used both morphological as well as molecular approaches to study this plant-fungal interaction. Scanning electron microscopy showed that fungi grow and proliferate in the middle layers of the cortex. Also, spiral-root hairs were foundalong with root hairs, which is an unusual observation. Spiral-root hairs provide more surface area for fluid absorption and entrance of colonizers. Further, total root genomic DNA was isolated and fungal internal-transcribed spacer (ITS) regions were polymerase chain reaction (PCR)-amplified using specific primer combinations ITS1F/ITS4 and ITS1/ITS4tul. ITS sequences were obtainedand analysed to know the closest sequence matche in the GenBank using BLASTn hosted by NLM-NCBI. Subject sequences were identified to be belonging to three main genera, namely, Tulasnella, Aspergillus and Penicillium. Results indicate that mycorrhizal association is necessary for the growth and development of the plant. In addition, this symbiosis influences the distribution and rarity of this medicinally valuable taxon. Specific fungal partners may lead to an enhanced seed germination rate and increased efficiency of nutrient exchange between both the partners. Hence, knowledge of mycorrhizal fungi is essential for future in vitro germination and seedling establishment programmes, because they rely on fungi for germination. Identification of mycorrhizal fungi can be usedfor orchid propagation and conservation programmes.

Identification of Virulences of the Rust Fungus Melampsora larici-populina Occurring in Chile.

Melampsora larici-populina Kleb. is a Eurasian species that causes leaf rust of many species of Populus from sections Tacamahaca and Aigeiros. This rust has been inadvertently introduced to many parts around the world affecting poplar species that grow naturally, which may be susceptible to this fungus. In Chile, early European settlers introduced poplars; rust, attributed to M. larici-populina, has been reported in these trees since 1918. However, a modern confirmation has been lacking, and pathogenic variation of the Chilean population of M. larici-populina has not been investigated. Using a morphological analysis of urediniospores and sequencing of internal transcribed spacer (ITS) regions, we confirmed the presence of M. larici-populina in Chile. ITS regions exhibited 100% homology with M. larici-populina. Scanning electron microscopy showed that spores were 26 to 47 µm in length, 13 to 16 µm in width, and echinulate except for apices, which are smooth, characteristics described for this species of rust. The variability of M. larici-populina is characterized by the presence of pathotypes, which allows the fungus to infect despite the resistance of certain poplar hybrids. We concluded that the identified spores belong to M. larici-populina, with virulences 1, 2, 3, 4, 5, and 6. These results describe variation in virulence of M. larici-populina, which suggests the presence of a sexual stage in Chile.

A taxonomic revision of the genus Puccinia on Lycieae, a tribe of Solanaceae.

We present a taxonomic and phylogenetic study of Puccinia species (rust fungi) infecting tribe Lycieae (Solanaceae), with focus on the New World taxa. Phylogenetic analyses using nuclear (nuc) rDNA 5.8S-ITS2 (ITS2) and mitochondrial (mt) cytochrome oxidase subunit 3 (CO3) show that Puccinia species occurring on Lyciae are grouped in two major lineages, one New World and one Old World. We assessed the value of morphological traits and geographic range as important features for discriminating lineages. The morphology of teliospore pedicels and rust geographic ranges explained the relationships within this Puccinia species group. Four Puccinia species are recognized on Lycieae in the New World lineage and four in the Old World lineage. Puccinia tumidipes from North America is resurrected and P. dimidipes described as new from South America. In addition, P. spinulosa from Madagascar is reduced to a synonym of P. engleriana. Descriptions and a dichotomous key are presented for the accepted species.

Effectors involved in fungal-fungal interaction lead to a rare phenomenon of hyperbiotrophy in the tritrophic system biocontrol agent-powdery mildew-plant.

Tritrophic interactions involving a biocontrol agent, a pathogen and a plant have been analyzed predominantly from the perspective of the biocontrol agent. We have conducted the first comprehensive transcriptomic analysis of all three organisms in an effort to understand the elusive properties of Pseudozyma flocculosa in the context of its biocontrol activity against Blumeria graminis f.sp. hordei as it parasitizes Hordeum vulgare. After inoculation of P. flocculosa, the tripartite interaction was monitored over time and samples collected for scanning electron microscopy and RNA sequencing. Based on our observations, P. flocculosa indirectly parasitizes barley, albeit transiently, by diverting nutrients extracted by B. graminis from barley leaves through a process involving unique effectors. This brings novel evidence that such molecules can also influence fungal-fungal interactions. Their release is synchronized with a higher expression of powdery mildew haustorial effectors, a sharp decline in the photosynthetic machinery of barley and a developmental peak in P. flocculosa. The interaction culminates with a collapse of B. graminis haustoria, thereby stopping P. flocculosa growth, as barley plants show higher metabolic activity. To conclude, our study has uncovered a complex and intricate phenomenon, described here as hyperbiotrophy, only achievable through the conjugated action of the three protagonists.

Inhibition coefficient and molecular diversity of multi stress tolerant Trichoderma as potential biocontrol agent against Sclerotium rolfsii Sacc.

Trichoderma is one of the most exploited biocontrol agent for the management of plant diseases. Twenty strains of Trichoderma (six of T. harzianum, four of T. viride, three of T. virens, three of T. koningii, each one of T. hamatum, T. reesei, T. parceramosum and Trichoderma spp.) subjected to in vitro antagonism up to 12days after inoculation against Sclerotium rolfsii Sacc. causing stem rot in groundnut. A new concept was developed to determine inhibition coefficient representing pathogen biology and biocontrol related biophysical variables. Results explained differential inhibition coefficient of test pathogen by Trichoderma antagonists. The inhibition coefficient of test pathogen was examined highest (91.13%) by T. virens NBAII Tvs12 followed by T. virens MTCC 794 (89.33%) and T. koningii MTCC 796 (62.39%). Microscopic study confirmed biocontrol mechanism as mycoparasitism for Tvs12 and antibiosis for T. koningii MTCC 796. The sclerotial biogenesis of test pathogen was elevated during weak antagonism and diminished in interactions with strong antagonists. The inhibition coefficient of S. rolfsii was significantly negatively correlated with sclerotia formation and lipid peroxidation during the antagonism. Trichoderma strains were screened for fungicides (carbendazim and tebuconazole, thiram and mancozeb) and abiotic stress (drought and salt) tolerance. Results indicated that T. koningii MTCC 796 efficiently grew better than the other strains with maximum radial growth under adverse conditions. The genetic variability among the Trichoderma was determined using 34 gene specific markers which amplified 146 alleles. The SSR similarities explained substantial diversity (15 to 87%) across Trichoderma strains and pathogen S. rolfsii. Principal coordinates analysis (PCA) were comparable to the cluster analysis and first three most informative PC components explained 64.45% of the total variation. In PCA, potent antagonists appear to be distinct from other strains. Five SSR markers T1F/T1R(311), TvCTT56f/TvCTT56r(387), TvGAT18f/TvGAT18r(364), TvCA39f/TvCA39r(196) and TvAG29f/TvAG29r(418) found to be unique to distinguish best antagonist strain Tvs12. However, MTCC 796 was examined most stress tolerant strain with better inhibition coefficient which might be useful to control the disease under adverse conditions or as a part of integrated pest management.

Three-dimensional ultrastructural study of the anther of Silene latifolia infected with Microbotryum lychnidis-dioicae.

When Microbotryum lychnidis-dioicae infects a male Silene latifolia, M. lychnidis-dioicae smut spores develop in the pollen sac instead of pollen. In contrast, when M. lychnidis-dioicae infects a female S. latifolia, the female flowers become male-like, promoting stamen formation. However, it is unclear when and how M. lychnidis-dioicae invades the anther. It is important to investigate not only whether hyphae exist when the apical meristem tissue differentiates into flowers and anthers, but also whether hyphae exist when stamen filaments form. We used Grocott's methenamine silver stain and lectin stain, which stain chitin in the fungal cell wall, to search for M. lychnidis-dioicae in flower tissues. A few M. lychnidis-dioicae hyphae were observed intercellularly in the center of the connective of vascular bundles at the early anther developmental stage. Subsequently, large numbers of deeply stained M. lychnidis-dioicae hyphae were observed intercellularly in the cells surrounding the pollen sac, as well as in the center of the pollen sac. Hyphae stained with lectin were observed intercellularly in all of the stamen filaments at flower development stages. Hyphae were observed in the peduncle connecting the flower and stem. It is thought that M. lychnidis-dioicae invaded the anther via the stamen filament over a long period. Additionally, in total, 163 sections of connective were obtained, and the cell structure of each anther was colored and subjected to three-dimensional reconstruction. The M. lychnidis-dioicae hyphae observed in the connective were mainly old hyphae with large vacuoles or dead hyphae (S1 Fig). These hyphae branched out, towards the pollen sac, while growing between the cells. We also observed that the host cells that collapsed near the hyphae had thick cell walls and teliospores. Cell wall collapse and cell degeneration were observed only around hyphae with thick cell walls.

Efficacy of propidium iodide and FUN-1 stains for assessing viability in basidiospores of Rhizopogon roseolus.

The use of spores in applications of ectomycorrhizal fungi requires information regarding spore viability and germination, especially in genera such as Rhizopogon with high rates of spore dormancy. The authors developed a protocol to assess spore viability of Rhizopogon roseolus using four vital stains to quantify spore viability and germination and to optimize storage procedures. They showed that propidium iodide is an excellent stain for quantifying nonviable spores. Observing red fluorescent intravacuolar structures following staining with 2-chloro-4-(2,3-dihydro-3-methyl-(benzo-1,3-thiazol-2-yl)-methylidene)-1-phenylquinolinium iodide (FUN-1) can help identify viable spores that are activated. At 6 mo and 1 y, the spores kept in a water suspension survived better than those left within intact, dry gasterocarps. Our work highlights the importance of temperature, nutrients, and vitamins for maturation and germination of spores of R. roseolus during 1 y of storage.

Atractiella rhizophila, sp. nov., an endorrhizal fungus isolated from the Populus root microbiome.

Among fungi isolated from healthy root mycobiomes of Populus, we discovered a new endorrhizal fungal species belonging to the rust lineage Pucciniomycotina, described here as Atractiella rhizophila. We characterized this species by transmission electron microscopy (TEM), phylogenetic analysis, and plant bioassay experiments. Phylogenetic sequence analysis of isolates and available environmental and reference sequences indicates that this new species, A. rhizophila, has a broad geographic and host range. Atractiella rhizophila appears to be present in North America, Australia, Asia, and Africa and is associated with trees, orchids, and other agriculturally important species, including soybean, corn, and rice. Despite the large geographic and host range of this species sampling, A. rhizophila appears to have exceptionally low sequence variation within nuclear rDNA markers examined. With inoculation studies, we demonstrate that A. rhizophila is nonpathogenic, asymptomatically colonizes plant roots, and appears to foster plant growth and elevated photosynthesis rates.