Protect Host Plants Research Articles

Community assembly and potential function analysis of the endophyte in Eucommia ulmoides

Endophytes play a pivotal role in protecting host plants from both biotic and abiotic stresses, promoting the production of active components (AC) and plant growth. However, the succession of the endophyte community in Eucommia ulmoides (E. ulmoides), particularly the community assembly and function, has not been extensively investigated. In this study, we employed high-throughput sequencing and bioinformatics tools to analyze endophyte diversity across different tree ages, parts, and periods. We examined the population differences, correlations, community assembly mechanisms, and functional roles of these endophytes. Functional predictions via PICRUSt2 revealed that most endophytic fungal functions were linked to biosynthesis, with significant differences in biosynthetic functional abundance across parts and periods. In contrast, the metabolic activity of endophytic bacteria remained stable across different periods and parts. Correlation analysis further confirmed a strong positive relationship between ACs and certain endophytic fungi. Among them, the fungal phyla Ascomycota and Basidiomycota were identified as key contributors to the metabolism of chlorogenic acid (CA), while Aucubin was significantly positively correlated with several endophytic bacteria. These findings provide valuable insights into the functional roles and community assembly mechanism of E. ulmoides endophytes, as well as their symbiotic relationships.

Pseudomonas produce various metabolites displaying herbicide activity against broomrape

Pseudomonads are well-known for their plant growth-promoting properties and biocontrol capabilities against microbial pathogens. Recently, their potential to protect crops from parasitic plants has garnered attention. This study investigates the potential of different Pseudomonas strains to inhibit broomrape growth and to protect host plants against weed infestation.Four Pseudomonas strains, two P. fluorescens JV391D17 and JV391D10, one P. chlororaphis JV395B and one P. ogarae F113 were cultivated using various carbon sources, including fructose, pyruvate, fumarate, and malate, to enhance the diversity of potential Orobanche growth inhibition (OGI)-specialized metabolites produced by Pseudomonas strains. Both global and targeted metabolomic approaches were utilized to identify specific OGI metabolites.Both carbon sources and Pseudomonas genetic diversity significantly influenced the production of OGI metabolites. P. chlororaphis JV395B and P. ogarae F113 produced unique OGI metabolites belonging to different chemical families, such as hydroxyphenazines and phloroglucinol compounds, respectively. Additionally, metabolomic analyses identified an unannotated potential OGI ion, M375T65. This ion was produced by all Pseudomonas strains but was found to be over-accumulated in JV395B, which likely explains its superior OGI activity. Then, greenhouse experiments were performed to evaluate the biocontrol efficacy of selected strains: they showed the efficacy of these strains, particularly JV395B, in reducing broomrape infestation in rapeseed.These findings suggest that certain Pseudomonas strains, through their metabolite production, can offer a sustainable biocontrol strategy against parasitic plants. This biocontrol activity can be optimized by environmental factors, such as carbon amendments. Ultimately, this approach presents a promising alternative to chemical herbicides.

Plant growth‐promoting rhizobacteria and Trichoderma shift common vetch (Vicia sativa) physiology and phyllosphere bacteria toward antagonism against anthracnose caused by Colletotrichum spinaciae

AbstractBackgroundPlant phyllosphere microbes are important for the host plant's protection. Plant growth‐promoting rhizobacteria (PGPR) and Trichoderma are common biocontrol agents (BCAs) for disease management. Pathogens and BCAs can change the rhizosphere microbial composition; however, the effect of PGPR or Trichoderma on plant phyllosphere microbes, particularly for mesocosms involving the interaction between pathogens and BCAs, is not well known.MethodsHigh‐throughput sequencing was used to identify the phyllosphere bacterial community of common vetch interacting with Colletotrichum spinaciae, two PGPRs (Bacillus subtilis and Bacillus licheniformis), and Trichoderma longibrachiatum. We evaluated anthracnose severity, phyllosphere bacteria diversity and composition, and the relationship between the activities of plant defense enzymes and hormonal molecules in plants treated with individual and combined inoculations of PGPRs, Trichoderma, and C. spinaciae.ResultsPGPR or Trichoderma alone reduced disease severity. Trichoderma reduced the salicylic acid content, PGPR increased the catalase activity in plants, and co‐inoculation of PGPR and Trichoderma decreased the salicylic acid content. Inoculation of PGPR and Trichoderma individually or in combination changed the disease‐associated phyllosphere bacteria, and this effect was related to plant defense enzymes and hormonal molecules.ConclusionsWe suggest that the plant defense response induced by PGPR and Trichoderma results in the enrichment of a fraction of favorable chloroplastic bacteria, which facilitates plant defense against diseases.

Transcriptome analysis of the synergistic mechanisms between two strains of potato virus Y in Solanum tuberosum L.

Many viruses employ a process known as superinfection exclusion (SIE) to block subsequent entry or replication of the same or closely related viruses in the cells they occupy. SIE is also referred to as Cross-protection refers to the situation where a host plant infected by a mild strain of a virus or viroid gains immunity against a more severe strain closely related to the initial infectant. The mechanisms underlying cross-protection are not fully understood. In this study, we performed a comparative transcriptomic analysis of potato (Solanum tuberosum L.) leaves. The strains PVYN−Wi-HLJ-BDH-2 and PVYNTN−NW-INM-W-369-12 are henceforth designated as BDH and 369, respectively. In total, 806 differentially expressed genes (DEGs) were detected between the Control and JZ (preinfected with BDH and challenge with 369) treatment. Gene Ontology (GO) analysis showed that the response to external biological stimulation, signal transduction, kinase, immunity, redox pathways were significantly enriched. Among these pathways, we identified numerous differentially expressed metabolites related to virus infection. Moreover, our data also identified a small set of genes that likely play important roles in the establishment of cross-protection. Specifically, we observed significant differential expression of the A1-II gamma-like gene, elongation factor 1-alpha-like gene, and subtilisin-like protease StSBT1.7 gene, with StSBT1.7 being the most significant in our transcriptome data. These genes can stimulate the expression of defense plant genes, induce plant chemical defense, and participate in the induction of trauma and pathogenic bacteria. Our findings provided insights into the mechanisms underlying the ability of mild viruses to protect host plants against subsequent closely related virus infection in Solanum tuberosum L.

Unlocking the potential of bacterial endophytes from medicinal plants for drug discovery.

Among the plant-associated microorganisms, the so-called endophytes continue to attract much attention because of their ability not only to protect host plants from biotic and abiotic stress factors, but also the potential to produce bioactive secondary metabolites. The latter property can elicit growth-promoting effects on plants, as well as boost the production of plant-specific secondary metabolites with valuable pharmacological properties. In addition, endophyte-derived secondary metabolites may be a rich source for the discovery of drugs to treat various diseases, including infections and cancer. However, the full potential of endophytes to produce bioactive secondary metabolites is often not revealed upon conventional cultivation in the laboratory. New advances in genomics and metabolic engineering offer exciting opportunities for the exploration and exploitation of endophytes' biosynthetic potential. This review focuses on bacterial endophytes of medicinal plants, some of their secondary metabolites and recent advances in deciphering their biosynthesis. The latter may assist in genetic engineering efforts aimed at the discovery of novel bioactive compounds with the potential to be developed into drugs.

Spatiotemporal distribution of sudden oak death in the US and Europe

Sudden Oak Death (SOD) is a devastating forest disease caused by Phytophthora ramorum, leading to rapid branch and leaf wilting. This study analyzed SOD data from various sources to study the spatiotemporal distribution of this pathogen globally. The spatial autocorrelation analysis shows that seven counties in the US have positive spatial correlations with high clustering values, whereas, the other six counties have negative correlations with low clustering values. In Europe, the regions with positive spatial correlations with high clustering values are located in England, Scotland, southern Finland, northern Germany, western France, and northern Spain, and many areas show negative correlations with low clustering values. The results of time series analysis reveal a clear seasonal pattern of pathogen incidence in the western US, with the peak of pathogen occurrences mainly in May and June. Furthermore, our spatiotemporal permutation scanning approach detects six clusters in the US and four in Western Europe during 2005–2006, 2012–2013, and 2021, providing insight into temporal dynamics and geographical hotspots of SOD. Our study also explored the impact of El Niño-Southern Oscillation (ENSO) on SOD for the first time, revealing a lag correlation up to 6 months. By improving our understanding of SOD spatiotemporal patterns and dynamics, we can better predict future trends and mitigate its impact. We recommend strengthening priority protection of host plants in areas where SOD outbreaks were clustered during La Niña events, and containing outbreak risks through effective detection, early warning and isolation of susceptible plants. This study provides a basis for global forest protection and disease prevention efforts to save susceptible plants.

Dynamics of Endophytic Fungal Communities Associated with Cultivated Medicinal Plants in Farmland Ecosystem.

Microorganisms are an important component of global biodiversity and play an important role in plant growth and development and the protection of host plants from various biotic and abiotic stresses. However, little is known about the identities and communities of endophytic fungi inhabiting cultivated medicinal plants in the farmland ecosystem. The diversity and community composition of the endophytic fungi of cultivated medicinal plants in different hosts, tissue niches, and seasonal effects in the farmland of Northern China were examined using the next-generation sequencing technique. In addition, the ecological functions of the endophytic fungal communities were investigated by combining the sequence classification information and fungal taxonomic function annotation. A total of 1025 operational taxonomic units (OTUs) of endophytic fungi were obtained at a 97% sequence similarity level; they were dominated by Dothideomycetes and Pleosporales. Host factors (species identities and tissue niches) and season had significant effects on the community composition of endophytic fungi, and endophytic fungi assembly was shaped more strongly by host than by season. In summer, endophytic fungal diversity was higher in the root than in the leaf, whereas opposite trends were observed in winter. Network analysis showed that network connectivity was more complex in the leaf than in the root, and the interspecific relationship between endophytic fungal OTUs in the network structure was mainly positive rather than negative. The functional predications of fungi revealed that the pathotrophic types of endophytic fungi decreased and the saprotrophic types increased from summer to winter in the root, while both pathotrophic and saprotrophic types of endophytic fungi increased in the leaf. This study improves our understanding of the community composition and ecological distribution of endophytic fungi inhabiting scattered niches in the farmland ecosystem. In addition, the study provides insight into the biodiversity assessment and management of cultivated medicinal plants.

Novel 1,3,4-Thiadiazole Derivatives: Synthesis, Antiviral Bioassay and Regulation the Photosynthetic Pathway of Tobacco against TMV Infection.

Tobacco mosaic virus (TMV) is a systemic virus that poses a serious threat to crops worldwide. In the present study, a series of novel 1-phenyl-4-(1,3,4-thiadiazole-5-thioether)-1H-pyrazole-5-amine derivatives was designed and synthesized. In vivo antiviral bioassay results indicated that some of these compounds exhibited excellent protective activity against TMV. Among the compounds, E2 (EC50 = 203.5 μg/mL) was superior to the commercial agent ningnanmycin (EC50 = 261.4 μg/mL). Observation of tobacco leaves infected with TMV-GFP revealed that E2 could effectively inhibit the spread of TMV in the host. Further plant tissue morphological observation indicated that E2 could induce the tight arrangement and alignment of the spongy mesophyll and palisade cells while causing stomatal closure to form a defensive barrier to prevent viral infection in the leaves. In addition, the chlorophyll content of tobacco leaves was significantly increased after treatment with E2, and the net photosynthesis (Pn) value was also increased, which demonstrated that the active compound could improve the photosynthetic efficiency of TMV-infected tobacco leaves by maintaining stable chlorophyll content in the leaves, thereby protecting host plants from viral infection. The results of MDA and H2O2 content determination revealed that E2 could effectively reduce the content of peroxides in the infected plants, reducing the damage to the plants caused by oxidation. This work provides an important support for the research and development of antiviral agents in crop protection.

Potential of endophytic fungi as therapeutics: Antibiotics, Antiviral and Anticancer properties

Antibiotic resistance, an emerging threat to human health, is the world's major challenge today. Endophytic microbes found in medicinal plants aid in the resolution of these issues. It is critical to select the plant that will be used to investigate endophytes for bioactive metabolites. As a result, medicinal plants which have been used as a traditional source of medicine for centuries, are a valuable source for bioprospecting endophytes. Fungi are the most commonly reported organisms among endophytes. Endophytic fungi are a diverse group of microbes that invade plant interior tissues without creating any symptoms. Endophytic fungi represent an abundant source of novel bioactive secondary metabolites with diversified structures that can be exploited for various applications in the field of therapeutics. Endophytic fungi produce secondary metabolites such as alkaloids, enzymes, steroids, terpenoids, phenols, quinones, peptides, polyketides etc. which have a higher therapeutic value. They produce a wide range of bioactive molecules with various biological activities such as antibacterial, antiviral, antifungal, antioxidants, cytotoxic and antimalarial compounds. The chemical diversity of endophytic fungi also serves to protect host plants from pathogens by hindering their growth and stimulating the host immune system, thereby enhancing plant defense mechanisms. Endophytic fungi synthesize metabolites that are identical to their host medicinal plant (azadirachtin, taxol, ginkgolide, jasmonic acid, camptothecin etc.) due to their specific capacity to form a symbiotic association with the host. Endophytic fungi can serve as substitutes for secondary metabolite production, aiding in biodiversity conservation. This review discusses numerous bioactive metabolites produced by endophytic fungi that have diverse biological activities. The majority of these metabolites have the potential to be utilized as drugs to treat a wide range of diseases.

Culturable Endophyte Fungi of the Well-Conserved Coastal Dune Vegetation Located on the East Coast of the Korean Peninsula

This study aimed to determine the diversity and distribution of endophytic fungi in coastal dune vegetation. Endophytic fungi promote plant growth and protect host plants from environmental stress and pathogens. Plants that have flourished as a result are critical for protecting coastal sand dunes from erosion. A total of 361 root-colonizing fungal endophytes were purely isolated from 24 halophyte species comprising all dune plant communities indigenous to a well-conserved coastal area based on morphological differences. Molecular identification and phylogeny using amplified ribosomal RNA sequences and internal transcribed spacer regions identified that the fungal isolates belong to seven classes and 39 genera. Penicillium (43.21%) was the most dominant genera, followed by Talaromyces (16.90%) and Aspergillus (11.91%). Furthermore, these genera present a wide host range. However, 16 other genera exhibited strong host specificity. When compared to other herbaceous or shrub host plant species, Talaromyces predominated as endophytes of the roots of the canopy-forming coastal windbreak tree Pinus thunbergii. Based on Margalef’s, Menhinick’s, Shannon’s, and Simpson’s diversity indices, the root-colonizing endophytes of P. thunbergii had higher morphological diversity. The endophyte fungi associated with five of the coastal plants studied are heretofore unreported. In fact, of all fungal genera characterized here, 13 genera (30%) have not been previously reported as marine fungal endophytes or coastal fungi. The foregoing results suggest that future coastal sand dune conservation studies should examine the biological resources of entire bioclusters and not merely the dominant plants or their endosymbionts.

Microbiome analysis revealed distinct microbial communities occupying different sized nodules in field-grown peanut.

Legume nodulation is the powerhouse of biological nitrogen fixation (BNF) where host-specific rhizobia dominate the nodule microbiome. However, other rhizobial or non-rhizobial inhabitants can also colonize legume nodules, and it is unclear how these bacteria interact, compete, or combinedly function in the nodule microbiome. Under such context, to test this hypothesis, we conducted 16S-rRNA based nodule microbiome sequencing to characterize microbial communities in two distinct sized nodules from field-grown peanuts inoculated with a commercial inoculum. We found that microbial communities diverged drastically in the two types of peanut nodules (big and small). Core microbial analysis revealed that the big nodules were inhabited by Bradyrhizobium, which dominated composition (>99%) throughout the plant life cycle. Surprisingly, we observed that in addition to Bradyrhizobium, the small nodules harbored a diverse set of bacteria (~31%) that were not present in big nodules. Notably, these initially less dominant bacteria gradually dominated in small nodules during the later plant growth phases, which suggested that native microbial communities competed with the commercial inoculum in the small nodules only. Conversely, negligible or no competition was observed in the big nodules. Based on the prediction of KEGG pathway analysis for N and P cycling genes and the presence of diverse genera in the small nodules, we foresee great potential of future studies of these microbial communities which may be crucial for peanut growth and development and/or protecting host plants from various biotic and abiotic stresses.

Influence of arbuscular mycorrhizal fungi on biological control of coffee leaf rust (Hemileia vastatrix BERK. & BROOME)

Inoculating plants with arbuscular mycorrhizal fungi (AMF) protects host plants against biotic stressors such as diseases. Therefore, the objective of this study was to evaluate the influence of arbuscular mycorrhizal fungi in the biological control of coffee leaf rust (CLR) infections. The research involved two varieties of coffee (Caturra and Pache) and three inocula of AMF: Moyobamba (Acaulospora mellea, Acaulospora sp.1, Glomus geosporum, Glomus sp.1, and Glomus sp.2), El Dorado (Acaulospora rugosa, Acaulospora spinosissima, Acaulospora lacunosa, Glomus sinuosum and Ambispora appendicula) and Huallaga (Acaulospora mellea, Acaulospora sp.1, Acaulospora sp.2, Glomus macrocarpum and Glomus sp.2), in addition to a control treatment without application of AMF (non-AMF). Inoculation of vegetatively propagated coffee plants with AMF was observed to induce tolerance to CLR. The incidence of CLR in non-AMF coffee plants was 43.7 %, while in the coffee plants subjected to the inocula Moyobamba, El Dorado and Huallaga, the incidences were 22.1, 22.7 and 13.2 %, respectively. Likewise, the severity in non-AMF coffee plants was 34.8 %, while in the coffee plants subjected to the three kinds of inocula, the severities were 21.1, 20.4 and 12.0 %, respectively. Thus, mycorrhizal inoculation of coffee plants at the nursery stage reduces the negative effect of CLR infection after the plants are taken to field conditions, representing a sustainable option for their biological control.

Symbiotic ant traits produce differential host-plant carbon and water dynamics in a multi-species mutualism.

Cooperative interactions may frequently be reinforced by "partner fidelity feedback," in which high- or low-quality partners drive positive feedbacks with high or low benefits for the host, respectively. Benefits of plant-animal mutualisms for plants have been quantified almost universally in terms of growth or reproduction, but these are only two of many sinks to which a host-plant allocates its resources. By investigating how partners to host-plants impact two fundamental plant resources, carbon and water, we can better characterize plant-partner fidelity and understand how plant-partner mutualisms may be modulated by resource dynamics. In Laikipia, Kenya, four ant species compete for Acacia drepanolobium host-plants. These ants differ in multiple traits, from nectar consumption to host-plant protection. Using a 5-year ant removal experiment, we compared carbon fixation, leaf water status, and stem non-structural carbohydrate concentrations for adult ant-plants with and without ant partners. Removal treatments showed that the ants differentially mediate tree carbon and/or water resources. All three ant species known to be aggressive against herbivores were linked to benefits for host-plant resources, but only the two species that defend but do not prune the host, Crematogaster mimosae and Tetraponera penzigi, increased tree carbon fixation. Of these two species, only the nectivore C. mimosae increased tree simple sugars. Crematogaster nigriceps, which defends the tree but also castrates flowers and prunes meristems, was linked only to lower tree water stress approximated by pre-dawn leaf water potential. In contrast to those defensive ants, Crematogaster sjostedti, a poor defender that displaces other ants, was linked to lower tree carbon fixation. Comparing the effects of the four ant species across control trees suggests that differential ant occupancy drives substantial differences in carbon and water supply among host trees. Our results highlight that ant partners can positively or negatively impact carbon and/or water relations for their host-plant, and we discuss the likelihood that carbon- and water-related partner fidelity feedback loops occur across ant-plant mutualisms.

The Multifunctions and Future Prospects of Endophytes and Their Metabolites in Plant Disease Management.

Endophytes represent a ubiquitous and magical world in plants. Almost all plant species studied by different researchers have been found to harbor one or more endophytes, which protect host plants from pathogen invasion and from adverse environmental conditions. They produce various metabolites that can directly inhibit the growth of pathogens and even promote the growth and development of the host plants. In this review, we focus on the biological control of plant diseases, aiming to elucidate the contribution and key roles of endophytes and their metabolites in this field with the latest research information. Metabolites synthesized by endophytes are part of plant disease management, and the application of endophyte metabolites to induce plant resistance is very promising. Furthermore, multi-omics should be more fully utilized in plant–microbe research, especially in mining novel bioactive metabolites. We believe that the utilization of endophytes and their metabolites for plant disease management is a meaningful and promising research direction that can lead to new breakthroughs in the development of more effective and ecosystem-friendly insecticides and fungicides in modern agriculture.

Potential biocontrol and plant growth promotion of an endophytic bacteria isolated from Glycyrrhiza uralensis seeds

BackgroundEndophytic bacteria have been demonstrated to be one of the most potentially important biocontrol agents for their efficiently improved plant growth and protection of host plants from infection by phytopathogens.ResultsNine strains of endophytic bacteria isolated from Glycyrrhiza uralensis Fisch. (G. uralensis) seeds were screened for the inhibitory effect against 5 fungal phytopathogens by using dual culture method. Among which, the isolate FT2 showed the highest percentage of inhibition to all the test fungal phytopathogens. Detached root assay showed that FT2 significantly reduced disease index and rotted area on Angelica sinensis root slices caused by Fusarium acuminatum. FT2 also exhibited multiple plant growth promotion traits by qualitative analytical method. Based on phenotypic, physiological and biochemical characterization and genotypic characterization, the FT2 strain was identified as Stenotrophomonas rhizophila. Application of strain FT2 reduced the disease index of Cucumber Fusarium Wilt, and the biocontrol effect was equal to chemical fungicide, carbendazim. Moreover, strain FT2 increased the plant height, stem diameter, leaf number and fresh weight of cucumber seedlings and the activities of the defense-related enzymes including phenylalanine ammonia-lyase, polyphenol oxidase and peroxidase. In addition, strain FT2 could promote seed germination and seedling growth of G. uralensis and increase enzyme activities, available nutrient contents and bacterial count in G. uralensis rhizosphere soil.ConclusionsThe results demonstrated that the strain FT2 could be used to develop environmentally friendly microbial products to improve the activity against pathogenic and promote plant growth.

Rhizophagus intraradices improves arsenic tolerance in Sophora viciifolia Hance

PurposeArbuscular mycorrhizal fungi (AMF) are capable of protecting host plants against heavy metal toxicity, whereas rare knowledge has been acquired on the underlying effects of AMF on woody leguminous species under arsenic (As) stress. This study was aimed that whether AMF inoculation improves the As tolerance in Sophora viciifolia (a king of leguminous shrub).MethodsS. viciifolia seedlings were inoculated with AMF Rhizophagus intraradices, and then the seedlings were grown at three levels (0, 50, and 100 mg As kg−1 soil) of As-polluted soil by performing the potted experiments. The plant growth, photosynthetic parameter, oxidative damage, antioxidant enzyme activities and gene expression of phytochelatin synthase in R. intraradices- and non-inoculated S. davidii seedlings under the different levels of As stress were analyzed.ResultCompared with non-inoculated S. viciifolia at the identical As level, R. intraradices-inoculated S. viciifolia were higher in the shoot and root dry weight, plant height, root length, photosynthetic rate, stomatal conductance, transpiration rate, maximal photochemical efficiency of PSII photochemistry, actual quantum yield, and photochemical quenching values, while the intercellular CO2 concentration and non-photochemical quenching values were lower. As-induced oxidative stress generating malondialdehyde, hydrogen peroxide and superoxide in the S. viciifolia leaves and roots reduced significantly by R. intraradices inoculation, whereas the activities of antioxidative enzymes (e.g., superoxide dismutase, peroxidase, and catalase) in S. viciifolia leaves and roots were increased by R. intraradices inoculation. Notably, R. intraradices inoculation up-regulated the gene expression of S. viciifolia phytochelatins in the leaves and roots.ConclusionThese results demonstrated that R. intraradices inoculation enhanced the As tolerance in S. viciifolia seedlings by improving the plant growth, gas exchange, chlorophyll fluorescence, reactive oxygen species, antioxidant enzymes and gene expression of S. viciifolia phytochelatins. The present study verified a multifarious positive role of AMF for woody leguminous species under As stress.

Olive Fungal Epiphytic Communities Are Affected by Their Maturation Stage.

The phyllosphere comprises the aerial parts of plants and is colonized by a great diversity of microorganisms, either growing inside (as endophytes) or on the surface (as epiphytes) of plant tissues. The factors that structure the diversity of epiphytes and the importance of these microorganisms for host plant protection have been less studied when compared to the case of endophytes. In this work, the epiphytic fungal communities from fruits of the olive tree (olives) in different maturation stages (green and semi-ripened), obtained from different olive orchard managements (integrated and organic production) and from distinct cultivars displaying different susceptibilities to olive anthracnose (Cobrançosa and Madural), are compared by using a metabarcoding approach. We discuss whether such differences in host resistance against anthracnose depend on both the fungal taxa or fungal community composition. A total of 1565 amplicon sequence variants (ASVs) were obtained, mainly belonging to the Ascomycota phylum and Saccharomycetes class. Although significant differences on epiphytic fungal richness were observed among olives obtained in different production systems and maturation stages, these factors in addition to host cultivar did not influence the composition of the epiphytes. Despite these results, a co-inertia analysis showed that Aureobasidium spp. and Sporocadaceae spp. were positively associated with the green olives of the cv. Madural produced under integrated production, while Saccharomycetales spp. (Kluyveromyces, Candida, Kazachstania and Saccharomyces) were positively associated with the semi-ripened olives of the cv. Cobrançosa obtained from organic production. The discriminant power of these fungi, some of them recognized as biocontrol agents, suggest that they might be important in conferring differences on host plant susceptibility to anthracnose.

Omics Profiles of Non-transgenic Scion Grafted on Transgenic RdDM Rootstock.

Grafting of commercial varieties onto transgenic stress-tolerant rootstocks is attractive approach, because fruit from the non-transgenic plant body does not contain foreign genes. RNA silencing can modulate gene expression and protect host plants from viruses and insects, and small RNAs (sRNAs), key molecules of RNA silencing, can move systemically. Here, to evaluate the safety of foods obtained from sRNA-recipient plant bodies, we investigated the effects of rootstock-derived sRNAs involved in mediating RNA-directed DNA methylation (RdDM) on non-transgenic scions. We used tobacco rootstocks showing RdDM against the cauliflower mosaic virus (CaMV) 35S promoter. When scions harboring CaMV 35S promoter sequence were grafted onto RdDM-inducing rootstocks, we found that RdDM-inducing sRNAs were only weakly transported from the rootstocks to the scion, and we observed a low level of DNA methylation of the CaMV 35S promoter in the scion. Next, wild-type (WT) tobacco scions were grafted onto RdDM-inducing rootstocks (designated NT) or WT rootstocks (designated NN), and scion leaves were subjected to multi-omics analyses. Our transcriptomic analysis detected 55 differentially expressed genes between the NT and NN samples. A principal component analysis of proteome profiles showed no significant differences. In the positive and negative modes of LC-ESI-MS and GC-EI-MS analyses, we found a large overlap between the metabolomic clusters of the NT and NN samples. In contrast, the negative mode of a LC-ESI-MS analysis showed separation of clusters of NT and NN metabolites, and we detected 6 peak groups that significantly differed. In conclusion, we found that grafting onto RdDM-inducing rootstocks caused a low-level transmission of sRNAs, resulting in limited DNA methylation in the scion. However, the causal relationships between sRNA transmission and the very slight changes in the transcriptomic and metabolomic profiles of the scions remains unclear. The safety assessment points for grafting with RdDM rootstocks are discussed.

Isobenzofuranones and isocoumarins from kiwi endophytic fungus Paraphaeosphaeria sporulosa and their antibacterial activity against Pseudomonas syringae pv. actinidiae

Development of the kiwifruit industry has been severely hindered by the canker disease, which is caused by the bacterium Pseudomonas syringae pv. Actinidiae (Psa). However, endophytic fungi associated with healthy kiwi plants may protect host plants through the production of metabolites with potent anti-Psa activity. In the current study, four undescribed isobenzofuranones, namely sporulactones A‒D, two undescribed isocoumarins, namely sporulactones E and F, together with eight known analogs were isolated from the kiwi endophytic fungus Paraphaeosphaeria sporulosa. The structures with absolute configurations were established by extensive spectroscopic methods, quantum chemistry calculations, and X-ray diffraction experiments. In addition, five of the compounds exhibited anti-Psa activity, with minimum inhibitory concentration (MIC) values ranging from 25 to 100 μg/mL. These findings suggest that the small polyketide metabolites produced by P. sporulosa play an important role in the antibacterial properties of the endophyte.

Impact of Gamma Irradiation on Tomato, and Pepper Growth Parameters, Phytochemical, Nematode Infectivity and detection of DNA Damage by Comet Assay

Root -knot nematode is a challenge of most vegetable production and there is a critical need to an alternative, effective, safe technique for control. The main objective of this study was to detect the effect of five doses of gamma irradiation on Meloidogyne incognita (Mi) infectivity, host growth, and DNA damage. Three-week-old- seedlings of: tomato, (Solanum lycopersicum), and pepper (Capsicum annum), were irradiated with five doses i.e. 100, 250,500,750, and 1000 Gy and transplanted in 20cm diameter pots in the screen-house. Halves of the replicates/ dose were inoculated with 1000 2IJs, while others were kept as controls. DNA damage was measured by comet assay which performed on the host leaves. Data demonstrated that, all nematode parameters were decreased beginning from the lowest does (100Gy), while, the plant growth parameters were enhanced significantly at 100 and 250Gy even when infected with nematodes and so did the chlorophyll a,b, carotenoids, and total phenols, antioxidative enzymes; Polyphenol oxidase (PPO), peroxidase (POX), Catalase (CAT) and Superoxide dismutase (SOD). Likewise, quantity of DNA damage was represented as mean of % DNA in tail, tail moment, tail length, and olive tail moment which were more pronounced than the control. As a conclusion, gamma irradiation at 100 and 250 Gy could protect host plants of nematode infection and increase the plant growth. Therefore, this approach introduces a promising technique in the integrated pest programs without any suppressive effects on the growth of plant hosts.