Biological Control Strategies Research Articles

Pathogenicity of Serratia marcescens strains as biological control agent: Implications for sustainable pest management.

The escalating demand for sustainable and eco-friendly pest management strategies has raised interest in harnessing the pathogenic potential of microorganisms. Serratia marcescens, a Gram-negative bacterium, has emerged as a potential biological control agent for sustainable pest management. This review critically examines the history, biology, identification, and pathogenicity of S. marcescens strain with their potential application in pest management. The diverse mechanisms employed by the strain to exert control over pests, including the production of metabolites and the induction of systemic resistance in plants, are examined. The review also summarizes the ecological significance and global distribution of S. marcescens associated with the use of S. marcescens in biological control strategies. Furthermore, the usage efficacy of S. marcescens over other conventional chemicals is discussed. A comprehensive understanding of the pathogenic potential of S. marcescens strains as biological control agents is crucial for developing effective and sustainable pest management strategies. This review consolidates current research advances on S. marcescens, and provides insights into the prospects and challenges of using S. marcescens for integrated pest management.

Application of omics technology in ecotoxicology of arthropod in farmland

Abstract Arthropods, abundant in farmland, have unique biological traits that make them valuable for studying the ecotoxicological impacts of pollutants. Recent advancements in multi-omics technologies have enhanced their use in assessing pollution risks and understanding toxicity mechanisms. This paper reviews recent developments in applying omics technologies—genomics, transcriptomics, proteomics, metabolomics and meta-omics to ecotoxicological research on farmland arthropods. Agricultural arthropods manage genes and proteins like metallothioneins (MTs), antioxidant enzyme systems, heat shock proteins, cytochrome P450 (CYP450), carboxylesterases (CarEs), and glutathione S-transferases (GSTs), for detoxification and antioxidant purposes. They adjust amino acid, sugar, and lipid metabolism to counteract pollutant-induced energy drain and modify gut microbiota to aid in detoxification. This study advocates for enhanced analysis of compound pollution and emerging pollutants using multi-omics, especially meta-omics, to clarify the toxicological mechanisms underlying arthropod responses to these pollutants. Furthermore, it underscores the urgent need for subsequent gene function mining and validation to support biological control strategies and promote sustainable agricultural practices. The findings of this research provide significant insights into the toxicological impacts and mechanisms of pollutants within farmland ecosystems, thereby contributing to the preservation of arthropod diversity.

Mathematical Modeling of Host-Parasitoid Dynamics for Sustainable Pest Management

Aims: The management of agricultural pest populations represents a critical challenge in sustainable crop production, particularly for challenging species like the tomato fruit borer, Helicoverpa armigera. The research work aimed in developing and analysing a novel mathematical model describing the interaction between the tomato fruit borer and its egg parasitoid, Trichogramma chilonis. The main objective of this study to analyze the stability of the proposed system of differential equations. Model Formulation: The model incorporates stage-structured population dynamics and impulsive control measures, providing insights into biological pest control strategies. In this model the tomato borer is represented by the egg and larval stages, and the parasitoid is considered in terms of the parasitized eggs. This model assumes uniform spatial distribution of both host and parasitoid populations, constant environmental conditions affecting parameters like reproduction and mortality rates, and idealized parasitoid release conditions where the released amount p remains consistent across interventions. Methodology: We used existing secondary data from research articles' instead of conducting primary field experiments for parameter identification for this mathematical model. The use of secondary data from peer-reviewed literature not only provides validated parameter values that have been rigorously tested and verified by multiple researchers, but also allows for the incorporation of findings from diverse geographical locations and climatic conditions. Results: Stability analysis identified three equilibrium points: the trivial, host-only E0,coexistence equilibria E1, and E2. The coexistence equilibirium E2 found to be locally stable under optimal parasitoid release intervals and quantities. The equilibrium point E2= (9.14,0.02,5.71) represents a coexistence state in the host-parasitoid dynamics, where the tomato fruit borer's egg density stabilizes at 9.14, the density of parasitized eggs at 0.02, and the larval density stabilizes at 5.71. This equilibrium is analyzed through its associated eigenvalues. This stability provides a reliable basis for implementing successful biological pest control strategies in tomato cultivation, ensuring a resilient and sustainable ecosystem.

Exploring Bacterial Communities and Functions in Phytophagous Halyomorpha halys and Predatory Arma chinensis

The phytophagous Halyomorpha halys (Hemiptera: Pentatomidae) is a global agricultural pest that damages many crops. Conversely, the predatory Arma chinensis (Hemiptera: Pentatomidae) shows promise as a biological control agent against lepidopteran and coleopteran pests. Halyomorpha halys and A. chinensis are closely related species with different feeding habits, as confirmed via genomic and morphological analyses. However, no study investigating the implications of these differences has been reported. Herein, 16S rRNA sequencing technology was employed to analyze the microbiota diversity and function in different tissues (salivary glands, gut, sperm, and ovaries) of H. halys and A. chinensis to elucidate these differences from a microbial perspective. Additionally, the adult male-to-female ratio in A. chinensis organs was statistically similar, while that in H. halys was not. Based on the dominance of the symbionts in the two bug species, we inferred that Sodalis is involved in reproduction and digestion in A. chinensis, while Spiroplasma and Pantoea play essential roles in H. halys reproduction and digestion. We analyzed the data on the microbial diversity of two bug species, laying a foundation for further understanding microbial symbiosis in A. chinensis and H. halys, which may inform the development of biological control strategies.

Impact of synthetic insecticides on the life table parameters of Trichogramma chilonis under laboratory conditions.

Trichogramma chilonis (Ishii) is an important egg parasitoid of Helicoverpa species in tomato growing areas of Pakistan. Different insecticides are used for the management of H. armigera, but these insecticides have significantly reduced the effectiveness of T. chilonis. Therefore, this research aims to understand the compatibility of the selected insecticides with biological control strategies involving T. chilonis for managing Helicoverpa armigera in tomato-growing areas. For this purpose, the effects of five insecticides namely Novaluron, Bifenthrin, Emamectin Benzoate, Chlorantraniliprole and Imidacloprid were assessed against T. chilonis under laboratory conditions. The assays involved direct applications of different insecticides on Sitotroga cerealella eggs and their subsequent effect of T. chilonis life history parameters. A total of 200 eggs were used in each treatment. The results revealed that all the tested insecticides had subsequent negative effects on T. chilonis performance. The results showed that the insecticides Imidacloprid and Chlorantraniliprole led to low mean fecundity, minimum number of male and female adults emergence and prolonged the total pre-oviposition period of T. chilonis as compared to Bifenthrin and Novaluron. The bootstrap results recorded the highest value of the net reproductive rate (R0), intrinsic rate of increase (r) and the finite rate of increase (λ) of T. chilonis in host eggs treated with Bifenthrin and Novaluron as compared to the other tested chemicals. The results regarding percent parasitism showed that maximum percent parasitism was noted in control, Bifenthrin and Novaluron, while the insecticides Imidacloprid and Chlorantraniliprole resulted in minimum % parasitism (63.5% and 71%) respectively. The study revealed that Bifenthrin and Novaluron are relatively more compatible with the T. chilonis in the different integrated pest management programs for H. armigera as compared to other tested chemicals.

Evaluation of the biocontrol potential of Episyrphus balteatus (Diptera: Syrphidae) on wheat aphids in northern China.

Marmalada hoverfly, Episyrphus balteatus De Geer (Diptera: Syrphidae), is a cosmopolitan fly species providing pest control and pollination services. As wheat aphids cause significant losses to global wheat production, a systematic evaluation of the predatory potential and biocontrol service functions of E. balteatus in wheat ecosystems was undertaken. The daily maximum prey consumption of third instar E. balteatus on the adult of Rhopalosiphum padi Linnaeus, Schizaphis graminum Rondani, and Sitobion miscanthi Takahashi (Hemiptera: Aphididae) were 250, 500, and 100 individuals/third instar larvae, respectively. The S. graminum population decline rates in cages after release of the third instars at ratios of 1:100 and 1:200 were 100% and 94.17%, respectively, 72-h after exposure. Feeding assays involving R. padi, S. graminum, and S. miscanthi showed a DNA detectability half-life of 4.17, 6.44, and 4.83h, respectively, in third instar larvae of E. balteatus. Using multiplex polymerase chain reaction-based gut content analysis to detect prey DNA remains, we confirmed that E. balteatus larvae preyed upon R. padi, S. graminum, S. miscanthi, and Metopolophium dirhodum Walker (Hemiptera: Aphididae) in the field experiments during 2022 to 2024. A significant positive correlation was also found between corrected prey detection rate and aphid population dynamics. These results provide an entry point for understanding the ecological service function of E. balteatus and developing the biological control strategy of the wheat aphid management.

Unlocking olive rhizobacteria: harnessing biocontrol power to combat olive root rot and promote plant growth.

Olive trees are susceptible to various diseases, notably root rot caused by Pythium spp., which presents significant challenges to cultivation. Conventional chemical control methods have limitations, necessitating exploration of eco-friendly alternatives like biological control strategies. This study aims to evaluate the potential of rhizobacteria in managing Pythium schmitthenneri-induced root rot in olive trees. We screened 140 bacteria isolated from olive tree rhizospheres for antifungal activity against the pathogen in vitro. Twelve isolates exhibited promising antifungal activity, identified through 16S rDNA gene sequencing as primarily Bacillus, Pseudomonas, Stenotrophomonas, and Alcaligenes species. Particularly, Pseudomonas koreensis (A28 and A29), Pseudomonas reinekei (A16), and Bacillus halotolerans (A10) were the highest effective strains. Mechanistic investigations revealed positive protease production in all twelve isolates, with eight producing amylase and cellulase. Chitinase activity was absent, while five solubilized tricalcium phosphate. Furthermore, eight secreted hydrocyanic acid (HCN), ten synthesized indole-3-acetic acid (IAA), and nine produced siderophores. Variability existed in antimicrobial substance production, including bacillomycin (seven isolates), iturin (eleven isolates), fengycin (two isolates), and surfactin (three isolates). Plant growth-promoting rhizobacteria (PGPR) capabilities were assessed using canola (Brassica napus) seedlings, showing enhanced growth in treated seedlings compared to controls. Greenhouse experiments confirmed the biocontrol efficacy of P. koreensis A28 and Bacillus subtilis C6 against root rot disease. These findings suggest these strains could serve as promising tools for managing olive tree root rot, offering a sustainable alternative to hazardous agrochemicals.

Morphological and Molecular Characterization of Trichoderma Isolates from Vegetable Crop Rhizospheres in Nepal.

Trichoderma spp. hold significant potential as biocontrol agents in agriculture due to their antagonistic properties against plant pathogens. The study aimed to characterize and identify Trichoderma isolates from rhizospheric regions of vegetable crops. In this study, Trichoderma isolates were collected from rhizospheric soil samples of vegetable crops from different ecological zones and were selected for comprehensive morphological and molecular characterization. The isolates were visually assessed for colony color, growth pattern, aerial mycelium presence, phialide and conidial morphology, and chlamydospore presence. Molecular analysis was employed based on ITS and tef-1α sequences. Diversity indices were also computed for different ecological zones. The morphological characteristics and phylogenetic trees for both regions provided a clear species resolution, with four main clades: Harzianum, Viride, Brevicompactum and Longibrachiatum with 12 species T. harzinaum, T. afroharzianum, T. lentiforme, T. inhamatum, T. camerunense, T. azevedoi, T. atroviride, T. asperellum, T. asperelloides, T. koningii, T. longibrachiatum and T. brevicompactum and nine species as a new country record. Diversity indices indicated that high mountain regions displayed the highest species diversity and evenness (H = 1.724 [0.28], J = 0.84, D = 0.28), followed by hilly regions (H = 1.563 [0.28], J = 0.72, D = 0.28). Plains, on the other hand, exhibited lower species diversity (H = 1.515, J = 0.66, D = 0.33). The calculated species abundance values showed that plains (E = 2.11), mid-hills (E = 1.95), and high mountains (E = 1.99) each had their unique diversity profiles. Notably, T. afroharzianum and T. asperellum were predominant. Overall, the study unveiled a rich diversity of Trichoderma species in different agricultural zones of Nepal. These findings shed light on the ecological distribution and diversity of Trichoderma spp., which could have significant implications for sustainable agriculture and biological control strategies.

A Review of Two Emerging Rice Diseases, in the Major Rice Growing Areas of the World

The illness known as kernel smut, which is brought on by Tilletia horrida, is typified by the sooty black masses of teliospores or chlamydospores that replace rice grains. The color of the chlamydospores in kernel smut is different from that of rice fake smut, which is generated by Ustilaginoidea virens. Spore balls that are globose and velvety, with colors ranging from orangish yellow to greenish black, are the hallmark of false smut. Due to their irregular breakouts and little economic impact, kernel smut and fake smut which were first identified in the late 1870s and continued to persist are regarded as minor illnesses in many nations. However, in many nations, particularly the US, kernel smut and fake smut have become two of the most commercially significant illnesses affecting rice, including organic rice, in recent years. Grain production and quality have significantly decreased as a result of the growing use of sensitive rice cultivars particularly hybrids, excessive nitrogen fertilizer use, and short crop rotations. These factors have also led to a rise in kernel smut and fake smut. The distribution and economic significance of kernel smut are reviewed in this article, along with our current knowledge of the taxonomy, biology, and epidemiology of kernel smut and the genomics of the kernel smut fungus in comparison to fake smut and its causative agent. We also provide an update on the current management strategies of pathogen exclusion, cultivar resistance, fungicides, biological control, and cultural practices for kernel smut and false smut of rice.

Potential of Bacillus thuringiensis isolates to manage Gonipterus platensis (Coleoptera: Curculionidae) larvae populations.

The growing expansion of eucalyptus plantations in Brazil and the impact of exotic pests, such as Gonipterus platensis, demand effective, and sustainable biological control strategies. The aim of this study was to assess the pathogenicity of 10 Bacillus thuringiensis (Bt) isolates to neonate Gonipterus platensis larvae, commonly known as the eucalyptus weevil (Coleoptera: Curculionidae) with the specific focus of evaluating their potential to manage this pest while preserving its egg parasitoid, Anaphes nitens. To achieve this, the genomic DNA of the 10 Bt isolates was extracted using the thermal lysis method for molecular characterization of their Cry and Vip proteins. Neonate G. platensis larvae were subjected to bioassays with each isolate, at a concentration of 1 × 109 spores/ml, was applied on 10 larvae per replication (3 replications). The concentration and lethal time to kill 50% of the larvae were determined for the most effective isolates. The Bt isolates 107 and 178 isolates even at concentrations 10× lower than those recommended for commercial Bacillus thuringiensis var. tenebrionis (Btt) formulations against Coleoptera pests, achieved 100% mortality of G. platensis larvae. These isolates, with coleopteran-specific genes, caused high mortality of neonate Gonipterus platensis larvae. This indicates their potential for the biological control of this pest and maybe of other Coleoptera pests. Their use poses minimal risk to non-target organisms such as the egg parasitoid A. nitens and indicates a promising avenue for integrated pest management strategies with effective pest control while preserving the ecological balance.

Divergence in the Morphology and Energy Metabolism of Adult Polyphenism in the Cowpea Beetle Callosobruchus maculatus.

Adult polyphenism is a prevalent form of adaptive evolution that enables insects to generate discrete phenotypes based on environmental factors. However, the morphology and molecular mechanisms underlying adult dimorphism in Callosobruchus maculatus (a global storage pest) remain elusive. Understanding these mechanisms is crucial for predicting the dispersal and population dynamics of C. maculatus. This knowledge can also provide a theoretical basis for biological control strategies. In this study, we compared the morphology of the hind wing and chest muscles, the transcriptional profiles, the energy metabolism substances, and the fecundity between the flight form and the normal form. The flight form displays a lighter overall appearance with small black spots, while the normal form lacks most flight muscles. Moreover, there are differences in the energy metabolism pathways between the two forms, including carbohydrate metabolism and oxidative phosphorylation. The flight form exhibits higher contents of carbohydrates, lipids, and mitochondrial energetic storage. The normal form exhibits better fertility but has lost its ability to fly. This is the first study to analyze the morphology and molecular characteristics of adult polyphenism in C. maculatus using morphological, physiological, and behavioral approaches, providing a foundational understanding of these aspects. Our study on C. maculatus also provides supporting evidence of a trade-off between dispersion and reproduction, where the flight form is capable of flying while the normal form has more reproductive benefits.

Bacterial community of brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) revealed by high throughput amplicon sequencing

The bacterial symbionts of brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), a key sucking insect pest of rice in India and Asia, have been known to play many important physiological functions. Reports of yeast-like symbionts of N. lugens are widely known, but little is known about the bacterial microbes. In this study, the bacterial community structure and diversity were examined in N. Lugens collected from four major rice-growing regions of India utilizing culture-independent high throughput sequencing. The Mi seq technology identified a total of 1277 operational taxonomic units (OTUs) representing 4 phyla mainly (Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes) by analyzing 16S rDNA gene libraries. The major microbial groups were similar in the four samples, but their distribution patterns were different, especially in Raichur. While the top three bacterial genera linked to Imphal, Pantnagar, and Raichur were Methylobacterium, Sphingomonas, and Acinetobacter; Wolbachia accounted for 87.46% of the total genera found in Raipur. The identified dominant microbial groups have been known for their crucial role in insect’s life cycle. Diversity analysis tests revealed Raichur has the highest species diversity as determined by the high Shannon and Simpson index. According to ACE and Chao1 diversity estimates, Pantnagar has the highest species richness. Understanding the bacterial communities and studying their functional roles will help in formulating biological control strategies specific to this sucking pest.

Lifecycle Completion and Reproductive Improvement of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), Following a Prey Shift Routine During Larval Development.

The present study aimed to assess the lifecycle completion and reproductive improvement of green lacewing, Chrysoperla carnea (Stephens), larval instars in a prey shift routine while alternatively feeding on motiles of two-spotted spider mite, Tetranychus urticae Koch (natural prey), and the eggs of almond moth, Ephestia cautella (Walker) (factitious prey). The results showed that C. carnea larvae successfully completed their lifecycle and life span in the treatments where either the 2nd (T2) or 3rd (T3) instar larvae were fed with the eggs of E. cautella while other instars were provided with motiles of T. urticae, i.e., 1st-3rd and 1st-2nd, respectively. The predator larvae failed to transform from pupae to adults when only the 1st instar larvae were fed on the E. cautella eggs (T1). Similar results were found when all predator instars were reared on the motiles of T. urticae (T4). The shortest mean total larval duration and preoviposition period, the highest fecundity and fertility, and balanced sex ratio were recorded when 3rd instar larvae were fed only on E. cautella eggs (T3). The longest adult longevity and oviposition period were recorded when only the 2nd instar larvae were fed on E. cautella eggs (T2). The findings of the present study would be helpful in developing a self-sustained mite biological control strategy using C. carnea and provide a roadmap for future studies to elucidate the larval release efficiency of C. carnea with the supplementary diet for the management of greenhouse mite pests.

Hydration conditions as a critical factor in antibiotic-mediated bacterial competition outcomes.

Antibiotic secretion plays a pivotal role in bacterial interference competition; yet, the impact of environmental hydration conditions on such competition is not well understood. Here, we investigate how hydration conditions affect interference competition among bacteria, studying the interactions between the antibiotic-producing Bacillus velezensis FZB42 and two bacterial strains susceptible to its antibiotics: Xanthomonas euvesicatoria 85-10 and Pseudomonas syringae DC3000. Our results show that wet-dry cycles significantly modify the response of the susceptible bacteria to both the supernatant and cells of the antibiotic-producing bacteria, compared to constantly wet conditions. Notably, X. euvesicatoria shows increased protection against both the cells and supernatants of B. velezensis under wet-dry cycles, while P. syringae cells become more susceptible under wet-dry cycles. In addition, we observed a reciprocal interaction between P. syringae and B. velezensis, where P. syringae inhibits B. velezensis under wet conditions. Our findings highlight the important role of hydration conditions in shaping bacterial interference competition, providing valuable insights into the microbial ecology of water-unsaturated surfaces, with implications for applications such as biological control of plant pathogens and mitigating antibiotic resistance.IMPORTANCEOur study reveals that hydration conditions, particularly wet-dry cycles, significantly influence antibiotic-mediated competition between bacterial species. We revealed that the effectiveness of antibiotics produced by Bacillus velezensis against two susceptible bacterial species: Xanthomonas and Pseudomonas varies based on these hydration conditions. Unlike traditional laboratory environments, many real-world habitats, such as soil, plant surfaces, and even animal skin, undergo frequent wet-dry cycles. These conditions affect bacterial competition dynamics and outcomes, with wet-dry cycles providing increased protection for some bacteria while making others more susceptible. Our findings highlight the importance of considering environmental hydration when studying microbial interactions and developing biological control strategies. This research has important implications for improving agricultural practices and understanding natural microbial ecosystems.

Determination of Larval Instars of Dastarcus helophoroides (Coleoptera: Bothrideridae) Using Head Capsule Width Frequency Distribution.

Long-horned beetles are among the major insect pests that can cause significant economic and ecological damage globally. The control of long-horned beetles is crucial to sustain the forest ecosystem. Dastarcus helophoroides, an economically important ectoparasitoid of long-horned beetles, is widely utilized in biological control strategies. However, the number of larval instars in D. helophoroides remains underexplored. Larval instar determination is crucial for constructing growth prediction models and ecological life tables for insect populations. In this study, we analyzed the frequency distribution of head capsule widths utilizing a visual approach, followed by a non-linear least squares (NLLS) estimation, and found that D. helophoroides undergo four larval instars before entering the pupal stage. The theoretical and observed data for each larval instar yielded identical mean Brooks-Dyar's ratios (1.80). Re-correlation of the number of instars with their respective mean head capsule widths using linear regression (R²) verified that no larval instar was missed. The Crosby's growth ratio (1% and 2%) indicates a very low likelihood of misclassifying an instar into an adjacent one. Given that the accurate determination of larval instars is crucial for developing effective control programs and predicting future population levels, our findings provide valuable insights for implementing biological control strategies against long-horned beetles.

The efficacy of Serratia nematodiphila and Neem Azal T/S on Macrosiphum rosae: new approaches in biological control

The rose aphid, Macrosiphum rosae (L.) (Hemiptera: Aphididae), is one of the most common pests of rose plants. This study evaluated the effects of four different doses of Neem Azal-T/S, containing the active ingredient Azadirachtin A, and a dose of Serratia nematodiphila (1x108 cfu/ml) on M. rosae over 72 hours. The experiment was conducted in a climate chamber under controlled conditions (25±1 °C, 60±5% relative humidity, and a 16:8 light-dark photoperiod). The results showed that Neem Azal-T/S led to mortality rates of 12.5%, 17.5%, 60%, and 77.5%, respectively, while S. nematodiphila resulted in a 78% mortality rate after 72 hours. In the control group, mortality was 0.75%, while mortality rates for the treatment groups were 1.25 (Neem_1), 1.75 (Neem_2), 6.00 (Neem_3), 7.00 (Neem_4), and 8.25 (S. nematodiphila). Statistical analyses showed significant differences between all treatment groups and the control. In conclusion, this study demonstrated that both Neem Azal-T/S and S. nematodiphila significantly increased mortality rates in M. rosae compared with the control. Additionally, this study is the first record of the presence of S. nematodiphila in Türkiye and the first information on its entomopathogenic effect on M. rosae in the worldwide, supporting the potential of biological methods in managing rose aphids and emphasizing the importance of biological control strategies in agricultural pest management.

Evidence of horizontal transmission of Wolbachia wCcep in rice moths parasitized by Trichogramma chilonis and its persistence across generations

The horizontal transmission of endosymbionts between hosts and parasitoids plays a crucial role in biological control, yet its mechanisms remain poorly understood. This study investigates the dynamics of horizontal transfer of Wolbachia (wCcep) from the rice moth, Corcyra cephalonica, to its parasitoid, Trichogramma chilonis. Through PCR detection and phylogenetic analysis, we demonstrated the presence of identical wCcep strains in both host and parasitoid populations, providing evidence for natural horizontal transmission. To investigate thoroughly, Wolbachia-free colonies were acquired through tetracycline treatment, and the initial density of wCcep in host eggs significantly influences transmission efficiency. High-density wCcep infections led to rapid transmission, with F1 parasitoid titers increasing by as much as 100-fold, while low-density infections exhibited more gradual increases. Additionally, without continuous exposure to infected hosts, wCcep density in T. chilonis diminished over generations. These findings enhance our understanding of Wolbachia’s transfer dynamics and have important implications for developing effective and sustainable biological control strategies using parasitoid wasps, particularly in managing Wolbachia-related pest populations in agricultural systems.

First metagenomic sequencing for the analysis of microbial community populations of adults and pupae of Melophagus ovinus in Xinjiang, China.

Melophagus ovinus, a parasite on the body surface of sheep, directly attacks the host through biting and sucking blood and may also transmit pathogens in the process. There are currently only a few studies on the microbial composition of M. ovinus, while there are no such studies on pupae. In this study, samples AT-1 to AT-4 each contained four M. ovinus individuals, while sample AT-5 comprised four M. ovinus pupae, all used for metagenomic sequencing and analysis. Melophagus ovinus adults and pupae were collected from four regions in Xinjiang, China. DNA was extracted from the samples, amplified, and sequenced using the Illumina Novaseq 6000 System; finally, the sequencing data were analyzed using molecular biology software. From all samples, a total of 32 phyla, comprising 372 genera and 1,037 species, were detected. The highest microbial diversity was observed in Kuqa City (AT-2) and Qira County (AT-4). Pupae exhibited 40 unique microbial genera (AT-5) but did not have the highest microbial diversity. Proteobacteria was the dominant phylum in all samples. The dominant genera included Bartonella, Wolbachia, Pseudomonas, and Arsenophonus. This is the first study to report most of the bacteria (e.g., Pseudomonas versuta and Arsenophonus nasoniae), fungi (e.g., Saitoella complicata), viruses (e.g., Orf virus and Wolbachia phage WO), and protozoa (e.g., Trypanosoma theileri and Babesia bigemina) in M. ovinus. This study has enriched the microbial diversity data of M. ovinus, and the pathogens it carries may pose a threat to public health safety and the economy of related industries, necessitating further research to develop effective biological control strategies.

Biocontrol yeast Kurtzmaniella quercitrusa BS-AY-S1 controls postharvest green mold of citrus fruit by producing metabolites with antifungal activity

Green mold caused by Penicillium digitatum is the leading postharvest disease in citrus fruit. While chemical fungicides are commonly used for management, yeast-based biological control strategy offers a promising and eco-friendly alternative. In this study, yeast strains were isolated from citrus orchards and the strain with the best biocontrol efficacy was screened to investigate its mechanisms for controlling postharvest green mold in citrus fruit. In total, 30 yeast strains were isolated from fruits, leaves and soil of two citrus orchards. Subsequently, 8 yeast strains tested in vivo effectively inhibited green mold in citrus fruit, with Kurtzmaniella quercitrusa BS-AY-S1 achieving the best biocontrol efficacy by reducing the disease incidence (DI) by 58.33 % and lesion diameter (LD) by 73.36 % compared to the control on the 6th day. BS-AY-S1 exhibited excellent colonization ability, laying the foundation for its biocontrol efficacy. Furthermore, the antifungal properties of BS-AY-S1 metabolites were evaluated. The fermentation supernatant of BS-AY-S1 effectively inhibited the growth of P. digitatum and controlled green mold in citrus fruit. Additionally, the volatile organic compounds (VOCs) from BS-AY-S1 markedly reduced the spore germination, spore production and mycelial growth of P. digitatum, and slowing down the progression of green mold in citrus fruit. In total, 20 VOCs, including alcohols, aldehydes, esters, ethers and ketones produced by BS-AY-S1, were identified by gas chromatography-ion mobility spectrometry (GC-IMS). In conclusion, BS-AY-S1 demonstrated potential for controlling postharvest green mold in citrus fruit, with its mechanisms of action including the ability to colonize citrus fruit wounds and produce antifungal metabolites and VOCs.

The Killer Saccharomyces cerevisiae Toxin: From Origin to Biomedical Research

The killer systems of S. cerevisiae are defined by the co-infection of two viral agents, an M virus and a helper virus. Each killer toxin is determined by the type of M virus (ScV-M1, ScV-M2, ScV-M28, and ScV-Mlus), which encodes a specific toxin (K1, K2, K28, and Klus). Since their discovery, interest in their potential use as antimicrobial agents has driven research into the mechanisms of action of these toxins on susceptible cells. This review provides an overview of the key aspects of killer toxins, including their origin and the evolutionary implications surrounding the viruses involved in the killer system, as well as their potential applications in the biomedical field and as a biological control strategy. Special attention is given to the mechanisms of action described to date for the various S. cerevisiae killer toxins.