The compound negative impact of insect pests attacking agricultural ecosystems includes (i) direct yield losses from damaged crops, (ii) the economic cost of the attempt to prevent these losses and ...(iii) the negative short- and long-term hazard effects of chemical pesticides on human and environmental health. Entomopathogenic fungi (EMPF) are a group of microorganisms that represent the natural enemies of a number of crop pests, presenting an opportunity to harness their evolutionary fine-tuned relationship with their insect hosts as biocontrol agents in integrated pest management programs. The aim of this study was to establish an indigenous EMPF collection via the
(greater wax moth) entrapment method from the soils of Nile Delta, Egypt. Obtained insect associated fungal isolates were bio-assayed for pathogenicity against the serious pest
and
and the seven outperforming isolates were selected for molecular identification and thermotolerance assay. Based on ITS sequence analysis and phylogeny, selected isolates were identified as
(four isolates),
(two isolates) and one isolate of
. The obtained results demonstrated (i) the efficacy of using insect baiting coupled with molecular identification and pathogenicity screening to isolate EMPF to control insect pests, and (ii) the availability of indigenous virulent EMPF in Nile Delta's soil, which can be exploited for the development of sustainable crop protection strategies.
Members of the fungal genus
(Ascomycota, Hypocreales, Hypocreaceae) are ubiquitous and commonly encountered as soil inhabitants, plant symbionts, saprotrophs, and mycoparasites. Certain species have ...been used to control diverse plant diseases and mitigate negative growth conditions. The versatility of
's interactions mainly relies on their ability to engage in inter- and cross-kingdom interactions. Although
is by far the most extensively studied fungal biocontrol agent (BCA), with a few species already having been commercialized as bio-pesticides or bio-fertilizers, their wide application has been hampered by an unpredictable efficacy under field conditions. Deciphering the dialogues within and across
ecological interactions by identification of involved effectors and their underlying effect is of great value in order to be able to eventually harness
's full potential for plant growth promotion and protection. In this review, we focus on the nature of
interactions with plants and pathogens. Better understanding how
interacts with plants, other microorganisms, and the environment is essential for developing and deploying
-based strategies that increase crop production and protection.
Development of new effective biocontrol agents is largely based on the antagonistic capacity of candidate agents against targeted pathogens in vitro. Different mechanisms contribute to such capacity, ...including the activity of cell wall-degrading enzymes, secretion of antimicrobial secondary metabolites, growth vigour and resistance to exogenous and endogenous toxins. In this study, a series of laboratory experiments were designed to improve the antagonistic activities of Trichoderma spp. against two plant fungal pathogens, Sclerotium rolfsii and Rhizoctonia solani. A simple but efficient mutagenesis programme was carried out using ultraviolet light to induce modifications in the genetic structure of two Trichoderma biocontrol agents, T. virens and T. asperellum. The obtained mutants were subjected to a) initial screening for media-permeable antifungal metabolites using the cellophane membrane-based method, and b) selected mutants were subjected to a series of antagonistic tests. Results revealed that the antagonistic potential of selected mutants was significantly improved against the two plant pathogens. Genetic stability test results indicated that the UV-derived mutant Tv3, maintained its elevated performance after 12 rounds of sub-culture. Gene expression analysis for five antagonism-associated genes were examined using real-Time PCR. Results revealed that the gene expression of two genes, chitinase 33, a cell wall degrading enzyme and, polyketide synthase, which is responsible for polyketide biosynthesis, a class of secondary metabolites with antimicrobial roles, were significantly upregulated in one of the mutated T. virens strains. Results of our in vitro antagonistic studies along with our molecular analysis indicate that the UV mutagenesis could be an effective strategy to improve Trichoderma antagonistic potential.
Certain
strains protect plants from diverse pathogens using multiple mechanisms. We report a novel mechanism that may potentially play an important role in
-based biocontrol.
and
significantly ...increased the amount/activity of secreted antifungal metabolites in response to volatile compounds (VCs) produced by 13 strains of
, a soilborne fungus that infects diverse plants. This response suggests that both
spp. recognize the presence of
by sensing pathogen VCs and prepare for attacking pathogens. However,
did not respond to any, while
responded to VCs from only a few strains. Gene expression analysis via qPCR showed up-regulation of several biocontrol-associated genes in
in response to
VCs. Analysis of VCs from seven
strains tentatively identified a total of 28 compounds, including six that were produced by all of them. All four
species produced VCs that inhibited
growth. Analysis of VCs produced by
and
revealed the production of compounds that had been reported to display antifungal activity.
also recognizes
spp. by sensing their VCs and releases VCs that inhibit
, suggesting that both types of VC-mediated interaction are common among fungi.
Microbes communicate with each other using a wide array of chemical compounds, including volatile organic compounds (VOCs). Usually, such volatile-mediated interactions are studied by growing two ...different microbes in a shared, confined environment and by subsequently collecting and analyzing the emitted VOCs by gas chromatography. This procedure has several drawbacks, including artificial volatile overaccumulation and potential oxygen limitation, as well as the impossibility to assign a producer to the compounds newly emitted during the interaction. To address these challenges, we have developed a novel system specifically designed to analyze volatile-mediated interactions allowing for sequential unidirectional exposure of a “receiver” microorganism to the VOCs of an “emitter” microorganism. Using hermetically sealed systems connected to an air compressor, a constant unidirectional airflow could be generated, driving emitted volatiles to be absorbed by a collection charcoal filter. Thus, our developed system avoids artificial overaccumulation of volatile compounds and lack of oxygen in the headspace and enables the univocal assignment of VOCs to their producers. As a proof of concept, we used this newly developed experimental setup to characterize the reaction of plant growth-promoting and biocontrol fungus (
Trichoderma simmonsii
) to the perception of VOCs emitted by two plant pathogens, namely
Botrytis cinerea
and
Fusarium oxysporum
. Our results show that the perception of each pathogen's volatilome triggered a specific response, resulting in significant changes in the VOCs emitted by
Trichoderma
.
Trichoderma
's volatilome modulation was overall stronger when exposed to the VOCs from
Fusarium
than to the VOCs from
Botrytis
, which correlated with increased siderophore production when co-incubated with this fungus. Our newly developed method will not only help to better understand volatile-mediated interactions in microbes but also to identify new molecules of interest that are induced by VOC exposure, as well as the putative-inducing signals themselves.
Impairing plant growth and reducing crop production, salinity is considered as major problem in modern agriculture. The current study aimed to investigate the role of seeds' heat pretreatment at ...45 °C as well as application of two different nanoparticles nanosilica (N1) and nanoselenium (N2) in reducing salinity stress in three genotypes of Egyptian commercial soybeans (Glycine max L.). Two levels of salt stress using diluted sea water (1/12 and 1/6) were tested either alone or in combination with protective treatments. Obtained results revealed that salinity caused a significant reduction in all tested physiological parameters such as germination rate and membrane stability in soybean plants. A significant reduction in mitotic index and arrest in metaphase were recorded under both tested levels of salinity. It was also revealed that chromosomal abnormalities in soybean plants were positively correlated with the applied salinity concentrations. The fragmentation effect of salinity on the nuclear DNA was investigated and confirmed using Comet assay analysis. Seeds heat pre-treatment (45 °C) and both types of nanoparticles' treatments yielded positive effects on both the salt-stressed and unstressed plants. Quantitative real-time reverse transcription PCR (qRT-PCR) analysis for salt stress responsive marker genes revealed that most studied genes (CAT, APX, DHN2, CAB3, GMPIPL6 and GMSALT3) responded favorably to protective treatments. The modulation in gene expression pattern was associated with improving growth vigor and salinity tolerance in soybean plants. Our results suggest that seeds’ heat pretreatment and nanoparticle applications support the recovery against oxidative stresses and represent a promising strategy for alleviating salt stress in soybean genotypes.
Potato production worldwide is plagued by several disease-causing pathogens that result in crop and economic losses estimated to billions of dollars each year. To this day, synthetic chemical ...applications remain the most widespread control strategy despite their negative effects on human and environmental health. Therefore, obtainment of superior biocontrol agents or their naturally produced metabolites to replace fungicides or to be integrated into practical pest management strategies has become one of the main targets in modern agriculture. Our main focus in the present study was to elucidate the antagonistic potential of a new strain identified as Bacillus subtilis EG21 against potato pathogens Phytophthora infestans and Rhizoctonia solani using several in vitro screening assays. Microscopic examination of the interaction between EG21 and R. solani showed extended damage in fungal mycelium, while EG21 metabolites displayed strong anti-oomycete and zoosporecidal effect on P. infestans. Mass spectrometry (MS) analysis revealed that EG21 produced anti-fungal and anti-oomycete cyclic lipopeptides surfactins (C12-C19). Further characterization of EG21 confirmed its ability to produce siderophores and the extracellular lytic enzymes cellulase, pectinase and chitinase. The antifungal activity of EG21 cell-free culture filtrate (CF) was found to be stable at high-temperature/pressure treatment and extreme-pH values, and was not affected by proteinase K treatment. Disease-inhibiting effect of EG21 CF against P. infestans and R. solani infection was confirmed using potato leaves and tubers, respectively. Biotechnological applications of using microbial agents and their bioproducts for crop protection hold great promise to develop into effective, environment-friendly and sustainable biocontrol strategies.
Diverse fungi are intimately associated with plants, and molecules secreted from both the plant and fungal sides play critical roles in the establishment of their associations and affect plant growth ...and health. Through evolutionary arms races or strategic alliances with plants, fungi and other microbes have invented a bewildering array of secreted molecules to parasitize or communicate with plants. Research empowered by omics data and tools has greatly advanced understanding of the nature, role and mechanism of action of many secreted fungal proteins that affect plants directly or indirectly. However, available information about fungal volatile metabolites with similar functions is quite limited. Through this review, we aim to stimulate expeditions to this vastly under-explored frontier of fungal chemical ecology.
•Some fungal volatile metabolites function as intra- or inter-organismal signals.•Fungal volatile metabolites affect plant growth, development and/or health.•Information about how fungal volatile metabolites affect plants is limited.•Research on the chemical ecology underpinning plant-fungal interactions is needed.
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