Potential Biocontrol Research Articles

Assembly and Annotation of the Complete Genome Sequence of the Paenibacillus Bacteriophage phJNUCC32

A potential biocontrol agent for American foulbrood (AFB), the Paenibacillus bacteriophage phJNUCC32, was isolated from Baengnokdam in Halla Mountain. This study aimed to investigate its genomic characteristics through whole-genome sequencing. The genome of phJNUCC32 was found to be 62,871 base pairs in length, with a G + C content of 51.98%. Phylogenetic analysis classified phJNUCC32 within the unclassified Caudoviricetes bacteriophage category. The genome prediction confirmed the absence of virulence factors and antibiotic-resistance genes, ensuring its genetic safety. A total of 63 coding DNA sequences were identified, revealing a modular arrangement. Notably, the annotation of gene function indicates that phJNUCC32 harbors the holin/lysin system, suggesting significant potential for controlling bacterial infections in AFB and agriculture.

Biocontrol potential of endophytic fungi against phytopathogenic nematodes on potato (Solanum tuberosum L.)

Root-knot nematodes (RKNs) are a vital pest that causes significant yield losses and economic damage to potato plants. The use of chemical pesticides to control these nematodes has led to environmental concerns and the development of resistance in the nematode populations. Endophytic fungi offer an eco-friendly alternative to control these pests and produce secondary metabolites that have nematicidal activity against RKNs. The objective of this study is to assess the efficacy of Aspergillus flavus (ON146363), an entophyte fungus isolated from Trigonella foenum-graecum seeds, against Meloidogyne incognita in filtered culture broth using GC–MS analysis. Among them, various nematicidal secondary metabolites were produced: Gadoleic acid, Oleic acid di-ethanolamide, Oleic acid, and Palmitic acid. In addition, biochemical compounds such as Gallic acid, Catechin, Protocatechuic acid, Esculatin, Vanillic acid, Pyrocatechol, Coumarine, Cinnamic acid, 4, 3-indol butyl acetic acid and Naphthyl acetic acid by HPLC. The fungus was identified through morphological and molecular analysis, including ITS 1–4 regions of ribosomal DNA. In vitro experiments showed that culture filtrate of A. flavus had a variable effect on reducing the number of egg hatchings and larval mortality, with higher concentrations showing greater efficacy than Abamectin. The fungus inhibited the development and multiplication of M. incognita in potato plants, reducing the number of galls and eggs by 90% and 89%, respectively. A. flavus increased the activity of defense-related enzymes Chitinas, Catalyse, and Peroxidase after 15, 45, and 60 days. Leaching of the concentrated culture significantly reduced the second juveniles’ stage to 97% /250 g soil and decreased the penetration of nematodes into the roots. A. flavus cultural filtrates via soil spraying improved seedling growth and reduced nematode propagation, resulting in systemic resistance to nematode infection. Therefore, A. flavus can be an effective biological control agent for root-knot nematodes in potato plants. This approach provides a sustainable solution for farmers and minimizes the environmental impact.

One stone two birds: Endophytes alleviating trace elements accumulation and suppressing soilborne pathogen by stimulating plant growth, photosynthetic potential and defense related gene expression

In the present investigation, we utilized zinc nanoparticles (Zn-NPs) and bacterial endophytes to address the dual challenge of heavy metal (HM) toxicity in soil and Rhizoctonia solani causing root rot disease of tomato. The biocontrol potential of Bacillus subtilis and Bacillus amyloliquefaciens was harnessed, resulting in profound inhibition of R. solani mycelial growth and efficient detoxification of HM through strong production of various hydrolytic enzymes and metabolites. Surprisingly, Zn-NPs exhibited notable efficacy in suppressing mycelial growth and enhancing the seed germination (%) while Gas chromatography-mass spectrometry (GC-MS) analysis unveiled key volatile compounds (VOCs) crucial for the inhibition of pathogen. Greenhouse trials underscored significant reduction in the disease severity (%) and augmented biomass in biocontrol-mediated plants by improving photosynthesis-related attributes. Interestingly, Zn-NPs and biocontrol treatments enhanced the antioxidant enzymes and mitigate oxidative stress indicator by increasing H2O2 concentration. Field experiments corroborated these findings, with biocontrol-treated plants, particularly those receiving consortia-mediated treatments, displayed significant reduction in disease severity (%) and enhanced the fruit yield under field conditions. Root analysis confirmed the effective detoxification of HM, highlighting the eco-friendly potential of these endophytes and Zn-NPs as fungicide alternative for sustainable production that foster soil structure, biodiversity and promote plant health.

In vitro Evaluation of Bio Control Agents and Botanicals against Mulberry Root Rot Pathogen Lasiodiplodia theobromae

Mulberry root rot is fast spreading disease caused by L. theobromae. The pathogen can be managed by synthetic fungicides. However, enormous use of synthetic fungicides leads to residual toxicity which affects the growth and development of silkworm. In this context, an attempt was made to use potential bio control agents for the management of this pathogen. Seven fungal and five bacterial bio agents evaluated out of them T. viride (Tv – B2), T. harzianum (Th - 44), B. subtilis (Bs - M) and (Bs - O) proved as best for inhibition of mycelial growth of the pathogen. Out of eleven botanical extracts used, garlic proved best at 15 per cent and 20 per cent and agave at 20 per cent concentration against root rot causing pathogen L. theobromae.

Deciphering the biocontrol and immunomodulatory potential of Metarhabditis amsactae (Nematoda: Rhabditidae) against Corcyra cephalonica (Lepidoptera: Pyralidae)

ABSTRACT In the present work, laboratory assays were performed to appraise the biocontrol potential of Metarhabditis amsactae, a Rhabditid nematode, against fifth instar larvae of Corcyra cephalonica. Virulence was tested at four different doses, i.e. 20, 40, 80 and 160 IJs/L (infective juveniles per larva) and mortality was documented from 24 up to 96 h of nematode treatment. Concentration and time-based enhancement in larval mortality was observed with 100% mortality recorded at 160 IJs/L after 96 h. Even at 20 IJs/L concentration, 60% and 76.7% larval mortality was recorded after 72 and 96 h, respectively. At 80 IJs/L, the mortality increased from 33.3% at 48 h to more than 90% at 96 h of nematode inoculation. Whereas, at 40 IJs/L, it enhanced from 16.7% at 48 h to 83.3% at 96 h. The effect of M. amsactae infection on the immune system of C. cephalonica was also evaluated at a dose of 100 IJs/L after 12, 24, 36 and 48 h time intervals. Insect larvae displayed augmented levels of antioxidant and detoxifying enzymes. The peak activities of superoxide dismutase, catalase, ascorbate peroxidase, phenol oxidase and glutathione-S-transferase in infected larvae were observed after 36 h, whereas acetylcholine esterase levels peaked after 48 h, as compared to control. Malondialdehyde content was also increased post nematode infection. Thus the current study is the first report that depicts the significant bioefficacy and immunomodulatory effects of M. amsactae against C. cephalonica under laboratory conditions. However, further research to assess its efficiency under field conditions is required.

Phylogeny, biogeography, and host range of gall midges (Diptera: Cecidomyiidae) feeding on spores of rust fungi (Basidiomycota: Pucciniales).

Rust fungi (Pucciniales) are plant pathogens that can cause devastating yield losses to economically important crops and threaten native plants with extinction. Rusts are usually controlled with fungicides when rust-resistant plant varieties are unavailable. However, natural enemies may offer an alternative to chemicals by acting as biological controls. The larvae of Mycodiplosis Rübsaamen (49 spp.) feed on the spores of rusts and powdery mildew fungi and have been suggested as a potential biocontrol candidate for disease-causing rusts. However, little is known about the phylogenetic relationships, biogeography, and host range of this genus. We screened 5,665 rust specimens from fungarium specimens and field collections and recovered a total of 363 larvae on 315 rust specimens from 17 countries. Three mitochondrial and 2 nuclear loci were amplified and sequenced for the phylogenetic reconstruction of 129 individuals. We recovered 12 clades, of which 12 and 10 were supported with maximum likelihood and Bayesian inference, respectively. Of the 12 clades, 7 comprised species from multiple continents and climatic regions, and 5 comprised species from a single region. Individuals forming clades were collected from 2 to 18 rust species, suggesting that Mycodiplosis species have a broad host range. In total, Mycodiplosis larvae were identified on 44 different rust species collected from 18 plant families. Future studies should focus on expanding field sampling efforts, including data from additional gene regions, and incorporating morphological data to further elucidate species diversity and distribution patterns.

Biocontrol potential of plant growth-promoting rhizobacteria against plant disease and insect pest.

Biological control is a promising approach to enhance pathogen and pest control to ensure high productivity in cash crop production. Therefore, PGPR biofertilizers are very suitable for application in the cultivation of tea plants (Camellia sinensis) and tobacco, but it is rarely reported so far. In this study, production of a consortium of three strains of PGPR were applied to tobacco and tea plants. The results demonstrated that plants treated with PGPR exhibited enhanced resistance against the bacterial pathogen Pseudomonas syringae (PstDC3000). The significant effect in improving the plant's ability to resist pathogen invasion was verified through measurements of oxygen activity, bacterial colony counts, and expression levels of resistance-related genes (NPR1, PR1, JAZ1, POD etc.). Moreover, the application of PGPR in the tea plantation showed significantly reduced population occurrences of tea green leafhoppers (Empoasca onukii Matsuda), tea thrips (Thysanoptera:Thripidae), Aleurocanthus spiniferus (Quaintanca) and alleviated anthracnose disease in tea seedlings. Therefore, PGPR biofertilizers may serve as a viable biological control method to improve tobacco and tea plant yield and quality. Our findings revealed part of the mechanism by which PGPR helped improve plant biostresses resistance, enabling better application in agricultural production.

Biocontrol potentials of Trichoderma species in the control of Fusarium wilt in five tomatoes (Lycopersicon esculentum L.) varieties cultivated under greenhouse conditions in Southwest Nigeria

Important pathogenic fungi such as Fusarium species are mostly associated with the wilting of tomato plant leaves and constitute a serious limiting factor for tomato production. Therefore, this study aimed to screen tomato varieties commonly cultivated in Nigeria to determine their host resistance status to Fusarium oxysporum. The treatments included Trichoderma asperellum, T. harzianum, and Mancozeb fungicide. Data recorded included the incidence and severity of the pathogen, plant height, leaf number, and fruit yield of the tomato plants. Tomato plants grown with Trichoderma sp. exhibited better performance in terms of average fruit yield count of 6.5 for T. asperellum and 6.7 for T. harzianum compared to the average yield of 1.7 fruit count for Mancozeb fungicide. The lowest disease incidence was recorded in the variety 3 (NGB00737) with a 5.81% incidence in the Mancozeb-treated plants. Conversely, T. asperellum-treated plants in variety 3 (NGB00737) had the highest disease incidence of 46.49%. For variety 4 (NGB00695), plants treated with Mancozeb had the least disease with a severity rating of 1. Similarly, variety 5 (NGB00725) plants treated with T. asperellum showed the least disease severity rating of 1. All other treated plants showed higher severity values of 4. The Trichoderma species also improved the fruit yield and some agronomic parameters of the tomato plants compared to the chemical control. Agro-business enthusiasts, commercial growers and local farmers are therefore encouraged to further exploit the potential of Trichoderma species as means of control for fungus-based diseases in tomato plants such as those caused by Fusarium.

Biocontrol of Fusarium spp. in vitro and in vine cuttings using Bacillus sp. F62

Fusarium spp., the causal agent of Fusarium wilt, cause substantial economic losses in viticulture, mainly in tropical regions. This study aimed to assess the biocontrol potential of Bacillus sp. F62 against Fusarium spp., both in vitro and in rootstock cuttings of the SO4 variety. To this end, the in vitro antagonism was evaluated through diffusible and volatile compounds synthesized by Bacillus sp. F62 on three Fusarium spp. isolates. Subsequently, the isolate FusA06-18 was selected for a rootstock cutting experiment. The vine cuttings underwent the following treatments: control, pathogen inoculation (Fus), bacterial inoculation (Bac), and bacterial followed by pathogen inoculation (Bac + Fus). Our findings revealed an average reduction of 39.1% in the mycelial growth of the pathogen through dual culture assay and a decrease of 11.6% in the Fusarium spp. radial growth due to the effects of volatile compounds. In the experiment with vine cuttings, applying Bacillus sp. F62 reduced the pathogen re-isolation frequency from 81.7% (Fus) to 63.3% (Bac + Fus). Therefore, Bacillus sp. F62 effectively suppressed the mycelial growth of Fusarium spp. and reduced the Fusarium wilt incidence in vine cuttings of the rootstock ‘SO4’.

Biocontrol potentiality of <i>Burkholderia vietnamiensis</i> nrv12 against the rice blast fungus <i>magnaporthe oryzae</i>

Rice blast disease, caused by the pathogenic fungus Magnaporthe oryzae, is a widespread infection leading to serious crop loss worldwide. In order to achieve sustainable agriculture, root-associated bacteria have been applied to manage fungal diseases and promote growth. The present study aimed to evaluate in vitro the growth-promoting ability and in vivo biocontrol activity against M. oryzae of rice rhizosphere bacterium. Out of sixty-eight isolates recovered from the rhizosphere of blast-infected rice plants, isolate NRV12 exhibited the highest antifungal activity against M. oryzae SH, with an inhibition percentage of 72.7±3.44%. By analysis of 16S rRNA sequence associated with morphology, physiological and biochemical tests, the strain was identified as Burkholderia vietnamiensis. In addition, NRV12 produced hydrolytic enzymes (amylase, cellulase, protease), indole acetic acid (IAA), exhibited nitrogen-fixing potential and the ability to solubilize phosphate and zinc. Innoculation with NRV12 significantly promoted in vivo rice seedling growth to 23.3% as compared to the non-bacteria-treated seedlings. Importantly, infected rice seedlings treated with NRV12 led to a 40% disease reduction in rice blast. These findings suggest that NRV12 is a valuable and promising isolate with biocontrol potential against rice blast caused by M. oryzae.

Biocontrol of Southern Blight Caused by Sclerotium rolfsii in Pepper Plants Using Bacillus subtilis GJ6-14

Southern blight, caused by the soil-borne fungus Sclerotium rolfsii, is a serious disease that affects many economically important crops. In this study, we selected Bacillus subtilis GJ6-14, from a total of 260 strains, to control Southern blight in pepper plants. In both seedling and plant tests, GJ6-14 significantly suppressed disease incidence and severity compared to control, furthermore, GJ6-14 demonstrated efficient colonization in the rhizosphere by maintaining the population from log 5.41 to log 3.92 in the pathogen-inoculated plants, indicating its potential as a biocontrol agent. Molecular analysis revealed up-regulation of defense-related genes, such as a 7.6-fold increase in LOX1 and 15.5-fold increase in PR1, at 72 hr after inoculation of S. rolfsii in GJ6-14-treated plants, suggesting activation of plant defense mechanisms. Overall, our findings highlight the promising role of B. subtilis GJ6-14 as a potential biocontrol agent in sustainable management of Southern blight in pepper plants.

Controlling Soil-Borne Fungus Aspergillus niger in Groundnut By Optimizing The Function of Isolated Bacillus Bacteria

Collar rot is a devastating disease caused by the soil-borne pathogen Aspergillus niger that greatly affects groundnut production worldwide. The long-term persistence of the fungus in the soil can reduce the effectiveness of synthetic fungicides. Recently, significant attention has been raised to the use of the biological control method such as the application of antagonistic microorganisms, which potentially decline the number of spores and eradicated A. niger from the soil. In the present study, three Bacillus strains (Bacillus siamensis 101, B. siamensis 112 and B. velezensis 137) isolated from the rhizosphere soil of groundnut cultivation farms were found to inhibit the growth of A. niger mycelia by 53.6% to 60.8% in vitro. In pot experiments, the supplementation of this mixture of three bacterial strains (namely BAZ04) strongly reduced the collar rot symptoms of groundnut with a biocontrol efficacy of 100% compared to nil (no treatment). Field trials demonstrated the efficiency of BAZ04 in controlling collar rot disease, which increased the yield by 20.5–22.7% compared to the untreated plots. These results suggest that BAZ04 is a potential biocontrol agent for collar rot disease.

Compatibility of Entomopathogenic Nematodes with Agrochemicals and Biocontrol Potential of their Combinations against Insect Pests: An Updated Review

Compatibility of Entomopathogenic Nematodes with Agrochemicals and Biocontrol Potential of their Combinations against Insect Pests: An Updated Review

Characterization and biocontrol potential of some rhizobacteria against fungal pathogens causing foliar diseases in maize

Maize is one of the most consumed cereal crops worldwide, and it is a strategic crop to the attainment of SDG 2 of Zero hunger. Despite its importance, the cultivation of maize has been significantly impaired by fungal pathogens causing foliar diseases. The occurrence of this disease in maize plantations at the Research Farm of the North-West University, Molelwane, Mafikeng, South Africa prompted this investigation. Samples of diseased maize rhizosphere soil were aseptically collected. Bacteria species associated with the rhizosphere were isolated and characterized as Bacillus siamensis, Enterobacter asburiae, Enterobacter chengduensis, Priestia aryabhattai, Burkholderia sp., Priestia megaterium strain AOA6 and Priestia megaterium strain AOA7. The anti-fungicidal potentials of the bacterial species were evaluated against pathogenic fungal species, Nigrospora sphaerica, Alternaria alternata and Fusarium equiseti in-vitro. The percentage mycelia growths were calculated and the data were subjected to ANOVA using SAS version 9.8. All the seven bacteria isolates tested positive to ammonia production, phosphate solubilization, siderophore production and ACC deaminase tests. The percentage mycelia inhibition showed Nigrospora sphaerica (36.29%), A. alternata (26.19%) and F. equiseti (20.63%) as the order of fungal inhibition by the bacteria species. Furthermore, E. asburiae > P. megatarium strain AOA7 > B. siamensis > P. aryabhattai > E. chengduensis > Bulkholderia sp. were the order of antifungal efficacy of the bacteria species evaluated. In conclusion, the efficacy of the bacteria especially E. asburiae, P. megatarium strain AOA7 and B. siamensis over various fungal pathogens. The result obtained, therefore, justifies the further investigation, formulation and deployment of the bacteria species as biofungicide in the management of foliar diseases of maize. Keywords: antifungicidal potential, biofungicide, microbial formulations, rhizosphere, zero hunger.

Biocontrol potential of Pseudomonas syringae against Emerging Phyto-Fungal Pathogens

Biocontrol potential of Pseudomonas syringae against Emerging Phyto-Fungal Pathogens

Anti-fungal effects of lactic acid bacteria from pickles on the growth and sterigmatocystin production of Aspergillus versicolor

Sterigmatocystin (STC) is an emerging mycotoxin that poses a significant threat to the food security of cereal crops. To mitigate STC contamination in maize, this study employed selected lactic acid bacteria as biocontrol agents against Aspergillus versicolor, evaluating their biocontrol potential and analyzing the underlying mechanisms. Lactiplantibacillus plantarum HJ10, isolated from pickle, exhibited substantial in vitro antifungal activity and passed safety assessments, including antibiotic resistance and hemolysis tests. In vivo experiments demonstrated that L. plantarum HJ10 significantly reduced the contents of A. versicolor and STC in maize (both >84 %). The impact of heat, enzymes, alkali, and other treatments on the antifungal activity of cell-free supernatant (CFS) was investigated. Integrated ultra-high-performance liquid chromatography (UPLC) and gas chromatography–mass spectrometry (GC–MS) analysis revealed that lactic acid, acetic acid, and formic acid are the key substances responsible for the in vitro antifungal activity of L. plantarum HJ10. These metabolites induced mold apoptosis by disrupting cell wall structure, increasing cell membrane fluidity, reducing enzyme activities, and disrupting energy metabolism. However, in vivo antagonism by L. plantarum HJ10 primarily occurs through organic acid production and competition for growth space and nutrients. This study highlights the potential of L. plantarum HJ10 in reducing A. versicolor and STC contamination in maize.

Novel transinfections of Rickettsiella do not affect insecticide tolerance in Myzus persicae, Rhopalosiphum padi, or Diuraphis noxia (Hemiptera: Aphididae).

Aphids (Hemiptera: Aphidoidea) are economically important crop pests worldwide. Because of growing issues with insecticide resistance and environmental contamination by insecticides, alternate methods are being explored to provide aphid control. Aphids contain endosymbiotic bacteria that affect host fitness and could be targeted as potential biocontrol agents, but such novel strategies should not impact the effectiveness of traditional chemical control. In this work, we used a novel endosymbiont transinfection to examine the impact of the endosymbiont Rickettsiella viridis on chemical tolerance in 3 important agricultural pest species of aphid: Myzus persicae (Sulzer) (Hemiptera: Aphididae), Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae), and Diuraphis noxia (Mordvilko ex Kurdjumov) (Hemiptera: Aphididae). We tested tolerance to the commonly used insecticides alpha-cypermethrin, bifenthrin, and pirimicarb using a leaf-dip bioassay. We found no observed effect of this novel endosymbiont transinfection on chemical tolerance, suggesting that the strain of Rickettsiella tested here could be used as a biocontrol agent without affecting sensitivity to insecticides. This may allow Rickettsiella transinfections to be used in combination with chemical applications for pest control. The impacts of other endosymbionts on insecticide tolerance should be considered, along with tests on multiple aphid clones with different inherent levels of chemical tolerance.

Bacterial communities varied in different Coccinella transversoguttata populations located in Tibetan plateau

Coccinella transversoguttata is an important predatory beetle in Asia and America. Currently, few studies have investigated C. transversoguttata in China especially in the Tibetan plateau. In this study, full-length 16 s rRNA sequencing and qPCR experiment were performed on eight C. transversoguttata populations collected from Tibet to analyze their bacterial communities and bacteria abundance. In summary, our results revealed the microbial compositions, diversities and bacterial titers in the bacterial communities in C. transversoguttata populations in the Tibetan plateau. In future, there is a need to explore the differences in microbiota among various C. transversoguttata populations collected from different locations. These results add to our understanding of the complex bacterial communities of C. transversoguttata and their utilization as potential biocontrol factors.

Bioactive Bioxanthracene and Cyclodepsipeptides from the Entomopathogenic Fungus Blackwellomyces roseostromatus BCC56290.

In the course of our ongoing research targeting the identification of potential biocontrol agents from entomopathogenic fungi (EPF), we explored a solid-state rice fungal extract of Blackwellomyces roseostromatus BCC56290 derived from infected lepidopteran larvae. Chemical and biological prospections afforded four unprecedentedly reported natural products differentiated into a dimeric naphthopyran bioxanthracene ES-242 derivative (1) and three cyclodepsipeptides (2-4) in addition to two known cyclodepsipeptides, cardinalisamides B (5) and C (6). Chemical structures of the isolated compounds were elucidated through comprehensive 1D/2D NMR and HR-ESI-MS data together with comparisons to the reported literature. The absolute configuration of the isolated cyclodepsipeptides was determined using Marfey's method. All isolated compounds were assessed for their antimicrobial, cytotoxic, and nematicidal activities with some compounds revealing significant activities.

Evaluation of indigenous isolates of Beuveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) against the cotton aphid Aphis gossypii Glover

AbstractThe cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), is one of the most important pests and causes major damage to cultivated plants in Turkey. It has recently become a serious problem in Antalya (southwestern Turkey) due to its high resistance to insecticides used. To address this problem, the present study aimed to evaluate the pathogenicity of five indigenous Beuveria bassiana (Balsamo) Vuillemin (Deuteromycotina: Hyphomycetes) isolates (BbFn-2, BbKm-2, BbSr-2, BbDs-4, and BbDm-2) with high virulence in previous studies against the pest. All the isolates were tested at five different conidial concentrations (1 × 105, 1 × 106, 1 × 107, 1 × 108 and 1 × 109 conidia mL−1) against the nymphs and adults of A. gossypii using Petri dish and pot trials in the laboratory. The results from the bioassays showed that virulence of the isolates increased significantly with elapsed time up to 10 days after inoculation. All five B. bassiana isolates at the highest concentration (1 × 109 conidia mL−1) caused mortalities ranged from 83.3% to 100% in both nymphs and adults 10 days post-treatment. While the LT50 and LT95 values of the isolates were 1.72–2.12 days and 4.81–8.49 days, respectively, for the nymphs, they were calculated for the adults as 1.65–2.54 days and 4.66–12.93 days, respectively. Results of the phylogenetic analysis showed that these five B. bassiana isolates had high similarities (ranging from 99 to 100%) with the other B. bassiana isolates in GenBank. All the results suggest that above-mentioned five indigenous B. bassiana isolates have significant biocontrol potential against A. gossypii.