Inhibition Of Plant Pathogens Research Articles

Suppression of Thielaviopsis ethacetica wilt and root rot, the emerging pathogen on bell pepper (Capsicum annuum), and plant growth promotion properties by the safety indigenous Streptomyces SBcT04

Thielaviopsis ethacetica is an emerging pathogen responsible for wilt and root rot in bell peppers, significantly impacting crop yield. Biological control of the fungal pathogen provides significant advantages as a safe and efficient alternative to excessive chemical fungicides for managing plant diseases. Studying the screened and selected potential actinomycete strain from the indigenous collection is a quick and efficient measure to protect the yield of local bell pepper crops. The research assessed the indigenous actinomycete's ability to inhibit plant pathogens and promote plant growth both in vitro and in vivo. The Streptomyces SBcT04 was the most effective against T. ethacetica TROC-2 pathogen in vitro. The inhibition percentage reached 89.15 ± 0.46 %. SBcT04 also effectively promoted plant growth properties in vitro. This strain fixed nitrogen and produced substantial amountsof indole-3-acetic acid (IAA), siderophores, and enzymes. Furthermore, the safety characteristics of SBcT04 for both the host plant (in vivo) and animals (in vitro) were confirmed. Streptomyces SBcT04 significantly processed pathogens, resulting in a reduction of approximately 40 % in disease severity. Additionally, SBcT04 significantly promoted the host plant's growth, even in the presence of T. ethacetica TROC-2 infection. The indigenous Streptomyces SBcT04 efficiently inhibited T. ethacetica and significantly enhanced bell pepper plant growth. These advantageous characteristics of SBcT04 indicate its potential to foster secure and sustainable local bell pepper agricultural output.

Biocontrol Ability of Strain Bacillus amyloliquefaciens SQ-2 against Table Grape Rot Caused by Aspergillus tubingensis.

Bacillus amyloliquefaciens strain SQ-2, isolated from a cured product, has been demonstrated to exhibit a highly efficacious performance against phytopathogens, including Stemphylium solani, Fusarium moniliforme, Fusarium graminearum, and Aspergillus tubingensis. In particular, with regard to A. tubingensis, which causes summer bunch rot, SQ-2 has been observed to suppress the mycelial growth of all tested grape cultivars by over 40%. Especially on Kyoho grapes, it has the highest inhibition rate of 53%. Scanning electron microscopy (SEM) confirms that SQ-2 is an effective agent for suppressing the mycelia proliferation, differentiation, and spore formation of A. tubingensis. Furthermore, an LC/MS analysis revealed that SQ-2 produces two principal lipopeptides, namely, bacillibactin and surfactin, in addition to a polyketide, bacillaene. Further analysis through gas chromatography-mass spectrometry (GC/MS) identified 41 distinct volatile organic compounds secreted by SQ-2. Transcriptomic analysis indicated that exposure to the metabolite of SQ-2 induced substantial gene expression alterations in A. tubingensis. These data suggest that B. amyloliquefaciens strain SQ-2 exhibits promising crop protection potential of inhibiting plant pathogens through the secretion of bacillibactin, surfactin, bacillaene, and VOCs.

Roles of Endophytic Fungi Isolated from Mangifera indica L. in Promoting Plant Growth.

Endophytic fungi have been shown to synthesize bioactive secondary metabolites, some of which promote plant growth through various mechanisms. In our previous study, endophytic fungi were isolated from mango trees (Mangifera indica L.). The present study examined fifty endophytic fungal isolates for mineral solubilization activity, ammonia production, and siderophore production. It was shown that these isolates could produce phytohormones indole-3-acetic acid and gibberellic acid, as well as inhibit plant pathogens, specifically Colletotrichum gloeosporioides and Lasiodiplodia theobromae. The results showed that all the isolated fungal endophytes exhibited various activities. Based on the findings, two fungal endophytes-Aureobasidium pullulans CY.OS 13 and Aspergillus tamarii CY.OS 144-were selected for dual inoculation in chili plants under pot-scale conditions to investigate their potential to improve growth-related traits such as seed germination, shoot and root length, biomass, and chlorophyll content. Seed treated with A. pullulans CY.OS 13 and/or A. tamarii CY.OS 144 showed a significant (p < 0.05) increase in seed germination and growth parameters of chili plants grown under pot-scale conditions. Particularly, chili plants whose seeds were injected with a combination of the two selected endophytic fungi showed the highest plant development traits. Therefore, the selected endophytic fungi have the potential to be used as biofertilizers, especially when combined. They could eventually replace chemical fertilizers because they are environmentally friendly, beneficial to humans, and can even promote sustainable agriculture.

Perillyl alcohol, a natural monoterpene, controls the gray mold on tomato via inducing jasmonic acid and kaempferol production

Perillyl alcohol (POH), a natural monoterpene, exhibits potent anticancer activity and may also play a role in inhibiting plant pathogens. However, its mechanism of action on controlling gray mold of tomato remains unclear. In this study, we investigated the effect of POH on Botrytis cinerea infected tomato. The results demonstrate that POH inhibits the in vitro growth of B. cinerea by disrupting plasma membrane integrity, thereby exhibiting broad-spectrum antimicrobial activity. Metabolomic analysis revealed that POH activated jasmonic acid (JA) biosynthesis and induced JA production in B. cinerea-treated tomato. Furthermore, POH upregulated the expression of defense-related genes and induced ROS accumulation. Specifically, POH induced the accumulation of kaempferol in tomato and exogenous kaempferol disrupted the plasma membrane of B. cinerea and induced ROS production. Taken together, POH can inhibit the development of gray mold, besides enhancing plant immunity against B. cinerea by inducing JA accumulation and promoting kaempferol biosynthesis.

Bioprospecting of endophytic diazotrophic microbes in sustainable agriculture: Review and prospects

Endophytic diazotrophic bacteria play an important role in developing sustainable modern agriculture. Endophytic bacteria can increase plant growth and yield by exhibiting antibiosis against phytopathogens. Biological mechanisms of atmospheric nitrogen fixation, phosphate solubilization, production of phytohormones and inhibition of plant pathogens and pests promote plant growth avoiding the need for chemical fertilizers and control agents. This review evaluates the groups of different endophytic bacteria, their prospects and challenges for sustainable agriculture. Several new bacterial strains were protected as bioinoculants or biopesticides. Formulations containing endophytic bacteria mainly were intended for seed coating or spraying and acted directly in the control of pests and diseases, as well as in increasing resistance to environmental stress. In many cases, they performed well in promoting the growth of plants by producing hormones that regulate or increase nutrient uptake. Bioprospecting in the case of this review is a systematic overview of the rational approach in harnessing beneficial plant-associated microbes to ensure food security in the future.

De novo Synthesis of Chiral 3,4‐DihydroquinazolinesviaOne‐Pot Enantioselective Ugi‐Azide/Cyclization Sequences†

Comprehensive SummaryHerein, we reported a precise de novo synthesis of chiral 3,4‐dihydroquinazoline frameworks via a one‐pot anionic stereogenic‐at‐cobalt(III) complex‐catalyzed enantioselective Ugi‐azide/Pd‐catalyzed cyclization sequence. This powerful protocol involves 5 components and 2 catalytic systems, delivering chiral 3,4‐dihydroquinazolines with excellent enantioselectivities (up to 94% ee). The preliminary antifungal experiments suggest that both Ugi‐adducts and 3,4‐dihydroquinazolines have great potential in inhibiting plant pathogens such as Trichoderma viride and Fusarium graminearum.

Description of Streptomyces naphthomycinicus sp. nov., an endophytic actinobacterium producing naphthomycin A and its genome insight for discovering bioactive compounds.

Endophytic actinobacteria are a group of bacteria living inside plant tissue without harmful effects, and benefit the host plant. Many can inhibit plant pathogens and promote plant growth. This study aimed to identify a strain of Streptomyces as a novel species and study its antibiotics production. An endophytic actinobacterium, strain TML10T was isolated from a surface-sterilized leaf of a Thai medicinal plant (Terminalia mucronata Craib and Hutch). As a result of a polyphasic taxonomy study, strain TML10T was identified as a member of the genus Streptomyces. Strain TML10T was an aerobic actinobacterium with well-developed substrate mycelia with loop spore chains and spiny surface. Chemotaxonomic data, including cell wall components, major menaquinones, and major fatty acids, confirmed the affiliation of strain TML10T to the genus Streptomyces. The results of the phylogenetic analysis, including physiological and biochemical studies in combination with a genome comparison study, allowed the genotypic and phenotypic differentiation of strain TML10T and the closest related type strains. The digital DNA-DNA hybridization (dDDH), Average nucleotide identity Blast (ANIb), and ANIMummer (ANIm) values between strain TML10T and the closest type strain, Streptomyces musisoli CH5-8T were 38.8%, 88.5%, and 90.8%, respectively. The name proposed for the new species is Streptomyces naphthomycinicus sp. nov. (TML10T = TBRC 15050T = NRRL B-65638T). Strain TML10T was further studied for liquid and solid-state fermentation of antibiotic production. Solid-state fermentation with cooked rice provided the best conditions for antibiotic production against methicillin-resistant Staphylococcus aureus. The elucidation of the chemical structures from this strain revealed a known antimicrobial agent, naphthomycin A. Mining the genome data of strain TML10T suggested its potential as a producer of antbiotics and other valuable compounds such as ε-Poly-L-lysine (ε-PL) and arginine deiminase. Strain TML10T contains the arcA gene encoding arginine deiminase and could degrade arginine in vitro.

Inhibition of Plant Pathogens by Parthenium hysterophorus: An Investigation into Antimicrobial Properties

Inhibition of Plant Pathogens by Parthenium hysterophorus: An Investigation into Antimicrobial Properties

Two distinct non-ribosomal peptide synthetase-independent siderophore synthetase gene clusters identified in Armillaria and other species in the Physalacriaceae.

Siderophores are important for ferric iron solubilization, sequestration, transportation, and storage, especially under iron-limiting conditions such as aerobic conditions at high pH. Siderophores are mainly produced by non-ribosomal peptide synthetase-dependent siderophore pathway, non-ribosomal peptide synthetase-independent siderophore synthetase pathway, or the hybrid non-ribosomal peptide synthetases/non-ribosomal peptide synthetases-independent siderophore pathway. Outcompeting or inhibition of plant pathogens, alteration of host defense mechanisms, and alteration of plant-fungal interactions have been associated with fungal siderophores. To understand these mechanisms in fungi, studies have been conducted on siderophore biosynthesis by ascomycetes with limited focus on the basidiomycetes. Armillaria includes several species that are pathogens of woody plants and trees important to agriculture, horticulture, and forestry. The aim of this study was to investigate the presence of non-ribosomal peptide synthetases-independent siderophore synthetase gene cluster(s) in genomes of Armillaria species using a comparative genomics approach. Iron-dependent growth and siderophore biosynthesis in strains of selected Armillaria spp. were also evaluated in vitro. Two distinct non-ribosomal peptide synthetases-independent siderophore synthetase gene clusters were identified in all the genomes. All non-ribosomal peptide synthetases-independent siderophore synthetase genes identified putatively encode Type A' non-ribosomal peptide synthetases-independent siderophore synthetases, most of which have IucA_IucC and FhuF-like transporter domains at their N- and C-terminals, respectively. The effect of iron on culture growth varied among the strains studied. Bioassays using the CAS assay on selected Armillaria spp. revealed in vitro siderophore biosynthesis by all strains irrespective of added FeCl3 concentration. This study highlights some of the tools that Armillaria species allocate to iron homeostasis. The information generated from this study may in future aid in developing molecular based methods to control these phytopathogens.

Potential of local Bacillus spp. isolates as wilt disease biocontrol agents for Fusarium oxysporum f. sp. cepae on Allium x wakegi

Abstract. Asrul. 2023. Potential of local Bacillus spp. isolates as wilt disease biocontrol agents for Fusarium oxysporum f. sp. cepae on Allium x wakegi. Biodiversitas 24: 4989-4997. Implementation of biological agents for eradication and inhibition of plant pathogens is often ineffective due to its protracted consequences. The objective of this research was to examine the potential of local isolates of Bacillus spp. as a biocontrol agent in suppressing Fusarium wilt disease (Fusarium oxysporum f. sp. cepae) on wakegi onions (Allium × wakegi Araki). The research was conducted in a completely randomized design (CRD) with the treatment of rhizospheric bacterial isolates. The treatments included control (without isolate application) and seven bacterial isolates, namely KP17, KP5, DB9, DB12, DB18, DG4 and DG11. Each treatment was repeated five times and each replication consisted of 10 wakegi onion plants. The results showed that a total of 46 isolates were isolated from the rhizosphere of wakegi onion and seven isolates among them were selected as biocontrol agents. These isolates had similarities with Bacillus spp. in accordance with the colony morphology, physiology and biochemical characteristics. Among the isolates found, DB12 emerged as the isolate that had the potential to be developed as a biocontrol agent.

Molecular Identification of Juglans Regia Endophyte LTL-G3, Its Antifungal Potential and Bioactive Substances.

Endophyte is one of the potential biocontrol agents for inhibiting plant pathogens. However, the mechanisms and characteristics involved in the inhibition of different phytopathogenic fungi by endophytes, especially walnut endophytes, are still largely unknown. The present study aimed to identify the walnut endophytic fungus LTL-G3 from a genetic point of view, assess the strain's antifungal activity, and determine the bioactivities of the substances it produces against plant pathogens. The homologous sequence of strain LTL-G3 was examined, and typical strains of the Trichoderma virens group were used to build NJ phylogenetic trees and analyze the taxonomic position of the strain. The biocontrol agent's antagonistic potential for many plant pathogenic fungi. By using silica gel G chromatography, the active components of the strain were separated and purified. The active components were identified using GC-MS and NMR. The strain LTL-G3 was identified as Trichoderma virens. Its fermentation and secondary metabolite extracts had a broad spectrum and strong inhibitory effect on the spread of six plant pathogens (Botrytis cinerea, Fusarium graminearum, Gloeosporium fructigenum, Phytophthora capsici, Rhizoctonia solani, and Valsa mali) evaluated, of which, its inhibition rate against Valsa mali reached 76.6% (fermentation extract) and 100% (ethyl acetate and n-butanol extracts). On silica gel G chromatography, bioactive compounds were divided into 6 fractions and 7 sub-fractions. Fr.2-2 was the sub-fraction that showed the greatest inhibitory against V. mali, as an inhibition percentage of 89.36% in 1 mg. mL-1. Fifteen key inhibitory chemicals identified using GC-MS. By examining the NMR data, the chemical make-up of the precipitated white solid was identified. The inhibition rate against V. mali increased by over 95% at a dosage of 1 mg. mL-1, indicating a significant linear association between compound A and that rate. The strain LTL-G3 can be applied as an efficient biological control agent against V. mali, and its highly inhibitive secondary metabolites provide the mechanism for this action.

Impact of Root Rot Disease of Zanthoxylum armatum on Rhizosphere Soil Microbes and Screening of Antagonistic Bacteria

Zanthoxylum armatum, a significant forest plant in southwestern China, is crucial for preserving soil and water resources. However, the presence of root rot disease has led to plant death, impacting the pepper sector. Effective control measures for this disease are still lacking. Rhizosphere microorganisms play a vital role in plant health by inhibiting plant pathogens and inducing plant resistance. This research aimed to isolate and characterize the pathogen responsible for root rot disease in Z. armatum. Comparative analysis of fungal and bacterial communities in the rhizosphere soil of healthy and diseased plants revealed Fusarium solani as the pathogenic fungus causing root rot disease. Diseased plants had a higher occurrence of Fusarium spp., while disease-free plants had a higher abundance of ecologically beneficial microbial communities that could potentially serve as biocontrol agents. Three bacterial strains (Bacillus subtilis, Bacillus amyloliquefaciens, and Bacillus siamensis) were identified as effective biocontrol agents, inhibiting the growth of the pathogenic fungus F. solani both in vivo and in vitro. This study deepens our understanding of the rhizosphere soil microbial community differences between diseased and healthy Z. armatum, providing potential biocontrol bacteria to enhance plant resistance against root rot disease.

Microbial Endophytes: Emerging Trends and Biotechnological Applications.

A plethora of knowledge on the role of endophytic microorganisms has been reported in recent years. The cooperative chemistry between the endophytes and the internal host tissue has turned them into a crucial aid for biotechnological applications. Microbial endophytes are ubiquitous among most plant species on earth and contribute to the benefit of host plants by generating a wide range of metabolites that provide the plant with survival value. Endophytes can either directly stimulate plant growth by producing phytohormones or indirectly stimulate plant growth by increasing the availability of soil nutrients to plants. Endophytes may also help suppress diseases in plants directly by neutralizing environmental toxic elements, and by inhibiting plant pathogens by antagonistic action, or indirectly by stimulating induced plant systemic resistance. Several natural compounds produced by endophytes as secondary metabolites are beneficial to both plants and humans. This is why endophytes are regarded as a significant source of novel natural products of value in modern medicine, agriculture, and industry. Endophytes are known for producing pigments, bioactive compounds, and industrially important enzymes, like glucanase, amylase, laccase, etc. Some endophytes can also produce nanoparticles that potentially have numerous applications in a variety of fields. They also play an important role in biodegradation and bioremediation, both of which are beneficial to the environment and ecology. In this review, we highlighted potential biotechnological applications of endophytic microbes, as well as their diverse importance in plant growth and public health.

Induced Resistance in Fruit and Vegetables: A Host Physiological Response Limiting Postharvest Disease Development.

Harvested fruit and vegetables are perishable, subject to desiccation, show increased respiration during ripening, and are colonized by postharvest fungal pathogens. Induced resistance is a strategy to control diseases by eliciting biochemical processes in fruits and vegetables. This is accomplished by modulating the progress of ripening and senescence, which maintains the produce in a state of heightened resistance to decay-causing fungi. Utilization of induced resistance to protect produce has been improved by scientific tools that better characterize physiological changes in plants. Induced resistance slows the decline of innate immunity after harvest and increases the production of defensive responses that directly inhibit plant pathogens. This increase in defense response in fruits and vegetables contributes to higher amounts of phenols and antioxidant compounds, improving both the quality and appearance of the produce. This review summarizes mechanisms and treatments that induce resistance in harvested fruits and vegetables to suppress fungal colonization. Moreover, it highlights the importance of host maturity and stage of ripening as limiting conditions for the improved expression of induced-resistance processes.

Culturable endophytic fungi community structure isolated from Codonopsis pilosula roots and effect of season and geographic location on their structures

BackgroundRhizosphere soil physicochemical, endophytic fungi have an important role in plant growth. A large number of endophytic fungi play an indispensable role in promoting plant growth and development, and they can provide protection for host plants by producing a variety of secondary metabolites to resist and inhibit plant pathogens. Due to the terrain of Gansu province is north–south and longitudinal, different climatic conditions, altitude, terrain and growth environment will affect the growth of Codonopsis pilosula, and the changes in these environmental factors directly affect the quality and yield of C. pilosula in different production areas. However, In C. pilosula, the connection between soil nutrients, spatiotemporal variation and the community structure of endophytic fungi isolated from C. pilosula roots has not been well studied.ResultsSeven hundred six strains of endophytic fungi were obtained using tissue isolation and the hyphaend-purification method from C. pilosula roots that picked at all seasons and six districts (Huichuan, HC; Longxi, LX; Zhangxian, ZX; Minxian, MX; Weiyuan, WY; and Lintao, LT) in Gansu Province, China. Fusarium sp. (205 strains, 29.04%), Aspergillus sp. (196 strains, 27.76%), Alternaria sp. (73 strains, 10.34%), Penicillium sp. (58 strains, 8.22%) and Plectosphaerella sp. (56 strains, 7.93%) were the dominant genus. The species composition differed from temporal and spatial distribution (Autumn and Winter were higher than Spring and Summer, MX and LT had the highest similarity, HC and LT had the lowest). physical and chemical of soil like Electroconductibility (EC), Total nitrogen (TN), Catalase (CAT), Urease (URE) and Sucrase (SUC) had significant effects on agronomic traits of C. pilosula (P < 0.05). AK (Spring and Summer), TN (Autumn) and altitude (Winter) are the main driving factors for the change of endophytic fungal community. Moreover, geographic location (such as altitude, latitude and longitude) also has effects on the diversity of endophytic fungi.ConclusionsThese results suggested that soil nutrients and enzyme, seasonal variation and geographical locations have an impact on shaping the community structure of culturable endophytic fungi in the roots of C. pilosula and its root traits. This suggests that climatic conditions may play a driving role in the growth and development of C. pilosula.

Changes in quality and microbiome composition of strawberry fruits following postharvest application of Debaryomyces hansenii, a yeast biocontrol agent

Microbial antagonists provide a new perspective on biological control by altering microbial diversity to control postharvest diseases of fruit. In this study, the biological control effect of Debaryomyces hansenii on postharvest diseases of strawberry and the influence on strawberry quality were determined. At the same time, the effect of D. hansenii on the composition of surface microbiome of strawberry fruit was analyzed by high-throughput sequencing technology. The results showed that D. hansenii treatment can inhibit the natural decay rate of strawberries, and the treatment group maintained a higher ascorbic acid content than the control group. However, there was no difference between the control and treatment groups in firmness, weight loss rate, soluble solids, titratable acidity, and other quality indicators. On the surface of strawberries treated with D. hansenii, the diversity of fungal community was changed, the composition and structure of the community were also altered (except the abundance of Debaryomyces spp.). Strawberries treated with D. hansenii could alter bacterial and fungal populations, inhibit plant pathogens, and lower the frequency of postharvest diseases in strawberries. This study helps to understand the microbial community structure on the surface of strawberries and guides the synthesis of strawberry postharvest disease complex biocontrol strains to achieve stable and sustainable postharvest disease control strategies of the fruits.

Implementing wood ants in biocontrol: Suppression of apple scab and reduced aphid tending.

Ants can become efficient biocontrol agents in plantation crops as they prey on pest insects and may inhibit plant pathogens by excreting broad-spectrum antibiotics. However, ants also provide a disservice by augmenting attended honeydew producing homopterans. This disservice may be avoided by offering ants artificial sugar as an alternative to honeydew. Here we tested the effect of artificial sugar feeding on aphid abundance in an apple plot with wood ants (Formica polyctena, Förster), and tested the effect of ant presence on apple scab (Venturia inaequalis, Cooke) disease incidence. Over a 2-year period, sugar feeding eliminated ant-attended aphid populations on the apple trees. Furthermore, scab symptoms on both leaves and apples were reduced considerably on ant trees compared to control trees without ants. The presence of ants on the trees reduced leaf scab infections by 34%, whereas spot numbers on fruits were reduced by between 53 and 81%, depending on apple variety. In addition, the spots were 56% smaller. This shows that problems with wood ant-attended homopterans can be solved and that ants can control both insect pests and plant pathogens. We therefore propose wood ants as a new effective biocontrol agent suitable for implementation in apple orchards and possibly other plantation crops. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Pulsed light reduces postharvest losses of Chinese bayberries by affecting fungal microbiota during cold storage

Non-thermal sterilization technology is considered a safe and effective approach in controlling postharvest losses of fruit. In this study, the effects of pulsed light (PL) on qualities of Chinese bayberries during storage at 10 °C, 95% RH for 12 d were investigated. At the same time, high-throughput sequencing was operated to identify fungal microbiota on Chinese bayberries. The results showed that PL treatment could inhibit the decay incidence and polyphenol oxidase (PPO) activity, maintain fruit firmness and enhance phenylalanine ammonia-lyase (PAL) activity, with no effect on titratable acid (TA), total soluble solids (TSS), malondialdehyde (MDA) content and superoxide dismutase (SOD) activity. Additionally, the PL treatment maintained alpha diversity and altered beta diversity. At the species level, the abundance of Monographella nivalis and Colletotrichum cordylinicota were reduced in PL samples, while Hanseniaspora uvarum and Diaporthe spp were enriched. M. nivalis and C. cordylinicota were positively correlated with weight loss and decay index according to canonical correspondence analysis (CCA). The data of microbial correlation network indicated that PL treatment reduced pathogenic fungal microbiotas and made fungal community more complex and steadier. This study demonstrated that PL affects fungal community by inhibiting plant pathogens, increasing the amounts of endophytes and consolidating microbial networks. It provides new insights into the dynamics of the microbiome of Chinese bayberries after PL treatment.

Diversity and Bioactivity of Endophytic Actinobacteria Associated with Grapevines

Grapevine trunk diseases (GTDs) are a significant problem for New Zealand viticulture. Endophytic actinobacteria are of interest as potential biocontrol agents due to their ability to inhibit plant pathogens and improve plant growth. However, no studies have investigated the diversity of actinobacteria associated with grapevines in New Zealand vineyards and their bioactivity. Actinobacteria diversity in different ‘Sauvignon blanc’ vine tissues from three vineyards (conventional and organic management, and different vine ages) was assessed using different methods and media. Forty-six endophytic actinobacteria were isolated, with more isolates recovered from roots (n = 45) than leaves (n = 1) and shoot internodes (n = 0). More isolates were recovered from the organic (n = 21) than conventional (n = 8) vineyard, mature (25-year old; n = 21) than young (2-year old; n = 2) vines and using a tissue maceration technique (n = 40). Actinomycete Isolation Agar, International Streptomyces Project 2, and Starch Casein media were effective for actinobacteria isolation. Most of the isolates recovered belonged to Streptomyces, with one isolate identified as Mycolicibacterium. Forty isolates were assessed for antifungal activity and plant growth-promoting (PGP) characteristics. Of these, 13 isolates had antifungal activity against test GTD pathogens (Dactylonectria macrodidyma, Eutypa lata, Ilyonectria liriodendri, Neofusicoccum parvum, and N. luteum). Eighteen isolates exhibited more than one PGP trait; 25siderophore production (n = 25), phosphate solubilization (n = 6), and indole acetic acid production (n = 16). Two strains, Streptomyces sp. LUVPK-22 and Streptomyces sp. LUVPK-30, exhibited the best antifungal and PGP properties. This study revealed the diversity of culturable endophytic actinobacteria from grapevines in New Zealand vineyards and their biocontrol potential against GTD pathogens.

Microbial Endophytes: A Hidden Plant Resident, Application and Their Role in Abiotic Stress Management in Plants

Microbial communities in nature involve complex interactions with several biotic and abiotic components. An endo-symbiotic association is one in which one organism lives within the host plant for at least a part of its life. It is often obligate and does not create visible disease and has been reported to exist for at least 400 million years. Beneficial endophytes promote plant nutrient uptake, host plant growth, reduce disease severity, inhibit plant pathogens and improve tolerance to environmental stresses. Stresses like salinity, alkalinity, drought, global warming, temperature and pollution will increase in prominence and endophytes are predicted to play a significant role and offer eco-friendly techniques to increase productivity under such conditions. There also exists the potential for genetic modification of endophytes to impart additional stress tolerance traits in hosts. The present review discusses the beneficial effect of fungal and bacterial endophytes, emphasizing improving crop productivity under abiotic stress conditions. The review also discusses the various aspects of physiological and molecular mechanisms determining the interaction and stress tolerance, enhancing plant functions and productivity.