Efficient Biocontrol Agent Research Articles

Age-gender-specific functional and age-specific numerical responses of Neoseiulus californicus (Acari: Phytoseiidae) on two-spotted spider mite.

The phytoseiid predatory mite Neoseiulus californicus (McGregor) is one of the most efficient biocontrol agents in integrated pest management (IPM) programs of greenhouse pests, with different feeding habits on pollen, thrips, eriophyiids, and spider mites. This study appraised the effect of the age and gender on functional response and age on numerical response of N. californicus fed on larvae and protonymph of Tetranychus urticae Koch under laboratory conditions at 25 ± 1℃, 70 ± 5% RH and a photoperiod of 16L: 8D h. In the functional response test, the 2, 4, 8, 16, 32, 64, and 128 densities of prey were offered to 3, 5, 7, 10, 15, 20, 25, 30, 35 and 40-day-old ages of female and 7, 10, 15, 20, 25 and 30-day-old ages of male individuals of N. californicus. The logistic regression was used to recognize the type of functional response. Type II functional response was recognized for all ages of the male and female individuals of N. californicus. The highest predation rate, and searching efficiency (a) was observed in the middle ages of the predator. A significant increase in oviposition was shown with increasing T. urticae density and increasing ages of the predator. Furthermore, in the middle age with low prey density, the efficiency of conversion of ingested food (ECI) was the highest. The results of this study showed that the different ages of N. californicus are influencing factors on its predation capacity and oviposition rate.

Field releases of Trichogramma cacoeciae (Marchal, 1927) (Hymenoptera: Trichogrammatidae) against the codling moth, Cydia pomonella (Linnaeus, 1758) (Lepidoptera: Tortricidae)

The codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae), is a key pest of apples in Tunisia and other countries around the world. Various management strategies have been applied to manage this pest including releases of parasitoids. Trichogramma wasps are known as efficient biocontrol agents tested against a large number of lepidopteran pests including C. pomonella. Two inundative releases of Trichogramma cacoeciae Marchal, at the rates of 25 000 and 50 000 parasitoids per ha, were performed when threshold was reached (2 to 3 adults per pheromone trap) in a commercial apple orchard, in 2018. Results indicated the occurrence of three flight peaks registered in the spring, summer and autumn of the growing season. The efficacy of the two release rates in reducing the infestation level of the population of the codling moth was proved herein. Average infestation level of fruits was significantly reduced after of the first release with reduction of about 27% for rate 1 and 22% for rate 2 compared to the untreated control (45%). Likewise, the average percentage of damaged apples was significantly reduced after the second release (23, 18.37 and 43.37 % respectively for the rate 1, rate 2 and the untreated control). The results showed the efficacy of T. cacoeciae parasitoids as efficient candidates to control C. pomonella.

Intestinal bacterium Bacillus siamensis M54 from Allomyrina dichotoma is a potential biocontrol agent against maize stalk rot

Maize stalk rot, caused by Fusarium spp., is a significant disease that adversely impacts the yield and quality of corn. Biological control plays a crucial role in managing numerous crop diseases, including maize stalk rot. Biocontrol agents are predominantly derived from soil and plant tissues, with limited reports on isolating highly efficient biocontrol agents from insects. In this study, 144 bacterial strains were isolated from the intestinal tract of third instar larvae of Allomyrina dichotoma. Through dual culture tests, twelve strains exhibiting strong antagonism against two maize stalk rot pathogens, F. graminearum and F. verticillioides, were identified. Among them, the M54 strain exhibited the most potent antagonistic effect against the two pathogenic fungi and was identified as Bacillus siamensis through 16S rRNA gene sequence analysis. The complete genome for M54 was assembled using PacBio single-molecule real-time (SMRT) and Illumina sequencing technologies. Whole genome phylogenetic analysis further confirmed M54 was B. siamensis. Microscopic examination revealed that M54 had the ability to inhibit the fungal spore germination and hyphal formation. Furthermore, M54 exhibited effective colonization in the maize rhizosphere and enhanced maize growth. It showed that treatment with M54 significantly suppressed lesion expansion induced by F. graminearum on maize stalks in the seedling and adult plant assays. Genomic analysis using antiSMASH revealed 11 gene clusters for secondary metabolite synthesis. This study provides a novel approach for isolating biocontrol agents to manage plant diseases and highlights B. siamensis M54 as a potential efficient biocontrol agent for maize stalk rot.

Bacillus velezensis B105-8, a potential and efficient biocontrol agent in control of maize stalk rot caused by Fusarium graminearum.

Maize stalk rot (MSR), caused by Fusarium graminearum, is the most serious soil borne disease in maize production, seriously affecting maize yield and quality worldwide. Microbial biocontrol agents are the best means of controlling MSR and reducing the use of chemical fungicides, such as Bacillus spp. In the study, a soil-isolated strain B105-8 was identified as B. velezensis (accession No. PP325775.1 and No. PP869695.1), demonstrated a broad spectrum against various pathogens causing maize diseases, which effectively controlled MSR, exhibited a high control efficacy of more than 60% and growth-promoting effect in the pot plant. B105-8 could effectively improve soil urease (S-UE), invertase (S-SC), and catalase (S-CAT) activities. S-NP activity showed an initial increase with a peak of 20,337 nmol/h/g, followed by a decrease, but activity remained significantly better than control treatment with chemical fungicides. The application of B105-8 repaired the damage caused by F. graminearum on soil activity. The antifungal compound B-1, extracted from B105-8, was purified using a protein purifier, revealing inhibitory effects against F. graminearum. Mass spectrometry analysis indicated the potential presence of C14 Bacillomycin, C15 Iturin, C15 Mycosubtilin, C17, and C15 fengycin in B-1. In pot experiments, a 5 μL/mL concentration of B-1 exhibited 69% control on MSR, enhancing maize root elongation, elevation, and fresh weight. At 10 μL/mL, B-1 showed 89.0 and 82.1% inhibition on spore production and mycelial growth, causing hyphal deformities. This study presents the innovative use of B. velezensis, isolated from maize rhizosphere in cold conditions to effectively control MSR caused by F. graminearum. The findings highlight the remarkable regional and adaptive characteristics of this strain, making it an excellent candidate to fight MSR in diverse environments. In conclusion, B. velezensis B105-8 demonstrated potential as a biocontrol agent for MSR.

Endophyte Bacillus vallismortis BL01 to Control Fungal and Bacterial Phytopathogens of Tomato (Solanum lycopersicum L.) Plants

Some strains of Bacillus vallismortis have been reported to be efficient biocontrol agents against tomato pathogens. The aim of our study was to assess the biocontrol ability of the endophytic strain BL01 Bacillus vallismortis through in vitro and field trials, as well as to verify its plant colonization ability and analyze the bacterial genome in order to find genes responsible for the biocontrol activity. We demonstrated in a gnotobiotic system and by confocal laser microscopy that the endophytic strain BL01 was able to colonize the endosphere and rhizosphere of tomato, winter wheat and oilseed rape. In vitro experiments demonstrated the inhibition activity of BL01 against a wide range of phytopathogenic fungi and bacteria. BL01 showed biological efficacy in two-year field experiments with tomato plants against black bacterial spotting by 40–70.8% and against late blight by 47.1% and increased tomato harvest by 24.9% or 10.9 tons per hectare compared to the control. Genome analysis revealed the presence of genes that are responsible for the synthesis of biologically active secondary metabolites, which could be responsible for the biocontrol action. Strain BL01 B. vallismortis can be considered an effective biocontrol agent to control both fungal and bacterial diseases in tomato plants.

Next-generation sequencing-based comparative mapping and culture-based screening of bacterial rhizobiome in Phytophthora capsici-resistant and susceptible Piper species.

Black pepper (Piper nigrum L.), a highly valued spice crop, is economically significant as one of the most widely traded spices in the world. The global yield and quality of black pepper (Piper nigrum L.) are affected by foot rot-causing soil-borne oomycete pathogen Phytophthora capsici. To gain initial insights toward developing an approach that utilizes microbial genetic resources for controlling foot rot disease in black pepper, we mapped the rhizobiome communities in susceptible Piper nigrum L. and wild-resistant Piper colubrinum. The analysis showed compositional differences in the rhizobiome of two Piper species, which revealed higher diversity and the presence of more differentially abundant genera in P. colubrinum. Furthermore, P. colubrinum rhizobiome had a significantly higher abundance of known anti-oomycete genera, such as Pseudomonas, and a higher differential abundance of Janthinobacterium, Variovorax, and Comamonas, indicating their probable contribution to pathogen resistance. Predictive functional profiling in P. colubrinum rhizobiome showed highly enriched functional gene orthologs (KOs), particularly chemotaxis proteins, osmoprotectants, and other transport systems that aid in pathogen resistance. Similarly, pathways such as phenylpropanoid biosynthesis and other antimicrobial synthesis were enriched in P. colubrinum rhizobiome. The culturable diversity of the resistant root endosphere, which harbors efficient biocontrol agents such as Pseudomonas, strengthens the possible role of root microbiome in conferring resistance against soil-borne pathogens. Our results depicted a clear distinction in the rhizobiome architecture of resistant and susceptible Piper spp., suggesting its influence in recruiting bacterial communities that probably contribute to pathogen resistance.

Eco-friendly Management of Plant Pathogens through Secondary Metabolites Released by Fluorescent Pseudomonads

Concerning sustainable agriculture, plant growth promoting rhizobacteria (PGPR), which are a subgroup of “fluorescent pseudomonads,” are crucial. They are widely known for supporting plant health through a variety of methods. The use of fluorescent pseudomonads in agri-biotechnology has gained traction due to their potential for safeguarding plants from a variety of phytopathogens. Fluorescent pseudomonads being commercialized as bioinoculants for the treatment of various plant diseases is currently regarded as highly successful on a global scale. Fluorescent pseudomonads are being employed as efficient bio-control agents (BCAs) against an array of phytopathogens. Due to their capacity to generate a wide range of secondary metabolites, they offer enormous promise as BCA. Thus, this review’s goal is to outline and evaluate the functions of fluorescent pseudomonads’ secondary metabolites in reducing phytopathogens and improving plant health. Prominent secondary metabolites linked to biocontrol through fluorescent pseudomonads include phenazines (PHZ), 2, 4-diacetylphloroglucinol (DAPG), pyoluteorin (PLT), pyrrolnitrin (PRN), cyclic lipopeptides (CLPs), and volatile organic compounds (VOCs), including hydrogen cyanide (HCN). The antifungal, antibacterial, antiviral, antitumor, and antinematicidal effects of these metabolites are well-established.

Bacillus velezensis Y6, a Potential and Efficient Biocontrol Agent in Control of Rice Sheath Blight Caused by Rhizoctonia solani.

Rice sheath blight is a serious disease caused by Rhizoctonia solani that reduces rice yield. Currently, there is a lack of efficient and environmentally friendly control methods. In this study, we found that Bacillus velezensis (B. velezensis) Y6 could significantly inhibit the growth of mycelium in Rhizoctonia solani, and its control efficiency against rice sheath blight was 58.67% (p < 0.01) in a pot experiment. Lipopeptides play an important role in the control of rice sheath blight by B. velezensis Y6, among which iturin and fengycin are essential, and iturin W, a novel lipopeptide in B. velezensis, plays a major role in lipopeptide antagonism to Rhizoctonia solani. In the field, we also found that inoculation with B. velezensis Y6 can increase rice yield (dry weight) by 11.75%. Furthermore, the transcriptome profiling results of the rice roots revealed that there were a total of 1227 differential genes (DEGs) regulated when treated with Y6, of which 468 genes were up-regulated and 971 genes were down-regulated in rice roots compared with the control. Among them, the DEGs were mainly distributed in biological processes (BP) and were mainly enriched in response to stimulus (GO:0050896), response to stress (GO:0006950), and response to abiotic stimulus (GO:0009628). According to the KEGG pathway analysis, there were 338 DEGs classified into 87 KEGG functional pathway categories. Compared with the control, a large number of enriched genes were distributed in phenylpropanoid biosynthesis (map00940), glutathione metabolism (map00480), glycolysis/gluconeogenesis (map00010), and amino sugar and nucleotide sugar metabolism (map00520). In summary, this investigation provides a new perspective for studying the molecular mechanism of B. velezensis in controlling rice sheath blight.

Identification and Evaluation of Antagonistic Potential of Different fluorescent pseudomonads in Northern Plains of West Bengal

To achieve future food security, reliable crop protection will be critically important. Development of biological control for soil borne disease is accepted as a safe, durable and ecofriendly alternative for chemical management strategy. Pseudomonads possess many traits like production antibiotics, lytic enzymes, siderophores, hydrogen cyanide (HCN) that make them well suited as biocontrol and growth-promoting agents. An attempt was taken to isolate and identify different fluorescent Pseudomonads and to evaluate their antagonistic ability. Twelve fluorescent Pseudomonads isolates were collected from different crop rhizosphere from different locations of northern parts of West Bengal. Isolates characterized morphologically and biochemically. All the isolates were gram negative rods with smooth and glossy colony on kings B and nutrient agar medium with convex elevation but variation was found in respect to pigment production. A huge variation was found in respect to biochemical characterization. From the result of biochemical analysis, the isolated sp. can be identified as Pseudomonas fluorescens or Pseudomonas putida or Pseudomonas aeruginosa. Some of the isolate produce green, some isolates produce yellowish green and rest of them produce red/pink pigments. Isolates showed a huge variation in respect to pathogenicity against soil borne pathogen Slerotium rolfsii. Percent inhibition varied from 31 to 74 %. Isolate 3 and 8 can be efficient biocontrol agent as highest growth inhibition of the pathogen Sclerotium rolfsii was obtained by the isolate 8 (74.37%) followed by isolate 3 (63.15%). In respect to growth parameter isolate 8, 9 and 10 were found better among the isolates where as in respect to disease reduction isolate 3, 8, 9 and 11 were promising under in vivo study.

Evaluation of Bacillus amyloliquefaciensTV‐17C as a potential biocontrol agent for controlling postharvest Penicillium digitatum on orange

AbstractPostharvest diseases in fruits result in significant losses in the agricultural sector. Among these, green mould, caused by Penicillium digitatum, poses a considerable threat to citrus fruits. This study evaluated the potential of Bacillus amyloliquefaciens strain TV‐17C as a biological control agent for managing green mould in oranges. Various concentrations of TV‐17C in aqueous suspension were applied to naturally infected orange fruits in the packinghouse at two locations (Hatay and Mersin provinces), while the chemical fungicide fludioxonil 230 SC served as a positive control. The application of B. amyloliquefaciens TV‐17C at the dosage of 250 mL 100 L−1 reduced green mould incidence by 90.3% and 89.8% in Hatay and Mersin provinces, respectively. Similarly, fludioxonil 230 SC displayed an efficacy of 91.4% in reducing disease incidence. In summary, this study underscores the potential of B. amyloliquefaciens TV‐17C as an efficient biocontrol agent against green mould in oranges. Moreover, a positive correlation between higher concentrations and enhanced efficacy was evident. These findings hold promise for the adoption of sustainable disease management practices in the postharvest citrus industry.

Genetic diversity and antagonistic properties of Trichoderma strains from the crop rhizospheres in southern Rajasthan, India

There are fewer studies on Trichoderma diversity in agricultural fields. The rhizosphere of 16 crops was analyzed for Trichoderma species in 7 districts of Rajasthan state of India. Based on DNA sequence of translation elongation factor 1α (tef-1α), and morphological characteristics, 60 isolates were identified as 11 species: Trichoderma brevicompactum, species in Harzianum clade identified as T. afroharzianum, T. inhamatum, T. lentiforme, T. camerunense, T. asperellum, T. asperelloides, T. erinaceum, T. atroviride, T. ghanense, and T. longibrachiatum. T. brevicompactum is the most commonly occurring strain followed by T. afroharzianum. No new species were described in this study. T. lentiforme, showed its first occurrence outside the South American continent. The morphological and cultural characteristics of the major species were observed, described, and illustrated in detail. The isolates were tested for their antagonistic effect against three soilborne plant pathogens fungi: Sclerotium rolfsii, Rhizoctonia solani, and Fusarium verticillioides in plate culture assays. One of the most potent strains was T. afroharzianum BThr29 having a maximum in vitro inhibition of S. rolfsii (76.6%), R. solani (84.8%), and F. verticillioides (85.7%). The potential strain T. afroharzianum BThr29 was also found to be efficient antagonists against soil borne pathogens in in vivo experiment. Such information on crop selectivity, antagonistic properties, and geographic distribution of Trichoderma species will be beneficial for developing efficient Trichoderma-based biocontrol agents.

Metabolites from a co-culture of Trichoderma yunnanense and Paenibacillus peoriae improve resistance to corm rot disease in Crocus sativus

The stigmas of the medicinal plant Crocus sativus are utilized as an expensive traditional Chinese medicine to treat irregular menstruation, depression, postpartum thrombosis, and bruises. As one of the most severe diseases of C. sativus, corm rot has hindered development of the C. sativus industry. Synthetic microbial communities (SMCs) have shown significant promise for the control of plant diseases, but there are few reports on their use for control of C. sativus corm rot. In this study, we co-cultured pairs of C. sativus rhizosphere soil-isolated fungi and bacteria, performed compatibility experiments on them to obtain SMCs with good compatibility, and evaluated their ability to improve disease resistance against C. sativus corm rot induced by Fusarium oxysporum. The fermentation broth of the most effective SMC was partitioned into five fractions, and disease resistance activity assays were conducted to identify the fraction in which active metabolites were concentrated. Metabolomic analyses were carried out to analyze the chemical composition of this fraction and determine how it differed from that of single cultures. We constructed four SMCs and found that SMC03 (Trichoderma yunnanense SR38 + Paenibacillus peoriae SR235) showed the best disease resistance activity, which was significantly higher than that of SR38 or SR235 alone (P < 0.05). The active metabolites produced by SMC03 were mainly concentrated in the aqueous fraction, which contained abundant organic acids and their derivatives. Co-cultivation of SR38 and SR235 increased overall production of DL-3-phenyllactic acid, 3-hydroxydecanoic acid, and (2S)-2-isopropylmalate, and we speculate that these components can bind membrane receptors of plant cells, induce local resistance, and subsequently generate plant immune response, thereby enhancing C. sativus disease resistance. In summary, co-cultivation of a fungus and a bacterium from the C. sativus rhizosphere may enhance host resistance to corm rot by accelerating the synthesis of certain organic acids. This study demonstrates for the first time the feasibility of developing SMCs for control of corm rot in C. sativus, which is of great significance in guiding the development of efficient biocontrol agents against C. sativus corm rot, thereby promoting sustainable cultivation of C. sativus. These findings also provide reference for the biocontrol of fungal diseases in other field cultivated medicinal plants.

TRICHODERMA AS A PROFICIENT BIOCONTROL AGENT FOR PHYTO-PATHOGENIC FUNGI – MECHANISM OF ACTION AND GENETIC ADVANCES

Plant disease management presently relies heavily on chemical fungicides. However, their harmful impact on human and ecosystem, and development of fungicide-resistant strains has emphasized on biological control as alternative eco-friendly strategy for disease management and sustainable agriculture. Trichoderma is a widely used as biocontrol agent against various phyto pathogenic fungi owing to its effective strategies to suppress plant pathogens. The control phenomenon involves direct mechanisms like mycoparasitism, secretion of hydrolytic enzymes which degrade the cell walls of pathogenic fungi, and indirect mechanisms like competition for resources, induction of plant defense mechanism and antibiosis. Trichoderma’s multifaceted approach to biological control makes it environment-friendly option for managing plant diseases. Recent biotechnological approaches have simplified the isolation and characterization of efficient biocontrol agents, along with the identification of their genetic by-products. These techniques facilitate the cloning of these microbes in plants, with aim to bolster their resistance to both biotic and abiotic stresses. Biotechnological advances have not only reinforced the symbiotic interaction between microbes and plants but also allowed the modification of processes through microbial biocontrol agents (MCBAs). Genome sequencing of MBCAs has provided valuable insights into their genetic makeup, aiding their characterization. The present comprehensive review provides an insight to the existing and recent molecular advances utilized to enhance the efficiency of MBCAs in managing plant diseases and understanding biocontrol mechanisms through various omics technologies.

Adapting the inoculation methods of kiwifruit canker disease to identify efficient biocontrol bacteria from branch microbiome.

Pseudomonas syringae pv. actinidiae (Psa), the bacterium that causes kiwifruit bacterial canker, is a common field occurrence that is difficult to control globally. Currently, exploring the resources for efficient biocontrol bacteria is a hot spot in the field. The common strategy for isolating biocontrol bacteria is to directly isolate biocontrol bacteria that can secrete diffusible antibacterial substances, most of which are members of Bacillus, Pseudomonas and Streptomycetaceae,from disease samples or soil. Here, we report a new approach by adapting the typical isolation methods of kiwifruit canker disease to identify efficient biocontrol bacteria from the branch microbiome. Using this unique approach, we isolated a group of kiwifruit biocontrol agents (KBAs) from the branch microbiome of Psa-resistant varieties. Thirteen of these showed no antagonistic activity invitro, which depends on the secretion of antibacterial compounds. However, they exhibited antibacterial activity via cell-to-cell contacts mimicked by co-culture on agar plates. Through biocontrol tests on plants, two isolates, KBA13 and KBA19, demonstrated their effectiveness by protecting kiwifruit branches from Psa infection. Using KBA19, identified as Pantoea endophytica, as a representative, we found that this bacterium uses the type VI secretion system (T6SS) as the main contact-dependent antibacterial weapon that acts via translocating toxic effector proteins into Psa cells to induce cell death, and that this capacity expressed by KBA19 is common to various Psa strains from different countries. Our findings highlight a new strategy to identify efficient biocontrol agents that use the T6SS to function in an antibacterial metabolite-independent manner to control wood diseases.

Serine protease CrKP43 interacts with MAPK and regulates fungal development and mycoparasitism in Clonostachys chloroleuca.

Serine proteases are a group of important hydrolytic enzymes that play vital roles in various cellular processes in fungi. In this study, the S8 serine protease-encoding gene CrKP43 was identified in the highly efficient Clonostachys chloroleuca 67-1 (formerly C. rosea 67-1) strain, which was markedly upregulated when parasitizing Sclerotinia sclerotiorum. The function of CrKP43 was investigated using gene deletion and complementation, and the results indicated that the lack of CrKP43 resulted in deformed fungal hyphae and cell morphology, inhibition of conidiation, and decreased antagonistic activity toward the pathogenic fungus Fusarium oxysporum f. sp. cucumerinum. Moreover, the mutants displayed much weaker mycoparasitic ability to S. sclerotiorum sclerotia and lower control efficiency against soybean Sclerotinia rot compared with the wild-type strain. All biological characteristics and biocontrol activities were recovered when the CrKP43 gene was reinserted into the fungus. Using qRT-PCR analysis and protein-protein interaction assays, it was further proved that the CrKP43 protein interacted with the mitogen-activated protein kinase (MAPK) Crmapk, suggesting serine proteases might be involved in the mycoparasitism of C. chloroleuca with the regulation of Crmapk. The findings improve our knowledge of serine proteases and their regulation in mycoparasites and help to illuminate the mechanisms underlying mycoparasitism of C. chloroleuca. IMPORTANCE Mycoparasites play important roles in the biocontrol of plant fungal diseases, during which they secret multiple hydrolases such as serine proteases to degrade their fungal hosts. In this study, we demonstrated that the serine protease CrKP43 was involved in C. chloroleuca development and mycoparasitism with the regulation of Crmapk. To the best of our knowledge, it is the first report on the functions and regulatory mechanisms of serine proteases in C. chloroleuca. Our findings will provide new insight into the regulatory mechanisms of serine proteases in mycoparasites and contribute to clarifying the mechanisms underlying mycoparasitism of C. chloroleuca, which will facilitate the development of highly efficient fungal biocontrol agents as well.

Susceptibility to cold suggests low risk of establishment of a tropical parasitoid attacking the corn pest Sesamia nonagrioides

Low temperatures limit the distribution and performance of many crop pests and their natural enemies in non-native areas. Here we evaluated the lower thermal thresholds for survival, development and reproduction of the tropical species Cotesia typhae Fernandez-Triana (Hymenoptera: Braconidae), a gregarious larval parasitoid of Sesamia nonagrioides Lefèbvre (Lepidoptera: Noctuidae), an important corn pest in southern Europe. C. typhae is highly host specific and a very efficient biocontrol agent of S. nonagrioides in greenhouse, with minimal impact on non-target species. Immature and adult stages of the parasitoid were exposed to five constant temperatures ranging from 5 to 27 °C. High mortality was observed in all immature stages below 15 °C and thresholds for egg, larval, and external pupal development were between 10 and 15 °C. Adult locomotor activity decreased dramatically within this temperature range, and males were more susceptible to cold than females. Given these thermal limitations and based on winter temperatures recorded over the past 20 years, we estimated that C. typhae had a low probability to survive in French winters. This finding supports the safe use of C. typhae as an augmentative biological control agent against S. nonagrioides.

Exploring the mechanisms of endophytic bacteria for suppressing early blight disease in tomato (Solanum lycopersicum L.).

Controlling early blight of tomatoes using endophytic bacteria is an eco-friendly and sustainable approach to manage this common fungal disease caused by Alternaria solani, Alternaria alternata, and Curvularia lunata. Endophytic bacteria are microorganisms that live inside plant tissues without causing harm and can help protect the host plant from pathogens. In this work, twenty endophytic bacterial isolates from tomato healthy plants were tested against pathogenic fungal isolates that caused early blight disease in vitro. Out of the 20 tested isolates, three (B4, B7, and B17) were considered effective isolates against the growth of fungal pathogens. The three isolates were recognized as Enterobacter cloacae HS-6 (B4), Pseudomonas gessardii HS-5 (B 7), and Pseudomonas mediterranea HS-4 (B17) using 16s-rDNA sequencing. Different concentrations of bacterial cultural diltrates at 20, 40, and 60% were tested for their antagonistic effects on the development of pathogenic fungi in vitro. The lowest dry weights of pathogenic isolates in all bacterial culture filtrates were discovered at 60%. In all culture filtrates, phenolic compounds showed the largest peak area. Under greenhouse conditions, the least disease severity of tomato early blight was found for E. cloacae and its culture filtrate compared to other treatments. Real-time PCR was used to examine the expression pattern of the defense response gene β-1.3 glucanase gene in infected tomato plants with pathogenic fungi (control) as well as its relations with efficient biocontrol agent (E. cloacae). The expression of the gene increased substantially and significantly after three days from the inoculation-infected plants with C. lunata and E. cloacae while it reached the maximum after five days from the inoculation with A. alternata, A. solani and E. cloacae. Our study concluded that the endophytic bacterial isolate E. cloacae can be considered a promising biocontrol agent for preventing tomato early blight.

Modelling the interaction between a pest (Aculops lycopersici), two predators (Pronematus ubiquitus and Macrolophus pygmaeus) and climate variables: a 3-year greenhouse study in a tomato crop.

The tomato russet mite, Aculops lycopersici, is a major pest in tomato crops, causing damage through leaf and stem browning, defoliation and russeting of fruit. Biological control of this mite on tomato plants is difficult. While several phytoseiid mites feed on the pest, they cannot survive, move, or reproduce on tomato plants due to the presence of glandular trichomes. Pronematus ubiquitus has recently been identified as a biocontrol agent of A. lycopersici in tomato crops, but the predator-prey interaction between these two species is not well studied. In this paper, we present a validated logistic regression predator-prey model based on a 3-year study supplemented with additional datasets. Besides the predator and the prey, this model takes into account an extra generalist predator, Macrolophus pygmaeus, and various climate parameters. The population trend of A. lycopersici is best explained by the presence of the predator P. ubiquitus, the relative humidity and the fact that the crop was lit or unlit using artificial light. P. ubiquitus has proved to be an efficient biocontrol agent of A. lycopersici. For P. ubiquitus the presence of M. pygmaeus, the vapour pressure deficit, the number of light hours and radiation explained the population trend best. For both the predator and the prey density-dependent interactions were identified. Model outcomes are discussed in detail. Our study provides insights into the potential use of P. ubiquitus as a biocontrol agent for A. lycopersici in tomato crops in combination with M. pygmaeus. However, we highlight the importance of considering the presence of other predators and environmental conditions when developing integrated pest management strategies. © 2023 Society of Chemical Industry.

Advancements in the Use of Entomopathogenic Microbes for Pest and Disease Management- A Review

This comprehensive review presents an in-depth analysis of the role of entomopathogenic microbes in insect pest and disease management. The study covers the taxonomy and classification of these organisms, including bacteria, fungi, viruses, and nematodes, all of which have shown efficacy in controlling various insect pests. Entomopathogenic microbes represent a valuable, sustainable, and eco-friendly alternative to synthetic pesticides, highlighting their significant role in Integrated Pest Management (IPM) strategies. The review reveals that entomopathogenic microbes affect pests at different developmental stages through various mechanisms, including disease induction, parasitism, and competition for resources. The effects are not just lethal but also sub-lethal, affecting pest reproductive capacity, growth, and development. The microbes secondary metabolites often have antimicrobial properties, contributing to plant disease management by suppressing plant pathogens. Despite their promising potential, challenges exist in the widespread application of these microbes. Factors such as formulation, delivery, and environmental conditions can influence their effectiveness. The paper also discusses the importance of genomics, proteomics, and metabolomics in understanding the complex interactions between microbes, insects, and plants, which could lead to the development of more targeted and efficient bio-control agents. The review outlines future directions for this field, emphasizing the necessity for more extensive research to enhance our understanding of entomopathogenic microbes, optimize their use, overcome the current challenges, and harness their potential for sustainable pest and disease management. The need for regulatory frameworks to ensure safe and effective utilization is also underscored. This paper underscores the untapped potential of entomopathogenic microbes as acritical component of sustainable agriculture.

Effect of prey density on the performance of Eupeodes corollae and its predation rate against the cabbage aphid, Brevicorynae brassicae (L.).

Eupeodes corollae (F.) (Diptera: Syrphidae) is the most abundant syrphid fly which is distributed worldwide and is the sole predator of aphids. Therefore, the present study was conducted to evaluate the predation rate and functional response of E. corollae against the cabbage aphid, Brevicoryne brassicae (L.). The experiment was carried out under laboratory conditions at 25 ± 2°C with 60-70% relative humidity. The results revealed that age-specific net predation rate (qx) increased after the 4th day and a peak was recorded on the 10th day of pivotal age in the third larval instar. The stable host kill rate and finite host kill rate of E. corollae were 18.63 and 21.07, respectively, against the B. brassicae and predicted that a mean of 20.78 aphids was needed for E. corollae to produce one offspring. A negative linear coefficient (P < 0) indicated the type II functional response for all larval instars of E. corollae against the B. brassicae. At higher prey density, the prey consumption was significantly at par with second and third instar larvae of E. corollae as the prey consumption was increased with increasing the prey density, which then decreased after attaining the upper asymptote (76.40 and 81.40% consumption, respectively). The Roger's predator random equation for type II functional response was fitted to estimate attack rate (a) and handling time (Th). The maximum prey consumption was recorded for third instar of E. corollae with a higher attack rate (0.336 h-1) and lower handling time (0.514 h) against B. brassicae, followed by the second and first instar. Thus, it is concluded that the third larval instar of E. corollae was the voracious feeder and used as an efficient biocontrol agent in the IPM programme.