Biocontrol Research Articles

Genomic Characterization and Establishment of a Genetic Manipulation System for Trichoderma sp. (Harzianum Clade) LZ117.

Trichoderma species have been reported as masters in producing cellulolytic enzymes for the biodegradation of lignocellulolytic biomass and biocontrol agents against plant pathogens and pests. In our previous study, a novel Trichoderma strain LZ117, which shows potent capability in cellulase production, was isolated. Herein, we conducted multilocus phylogenetic analyses based on DNA barcodes and performed time-scaled phylogenomic analyses using the whole genome sequences of the strain, annotated by integrating transcriptome data. Our results suggest that this strain represents a new species closely related to T. atrobrunneum (Harzianum clade). Genes encoding carbohydrate-active enzymes (CAZymes), transporters, and secondary metabolites were annotated and predicted secretome in Trichoderma sp. LZ117 was also presented. Furthermore, genetic manipulation of this strain was successfully achieved using PEG-mediated protoplast transformation. A putative transporter gene encoding maltose permease (Mal1) was overexpressed, which proved that this transporter does not affect cellulase production. Moreover, overexpressing the native Cre1 homolog in LZ117 demonstrated a more pronounced impact of glucose-caused carbon catabolite repression (CCR), suggesting the importance of Cre1-mediated CCR in cellulase production of Trichoderma sp. LZ117. The results of this study will benefit further exploration of the strain LZ117 and related species for their applications in bioproduction.

Patulin inhibition of specific apple microbiome members uncovers Hanseniaspora uvarum as a potential biocontrol agent.

Penicillium expansum is a major postharvest pathogen of apples, causing loss in fruits through tissue damage, as well as in apple products due to contamination with the mycotoxin patulin. During infections, patulin is a cultivar-dependent virulence factor that facilitates apple lesion development. Patulin also has characterized antimicrobial activity and is important for inhibiting other competitive phytopathogens, but the role of this inhibitory activity has not been investigated in the context of the apple microbiome. In our current study, we isolated 68 apple microbiota and characterized their susceptibility to P. expansum extracts. We found Gram-negative bacteria and Basidiomycete yeast to demonstrate largely patulin-specific growth inhibition compared to Gram-positive and Ascomycete isolates. From co-cultures, we identified a Hanseniaspora and Gluconobacter pairing that reduced P. expansum biomass and found that Hanseniaspora uvarum alone is sufficient to reduce apple disease progression in vivo. We investigated possible mechanisms of H. uvarum biocontrol activity and found modest inhibition on apple puree plates, as well as a trend toward lower patulin levels at the wound site. Active biocontrol activity required live yeast, which also were effective in controlling Botrytis cinerea apple infections. Lastly, we explored the breadth of H. uvarum biocontrol activity with over 30 H. uvarum isolates and found consistent inhibition of P. expansum apple disease.

Biocontrol potential of Bacillus velezensis SEC-024A against southern blight of industrial hemp

Agroathelia rolfsii is the causative agent of southern blight of industrial hemp, which is a soil-borne infection resulting in grave economic losses in industrial hemp (Cannabis sativa L.). Chemical pesticides are currently the primary means of controlling this disease, but their use is harmful to human health as well as to the environment. Urgent action is needed to screen eco-friendly biocontrol agents against this pathogen. An endophytic bacterium SEC-024A was isolated from the leaf tissue of industrial hemp and exhibited a significant antagonistic effect on A. rolfsii, with a plate inhibition rate of 80.5 % and a pot control effect of 74.1 %. Through whole genome sequencing, SEC-024A was identified to be Bacillus velezensis. It contained multiple gene clusters involved in secondary metabolite biosynthesis and the genes that promote plant growth, colonization, and pathogen defense. Bacillus velezensis SEC-024A produces volatile organic compounds (VOCs) that serve as its primary fungistatic agents. Nine VOCs produced by SEC-024A were detected through gas chromatography-mass spectrometry. These VOCs were individually tested for their antifungal effects. Four volatiles, namely isobutyric acid, tiglic acid, trans-2-octenal, and 2-decanone, exhibited notable inhibitory effects on A. rolfsii with EC50 values of 0.012, 0.038, 0.009, and 0.046 μL/mL, respectively. Additionally, trans-2-octenal demonstrated broad-spectrum antifungal activity against various soil-borne pathogens. Together, this study suggests that B. velezensis SEC-024A holds promise as a novel microbial agent for improving plant growth and controlling diseases.

Effects of Paecilomyces lilacinus and Bacillus pumilus on stem nematode and rhizosphere bacterial communities of sweet potato

Stem nematode (Ditylenchus destructor Thorne) is considered one of the most economically devastating species affecting sweet potato production. Biocontrol offers a sustainable strategy for nematode control. This study conducted a pot experiment to evaluate the biocontrol efficacy of Paecilomyces lilacinus CS-Z and Bacillus pumilus Y-26 against the stem nematode, as well as to examine their influence on the bacterial communities in the sweet potato rhizosphere. The findings indicated that B.pumilus Y-26 and P.lilacinus CS-Z exhibited respective suppression rates of 82.9% and 85.1% against the stem nematode, while also stimulating sweet potato plant growth. Both high-throughput sequencing and Biolog analysis revealed distinct impacts of the treatments on the bacterial communities. At the phylum level, B.pumilus Y-26 enhanced the abundance of Actinobacteria but reduced the abundance of Cyanobacteria, with P.lilacinus CS-Z exhibiting similar effects. Additionally, the treatment with B.pumilus Y-26 resulted in increased abundances of Crossiella, Gaiella, Bacillus, and Streptomyces at the genus level, while the treatment with P.lilacinus CS-Z showed increased abundances of Crossiella and Streptomyces. In contrast, the abundance of Pseudarthrobacter was reduced in the treatment with B.pumilus Y-26. Conversely, the application of the nematicide fosthiazate exhibited minor influence on the bacterial community. The findings indicated that the application of P.lilacinus CS-Z and B.pumilus Y-26 led to an increase in the relative abundances of beneficial microorganisms, including Gaiella, Bacillus, and Streptomyces, in the rhizosphere soil. In conclusion, P.lilacinus CS-Z and B.pumilus Y-26 demonstrated their potential as environmentally friendly biocontrol agents for managing stem nematode disease of sweet potato.

Prodigiosin, a promising biocontrol agent against Thaumetopoea wilkinsoni (Tams, 1926) (Lepidoptera: Notodontidae)

Serratia marcescens Bizio (Enterobacteriaceae: Serratia) is an entomopathogenic bacterium that produces hydrolytic enzymes and toxins. It also produces a pigment with various biological properties called prodigiosin. The study was conducted at Bilecik Seyh Edebali University in 2023. In this study, the effects of medium, incubation temperature and time on the process of prodigiosin production by S. marcescens strain Se9 and the extraction efficiency of different solvents were optimized for the first time using the orthogonal Taguchi array design. The optimal yield of pigment was achieved by methanol extraction from bacteria grown in tyriptic soy broth medium at 30ºC for 96 hours. The yield of prodigiosin pigment was 83.4±1.7 mg/L in the validation experiment conducted under the optimum conditions determined. The insecticidal potential of pigment against the larvae of Thaumetopoea wilkinsoni (Tams, 1926) (Lepidoptera, Notodontidae) was demonstrated for the first time. While the mortality rate in larvae exposed to 1000 ppm of the pigment was only 40%, it was observed that doubling the applied concentration led to a significant increase in larval mortality, reaching 91%. The LC50 value of the pigment for the fourth larval stage of T. wilkinsoni was determined to be 1192 ppm. The study showed that the pigment prodigiosin may be a promising biocontrol agent for the control of T. wilkinsoni.

Bioactive compounds from food-grade Bacillus.

Bacillus species have attracted significant attention in recent years due to their potential for producing various bioactive compounds with diverse functional properties. This review highlights bioactive substances from food-grade Bacillus strains and their applications in functional foods and nutraceuticals. The metabolic capacities of Bacillus species have allowed them to generate a wide range of bioactive substances, including vitamins, enzymes, anti-microbial peptides, and other non-ribosomal peptides. These substances have a variety of positive effects, including potential cholesterol-lowering and immune-modulatory qualities in addition to anti-oxidant and anti-bacterial actions. The uses and mechanisms of action of these bioactive chemicals can be used to improve the functional qualities and nutritional profile of food products. Examples include the use of anti-microbial peptides to increase safety and shelf life, as well as the use of Bacillus-derived enzymes in food processing to improve digestibility and sensory qualities. The exploitation of bioactive compounds from food-grade Bacillus strains presents a promising frontier in the development of functional foods and nutraceuticals with enhanced health benefits. Due to their wide range of activity and applications, they are considered as important resources for the development of novel medications, agricultural biocontrol agents, and industrial enzymes. Ongoing research into the biosynthetic pathways, functional properties, and applications of these compounds is essential to fully realize their potential in the food industry. This review underscores the significance of various bioactive compounds generated from Bacillus in tackling global issues like environmental sustainability, sustainable agriculture, and antibiotic resistance. Future developments in microbiology and biotechnology will enable us to fully utilize the potential of these amazing microbes, resulting in novel approaches to industry, agriculture, and health. © 2024 Society of Chemical Industry.

Biological Manifestation of Different Temperature Regimes and Certain Insecticides on Cheilomenes sexmaculata (Fab.) Preying on Cowpea Aphid, Aphis craccivora Koch

Background: Ladybird beetles are great bio-control agents and campodeiform grubs of these little predators are able to devour aphids in a voracious fashion. They feed on a wide array of aphid species most noticeably on the infamous black aphids or cowpea aphids Aphis craccivora (Koch). Methods: The growth and feeding potential of C. sexmaculata were studied in the laboratory of the Department of Entomology, Faculty of Agricultural Sciences (Institute of Agricultural Sciences), SOA Deemed to be University, Bhubaneswar, India at four different temperatures 20°C, 25°C, 30°C and 35°C during 2021-2022. Result: The life history parameters indicated that the duration of eggs, larvae, pupae, adult males and adult females was longest at 30°C and shortest at 20°C. Such variations were also observed in morphometry and feeding potential. The trend was 30°C greater than 25°C greater than 35°C greater than 20°C. In the case of feeding potential the trend was adult female greater than adult male greater than 4th instar greater than 3rd instar greater than 2nd instar greater than 1st instar across all temperatures. Adult females lived longer than males and thereby consumed more aphids than males. Maximum consumption was seen in case of adult female at 30°C which was 633±5.71 aphids and least feeding was seen at 20°C by 1st instar grub which was 8.9±0.56 aphids. The effect of insecticides in direct spray method indicated that dimethoate 30EC killed more ladybirds and clothianidin 50% WDG killed the least. This trend was strong across all temperatures and insect growth stages. The feed contamination method indicated that clothianidin 50% WDG, imidacloprid 17.8% SL and thiamethoxam 25% WG produced higher mortality rates than direct contamination method. All insecticides showed increased mortality up to 72 h and the mortality trend was 72 HAT greater than 48 HAT greater than 24 HAT. The mortality rate of immature individuals is higher than that of adults.

Exposure to Cyantraniliprole Adversely Impacts Fitness of Harmonia axyridis: Acute Toxicity and Sublethal Effects on Development, Fecundity and Antioxidant Responses.

Extensive utilization of pesticides and their persistent residues inadvertently pose threats to the effectiveness and fitness of biocontrol agents in agroecosystems. However, these ecological consequences are generally disregarded when executing integrated pest management strategies (IPM). Cyantraniliprole (CNAP) serves as a wide-spectrum diamide insecticide and its sublethal effects have been well characterized on multiple insect pests, whereas its impacts on beneficial natural enemies remain unfathomed. Herein we exposed Harmonia axyridis, a predacious generalist, to lethal and sublethal concentrations of CNAP via dipping treatment (egg stage) and topical applications (1st-instar stage + adult stage). The acute toxicity tests revealed that LC50 of CNAP were 90.11, 86.11 and 240.50 mg/L against embryos, 1st instar nymphs and female adults, respectively, with safety factors ranging from 1.14 to 5.34, suggesting its medium toxicity for H. axyridis and larval stage was the most susceptible. The embryonic, larval and pupal durations of coccinellids ecdysed from CNAP-treated eggs and 1st instars were all elongated under sublethal concentrations, of which LC30 triggered more pronounced and significant retardations relative to control. Besides, exposed coccinellids displayed substantially diminished pupal mass and pupation rate, most notably for insects molted from the 1st-instar stage upon CNAP sublethal treatments. With respect to reproductive performance, LC10 and LC30 of CNAP all significantly suppressed female fecundity, as evidenced by reduced vitellin content, a prolonged pre-oviposition period (POP), mitigated laid eggs and the egg hatching rate. Specifically, there existed positive correlations between vitellin level (Vn) and number of eggs deposited by per female, indicative of CNAP affecting fecundity by regulation of Vn. In addition, the antioxidant system was also profoundly disrupted by CNAP, with compromised POD activity at different concentrations over time and induced hormesis of SOD/CAT activities post LC10 exposure. Activities of SOD and TAC were enhanced to exert protective functions during the first 48 h, while defense collapsed at 72 h following LC30 treatments that depleted all enzymatic activities. We speculated that fitness trade-offs may occur between reproductive capacity and antioxidant defenses to sustain physiological homeostasis in response to CNAP stress. Collectively, this study evaluated the ecological risk of CNAP and unmasked its adverse implications for overall fitness of H. axyridis, which highlighted rational application of agrochemicals to conserve biocontrol agents when implementing IPM strategies for sustainable pest control.

Biocontrol agents enhance plant disease resistance by altering plant microbiomes

Biocontrol agents enhance plant disease resistance by altering plant microbiomes

Garlic as a companion plant for suppressing Myzus persicae infestation in Brassica rapa

Companion planting, the practice of growing different plant species together, can be a sustainable pest management strategy. However, the specific role of garlic as a companion plant for Brassica in aphid suppression, particularly against Myzus persicae (Sulzer) (Hemiptera: Aphididae), is not well understood. This study investigated the potential of planting garlic (Allium sativum L., Asparagales: Amaryllidaceae) with Brassica rapa L. (Brassicales: Brassicaceae) to reduce M. persicae infestations and explores its impact on the biocontrol agent Harmonia axyridis Pallas (Coleoptera: Coccinellidae). We hypothesized that the combination of A. sativum and B. rapa would synergistically reduce aphid infestations compared to Brassica monocultures. To test this, M. persicae performance was evaluated on Brassica plants under three conditions: a single Brassica plant (B), two Brassica plants (BB), and a Brassica plant with garlic (BG). Parameters such as aphid survival, fecundity, developmental time, and population increase were measured. Additionally, Y-olfactometer bioassays assessed the behavioral responses of M. persicae and H. axyridis. The results showed that the BG combination significantly reduced aphid survival, fecundity, and population growth while delaying developmental time compared to B and BB. M. persicae preferred volatiles from B and BB plants, while H. axyridis was more attracted to BG volatiles, indicating garlic's potential to enhance biocontrol agent recruitment. This study highlights the potential of garlic as a companion plant to improve Brassica crop protection against M. persicae and enhance the effectiveness of biocontrol agents.

Research progress of Bacillus velezensis in plant disease resistance and growth promotion

Bacillus velezensis has a wide range of beneficial activities, such as fighting plant diseases, promoting growth, improving crops’ ability to handle stress, and boosting plant defenses. These traits make it a strong candidate for agricultural use, especially as a biocontrol agent and growth-promoting bacteria. This review takes a close look at the origins, working mechanisms, and potential agricultural benefits of B. velezensis. Both lab and field studies have shown its success in reducing plant diseases and supporting crop growth by producing helpful compounds, taking up space in the environment, and strengthening plant defenses. Although B. velezensis is already used in some fertilizers and biopesticides, there are still challenges in scaling up production, selecting the right strains, and ensuring product stability. This review points out current research gaps and suggests future directions, such as improving strain selection, developing better biofertilizers, and advancing production techniques to make the most of B. velezensis in agriculture. These findings aim to guide further research and improve its use in sustainable farming.

Characterization and quantification of peptaibol produced by novel Trichoderma spp: Harnessing their potential to mitigate moisture stress through enhanced biochemical and physiological responses in black pepper (Piper nigrum L.).

Trichoderma spp. is primarily applied to manage biotic stresses in plants. Still, they also can mitigate abiotic stresses by the stimulation of antioxidative protective mechanisms and enhanced synthesis of secondary metabolites. The study optimized the conditions to enhance peptaibol production by novel Trichoderma spp, characterized and quantified peptaibol- alamethicin using HPLC and LC MS-MS. The present study investigated these isolates efficacy in enhancing growth and the associated physio-biochemical changes in black pepper plants under moisture stress. Under in vitro conditions, out of 51 isolates studied, six isolatesviz., T. asperellum (IISR NAIMCC 0049), T. erinaceum (IISR APT1), T. harzianum (IISR APT2), T. harzianum (IISR KL3), T. lixii (IISR KA15) and T. asperellum (IISR TN3) showed tolerance to low moisture levels (5, 10 and 20%) and higher temperatures (35 and 40°C). In vivo evaluation on black pepper plants maintained under four different moisture levels (Field capacity [FC]; 75%, 50%, and 25%) showed that the plants inoculated with Trichoderma accumulated greater quantities of secondary metabolites viz., proline, phenols, MDA and soluble proteins at low moisture levels (50% and 25% FC). In the present study, plants inoculated with T. asperellum and T.harzianum showed significantly increased growth compared to uninoculated plants. The shortlisted Trichoderma isolates exhibited differences in peptaibol production and indicated that the peptide might be the key factor for their efficiency as biocontrol agents. The present study also demonstrated that Trichoderma isolates T. harzianum and T. asperellum (IISR APT2 & NAIMCC 0049) enhanced the drought-tolerant capabilities of black pepper by improving plant growth and secondary metabolite production.

Exploration of Phage-Agrochemical Interaction Based on a Novel Potent Phage LPRS20-Targeting Ralstonia solanacearum.

Phage therapy has the potential to alleviate plant bacterial wilt. However, the knowledge gap concerning the phage-agrochemical interaction impedes the broader application of phages in agriculture. This study characterized a phage isolate and investigated its interactions with agrochemicals. A novel species within the Ampunavirus genus was proposed, serving phage LPRS20 as a type phage with a broad lytic range and significant antibacterial activity against Ralstonia solanacearum strains infecting tobacco, chili, or tomato. Sensory evaluation of the morphology of tobacco leaves suggested that phage application resulted in negligible harm to plants. Investigations into phage-agrochemical interactions revealed synergisms when LPRS20 was delivered 4 h before thiodiazole-copper as well as LPRS20 in combination with low-concentration berberine. Overall, our findings reveal that phage LPRS20 represents a novel, effective, and eco-friendly biocontrol agent against tobacco bacterial wilt in vivo and in vitro and contributes to the potential integration of phages and agrochemicals for controlling soil-borne pathogens.

Biological Control of Microbial Pectinolytic Plant Pathogens Causing Soft Rot of Fruits and Vegetables.

It is crucial to implement appropriate measures to prevent the spread of plant pathogens that lead to the decay of fruits and vegetables. From this perspective, we evaluated the biocontrol potential of five Bacillus-plant growth promoting rhizobacteria (PGPR) strains against twenty-one pectinolytic phytopathogens causing soft rot in fruits and vegetables. These phytopathogens had been previously studied. Three in vitro methods were utilized to accomplish this objective: competition, extraction of bioactive substances, and direct confrontation. The inhibitory effect of the direct confrontation method resulted in a slower growth of 11 microbial plant pathogens. In addition, it was noted that 11 strains of plant pathogens generated inhibitory constituents, while 15 plant pathogens produced inducible inhibitory substances. Furthermore, volatile inhibitory compounds were detected in the six tested strains. Overall, strains of PGPR-Bacillus demonstrated strong antifungal and antibacterial properties against phytopathogens. These PGPR can be regarded as potential biocontrol agents for soft microbial rot in fruits and vegetables as well as producers of substances that effectively suppress plant diseases.

Volatilome of the maize phytopathogenic fungus Fusarium verticillioides: potential applications in diagnosis and biocontrol.

Fusarium verticillioides is a maize fungal phytopathogen and a producer of volatile organic compounds (VOCs) and fumonisin B1 (FB1). Our aim was to study the volatilome, conidial production, ergosterol and FB1 biosynthesis in maize cultures over a 30-day incubation period (5, 10, 15, 20, 25, 30 days post inoculation [DPI]). The effect of pure VOCs on the same parameters was then evaluated to study their potential role as biocontrol agents. In total, 91 VOCs were detected, with volatile profiles being more similar between 5 and 10 DPI compared with 15, 20, 25 and 30 DPI. Ergosterol content increased steadily with incubation time, and three growth stages were identified: a lag phase (0 to 15 DPI), an exponential phase (15 to 20 DPI) and a stationary phase (20 to 30 DPI). The maximum concentration of FB1 was detected at 25 (0.030 μg FB1/μg ergosterol) and 30 DPI (0.037 μg FB1/μg ergosterol), whereas conidial production showed a maximum value at 15 DPI (4.3 ± 0.2 × 105 conidia/μg ergosterol). Regarding pure VOCs, minimal inhibitory concentration values ranged from 0.3 mm for 4-hexen-3-one to 7.4 mm for 2-undecanone. Pure VOCs reduced radial growth, conidial production and ergosterol and FB1 biosynthesis. The marked resemblance between VOC profiles at 5 and 10 DPI suggests that they could act as early indicators of fungal contamination, particularly 4-ethylguaiacol, 4-ethyl-2-methoxyanisole, heptanol and heptyl acetate. On the other hand, their role as inhibitors of fungal growth and FB1 biosynthesis prove their great potential as safer alternatives to control phytopathogenic fungi. © 2024 Society of Chemical Industry.

Pyrrolnitrin in Pseudomonas chlororaphis strain AFS009 metabolites reduces constitutive and DMI-induced MfCYP51 gene expression in Monilinia fructicola.

Brown rot, caused by Monilinia fructicola, is one of the most economically important diseases of peach. Demethylation inhibitor (DMI) fungicides play an important part in managing brown rot in the southeastern U.S., but over the last 20 years, reduced efficacy to DMIs has been reported in field isolates overexpressing the DMI target enzyme encoding MfCYP51 gene. Metabolites of the biocontrol agent (BCA) Pseudomonas chlororaphis strain AFS009 suppressed the MfCYP51 gene in sensitive and resistant M. fructicola isolates previousely, but it is not known what molecule was responsible. The goals of this study were to determine the presence and role of pyrrolnitrin (PRN), a common metabolite of P. chlororaphis and chemical analogue to fludioxonil with antifungal activity, in the suppression of the MfCYP51 gene and to investigate if MfCYP51 expression can also be suppressed by Bacillus subtilis. High-performance liquid chromatography (HPLC) detected pyrrolnitrin at 1.75 µg/mg in P. chlororaphis metabolites formulated as Howler EVO (Howler). PRN at 0.1 µg/ml, fludioxonil at 0.1 µg/ml, and Howler applied at a dose that contained 0.1 µg/ml PRN significantly reduced the MfCYP51 gene expression at similar levels in DMI-resistant isolates. Furthermore, MfCYP51 expression in DMI-sensitive and three DMI-resistant isolates treated with Howler (88.1 µg/ml), Theia (209.5 µg/ml), propiconazole (0.3 µg/ml), or the mixture of either Howler or Theia + propiconazole revealed that Howler significantly reduced the MfCYP51 target gene expression in two of three sensitive and all three resistant M. fructicola isolates. On the other hand, Theia showed no suppressive effect and even increased the MfCYP51 gene expression level in two of three resistant isolates. In detached fruit assays on apple with a DMI resistant isolate, only the mixture of Howler + 50 µg/ml propiconazole resulted in synergism. The results indicate that suppression of MfCYP51 target gene is BCA-dependent and can be induced by pyrrolnitrin.

A Pangenomic Analysis of the Diversity and Biological Functioning of the Genus Azotobacter

Azotobacter is a diverse genus of free-living soil bacteria that fixes atmospheric nitrogen and act as a biocontrol agent for different phytopathogens. This study utilized the genomic sequences from four different Azotobacter species, comprising thirty strains, to construct the genus pangenome. Through comparative genomics and pangenomics analysis, we elucidated the genomic diversity and functional relationship between and within the species of the Azotobacter genus. The selected Azotobacter strains exhibited an ANI of ≥ 85%, with core genes constituting up to 9% and a large proportion of 55% of unique genes. This indicated the sharing of a highly open pangenome of the Azotobacter genus. The COG analysis revealed that core, unique, and accessory genes play a significant role in the Azotobacter’s metabolic and information storage processes. The KEGG enrichment evaluation showed general functioning, amino acid transport and metabolism, as the major biological processes of the Azotobacter’s genomic content. Furthermore, the predominant BGCs present in the genomic structure of Azotobacter genus exhibited a 27% participation in the production of NRP-metallophores, 17% for the NI-siderophores and 17% for type III polyketide synthase (T3PKS). The genomic content analysis of the core genome revealed various genes that encoded for acid and universal stress proteins, playing a role in Azotobacters adaptation. For the biological functioning attributes, it was found that alginate production, riboflavin transporters, nitrogen-responsive regulatory flavoprotein, nitrogen-related phosphotransferase, and molybdenum cofactor genes were involved in its core genome for the major functioning of its nitrogen fixation.

Occurrence and Management of Blast and Leaf Blight in Browntop Millet [Brachiaria ramosa (L.) Stapf

Brown top millet is an underutilized millet crop and grown in Southern Peninsular region of India. Blast as well as leaf blight diseases are frequently noticed in Browntop millet. A study was carried to find out the seasonal occurrence and management of major diseases of the crop at Centre of Excellence in Millets, Athiyandal during 2022-23 and 2023-24. The crop was sown during Second week of July of both years and the blast symptom noticed from 10 days after sowing (DAS) and shows increasing trend upto 40 DAS and later shows decreasing trend till the maturity of the crop. However, the leaf blight noticed from 20 DAS and reached maximum level at 60 DAS in both years. Field experiments were conducted to study the effect of biocontrol agents and fungicides on incidence of blast as well as leaf blight in browntop millet. The results show significant variation observed between the treatments on the disease incidences in both the years. Seed treatment with B. subtilis @10g/kg of seed +Foliar spray of Azoxystrobin 23% SC @ 1ml/l at 20 and 40 DASrecorded the lower incidence of blast as well as leaf blight disease incidence and produced more grain yield when compared to other treatments.

Sustainable management of blister and grey blight diseases of tea using antagonistic and plant growth promoting microbes in Western Ghats of India

The blister and grey blights are the devastating leaf diseases in tea. The severity of blister and grey blight diseases in tea ranged from 22% to 68% and 11.41%–57.02%, respectively in a survey conducted in Southern India during 2022–2023. The morphological and molecular identifications of pathogens revealed that Exobasidium vexans and Neopestalotiopsis clavispora were responsible for causing blister and grey blights on tea in southern India. The conventional management strategy with foliar spray of synthetic fungicides result in fungicidal residue in tea causes environmental pollution and health hazards to human. To overcome this the current study aims to manage the blister and grey blight diseases of tea through the microbial biocontrol agents. The bacterial biocontrol agents viz., Bacillus subtilis (BBV57), Bacillus amyloliquefaciens (TNAU), Pseudomonas fluorescens (Pf1) and the fungal antagonist, Trichoderma asperellum (TV 1) were evaluated for their efficacy against the both blight diseases. All the bio agents have significantly reduced the basidiospore germination and the mycelial growth of E. vexans and N. clavispora, respectively. Among the bio agents, B. amyloliquefaciens registered 88.36% reduction in the germination of E. vexans basidiospore and 85.56% of mycelial growth reduction of N. clavispora in vitro (P < 0.05). Under field conditions the combined soil and foliar application of bacterial antagonists viz., B. subtilis, B. amyloliquefaciens and P. fluorescens each with 1 ˟ 1011 CFU/ml @ 5% concentration at 7 days interval significantly reduced the blister blight incidence with 53.53% & 51.53% reduction over control and 51.53% & 43.65% of reduction over initial during first and second year, respectively. The combined application also reduced the grey blight incidence with 53.53% & 52.00% reduction over control and 56.81% & 47.65% of reduction over initial during first and second year, respectively. This treatments with bioagents were almost comparable with synthetic treatments, such as copper oxy chloride (0.25%) and hexaconazole (0.25%) with 64.63% and 64.76% reduction of blister and grey blight reduction in first year; 59.74%, 51.11% reduction in second year over control (P < 0.05), respectively. Thus, the application of B. subtilis, B. amyloliquefaciens and P. fluorescens can be recommended for the sustainable management of tea blister and grey blight diseases in tea gardens.

Exploration of antimicrobial activities and mechanisms of biocontrol agent Serratia nematodiphila BC-SKRU-1 against Penicillium digitatum in tangerine fruit

The isolate BC-SKRU-1, identified as Serratia nematodiphila from fungal culture contamination, was investigated for its biocontrol potential against Penicillium digitatum in vitro and on tangerine fruit, with a focus on its mechanisms of action. In vitro tests on PDA plates revealed BC-SKRU-1's broad-spectrum antifungal activity, achieving up to 74.68% inhibition against seven plant pathogenic fungi, including P. digitatum NKP4321. Bacterial culture filtrates from BC-SKRU-1 (BCF BC-SKRU-1) at 5–10% concentrations inhibited NKP4321 mycelial growth in PDB medium (78.41–83.68%) more effectively than in PDA medium (46.20–72.61%), with complete suppression at 15% (v/v) in both media. BCF BC-SKRU-1's efficacy was comparable to chemical fungicides such as propiconazole®, prochloraz®, and mancozeb®. Notably, BCF BC-SKRU-1 retained its antifungal activity after dilution (1/1000), autoclaving (at 121 °C), and storage (at −20 °C). In vivo evaluations on tangerine fruit showed significant reduction in the severity of postharvest green mold disease with BC-SKRU-1 treatments, especially at a concentration of 108 CFU mL−1. Both preventive and curative applications were effective, with curative treatments being more successful. Mechanistic studies indicated that BCF BC-SKRU-1 reduces intracellular ergosterol content, compromises plasma membrane integrity, and attenuates antioxidant defense activities (SOD, CAT, GSH, GSSG, and GSH/GSSG ratio). These findings highlight BC-SKRU-1 and its metabolites as promising biocontrol agents against green mold in tangerine fruits and provide insights into their antifungal mechanisms.