<Emphasis Type="Italic">Epichloë</Emphasis> exudates promote in vitro and in vivo arbuscular mycorrhizal fungi development and plant growth

Background and aims

We studied, through exudates employment, the effect of Epichloë (endophytic fungi), both independently and in association with Bromus auleticus (grass), on arbuscular mycorrhizal fungi (AMF) colonization, host and neighbouring plants biomass production and soil changes.

Methods

Through in vitro and greenhouse experiments, Epichloë endophytes effect on AMF development was evaluated. In vitro studies of exudates effect on Gigaspora rosea and Rhizophagus intraradices were performed using root or endophyte exudates. A 6-month greenhouse experiment was conducted to determine Bromus auleticus endophytic status effect and endophyte exudates role in biomass production, neighbouring plants mycorrhizal colonization and soil properties.

Results

Endophyte exudates and E+ plant root exudates promoted in vitro AMF development in the pre-infective stage of G. rosea and in carrot root culture mycelium of R. intraradices in a dose-response relationship, while control media and E- plants exudates had no effect. R. intraradices colonization and plant growth was clearly increased by endophytes and their exudates.

Conclusions

This is the first work evidencing the direct effect of Epichloë endophytes and infected plants root exudates on AMF extramatrical development. While higher levels of AMF colonization were observed in E+ plants, no clear effect was detected in neighbouring plants colonization, plant biomass or soil properties.

     

Fungi from leaves of lotus (<Emphasis Type="Italic">Nelumbo nucifera</Emphasis>)

In spite of the self-cleaning property of its leaves called the lotus effect, leaves of lotus (Nelumbo nucifera) provide a habitat for an unknown fungal diversity. The aim of this study was to detect and identify fungi from leaves of N. nucifera, including ectophytic, parasitic and endophytic fungi, in Taiwan using different collection strategies, as well as morphological and diverse molecular markers established in the different systematic groups of fungi. Among ectophytic and parasitic fungi, a new species of Dissoconium and of Pseudocercospora are described, respectively. Phyllosticta nelumbonis Sawada is transferred to Diaporthe. Among plant parasitic fungi, Erysiphe takamatsui and Ps. nymphaeacea are recorded in Taiwan for the first time. Euryale is recorded as a new host genus for Ps. nymphaeacea. The basidiomycetous yeast Fereydounia khargensis is recorded for the first time from living plants and in East Asia. Endophytic fungi from lotus were studied for the first time. From 1002 plant segments, 476 endophytic isolates were produced in culture, comprising 33 typical terrestrial species mainly belonging to the genera Colletotrichum (mainly C. siamense), Diaporthe (D. tulliensis and D. ueckerae) and Fusarium (F. solani species 6, hitherto known from clinical samples), as well as to Xylariaceae, but no Ingoldian fungi. Most isolates were from leaf laminas (71%) compared to those from petioles (29%). From this observation, we conclude that the fungi of the aquatic lotus plant appear to have terrestrial origin and, after dispersal by wind and in spite of the lotus effect, may enter the plant from the lamina. Only three species isolated as endophytes were also found as ectophytic or parasitic fungi.     

Plant growth promoting potential of bacterial endophytes in novel association with <Emphasis Type="Italic">Olea ferruginea</Emphasis> and <Emphasis Type="Italic">Withania coagulans</Emphasis>

Microbially unexplored medicinal plants can have a genetically diverse microbial population with multi-functional plant growth promoting traits. In this aspect, 75 endophytic bacterial isolates with plant growth promoting traits were isolated from Withania coagulans Dunal and Olea ferruginea Royal. Many of these bacteria were able to solubilize phosphate, produce indole-3-acetic acid, ammonia as well as hydrogen cyanide, synthesize extracellular enzymes and show antagonistic activities against plant pathogenic fungi under in vitro conditions. These isolates were also characterized by morphological and biochemical analysis. Furthermore, four representative isolates with pronounced plant growth promoting activities were identified as Enterobacter cloacae, Enterobacter dissolvens, Enterobacter hormaechei and Cronobacter sakazakii by 16S rDNA sequencing analysis. This work for the first time, reported the isolation of endophytic bacteria, the novel association form selected plants, Withania coagulans and Olea ferruginea. The explored endophytes might have great potential in the field of biocontrol and plant growth promoting for sustainable agricultural practices.     

Isolation and molecular characterization of the fungal endophytic microbiome from conventionally and organically grown avocado trees in South Florida

Fungal endophytes are the most ubiquitous and highly diverse microorganisms that inhabit the interior of healthy plants. They are important in plant ecology and offer untapped potential to improve plant health and productivity in agroecosystems. The endophytic assemblage of avocado is poorly understood; therefore, surveys of fungal endophytes of Persea americana Mill. (Avocado) in South Florida organic and conventional orchards were conducted. A total of 17 endophytic fungal species were recovered from healthy avocado terminal branches. Endophytic fungal species were identified by rDNA sequencing of the internal transcribed spacer (ITS) region, using UNITE Species Hypotheses to reliably assign a taxon name, and determined as belonging to the genera Alternaria, Cladosporium, Colletotrichum, Corynespora, Diaporthe, Lasiodiplodia, Neofusicoccum, Neopestalotiopsis, Phyllosticta, and Strelitziana. Endophyte community assemblage differed between organic and conventional agroecosystems. This is the first report of Alternaria eichhorniae, Cladosporium tenuissimum, Corynespora cassiicola, Colletotrichum alatae, Diaporthe fraxini-angustifoliae, Lasiodiplodia gonubiensis, Neofusicoccum algeriense, Neofusicoccum andinum, Neopestalotiopsis foedans, Phyllosticta capitalensis, and Strelitziana africana as endophytes of avocado. Evaluation using pathogenicity tests on avocado leaves and terminal branches showed that endophytic fungal isolates did not cause disease symptoms.     

Phylogeny,antimicrobial, antioxidant and enzyme-producing potential of fungal endophytes found in <Emphasis Type="Italic">Viola odorata</Emphasis>

Viola odorata, a medicinal plant, is traditionally used to treat common cold, congestion and cough. Given its medicinal properties and occurrence in the northwestern Himalayas, we isolated and characterized endophytic fungi from this plant morphologically, microscopically and by internal transcribed spacer-based rDNA sequencing. In total, we isolated 27 morphotypes of endophytes belonging to phyla Ascomycota and Basidiomycota. The roots showed the highest diversity of endophyte as well as fungal dominance, followed by leaves and leaf nodes. The fungal extract of VOR16 (Fusarium oxysporum) displayed potent antimicrobial activity against Salmonella typhimurium, Klebsiella pneumoniae and Escherichia coli, with a minimum inhibitory concentration of 0.78, 0.78 and 1.56 μg/mL, respectively, while fungal extract VOLF4 (Aspergillus sp.) exhibited promising antioxidant activity (IC₅₀ of 17.4 μg/mL). To identify the components responsible for various bioactivities, we analyzed the content of penicillin G in the extract of bioactive endophytes. The results suggested that the expression of penicillin G under the fermentation conditions applied was too low to display antimicrobial effects. Thus, the activity may be contributed by a different, novel secondary metabolite. The antioxidant activity of VOLF4 may be attributed to its high content of flavonoids. Of the endophytic fungi assessed, 27% were found to be enzyme producers. The highest zone of clearance was observed in VOLN5 (Colletotrichum siamense) for protease production. Only VOR5 (Fusarium nematophilum) was found to be a producer of cellulase, glutenase, amylase and protease. In summary, this is the first report of the isolation of endophytes, namely Fusarium nematophilum, Colletotrichum trifolii, C. destructivum, C. siamense and Peniophora sp., from V. odorata and their bioactive and enzyme-producing potential.     

The genus <Emphasis Type="Italic">Diaporthe</Emphasis>: a rich source of diverse and bioactive metabolites

The genus Diaporthe (asexual state: Phomopsis) comprises pathogenic, endophytic and saprobic species with both temperate and tropical distributions. Although species of Diaporthe have in the past chiefly been distinguished based on host association, studies have confirmed several taxa to have wide host ranges, suggesting that they move freely between hosts, frequently co-colonizing diseased or dead tissue, while some species are known to be host-specific. They are also very frequently isolated as endophytes of seed plants. Due to their importance as plant pathogens, the genus has been thoroughly investigated for secondary metabolites, including during screening programs aimed at the discovery of novel bioactive natural products, but the respective information has never been compiled. Therefore, we have examined the relevant literature to explore and highlight the major classes of metabolites of Diaporthe and their Phomopsis conidial states. These fungi predominantly produce a large number of polyketides, but cytochalasins and other types of commonly encountered fungal secondary metabolites are also predominant in some species. Interestingly, not a single metabolite which is also known from the host plant has ever been isolated as a major component from an endophytic Diaporthe strain, despite the fact that many of the recent studies were targeting endophytic fungi of medicinal plants.     

Fungal endophytes of turmeric (<Emphasis Type="Italic">Curcuma longa</Emphasis> L.) and their biocontrol potential against pathogens <Emphasis Type="Italic">Pythium aphanidermatum</Emphasis> and <Emphasis Type="Italic">Rhizoctonia solani</Emphasis>

Endophytic fungi have been isolated from the healthy turmeric (Curcuma longa L.) rhizomes from South India. Thirty-one endophytes were identified based on morphological and ITS–rDNA sequence analysis. The isolated endophytes were screened for antagonistic activity against Pythium aphanidermatum (Edson) Fitzp., and Rhizoctonia solani Kuhn., causing rhizome rot and leaf blight diseases in turmeric respectively. Results revealed that only six endophytes showed >?70% suppression of test pathogens in antagonistic dual culture assays. The endophyte T. harzianum TharDOB-31 showed significant in vitro mycelial growth inhibition of P. aphanidermatum (76.0%) and R. solani (76.9%) when tested by dual culture method. The SEM studies of interaction zone showed morphological abnormalities like parasitism, shriveling, breakage and lysis of hyphae of the pathogens by endophyte TharDOB-31. Selected endophytic isolates recorded multiple plant growth promoting traits in in vitro studies. The rhizome bacterization followed by soil application of endophyte TharDOB-31 showed lowest Percent Disease Incidence of rhizome rot and leaf blight, 13.8 and 11.6% respectively. The treatment of TharDOB-31 exhibited significant increase in plant height (85 cm) and fresh rhizome yield/plant (425 g) in comparison with untreated control under greenhouse condition. The confocal microscopy validates the colonization of the TharDOB-31 in turmeric rhizomes. The secondary metabolites in ethyl acetate extract of TharDOB-31 were found to contain higher number of antifungal compounds by high resolution liquid chromatograph mass spectrometer analysis. Thereby, endophyte T. harzianum isolate can be exploited as a potential biocontrol agent for suppressing rhizome rot and leaf blight diseases in turmeric.     

Diversity of Culturable Plant Growth-Promoting Bacterial Endophytes Associated with Sugarcane Roots and Their Effect of Growth by Co-Inoculation of Diazotrophs and Actinomycetes

Application of environmentally friendly agents to reduce the use of chemicals and to enhance growth of plants is an ultimate goal of sustainable agriculture. The use of plant growth-promoting endophytes has become of great interest as a way to enhance plant growth and additionally protect plants from phytopathogens. In this study, 135 isolates of endophytic bacteria including actinomycetes were isolated from roots of commercial sugarcane plants cultivated in Thailand and were characterized for plant growth-promoting (PGP) traits. Based on morphological and 16S rRNA sequence analysis, the endophytes were distributed into 14 genera of which the most dominant species belong to Bacillus, Enterobacter, Microbispora, and Streptomyces. Two strains of endophytic diazotrophs, Bacillus sp. EN-24 and Enterobacter sp. EN-21; and two strains of actinomycetes, Microbispora sp. GKU 823 and Streptomyces sp. GKU 895, were selected based on their PGP traits including 1-aminocyclopropane-1-decarboxylate deaminase, indole-3-acetic acid, nitrogen fixation, phosphate solubilization, and siderophore production for evaluation of sugarcane growth enhancement by individual and co-inoculation. Sixty days after co-inoculation by endophytic diazotrophs and actinomycetes, the growth parameters of sugarcane plants were significantly greater than that of individual and un-inoculated plants. The results indicated that these endophytes have high potential as PGP agents that could be applied to promote sugarcane growth and could be developed as active added value biofertilizers in the future.     

Endophytic bacteria isolated from wild jojoba [<Emphasis Type="Italic">Simmondsia chinensis</Emphasis> L. (Schneider)] roots improve in vitro propagation

Endophytic bacteria promote plant growth, reduce stress caused by biotic and abiotic factors, and can trigger active defense reactions in plants. This study aimed to evaluate enzyme activity of in vitro jojoba (Simmondsia chinensis) plants inoculated with endophytic bacteria. In vitro shoots of female and male plants were inoculated with strains of Azospirillum brasilense (Cd), Methylobacterium aminovorans (JRR11), Rhodococcus pyridinivorans (JRR22) or co-inoculated with a mixture of JRR11?+?JRR22. A total of 10 treatments were performed to evaluate shoot and root length; changes in key enzymes involved in plant defense (superoxide dismutase, catalase, peroxidase, ascorbate peroxidase and phenylalanine ammonia lyase) after post-inoculation (45 days). All endophytic bacteria strains used promoted plant growth and rhizogenesis. Differences were found in enzyme activity between female and male plants. The plants inoculated with JRR22 strain, showed the highest enzyme activity suggesting an induced systemic response and a potential increase in plant resistance to pathogen attack.     

Infection by <Emphasis Type="Italic">Uromyces euphorbiae</Emphasis>: a trigger for the sporulation of endophytic <Emphasis Type="Italic">Colletotrichum truncatum</Emphasis> on the common host <Emphasis Type="Italic">Euphorbia hirta</Emphasis>

The common weed Euphorbia hirta (Euphorbiaceae) grows widely across tropical and subtropical regions. In this study, plants infected by an Uromyces species displayed characteristic rust pustules delimited by a necrotic band with a reddish-brown border. Observation of leaf tissues revealed 74% of lesions encircled by a row of dark brown setose acervuli, present exclusively within the necrotic area. Acervuli were never observed in the absence of Uromyces pustules. Isolation from healthy leaf tissues revealed the fungus to be endophytic. Morphological and molecular characterization confirmed Uromyces euphorbiae as the pathogen and revealed both the endophyte and the pustule-associated fungus to be members of the Colletotrichum trucatum complex, representing the first record of this fungus on E. hirta. As understanding of the interaction between host plants, endophytes and phytopathogens is currently limited, this system constitutes a model for investigation of the physiological processes involved in this endophyte-biotrophic pathogen interaction.     

Dark Septate Root Endophytic Fungus <Emphasis Type="Italic">Nectria haematococca</Emphasis> Improves Tomato Growth Under Water Limiting Conditions

The ascomycetous dark septate endophytic (DSE) fungi characterized by their melanized hyphae can confer abiotic stress tolerance in their associated plants in addition to improving plant growth and health. In this study inoculation of the DSE fungus Nectria haematococca Berk. & Broome significantly improved all the plant growth parameters like the plant height, stem girth, leaf characteristics and plant biomass of drought-stressed tomato. Root characters like the total root length, primary root diameter, 2nd order root number and diameter, root hair number and length were also significantly influenced by the fungal inoculation. Nevertheless, N. haematococca inoculation did not affect root colonization by native arbuscular mycorrhizal (AM) fungi and no significant correlation existed between the AM and DSE fungal variables examined. The proline accumulation in shoots of N. haematococca inoculated plants was significantly higher than uninoculated plants. The present study clearly indicates for the first time the ability of the DSE fungus, N. haematococca in inducing the drought stress tolerance and promoting the growth of the host plant under water stress.     

Evaluation of antifungal,phosphate solubilisation,and siderophore and chitinase release activities of endophytic fungi from <Emphasis Type="Italic">Pistacia vera</Emphasis>

Fungal endophytes use different strategies to protect host plants from abiotic and biotic stress. In this study, we isolated endophytic fungi from Pistacia vera and characterised their antifungal activity against Aspergillus flavus, Rhizoctonia solani and Sclerotinia sclerotiorum, and their release of some factors that can alter plant growth capability. Trichoderma harzianum TH 5-1-2, T. harzianum TH 10-2-2 and T. atroviride TA 2-2-1 exhibited the highest growth inhibition percentages in dual culture assays against A. flavus, R. solani and S. sclerotiorum, respectively. Among the fungal endophyte cultures, ethyl acetate extracts of T. harzianum TH 10-2-2, T. harzianum TH 5-1-2 and T. atroviride TA 2-2-1 exhibited the highest growth inhibition of S. sclerotiorum, R. solani and A. flavus, respectively. Phosphate solubilisation was induced by Byssochlamys nivea BN 1-1-1 in culture. Large amounts of siderophore production were observed with Quambalaria cyanescens QC 11-3-2 and Epicoccum nigrum EN1, but Trichoderma spp. also produced siderophore in lower amounts. Trichoderma harzianum TH 5-1-2 produced the highest chitinase activity (2.92 U/mL). In general, among the endophytes isolated, Trichoderma spp. appear to have the most promise for promoting healthy growth of P. vera.     

Plant growth promoting endophytic fungi <Emphasis Type="Italic">Asprgillus fumigatus</Emphasis> TS1 and <Emphasis Type="Italic">Fusarium proliferatum</Emphasis> BRL1 produce gibberellins and regulates plant endogenous hormones

Endophytes can serve as plant growth promoters as they secret a vast array of phytohormones to support host plants. Keeping the growth promoting activity of the endophytes in view, two endophytic fungi, Asprgillus fumigatus TS1 and Fusarium proliferatum BRL1 have been isolated from the roots of Oxalis corniculata. The isolates have been screened initially for growth promoting activities, including siderophores activity, phosphate solubilization, and secreation of indole acetic acid and gibberellins. Further, the isolates have assayed for the ability to promote the growth of mutant rice Waito-C. The plants associated with TS1 and BRL1 have shown higher chlorophyll content, root-shoot length, and biomass production. The growth promoting activity of the endophytes can be attributed to the various types of GAs and IAA that have been observed in the culture filtrates of the endophytes by the Gas chromatography/mass spectrometry (GC/MS). The GC/MS analysis revealed the presence of different gibberellins concentrations (ng/ml) in TS1 and BRL1 culture filtrate, i.e. GA₁ (0.091?±?0.009, 0.392?±?0.007), GA₃ (0.324?±?0.077, 0.089?±?0.0007) and GA₇ (0.023?±?0.002, 0.492?±?0.005), respectively. Besides, a significant up regulation of plant endogenous GA₁ (12.443?±?0.454 and 15.434?±?0.245) has been obsereved in TS1 and BRL1 associated plants compared to the control. Moreover, semi quantitative RT-PCR has confirmed the presence/invovment of GA pathways genes (P50–1, P450–3, P450–4, ggs2, and des). The results conclude that the endophytes isolated in this study can ably synthesize bioactive compounds, which play an important role in plant growth promotion.     

Synergistic plant–microbe interactions between endophytic bacterial communities and the medicinal plant <Emphasis Type="Italic">Glycyrrhiza uralensis</Emphasis> F.

Little is known about the composition, diversity, and geographical distribution of bacterial communities associated with medicinal plants in arid lands. To address this, a collection of 116 endophytic bacteria were isolated from wild populations of the herb Glycyrrhiza uralensis Fisch (licorice) in Xinyuan, Gongliu, and Tekesi of Xinjiang Province, China, and identified based on their 16S rRNA gene sequences. The endophytes were highly diverse, including 20 genera and 35 species. The number of distinct bacterial genera obtained from root tissues was higher (n?=?14) compared to stem (n?=?9) and leaf (n?=?6) tissue. Geographically, the diversity of culturable endophytic genera was higher at the Tekesi (n?=?14) and Xinyuan (n?=?12) sites than the Gongliu site (n?=?4), reflecting the extremely low organic carbon content, high salinity, and low nutrient status of Gongliu soils. The endophytic bacteria exhibited a number of plant growth-promoting activities ex situ, including diazotrophy, phosphate and potassium solubilization, siderophore production, auxin synthesis, and production of hydrolytic enzymes. Twelve endophytes were selected based on their ex situ plant growth-promoting activities for growth chamber assays to test for their ability to promote growth of G. uralensis F. and Triticum aestivum (wheat) plants. Several strains belonging to the genera Bacillus (n?=?6) and Achromobacter (n?=?1) stimulated total biomass production in both G. uralensis and T. aestivum under low-nutrient conditions. This work is the first report on the isolation and characterization of endophytes associated with G. uralensis F. in arid lands. The results demonstrate the broad diversity of endophytes associated with wild licorice and suggest that some Bacillus strains may be promising candidates for biofertilizers to promote enhanced survival and growth of licorice and other valuable crops in arid environments.     

Investigating the Role of Endophytic Fungi in <Emphasis Type="Italic">Gentiana scabra</Emphasis> bge. by Cross-Growth Period Inoculation

Gentiana scabra Bge. (gentian) is a Chinese medicinal plant. Endophytic fungi from the roots of gentian were isolated and cross-growth period inoculation was performed to study the roles of three Trichoderma spp. strains (F1, F2, and F9) in their original host plant. In treatments inoculated with F1, F2, and F9, gentiopicroside content increased 33.6, 23.7 and 13% than that in the control. Strains F1, F2, and F9 could also improve polysaccharide content by more than 6.6, 18.7 and 30% compared to the control. The incidence of spot blight in gentian inoculated with F1, F2, and F9 decreased by 31.2, 26.7 and 8.5%. Inconsistent changes in the activity of the three enzymes (superoxide dismutase, catalase and peroxidase) were observed when the plants were attacked by pathogens or inoculated with fungi. High enzymatic activity did not reflect mild disease. Cross-growth period inoculation, which takes into account the original living environment (gentian plant as “substrate” and different microorganisms as symbionts) of endophytic fungi, provides a new idea for studying effects of endophytes on their original hosts. This is the first research about the role of endophytic fungi in Gentiana scabra bge. in vivo.     

Phylogenetic analysis of <Emphasis Type="Italic">Plectosphaerella</Emphasis> species based on multi-locus DNA sequences and description of <Emphasis Type="Italic">P. sinensis</Emphasis> sp. nov.

Species in Plectosphaerella are well known as pathogens of several plant species causing fruit, root and collar rot and collapse. In an investigation of endophytic fungi associated with cucurbit plants in China, we isolated 77 strains belonging to the genus Plectosphaerella. To identify the isolated strains, we collected the type or reference strains of all currently accepted species in Plectosphaerella except P. oratosquillae and conducted a phylogenetic analysis. Phylogenetic analysis of the partial 28S rDNA sequences showed that all species in Plectosphaerella were located in one clade of Plectosphaerellaceae. Based on multi-locus phylogenetic analysis of the ITS, CaM, EF1, TUB and morphological characteristics, all species in Plectosphaerella were well separated. Three endophytic strains from stems of Cucurbita moschata, Citrullus lanatus and Cucumis melo from North China were assigned to a new species described as P. sinensis in this paper. The new species differs morphologically from other Plectosphaerella species by irregular chlamydospores, and the dimensions of phialides and conidia. The other endophytic strains from several cucurbit plants were identified as P. cucumerina.     

Effects of apical damage on plant growth and male and female reproductive investments in <Emphasis Type="Italic">Ambrosia artemisiifolia</Emphasis>, a wind-pollinated plant

In wind-pollinated plants, apical damage may decrease male fitness by reducing height-dependent pollen dispersal distance, but may not affect female fitness because plant height is not always correlated with female fitness. We hypothesized that Ambrosia artemisiifolia responds to apical damage by (1) restoring plant height through compensatory growth from lateral buds, and/or (2) increasing the sex allocation to female function to compensate for the loss of male fitness. We tested these hypotheses by comparing a group of experimental removal of the apical meristem with three control groups and by field surveys on apically damaged plants. Experimental apical damage suppressed main stem growth, but promoted vertical secondary growth from lateral buds. These responses resulted in compensation of stem height in the apically damaged plants to the same height as one of three control groups. The numbers of male and female flowers and male racemes did not differ between damaged and undamaged plants, indicating that apically damaged plants did not change their sex allocation. Therefore, our results support our first hypothesis. The results of a field survey of naturalized populations also supported the first hypothesis in that plant height and the number of male racemes did not change in plants with apical damage. Consequently, our results suggest that A. artemisiifolia has a high ability of fitness compensation after apical damage by restoring height and male function. This ability may contribute to its invasiveness in disturbed habitats.     

Cadmium and Nickel Toxicity for <Emphasis Type="Italic">Sinapis alba</Emphasis> Plants Inoculated with Endophytic Strains of <Emphasis Type="Italic">Bacillus subtilis</Emphasis>

We studied the effect of cadmium and nickel on Sinapis alba L. plants inoculated with endophytic strains of Bacillus subtilis. It was shown that treatment of S. alba seeds with endophytic strains of bacteria B. subtilis improves plant resistance to the toxic effect of cadmium and nickel and reduces manifestation of oxidative stress in the presence of higher levels of metal ions in the above-ground part of plants. Anti-stress effect and the ability of endophytic strains of B. subtilis to intensify uptake of cadmium and nickel ions by S. alba plants may be used for phytoextraction of heavy metals and stimulation of plant growth in contaminated areas.     

ITS2 sequence–structure phylogeny reveals diverse endophytic <Emphasis Type="Italic">Pseudocercospora</Emphasis> fungi on poplars

For matching the new fungal nomenclature to abolish pleomorphic names for a fungus, a genus Pseudocercospora s. str. was suggested to host holomorphic Pseudocercosproa fungi. But the Pseudocercosproa fungi need extra phylogenetic loci to clarify their taxonomy and diversity for their existing and coming species. Internal transcribed spacer 2 (ITS2) secondary structures have been promising in charactering species phylogeny in plants, animals and fungi. In present study, a conserved model of ITS2 secondary structures was confirmed on fungi in Pseudocercospora s. str. genus using RNAshape program. The model has a typical eukaryotic four-helix ITS2 secondary structure. But a single U base occurred in conserved motif of U-U mismatch in Helix 2, and a UG emerged in UGGU motif in Helix 3 to Pseudocercospora fungi. The phylogeny analyses based on the ITS2 sequence–secondary structures with compensatory base change characterizations are able to delimit more species for Pseudocercospora s. str. than phylogenic inferences of traditional multi-loci alignments do. The model was employed to explore the diversity of endophytic Pseudocercospora fungi in poplar trees. The analysis results also showed that endophytic Pseudocercospora fungi were diverse in species and evolved a specific lineage in poplar trees. This work suggested that ITS2 sequence–structures could become as additionally significant loci for species phylogenetic and taxonomic studies on Pseudocerospora fungi, and that Pseudocercospora endophytes could be important roles to Pseudocercospora fungi’s evolution and function in ecology.     

Land-use change impact on mycorrhizal symbiosis in female and male plants of wild <Emphasis Type="Italic">Carica papaya</Emphasis> (Caricaceae)

It has been acknowledged that land-use change has negative effects on genetic diversity and sex ratio in dioecious species, but less attention has been paid on the influence that land-use change has on the biotic interactions, especially between dioecious species and arbuscular mycorrhizal (AM) fungi. AM mutualism involves reciprocal transfer of carbohydrates and mineral nutrients between the host plant’s roots and these fungi. Here, we report spatial and temporal variation in AM colonization in dioecious wild Carica papaya plants growing in sites with different land use intensity. We tagged, recorded the basal stem circumference and collected roots of reproductive female and male Carica papaya plants in three wild sites during dry and rainy seasons of western Mexico. We also collected soil samples in each site to conduct soil chemical analyses. The sexes of C. papaya did not show significant differences in the frequency (percentage of root colonized by intraradical fungal structures) and abundance (length of intraradical hyphae) of AM fungi but the higher AM colonization was observed during the dry season, and in the site with the lowest disturbance. There was no relationship between soil chemistry and AM colonization. Overall, our findings suggest that land-use intensity has a negative effect on AM colonization and we discuss the consequences of habitat loss for the reproductive female and male plants, the implications of decreasing AM colonization for wild Carica papaya plants an important species that provides a source of genetic variation for the C. papaya varieties.