Biological Control Of Plant Diseases Research Articles

Assessing Aerated Vermicompost Tea Combined with Microbial Biological Control Agents for Suppression of Fusarium and Rhizoctonia.

Biological control of plant diseases is important in organic greenhouse vegetable production, where fungicide use is limited. Organic producers use microbially diverse substrates, including composts, as media for plant growth. Previous research into the impact of vermicompost on the efficacy of applied biocontrol agents is limited. An invitro assay was developed to test the efficacy of two biological control agents in a competitive microbial background. Suppression of the pathogen Fusarium oxysporum f. sp. radicis-cucumerinum by Clonostachys rosea f. catenulata (Gliocladium catenulatum strain J1446 [Prestop]) and Bacillus subtilis strain QST 713 (Rhapsody), was assessed on agar media amended with aerated vermicompost tea (ACT). Pathogen growth was reduced more by C. rosea than ACT alone, and C. rosea was equally effective when combined with ACT. In contrast, B. subtilis reduced pathogen growth less than ACT and, when combined, reduced pathogen growth no more than ACT alone. Both biocontrol agents were similarly tested with ACT against F. oxysporum f. sp. radicis-cucumerinum and Rhizoctonia solani on cucumber and radish. Additive, neutral, and antagonistic responses, depending on host, pathogen, and biocontrol agent, were observed. ACT alone provided more consistent disease suppression on cucumber compared with B. subtilis or C. rosea. In combination, disease suppression was most often better than each biocontrol alone but not better than ACT alone. ACT had antagonistic or additive interactions with C. rosea in the radish/R. solani pathosystem, depending on the experiment. The specific and general suppression of plant diseases by biological control agents in microbially rich environments is variable and warrants further study.

Prospects of Biological Control of Plant Diseases in Ghana: A Mini-Review

Prospects of Biological Control of Plant Diseases in Ghana: A Mini-Review

Novel and rapid agar plate methods for in vitro assessment of bacterial biocontrol isolates' antagonism against multiple fungal phytopathogens.

Biological control of plant diseases with antagonistic bacteria is a promising alternative to conventional chemical control strategies. In vitro screening for inhibition of mycelial growth of phytopathogenic fungi by bacterial isolates is the first step in selecting putative bacterial biocontrol agents. Dual culture plate assay is the most common method involved in this first-line selection process. However, it needs independent agar plates to test antagonism by a specific bacterial isolate against each of the fungal phytopathogen. Two modified in vitro antagonism tests are proposed here. Antagonistic activity of a putative biocontrol bacterial strain against four different fungal phytopathogens could be assessed in a single agar plate simultaneously. A comparison of the new methods with conventional dual culture plate assay was also done. The proposed methods are easy to perform and results of antagonism are obtained rapidly. Results of fungal inhibition were qualitatively comparable with that generated through dual culture plate assay. Quantity of resources such as agar medium and plates required for the modified antagonistic assays is several folds less than that required for dual culture plate assay.

Survivability and controlled release of alginate-microencapsulated Pseudomonas fluorescens VUPF506 and their effects on biocontrol of Rhizoctonia solani on potato

Preserving the efficacy of plant probiotic bacteria in soil is a major challenge to the biological control of plant diseases. The microencapsulation technique is an important step in preserving the viability and activity of probiotics in adverse environmental conditions. The main objective of this study was to choose an appropriate coating for probiotic encapsulation. For this purpose, the survivability and controlled release of Pseudomonas fluorescens VUPF506 encapsulated with alginate (Alg) combined with whey protein concentrate (WPC), carboxymethyl cellulose (CMC), and peanut butter (PB) were evaluated. Moreover, the encapsulated cells were evaluated to control for Rhizoctonia solani in potato plants under in vivo conditions. The results showed that all tested wall material maintained more than 80% of the bacterial cells. The Alg-WPC microcapsules provided a better controlled release over two months. Interestingly, the greenhouse experiment also revealed that the treatment of potato plants with Alg-WPC microcapsules was the most effective treatment, suppressing 90% of the pathogen. The results showed that Alg-WPC is the most promising combination to improve the survivability of P. fluorescens VUPF506. Moreover, it can be used as a fertilizer due to its content of valuable amino acids.

Characterization of the major antifungal extrolite from rice endophyte Lysinibacillus sphaericus against Rhizoctonia solani.

Sheath blight of rice caused byRhizoctonia solaniis regarded as one of the most widely distributed diseases of rice, and is one of the major production constraints for rice in India and most rice-growing countries of Asia. Biological control of plant diseases using antagonistic bacteria is now considered as a promising alternative to the use of hazardous chemical fungicides or bactericides. Several bacterial endophytes have been reported to support growth and improve the health of the plants and therefore, may be important as biocontrol agents.In the present study, putative antifungal metabolites were extracted from rice foliage endophyteLysinibacillus sphaericusKJ872548 by solvent extraction methods and purified using HPTLC techniques. Separated bands were subjected to assess thein vitroantagonistic activity toward rice sheath blight pathogenRhizoctonia solaniusing a dual culture method. Partially purified active fraction B2 obtained from HPTLC analysis showed the highest percentage of inhibition (76.9%). GC MS and FTIR analyses of B2 revealed the compound as1, 2-Benzenedicarboxylic acid butyl 2-Ethylhexyl ester, a strong antifungal volatile organic compound. Light microscopic analysis of the fungal mycelium from the dual culture plate of both culture filtrate and 1, 2-Benzenedicarboxylic acid butyl 2-Ethylhexyl ester disclosed strong mycolytic activity as evident by mycelial distractions and shrinkage. This is the first report on antifungal production by endophyticLysinibacillus sphaericusagainstR. solani,the rice sheath blight pathogen. The findings of this study biologically prospect the endophyteL. sphaericusas an inexpensive broad spectrum bioagent for eco-friendly, economic and sustainable agriculture.

A mycovirus modulates the endophytic and pathogenic traits of a plant associated fungus.

Fungi are generally thought to live in host plants with a single lifestyle, being parasitism, commensalism, or mutualism. The former, known as phytopathogenic fungi, cause various plant diseases that result in significant losses every year; while the latter, such as endophytic fungi, can confer fitness to the host plants. It is unclear whether biological factors can modulate the parasitic and mutualistic traits of a fungus. In this study, we isolated and characterized a mycovirus from an endophytic strain of the fungus Pestalotiopsis theae, a pathogen of tea (Camellia sinensis). Based on molecular analysis, we tentatively designated the mycovirus as Pestalotiopsis theae chrysovirus-1 (PtCV1), a novel member of the family Chrysoviridae, genus Alphachrysovirus. PtCV1 has four double-stranded (ds) RNAs as its genome, ranging from 0.9 to 3.4 kbp in size, encapsidated in isometric particles. PtCV1 significantly reduced the growth rates of its host fungus in vitro (ANOVA; P-value < 0.001) and abolished its virulence in planta (ANOVA; P-value < 0.001), converting its host fungus to a non-pathogenic endophyte on tea leaves, while PtCV1-free isolates were highly virulent. Moreover, the presence of PtCV1 conferred high resistance to the host plants against the virulent P. theae strains. Here we report a mycovirus that modulates endophytic and phytopathogenic fungal traits and provides an alternative approach to biological control of plant diseases caused by fungi.

Strategies to Improve Biological Control of Soilborne Plant Diseases

Biological control of plant soilborne diseases has appeared as an attractive alternative to other control methods. For the biological control of plant soilborne diseases, microorganisms mainly bacteria and fungi are used, which suppress growth and virulence traits or even kill pathogens and induce plant systemic acquired resistance. In recent years, the demand for organic food increased the use of biological control agents; however, complete control of plant diseases has not been achieved yet. The beneficial microbes used for biological control of plant diseases perform admirably under controlled greenhouse conditions but are not always successful under field conditions, which highly discourages the biological control methods. Hence, complete removal of chemicals from agricultural systems may not be impossible but a logical reduction in their application is feasible. Therefore, systematic integrated methods including both chemical and biological control and other control methods like cultural practices, resistant varieties and crop rotation are highly recommended.

Strategies to Improve Biological Control of Soilborne Plant Diseases

Biological control of plant soilborne diseases has appeared as an attractive alternative to other control methods. For the biological control of plant soilborne diseases, microorganisms mainly bacteria and fungi are used, which suppress growth and virulence traits or even kill pathogens and induce plant systemic acquired resistance. In recent years, the demand for organic food increased the use of biological control agents; however, complete control of plant diseases has not been achieved yet. The beneficial microbes used for biological control of plant diseases perform admirably under controlled greenhouse conditions but are not always successful under field conditions, which highly discourages the biological control methods. Hence, complete removal of chemicals from agricultural systems may not be impossible but a logical reduction in their application is feasible. Therefore, systematic integrated methods including both chemical and biological control and other control methods like cultural practices, resistant varieties and crop rotation are highly recommended.

Diversity of bacterial strains in biochar-enhanced Amazon soil and their potential for growth promotion and biological disease control in tomato

ABSTRACT The use of bacteria in growth promotion and biological control of plant diseases can minimize environmental contamination caused by the indiscriminate use of pesticides and chemical fertilizers. We aimed to evaluate growth promotion and biological control of Corynespora cassiicola in tomato seedlings mediated by beneficial bacteria isolated from a non-rhizospheric Amazon soil containing different amounts of biochar, and to identify to which groups of bacteria the strains belong. We obtained 200 strains of bacteria from experimental plots containing biochar doses of 0, 40, 80 and 120 t ha-1. Of these, 53 strains were selected by root colonization tests. Based on growth promotion parameters, 25 strains were screened, identified by molecular characterization and evaluated for indoleacetic acid (IAA) production, phosphate solubilization and biological control. The best dose of biochar for colony formation was 40 t ha-1, and a regression model indicated 34 t ha-1 as the optimal dose. The production of IAA was observed in 18 (75%) strains, and two (8%) strains were able to solubilize phosphate. The efficiency in root growth promotion was up to 125%, and the percentage of plant protection ranged from 50 to 59%. Molecular characterization showed that the bacteria used in this study belong to the genera Bacillus and Lysinibacillus.

Comparative Genomics Analysis Provides New Strategies for Bacteriostatic Ability of Bacillus velezensis HAB-2.

Biocontrol formulations prepared from biocontrol bacteria are increasingly applied in sustainable agriculture. Notably, inoculants prepared from Bacillus strains have been proven efficient and environmentally friendly alternatives to chemical bactericides. The bacterium Bacillus velezensis HAB-2 (formerly classified as B. amyloliquefaciens HAB-2) is used as a biological control agent in agricultural fields. In this study, we reported a high-quality genome sequence of HAB-2 using third-generation sequencing technology (PacBio RS II). The 3.89 Mb genome encoded 3,820 predicted genes. Comparative analysis among the genome sequences of reference strains B. velezensis FZB42, B. amyloliquefaciens DSM7 and B. subtilis 168 with the HAB-2 genome revealed obvious differences in the variable part of the genomes, while the core genome shared by FZB42 and HAB-2 was similar (96.14%). However, there were differences in the prophage region among the four strains. The numbers of prophage regions and coding genes in HAB-2 and FZB42 were smaller than the other two strains. The HAB-2 genome showed superior ability to produce secondary metabolites and harbored 13 gene clusters involved in synthesis of antifungal and antibacterial acting secondary metabolites. Furthermore, there were two unique clusters: one cluster which encoded lanthipeptide was involved in mersacidin synthesis and another cluster which encoded ladderane was shown to direct an unknown compound. Multidomain enzymes, such as non-ribosomal peptide synthetase and polyketide synthase, control the biosynthesis of secondary metabolites and rely on 4′-phosphopantetheinyl transferases (PPTases). Key genes lpaH2 and a encoded PPTases in HAB-2 encoded 224 and 120 amino acids, respectively. The genomic features revealed that HAB-2 possesses immense potential to synthesize antimicrobial acting secondary metabolites by regulating and controlling gene clusters. The prophage regions and genes encoding PPTases may provide novel insight for the bacteriostatic mechanism of Bacillus in the biological control of plant diseases.

Influence of chitinase production on the antagonistic activity of Trichoderma against plant-pathogenic fungi

Aim: The present study aimed to investigate the antagonistic activity of Trichoderma strains with high chitinase production against some plant pathogenic fungi. Methodology: A total of twenty-four Trichoderma isolates were extracted from soil samples collected at different geographical locations in Egypt and Saudi Arabia. These isolates were screened for their chitinase production ability using colloidal chitin media. Six isolates with high chitinase ability were identified as T. harzianum by internal transcribed spacer (ITS) region sequencing. These strains were tested for their ability to degrade chitin into N-acetyl-β-D-glucosaminidase. Finally, the biocontrol activities of these Trichoderma strains against pathogenic fungi were tested by dual culture technique. Results: The maximum activity among the chitinolytic enzymes was 0.051 units ml-1 in Trichoderma strain ABSA19, which showed an activity comparable to the control: pure enzyme, (0.047 units ml-1). The lowest activity (0.014 units ml-1) was found in Trichoderma strain MEG2. In dual culture, Trichoderma strain ABSA19 exerted the highest antagonistic activity in addition to hyphal intertwining and degradation using scanning electron microscopy. Finally, 11 inter simple sequence repeats (ISSR) primers were used to evaluate the genetic polymorphism among Trichoderma strains, which yielded 133 bands with fragment sizes of 130-3400 bp, 47 (35.3%) of which were polymorphic. Interpretation: The current study confirms the existence of several useful Trichoderma strains with the highest chitinase activity and antagonistic activity against some pathogenic plant fungi that may have a super potential for application in biological control of plant diseases.

Horizontal Gene Transfer and Tandem Duplication Shape the Unique CAZyme Complement of the Mycoparasitic Oomycetes Pythium oligandrum and Pythium periplocum.

Crop protection strategies that are effective but that reduce our reliance on chemical pesticides are urgently needed to meet the UN sustainable development goals for global food security. Mycoparasitic oomycetes such as Pythium oligandrum and Pythium periplocum, have potential for the biological control of plant diseases that threaten crops and have attracted much attention due to their abilities to antagonize plant pathogens and modulate plant immunity. Studies of the molecular and genetic determinants of mycoparasitism in these species have been less well developed than those of their fungal counterparts. Carbohydrate-active enzymes (CAZymes) from P. oligandrum and P. periplocum are predicted to be important components of mycoparasitism, being involved in the degradation of the cell wall of their oomycete and fungal prey species. To explore the evolution of CAZymes of these species we performed an in silico identification and comparison of the full CAZyme complement (CAZyome) of the two mycoparasitic Pythium species (P. oligandrum and P. periplocum), with seven other Pythium species, and four Phytophthora species. Twenty CAZy gene families involved in the degradation of cellulose, hemicellulose, glucan, and chitin were expanded in, or unique to, mycoparasitic Pythium species and several of these genes were expressed during mycoparasitic interactions with either oomycete or fungal prey, as revealed by RNA sequencing and quantitative qRT-PCR. Genes from three of the cellulose and chitin degrading CAZy families (namely AA9, GH5_14, and GH19) were expanded via tandem duplication and predominantly located in gene sparse regions of the genome, suggesting these enzymes are putative pathogenicity factors able to undergo rapid evolution. In addition, five of the CAZy gene families were likely to have been obtained from other microbes by horizontal gene transfer events. The mycoparasitic species are able to utilize complex carbohydrates present in fungal cell walls, namely chitin and N-acetylglucosamine for growth, in contrast to their phytopathogenic counterparts. Nonetheless, a preference for the utilization of simple sugars for growth appears to be a common trait within the oomycete lineage.

Structural and Functional Insights into Iturin W, a Novel Lipopeptide Produced by the Deep-Sea Bacterium Bacillus sp. Strain wsm-1.

In the present study, a deep-sea bacterial strain designated Bacillus sp. strain wsm-1 was screened and found to exhibit strong antifungal activity against many plant-pathogenic fungi, and corresponding antifungal agents were thereby purified and determined by tandem mass spectrometry to be two cyclic lipopeptide homologs. These homologs, which were different from any previously reported lipopeptides, were identified to possess identical amino acid sequences of β-amino fatty acid-Asn-Ser-Asn-Pro-Tyr-Asn-Gln and deduced as two novel lipopeptides designated C14 iturin W and C15 iturin W. Electron microscopy observation indicated that both iturin W homologs caused obvious morphological changes and serious disruption of plasma membrane toward fungal cells, while C15 iturin W exhibited more serious cell damages than C14 iturin W did, which was well consistent with the results of the antifungal activity assays. To improve the yield and antifungal activity of iturin W, the effects of different carbon and nitrogen sources and amino acids on production of C14 iturin W and C15 iturin W were investigated. The results indicated that supplements of most of the detected carbon and nitrogen sources could increase the yield of C14 iturin W, but inhibit the yield of C15 iturin W, while supplements of tryptone and most of the detected amino acids could increase the yield of both C14 iturin W and C15 iturin W.IMPORTANCE Plant disease caused by pathogenic fungi is one of the most devastating diseases, which affects the food safety of the whole world to a great extent. Biological control of plant diseases by microbial natural products is more desirable than traditional chemical control. In this study, we discovered a novel lipopeptide, iturin W, with promising prospects in biological control of plant diseases. Moreover, the effects of different carbon and nitrogen sources and amino acids on production of C14 iturin W and C15 iturin W would provide a reasonable basis for the optimization of the fermentation process of lipopeptides. Notably, the structure of iturin W was different from that of any previously reported lipopeptide, suggesting that deep-sea microorganisms might produce many novel natural products and have significant potential in the development of biological products in the future.

Functional characterization of the AGL1 aegerolysin in the mycoparasitic fungus Trichoderma atroviride reveals a role in conidiation and antagonism

Aegerolysins are small secreted pore-forming proteins that are found in both prokaryotes and eukaryotes. The role of aegerolysins in sporulation, fruit body formation, and in lysis of cellular membrane is suggested in fungi. The aim of the present study was to characterize the biological function of the aegerolysin gene agl1 in the mycoparasitic fungus Trichoderma atroviride, used for biological control of plant diseases. Gene expression analysis showed higher expression of agl1 during conidiation and during growth in medium supplemented with cell wall material from the plant pathogenic fungus Rhizoctonia solani as the sole carbon source. Expression of agl1 was supressed under iron-limiting condition, while agl1 transcript was not detected during T. atroviride interactions with the prey fungi Botrytis cinerea or R. solani. Phenotypic analysis of agl1 deletion strains (Δagl1) showed reduced conidiation compared to T. atroviride wild type, thus suggesting the involvement of AGL1 in conidiation. Furthermore, the Δagl1 strains display reduced antagonism towards B. cinerea and R. solani based on a secretion assay, although no difference was detected during direct interactions. These data demonstrate the role of AGL1 in conidiation and antagonism in the mycoparasitic fungus T. atroviride.

Вплив мікроорганізмів з фунгіцидною та інсектицидною діями на біологічну активність ґрунту кореневої зони кукурудзи

Вплив мікроорганізмів з фунгіцидною та інсектицидною діями на біологічну активність ґрунту кореневої зони кукурудзи

Three New Reports of Trichoderma in Algeria: T. atrobrunneum, (South) T. longibrachiatum (South), and T. afroharzianum (Northwest).

The genus Trichoderma (Hypocreaceae, Ascomycota) consists of globally distributed fungi. In Algeria, few studies have explored the diversity of this genus, and in the majority of works identification is based on phenotypic characters. Here, nine Trichoderma strains were collected from Algeria in different locations, namely: seven in the south and two in the northwest. Also, we used 17 reference strains that were taken from the NCBI database for the phylogeny analysis. Our study is based on an integrated approach using micro and macro phenotypic characters and multiple DNA analysis (internal transcribed spacer (ITS): ITS1–4 region; translation elongation factor 1: tef1 gene). Our study reports, for the first time, three species of Trichoderma in Algeria, namely: T. atrobrunneum (south), T. longibrachiatum (south), and T. afroharzianum (northwest). It is noteworthy that T. atrobrunneum is a species previously described in European Mediterranean countries, and its presence in the soil of southern Algeria indicates that the diversity of the geographic environments and different climates of Algeria offers the possibility for the survival of diverse Trichoderma species. Knowledge on the diversity of these fungi may contribute to their future exploitation in biotechnological applications and to the biological control of plant diseases.

Antifungal, antioxidant and photocatalytic activities of zinc nanoparticles synthesized by Sargassum vulgare extract

Zinc oxide nanoparticles (ZnO-NPs) have attracted considerable interest owing to their physicochemical properties and vigorous biological activity. In this research, ZnO-NPs were synthesized using aqueous extract of Sargassum vulgare (SVE) as a reducing and capping agent. Morphological and physical features were analyzed through Uv–visible, SEM, TEM, XRD, EDX, DLS and zeta potential studies. Subsequently, antifungal, antioxidant, cytotoxicity and photocatalytic activities were evaluated. FTIR and Uv–vis spectra showed absorption peaks of SVE metabolites and biosynthesized ZnO-NPs before and after the formation of NPs. According to the SEM and TEM micrographs, the biosynthesized ZnO-NPs were spherical with a diameter of about 50–150 nm. The XRD Spectrum indicated the existence of eight peaks corresponding to the crystal angle of the ZnO-NPs. The EDX analysis confirms the presence of oxygen and zinc in the ZnO-NPs structure. The DLS and Zeta potential revealed that the hydrodynamic diameter of ZnO-NPs was approximately 200 nm and +12.7 mV, respectively. The ZnO-NPs demonstrated wide-spectrum antifungal action against Aspergillus, Candida and saccharomyces cerevisiae. The antioxidant potential of ZnO-NPs was determined to be around 65% lower than that of ascorbic acid and BHA, but higher than that of SVE. The cytotoxic effect of ZnO-NPs against the HepG2 cell line was estimated to be an IC50 value of 128.0 μg/ml. Given the potent antioxidant and photocatalytic capacity as well as the robust antifungal activity of ZnO-NPs, a broad variety of applications such as the biological control of plant diseases and the removal of pesticide residues may be recommended.

Exploration of microbial stimulants for induction of systemic resistance in plant disease management

AbstractPlants are exposed to different environmental stresses (biotic or abiotic) in their habitats, these stresses often result in several diseases and decline in crop production which are major concerns to crop producers and scientists. Habitat‐imposed biotic stress is one of the most common problems of crop production. The use of chemical‐based pesticides has been widely reported to control plant diseases but the residual effects of excessive application of pesticides necessitates the use of biological control agents known to play important safety roles in plant disease management. Symbiotic associations between diverse microorganisms and plant roots have also been proven to have enormous impacts on their respective growths and survival; induced systemic resistance (ISR) is part of the mechanism through which plant‐growth‐promoting bacteria and fungi stimulate plant growth and resistance to pathogens. Many of these microorganisms act as stimulants which can be exploited for boosting nutrient uptake, pest control and to protect crops from environmental stresses for better growth. This review focuses on the plant diseases, microbial stimulants and their mechanisms as nutrient enhancers in crop production as well as their potentials in biological control of plant diseases through ISR.

Patents on Endophytic Fungi for Agriculture and Bio- and Phytoremediation Applications.

Plant endophytic fungi spend all or part of their lives inside host tissues without causing disease symptoms. They can colonize the plant to protect against predators, pathogens and abiotic stresses generated by drought, salinity, high concentrations of heavy metals, UV radiation and temperature fluctuations. They can also promote plant growth through the biosynthesis of phytohormones and nutrient acquisition. In recent years, the study of endophytic fungi for biological control of plant diseases and pests has been intensified to try to reduce the ecological and public health impacts due the use of chemicals and the emergence of fungicide resistance. In this review, we examine 185 patents related to endophytic fungi (from January 1988 to December 2019) and discuss their applicability for abiotic stress tolerance and growth promotion of plants, as agents for biocontrol of herbivores and plant pathogens and bio- and phytoremediation applications.

Volatile Organic Compounds From Lysobacter capsici AZ78 as Potential Candidates for Biological Control of Soilborne Plant Pathogens.

The genus Lysobacter includes several bacterial species which show potential for being used in biological control of plant diseases. It was shown recently that several Lysobacter type strains produce volatile organic compounds (VOCs) which controlled the growth of Phytophthora infestans in vitro when the bacteria were grown on a protein rich medium. In the present study, Lysobacter capsici AZ78 (AZ78) has been tested for its potential to produce VOCs that may contribute to the bioactivity against soilborne plant pathogens. To this end, split Petri dish assays of bacterial cultures have been combined with GC-MS measurements with the aim to reveal the identity of the VOCs which inhibit the growth of Pythium ultimum Rhizoctonia solani, and Sclerotinia minor. While AZ78 completely suppressed the growth of P. ultimum and S. minor, the growth of R. solani was still reduced significantly. The GC-MS analysis revealed 22 VOCs to be produced by AZ78, the majority of which were (putatively) identified as mono- and dialkylated methoxypyrazines. Based on additional cultivation and GC-MS experiments, 2,5-dimethylpyrazine, 2-ethyl-3-methoxypyrazine and 2-isopropyl-3-methoxypyrazine were selected as presumable bioactive compounds. Further bioassays employing indirect exposure to standard solutions (1–10 mg per Petri dish) of the synthetic compounds via the gas phase, revealed that each of these pyrazines was able to suppress the growth of the pathogens under investigation. The results of this study highlight the possible future implementation of pyrazine derivatives in the control of soilborne plant diseases and further support the biocontrol potential of L. capsici AZ78.