Potential Biological Control Agent Research Articles

Assessment of Kweilingia divina as a potential augmentative biological control agent against the gramineous weed Microstegium vimineum

Microstegium vimineum (Trin.) A. Camus, commonly called stiltgrass, is an exotic and indigenous troublesome weed in the United States and eastern Asia, respectively. Between 2020 and 2022, a damaging disease was observed on M. vimineum plants at the foot of Daluo Mountain in Wenzhou City, China, with an incidence of 90 %. Typical rust disease symptoms were prominently visible during the early monsoon season (June to July), consisting of chlorotic spots with many orange or orange-yellow uredinia on the abaxial surfaces of the M. vimineum leaves. Based on morphological and molecular characteristics, the fungus was identified as Kweilingia divina (Syd.) Buriticá. This article describes the studies carried out on one strain of the fungus (WZ-2) to ascertain its potential as a biocontrol agent of the weed. Host specificity testing on 61 plant species from 15 families proved that 25 major crops and 36 weeds were insensitive to this fungus, with only two other gramineous weed species being slightly susceptible. However, urediniospores were not observed on these slightly infected plants. Further research is required to assess the pathogenicity and safety of various plant species to K. divina, especially bamboos, which have been identified as susceptible. Temperature and dew period experiments have shown that the fungus has a relatively wide tolerance for infection between 15 and 40 °C, and with only 4 h of dew exposure some uredinia appeared on artificially infected M. vimineum plants. A field trial proved that urediniospores from the strain WZ-2 could infect naturally occurring M. vimineum plants, causing severe disease symptoms and plant death. Thus, strain WZ-2 has great potential as an augmentative biological control agent against M. vimineum. K. divina is a heteroecious rust fungus that requires an alternate host to complete its life-cycle. What the alternative hosts are, and the impact of the alternate hosts on outbreaks of the disease requires further study.

Edeine B1 produced by Brevibacillus brevis reduces the virulence of a plant pathogenic fungus by inhibiting mitochondrial respiration.

Plant pathogenic fungi cause serious diseases, which result in the loss of crop yields and reduce the quality of crops worldwide. To counteract the escalating risks of chemical fungicides, interest in biological control agents to manage plant diseases has significantly increased. In this study, we comprehensively screened microbial culture filtrates using a yeast screening system to find microbes exhibiting respiratory inhibition activity. Consequently, we found a soil-borne microbe Brevibacillus brevis HK544 strain exhibiting a respiration inhibitory activity and identified edeine B1 (EB1) from the culture filtrate of HK544 as the active compound of the respiration inhibition activity. Furthermore, against a plant pathogenic fungus Fusarium graminearum, our results showed that EB1 has effects on multiple aspects of respiration with the downregulation of most of the mitochondrial-related genes based on transcriptome analysis, differential EB1-sensitivity from targeted mutagenesis, and the synergistic effects of EB1 with electron transport chain complex inhibitors. With the promising plant disease control efficacy of B. brevis HK544 producing EB1, our results suggest that B. brevis HK544 has potential as a biocontrol agent for Fusarium head blight.IMPORTANCEAs a necrotrophic fungus, Fusarium graminearum is a highly destructive pathogen causing severe diseases in cereal crops and mycotoxin contamination in grains. Although chemical control is considered the primary approach to control plant disease caused by F. graminearum, fungicide-resistant strains have been detected in the field after long-term continuous application of fungicides. Moreover, applying chemical fungicides that trigger mycotoxin biosynthesis is a great concern for many researchers. Biocontrol of Fusarium head blight (FHB) by biological control agents (BCAs) represents an alternative approach and could be used as part of the integrated management of FHB and mycotoxin production. The most extensive studies on bacterial BCAs-fungal communications in agroecosystems have focused on antibiosis. Although many BCAs in agricultural ecology have already been used for fungal disease control, the molecular mechanisms of antibiotics produced by BCAs remain to be elucidated. Here, we found a potential BCA (Brevibacillus brevis HK544) with a strong antifungal activity based on the respiration inhibition activity with its active compound edeine B1 (EB1). Furthermore, our results showed that EB1 secreted by HK544 suppresses the expression of the mitochondria-related genes of F. graminearum, subsequently suppressing fungal development and the virulence of F. graminearum. In addition, EB1 exhibited a synergism with complex I inhibitors such as rotenone and fenazaquin. Our work extends our understanding of how B. brevis HK544 exhibits antifungal activity and suggests that the B. brevis HK544 strain could be a valuable source for developing new crop protectants to control F. graminearum.

Natural Prevalence, Molecular Characteristics, and Biological Activity of Metarhizium rileyi (Farlow) Isolated from Spodoptera frugiperda (J. E. Smith) Larvae in Mexico.

Entomopathogenic fungi have been considered potential biological control agents against the fall armyworm Spodoptera frugiperda (J. E. Smith), the world's most important pest of maize. In this study, we evaluated the natural infection, molecular characteristics, and biological activity of Metarhizium rileyi (Farlow) isolated from S. frugiperda larvae of this insect, collected from maize crops in five Mexican locations. Natural infection ranged from 23% to 90% across all locations analyzed. Twenty-four isolates were evaluated on S. frugiperda second instars at a concentration of 1.0 × 108 conidia/mL, causing 70% to 98.7% mortality and 60.5% to 98.7% sporulation. Isolates T9-21, Z30-21, PP48-21, and L8-22 were selected to determine their phylogenetic relationships by β-tubulin gene analysis and to compare median lethal concentration (CL50), median lethal time (LT50), and larval survival. These isolates were grouped into three clades. The T9-21, PP48-21, and J10-22 isolates were closely related (clade A), but phylogenetically distant from Z30-21 (clade B) and L8-22 (clade C) isolates. These genetic differences were not always reflected in their pathogenicity characteristics since no differences were observed among the LC50 values. Furthermore, isolates T9-21, J10-22, and L8-22 were the fastest to kill S. frugiperda larvae, causing lower survival rates. We conclude that native M. rileyi isolates represent an important alternative for the biocontrol of S. frugiperda.

Short- and long-term effects of commercial formulations of imidacloprid, spirotetramat, and mixtures of these active ingredients on pupae of Diaeretiella rapae (Hymenoptera: Braconidae) and its progeny.

Compatibility studies of insecticides and natural enemies usually focus on short-term lethal effects, without considering the long-term sublethal effects (including progeny). Even less-explored are the effects of commercial insecticides formulated with more than one active product. Short- and long-term lethal and sublethal effects were studied for the first time on the progeny of commercial formulations of spirotetramat, imidacloprid and a commercial mixture of these active ingredients on pupae of Diaeretiella rapae (M'ntosh) (Hymenoptera: Braconidae), an endoparasitoid of aphids considered to be a potential biological control agent. Insecticides were exposed topically on aphid mummies in which the parasitoid was in the pupal stage. Imidacloprid reduced adult emergence by more than 30% and prolonged intra-host development time with respect to control from half the maximum recommended field dose (MFRD). Spirotetramat and commercial mixture only showed significant effects on these endpoints at doses above the MFRD. The tested formulations did not affect adult longevity, sex ratio, and percentage of parasitism in the exposed generation. At low concentrations the active ingredients in the commercial mixture behave synergistically, whereas at medium and high concentrations they behave antagonistically. Considering the 10% lethal dose (LD10), imidacloprid showed the highest hazard coefficient, whereas the commercial mixture was more hazardous when considering the LD50 and LD90. The commercial mixture and imidacloprid induced higher adult emergence and altered the sex ratio in the progeny. The following order of toxicity on D. rapae can be established: imidacloprid > commercial mixture > spirotetramat. Joint use of this species with imidacloprid and commercial mixture should be avoided in integrated pest management programs. © 2024 Society of Chemical Industry.

Assessment of Puccinia polliniicola as a potential biological control agent for Microstegium vimineum.

Microstegium vimineum (Trin.) A. Camus, commonly called stiltgrass, is a dominant weed in the United States and China. Although a lot of control approaches have been attempted, an economic, effective and practical measure has not been available to control the weed so far. A serious rust disease of Microstegium vimineum was observed in three regions of Wenzhou city in China, from 2019 to 2021, with a disease incidence ranging from 82% to 97%. Typical rust disease symptoms on Microstegium vimineum were prominently visible during the early monsoon season (June-July), with chlorotic spots on the leaf surfaces. The morphological characterization of the strain WZ-1 which was isolated from the diseased leaves was consistent with Puccinia polliniicola. The virulence tests showed that the average disease index of Microstegium vimineum plants could reach 35% at 10 days post-inoculation. The host specificity of Puccinia polliniicola was tested on 64 plant species from 12 families and it did not cause any diseased symptoms on 24 major crops and 36 weeds, but slightly infected four gramineous weeds, Arthraxon hispidus, Polypogon fugax, Cynodon dactylon, and Microstegium ciliatum. However, newly-produced urediniospores were not observed on the slightly infected plants. The urediniospores of strain WZ-1 infected the Microstegium vimineum leaves by two main approaches: mycelium or appressorium invaded the stoma; and mycelium or appressorium directly invaded intercellular spaces. Field experiments showed that the rust disease naturally prevailed among Microstegium vimineum populations, causing severe rust disease symptoms on the leaf surface. The rust epidemic effectively controlled all of the target plants in the closed plot where the rust was released. Puccinia polliniicola strain WZ-1 has great potential to be used as a classical biological control agent against Microstegium vimineum. © 2024 Society of Chemical Industry.

Evaluation of Pseudomonas koreensis B17-12 as a potential biological control agent against postharvest diseases of tomato

Pathogenic fungi cause severe postharvest diseases on tomato, which has led to tremendous economic losses. In this study, we isolate 125 antagonistic bacteria from the roots of Fraxinus hupehensis, and screened them for antagonistic activity against Botrytis cinerea, Phytophthora infestans and Alternaria solani. Finally, the strain B17-12 was selected for further experiments. Based on sequence analyses of the 16S rDNA and rpoB genes, strain B17-12 was identified as Pseudomonas koreensis. The strain can produce volatile organic compounds (VOCs) that efficiently inhibit B. cinerea, P. infestans and A. solani, 25 VOCs were identified with solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS), and 7 VOCs had been reported to exhibit antimicrobial activity. P. koreensis B17-12 rapidly colonized on the root of tomato. The genome of B17-12 reveals numerous membrane-related genes and 7 secondary metabolite synthesis gene clusters that are crucial for its biological control properties. The study highlights that B17–12 may be an excellent candidate for biological control of postharvest diseases of tomato blight and gray mold.

Isolation, identification and occurrence of Plectosphaerella cucumerina (Lindf.) W. Gams, 1968 on sugar beets cultivation areas in Türkiye

As a result of the research conducted on the detection of severe root rot and drying in sugar beet (Beta vulgaris L.) fields in the Konya region of Türkiye in 2015-2017, a fungus named Plectosphaerella cucumerina was detected together with many different root pathogens. This fungus, which is known to occur in many hosts and on different substrates, is a new record for Türkiye. There are not many studies on this fungus, which was found to be low virulent in our study, neither in the world nor in our country. However, according to the limited number of studies, it has been found that there are pathogen strains of the pathogen that infect sugar beet in the Netherlands. Furthermore, it is a necrotrophic fungus that is used as a potential biological control agent against potato cyst nematodes, so it is considered a fungus that should be studied for this reason. We define this contribution as a new record for Türkiye mycobiota from P. cucumerina sugar beet seedlings

Effective biological control of chickpea rabies (Ascochyta rabiei) through systemic phytochemical defenses activation by Trichoderma roots colonization: From strain characterization to seed coating

Chickpea (Cicer arietinum) is a legume of great economic and agricultural importance worldwide, whose crop is severely affected by rust or Ascochyta blight, caused by the fungus Ascochyta rabiei. The fungal genus Trichoderma includes several species widely characterized as effective biological control agents against crop pathogens. First, this work characterized several species of the genus Trichoderma as potential biological control agents of A. rabiei directly (in vitro confrontation) or indirectly in chickpea plants (activation of systemic resistance), selecting T. harzianum EN1 as the most efficient strain. Subsequently, different materials were tested as coatings to apply the T. harzianum conidia on chickpea seeds, determining that gum arabic at 1 % concentration was the one that most promoted the germination of conidia and seeds. The third phase of the study was based on the application of the coating and T. harzianum conidia on chickpea seeds and to study plant survival after infection with the pathogen A. rabiei, characterizing root colonization by Trichoderma and systemic hormonal and metabolic changes related to the induction of systemic defenses. The treatment of chickpea seeds with gum arabic and T. harzianum conidia was found to increase Trichoderma-root colonization and to improve plant survival. The induction of systemic ethylene- and melatonin-mediated resistance, which led to the accumulation of nicotinic acid in plant tissues, was considered the cause of such a protection. Therefore, T. harzianum applied as seed coating with gum arabic could be a good biological control strategy against A. rabiei on chickpea, due to the induction of systemic resistance.

Phytic acid-mediated enhancement of Meyerozyma caribbica biocontrol of Aspergillus carbonarius infection in grape berries through regulation of ROS metabolism

Sour rot, an infection caused by Aspergillus carbonarius is one of the detrimental diseases that damage grape vines after harvest. To investigate the biocontrol of this mycotoxigenic fungus, the current study explored the efficiency of Meyerozyma caribbica pretreated with phytic acid (PA) in reducing sour rot in table grapes through the regulation of reactive oxygen species (ROS) production. The content of hydrogen peroxide (H2O2,), superoxide (O2.−) production rate, and the degree of lipid peroxidation were measured. Furthermore, antioxidant enzymes activities, superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and enzymes of the ascorbate–glutathione (AsA-GSH) and glutathione peroxidase (GPX) cycles were investigated. Enzymatic activity results of select genes were confirmed using real-time quantitative polymerase chain reaction (RT-qPCR). Meyerozyma caribbica pretreated with 10 μmol/mL PA (YE) was most efficient in reducing sour decay in grape berries as indicated by an 81.1 % reduction in disease incidence and 1.5 mm lesion diameter by the third day. Phytic acid treated M. caribbica showed a significant reduction in the contents of malondialdehyde (MDA), H2O2, and production rate of O2.− which was complemented by a marked rise in ROS scavenging enzymes’ activities. The H2O2 content in YE was the lowest (24.09 nmol/g FW) by the third day and O2.− production rate was about half that of CK; control (4.19 mmol/min.g FW) on the same day. The SOD, POD, and CAT activities were significantly higher in YE treated fruits (6.63, 18, and 6.64 U/mg FW, respectively) compared to the CK by the fifth day. Subsequently, AsA-GSH and GPX cycles also showed higher activity in grapes inoculated with YE compared to other treatments. Genes encoding SOD, POD, CAT, DHAR, GR, and APX were significantly overexpressed in grapes inoculated with YE compared to the CK, yeast alone, and PA treatments. These findings indicate that PA likely enhances the biocontrol efficacy of M. caribbica, leading to the induction of ROS scavenging mechanisms and subsequent mortality of A. carbonarius in table grapes. Consequently, M. caribbica pre-treated with PA holds promise as a potential biological control agent for A. carbonarius in future applications

Does intraspecific variation in Trissolcus japonicus affect its response to non-target hosts?

Host specificity is a key criterion for the implementation of any biological control program. In parasitoid wasps, host specificity is mediated by their response to chemical cues directly and indirectly associated with their hosts during foraging. Although intraspecific variation in foraging behaviour is documented, it is rarely integrated into risk assessment studies of potential biological control agents, as is the case for Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), an Asian egg parasitoid and biological control agent of the invasive Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). In the present study, we compared the behavioural response of T. japonicus females of an adventive line present in Switzerland and an Asian line (Beijing USDA), recently mass released in Italy, to cues of its target host H. halys and non-target host Pentatoma rufipes (L.) (Hemiptera: Pentatomidae). We observed minimal differences in host acceptance, exploitation and suitability in no-choice tests. In contrast, the behavioural response to host contact kairomones left on leaf substrates significantly differed between the two lines. While both lines preferred chemical footprints of H. halys in comparison to P. rufipes, females of the Beijing USDA line responded more strongly to host kairomones. The observed intraspecific variation in behavioural traits highlights the relevance of considering genetically distinct parasitoid lines and their host foraging behaviour in biological risk assessment studies. However, the implications of intraspecific variation in parasitoid foraging behaviour for biological control of a pest and non-target effects in the field remain challenging to predict.

Detection of Ochyromera ligustri (Coleoptera: Curculionidae: Curculioninae) in Ligustrum spp. (Oleaceae) Using Newly Developed PCR Primers.

Ligustrum spp. (Oleaceae) have become invasive species in the US and negatively affect native plant diversity and richness in forests. Ochyromera ligustri (Coleoptera: Curculionidae) is considered a potential biological control agent in the US because adults feed on the foliage and larvae are seed-feeders of Ligustrum spp. To discover the relationships between O. ligustri and Ligustrum spp., fruit dissections or rearing and field observations are required. In the current research project, novel PCR primers were developed to rapidly detect the DNA of O. ligustri in molecular analyses without rearing and observation. The developed PCR primers worked even with 0.01 ng of DNA and did not amplify the DNA of the other five curculionid species tested. When the novel primers were tested with three Ligustrum spp. species common in the southeastern US, the DNA of O. ligustri was detected from all three species. We expect that the novel primers will be utilized to find out the presence and impact of O. ligustri on Ligustrum spp rapidly and accurately.

Refining Gastrophysa atrocyanea (Coleoptera: Chrysomelidae) identification using UV marking in whole-plant assessment

The host plant quality is crucial for assessing the environmental safety of weed biological control agents, as they rely on the phenotypic characteristics of test plants in host specificity tests and for mass-rearing before field release. In this study, we explored the feasibility of using potted plants by applying ultraviolet (UV) fluorescent pigment to the elytra of the leaf beetle Gastrophysa atrocyanea. They were released separately on Rumex acetosa as the target weed and Buxus sinica var. insularis as a non-target plant in insect cages. UV marking reduced detection time by 2.7 times and increased the detection rates of female leaf beetles on the target weed compared to visible light, resulting in only 7.41% missing leaf beetles. Similarly, UV application reduced detection time by 2.3 times on the non-target plant, with no missing leaf beetles. Further, marking different sexes with UV pigments facilitated identification 4.8 times faster than visual light. The UV mark and recapture method exhibits promising potential in whole-plant testing, simplifying the identification of a potential biological control agent, G. atrocyanea, in insect cages under no-choice tests. Thus, UV marking enables the possibility of mass-rearing weed biological control agents and monitors the foraging behavior of phytophagous insects cost-effectively and non-disruptively in laboratory settings.

Screening native Bacillus strains as potential biological control agents against ginger bacterial wilt and for promoting plant growth

Bacterial wilt, caused by Ralstonia solanacearum, is a destructive disease that causes significant loss in ginger productivity. This disease is notoriously difficult to control by chemical measures, prompting the exploration of biological control as a more sustainable and effective alternative strategy. In our research, we aimed to develop effective microbial agents to combat R. solanacearum-induced bacterial wilt in ginger. Initially, 307 Bacillus-like strains were isolated from ginger rhizosphere soil. Among these, ten strains exhibited significant antibacterial activity after extensive in vitro screening, with Bacillus-like isolate F18 being the most effective. Further tests in a co-culture assay revealed six isolates, notably L70, that significantly reduced the pathogen's fitness. To further assess their effectiveness, six isolates of L3, L72, L73, F18, HC-5, and L70 were then subjected to a hydroponics assay, where they substantially lowered disease incidence in ginger seedlings, especially strains F18, HC-5, and L73. These three strains were identified as Bacillus velezensis, exhibiting beneficial traits such as IAA production, siderophore secretion, and phosphate and potassium solubilization. Additionally, they also harbored genes related to the production of the dipeptide bacilysin and the polyketides macrolactin, bacillaene and difficidin. In greenhouse experiments, these three B. velezensis strains, particularly F18 and HC-5, demonstrated remarkable efficacy in controlling bacterial wilt. Tubers soaked in these biocontrol agents showed reduced disease severity and pathogen population. Moreover, the treatments promoted ginger growth, notably in tuber fresh weight, with HC-5 showing the greatest improvement. Conclusively, this study suggests a highly efficient strategy for biologically controlling ginger bacterial wilt, with B. velezensis strains HC-5, L73, and F18 emerging as promising biocontrol agents.

Investigating the host finding behaviour of the weevil Phytobius vestitus for the biological control of the invasive aquatic weed Myriophyllum aquaticum

Biological control programmes involve pre-release studies that include host range tests to predict likely negative effects on native species. Behavioural responses of potential biological control agents to olfactory signals emitted by target and non-target species provide information on the host-finding and selection behaviour for safer agent selection. The weevil Phytobius vestitus (Coleoptera: Curculionidae) was identified as a potential biological control agent for the sustainable management of the aquatic weed Myriophyllum aquaticum (Haloragaceae). Using olfactometer-based bioassays, we analysed the host-finding and host-selection behaviour of P. vestitus across a variety of plant species closely related to M. aquaticum using a glass olfactometer. We further analysed the volatile organic compounds emitted by the target and non-target plant species to explain the weevil's observed preferences. We demonstrated that P. vestitus was able to recognise and discriminate between eight closely related Haloragaceae plant species and was significantly more attracted to the olfactory cues emitted by the target plant, M. aquaticum, compared to the other plant species. This study provides a first important indication of the specificity of P. vestitus and shows the role of plant chemistry in host selection and the possibility of refining host range assessment for potential biological control agents. However, exhaustive risk assessment for possible release into targeted new environments still requires further investigations.

Combined interaction between the diazotrophic Niallia circulans strain YRNF1 and arbuscular mycorrhizal fungi in promoting growth of eggplant and mitigating root rot stress caused by Rhizoctonia solani

Rhizoctonia root rot of eggplant, caused by Rhizoctonia solani, is an economically important disease. Niallia circulans YRNF1 and arbuscular mycorrhizal fungi (AMF) were assessed for their biocontrol and biofertilizing effects against R. solani, as potential replacements for synthetic fungicides and fertilizers. The diazotrophic N. circulans YRNF1, isolated from soil, reduced in vitro growth of R. solani by 42%. GC-MS analysis of culture filtrate of N. circulans YRNF1 detected bioactive compounds, including butyric acid (85%) and ethylene glycol (8%). In greenhouse experiments, combined application of N. circulans YRNF1 and AMF reduced the severity of eggplant root rot by 26%. This combined treatment triggered the transcriptional expression of five resistance genes (JERF3, PAL1, C3H, CHI2, and HQT) in the treated eggplants. Biochemical analyses of the infected eggplant roots treated with the combined bio-inoculants showed enhancement of the phenol content (+188%), and increased antioxidant enzyme activity, mainly of POD (+104%) and PPO (+72%). Combined application of N. circulans YRNF1 and AMF also promoted eggplant growth and improved the total NPK concentrations in treated plant leaves. Inoculation of eggplant with N. circulans YRNF1 in the presence of AMR increased the mycorrhization level. This is the first report of N. circulans and AMF as potential agents for biological control of Rhizoctonia root rot and growth promotion of eggplant.

Exogenous application of different antagonists and their secretory metabolites to manage root-knot nematodes in pea

Pea (Pisum sativum L.) is a grain legume, a member of the Leguminosae family. Root-knot nematodes cause severe losses ranging from 15 to 85%. Different species of nematodes including root-knot nematodes reduce the yield of pea significantly. To control root-knot nematodes biological control is a more environment-friendly approach. The main objective of the study is to assess the effect of different antagonistic microbes and their secretory metabolites to manage root-knot nematodes in peas. Through this research, we aim to identify potential biological control agents that can be used as eco-friendly alternatives to chemical nematicides, contributing to sustainable pest management practices in agriculture. For this purpose, firstly, a brinjal seedling was transplanted for inoculum development which was inoculated with infective 2nd stage juveniles of root-knot nematodes (Meloidogyne spp.) in Department of Plant Pathology research area, University of Agriculture Faisalabad (UAF). Then two pea varieties viz. Matar sabaz and Pea-2009 were sown in pots and inoculated with nematode larvae after four weeks of sowing. Moreover, the management of nematodes was done by using the antagonists and their secretory metabolites application. The data of different plant growth and nematode-related parameters was taken and subsequently analyzed using analysis of variance and least significant difference test (LSD). Results showed that the antagonist’s treatment subsequently controlled root-knot nematodes (RKNs). Maximum plant/shoot length (47 cm), root length (25.25 cm), shoot weight (22.25 g) pod length (8.50 cm), No. of secondary shoots (8) and minimum number of galls (2.5 cluster), was observed in plants treated with Bacillus spp. (T1) while maximum No. of fruits (5.75) was observed in plants treated with Pseudomonas spp. (T2). Similarly, the number of nodules (7.50 clusters) primary shoots (5) Root weight (4.6 g) was observed in plants treated with Enterobacter spp. (T3).

Genomic Insight into a Potential Biological Control Agent for Fusarium-Related Diseases in Potatoes: Bacillus cabrialesii Subsp. cabrialesii Strain PE1

Bacillus strain PE1, which was isolated from potatoes harvested in the Yaqui Valley, Mexico, was evaluated as a potential biological control agent against Fusarium languescens. The draft genome sequence was obtained through Illumina NovaSeq sequencing, revealing a genomic size of 4,071,293 bp, with a G + C content of 44.13%, an N50 value of 357,305 bp, and 27 contigs. The taxonomic affiliation was confirmed by analyzing the 16S rRNA gene and overall genome relatedness indices (OGRIs) and constructing a phylogenomic tree based on the whole genome, which showed a close relationship to Bacillus cabrialesii subsp. cabrialesii. Genomic annotation using RAST and Prokka identified 4261 coding DNA sequences (CDSs) distributed across 331 subsystems, highlighting genes associated with biocontrol, stress response, and iron acquisition. AntiSMASH 7.1 was used for genome mining, revealing seven biosynthetic gene clusters that potentially produce biocontrol-related metabolites. In vitro assays confirmed the antagonistic activity of strain PE1 against Fusarium languescens CE2, demonstrating its potential to inhibit mycelial growth. The study provides a genomic basis for investigating B. cabrialesii subsp. cabrialesii PE1 as a potential biological control agent in potato production.

Fungal plant pathogen Colletotrichum shisoi identified as a potential biological control agent of invasive Perilla frutescens in the United States

ABSTRACT Perilla frutescens (L.) Britton, an annual plant in the mint family, is considered invasive in the United States where it excludes native vegetation in natural areas and can cause respiratory illness in livestock. An effective biological control agent would improve perilla management, but none have been developed or proposed. This study investigated the biocontrol potential of a fungal pathogen, Colletotrichum shisoi, recently found infecting perilla in North America. The growth rates and morphology of seven Colletotrichum shisoi isolates were recorded. A virulence assay was performed on two perilla accessions, and the number and size of foliar lesions produced were used to select a single isolate, Colletotrichum shisoi isolate 21-072, exhibiting consistently high virulence for further evaluation of biocontrol efficacy and host specificity. Treatment with 0.5 mL of 1 × 107 spores/mL H2O caused a 52% reduction in shoot height and 84% reduction in root length of invasive perilla seedlings compared to a control treatment (P < 0.001). Seedlings treated with 1 × 108 spores/mL had a 100% mortality rate. Formulation of inoculum in a 1:1 water:oil emulsion reduced dew period requirements for causing >50% plant mortality from 48 to 24 h, but oil emulsions exhibited a mild phytotoxic effect on seedlings. Four additional perilla accessions were susceptible to C. shisoi, and none of 34 other species included in host range experiments developed disease symptoms following inoculation. These results suggest C. shisoi 21-072 could be an effective antagonist of perilla and likely poses a low risk of non-target impacts.

Assessing the Prey Specificity of Neoleucopis spp. against Marchalina hellenica

Marchalina hellenica Gennadius (Hemiptera: Marchalinidae) is a scale insect native to Greece and Turkey and presently invasive in Australia, where it damages pine plantations. The silver fly, Neoleucopis kartliana Tanasijtshuk (Diptera: Chamaemyiidae), is the most abundant predator of M. hellenica in Greece and is presently being investigated as a potential biological control agent following the scale’s introduction in Australia. This study, conducted in Northern Greece, revealed the presence of a second lineage, closely related to N. kartliana, referred to as Neoleucopis n. sp. B. Field surveys and laboratory experiments were conducted on M. hellenica and a taxonomically related scale insect, Icerya purchasi Maskell (Hemiptera: Monophlebidae), to test the larval growth and survival of the flies on the two prey species and assess their specificity for M. hellenica. The results suggest that both Neoleucopis spp. exhibit a high preference for M. hellenica when compared to I. purchasi. Larval growth was higher on M. hellenica than on I. purchasi but the difference was significant for N. kartliana only. Survival was significantly higher for both predators when provided M. hellenica compared to I. purchasi. Field surveys showed that both predators are abundant on M. hellenica colonies, whereas none of the two Neoleucopis lineages was found to have preyed on I. purchasi.

Biocontrol efficiency and potential mechanism of streptomyces distatochromogenes XT34 against postharvest anthracnose caused by colletotrichum musae on banana fruit

Banana anthracnose caused by Colletotrichum musae is a serious postharvest disease. Use of fungicides has potential adverse effects on the environment safety and human health. Application of biological control agents (BCA) is a promising strategy for managing postharvest fruit diseases. In this study, Streptomyces sp. XT34 was isolated from the banana rhizosphere soil and exhibited a strong antifungal activity against C. musae. Combining the phenotypic and whole-genomic alignment, strain XT34 was identified as Streptomyces diastatochromogenes. Strain XT34 extracts reduced the disease incidence of anthracnose and maintained the fruit quality of banana. Treatment of extracts reduced the colonization of C. musae on fruit surface. The activity inhibition of cell wall-degrading enzymes maintained the cell-wall strength of fruit. The activity increase of defense enzymes contributed to the low disease symptom. It was supported by the differentially expressed genes (DEGs) related to supramolecular fiber organization and flavonoid biosynthesis. In addition, spore germination of C. musae was effectively inhibited by extracts. The morphology of mycelia and spore become wrinkled and ruptured. The treatment of extracts increased the optical density of A260 and soluble sugar and protein contents of C. musae. The integrity of cell membrane was also destroyed, reflecting on an increase in electrical conductivity and malondialdehyde. Several metabolites were found in the genome of strain XT34 using antiSMASH. Eleven volatile compounds were identified by gas chromatography-mass spectrometer (GC-MS). Notably, strain XT34 and extracts exhibited a broad-spectrum antifungal activity against eight phytopathogenic fungi. Hence, S. diastatochromogenes XT34 provides a potential BCA to control banana anthracnose.