Effects of Simplicillium lanosoniveum on Phakopsora pachyrhizi, the soybean rust pathogen, and its use as a biological control agent

New Antibacterial Peptaibiotics against Plant and Fish Pathogens from the Deep-Sea-Derived Fungus Simplicillium obclavatum EIODSF 020

Bacterial diseases could severely harm agricultural production. To develop new antibacterial agents, the secondary metabolites of a deep-sea-derived fungus Simplicillium obclavatum EIODSF 020 with antibacterial activities against plant and fish pathogens were investigated by a bioassay-guided approach, which led to the isolation of 11 new peptaibiotics, simplicpeptaibs A-K (1-11). They contain 16-19 residues, including β-alanine, tyrosine, or tyrosine O-sulfate, that were rarely present in peptaibiotics. Their structures were elucidated by spectroscopic analyses (NMR, HRMS, HRMS2, and ECD) and Marfey's method. The primary and secondary structures of novel sulfated peptaibiotic 9 were reconfirmed by single-crystal X-ray diffraction analysis. Genome sequencing of S. obclavatum EIODSF 020 allowed the detection of a gene cluster encoding two individual NRPSs (totally containing 19 modules) that was closely related to simplicpeptaib biosynthesis. Antibacterial investigations of 1-11 together with the previously isolated linear and cyclic peptides from this strain suggested the antibacterial property of this fungus was attributed to the peptaibiotics and cyclic lipopeptides. Among them, compounds 4, 6, 7, and 9 showed significant activity against the tobacco pathogen Ralstonia solanacearum or tilapia pathogens Streptococcus iniae and Streptococcus agalactiae. The antibacterial activity of 6 against R. solanacearum could be enhanced by the addition of 1% NaCl. The structure-bioactivity relationship of simplicpeptaibs was discussed.

Understanding Phakopsora pachyrhizi in soybean: comprehensive insights, threats, and interventions from the Asian perspective

Soybean (Glycine max L.) is an important crop in Asia, accounting for 17% of global soybean cultivation. However, this crop faces formidable challenges from the devastating foliar disease, Asian Soybean Rust (ASR), caused by Phakopsora pachyrhizi, a biotrophic fungus with a broad host range, causing substantial yield losses (10-100%) in Asia. This comprehensive review consolidates knowledge on ASR, encompassing its impact, historical perspectives, genetic diversity, epidemic drivers, early detection, risk assessment, and sustainable management strategies of ASR in the region. ASR has expanded globally from Asia, reaching Africa and Americas, driven by wind-dispersed urediniospores. Genetic diversity studies reveal the complexity of P. pachyrhizi, with distinct populations exhibiting varying virulence patterns. Factors affecting ASR epidemics in Asia include host susceptibility, landscape connectivity, climate, and environmental conditions. Understanding the interplay of these factors is essential for early intervention and control of ASR in soybean fields. Effectively managing ASR can exploit the utilization of diverse intervention strategies, encompassing disease forecasting, automated early detection, disease resistance, fungicide application, and biological control. A pivotal aspect of successful, sustainable disease management lies in reducing the ASR pathogen virulence and preventing it from developing fungicide resistance, while the highpoint of effectiveness in disease control is attained through a synergistic approach, integrating various strategies. In summary, this comprehensive review provides insights into multifaceted approaches that contribute to the development of sustainable and economically impactful soybean production in the face of the persistent threat of ASR in Asia.

Drought stress-mediated differences in phyllosphere microbiome and associated pathogen resistance between male and female poplars

Phyllosphere-associated microbes play a crucial role in plant-pathogen interactions while their composition and diversity are strongly influenced by drought stress. As dioecious plant species exhibited secondary dimorphism between the two sexes in response to drought stress, whether such difference will lead to sex-specific differences in phyllosphere microbiome and associated pathogen resistance between male and female conspecifics is still unknown. In this study, we subjected female and male full siblings of a dioecious poplar species to a short period of drought treatment followed by artificial infection of a leaf pathogenic fungus. Our results showed that male plants grew better than females with or without drought stress. Female control plants had more leaf lesion area than males after pathogen infection, whereas drought stress reversed such a difference. Further correlation and in vitro toxicity tests suggested that drought-mediated sexual differences in pathogen resistance between the two plant sexes could be attributed to the shifts in structure and function of phyllosphere-associated microbiome rather than the amount of leaf main defensive chemicals contained in plant leaves. Supportively, the microbiome analysis through high-throughput sequencing indicated that female phyllosphere enriched a higher abundance of ecologically beneficial microbes that serve as biological plant protectants, while males harbored abundant phytopathogens under drought-stressed conditions. The results could provide potential implications for the selection of suitable poplar sex to plants in drought or semi-drought habitats.

Diverse environmental bacteria displaying activity against Phakopsora pachyrhizi, the cause of soybean rust

The management of soybean rust (SBR) caused by the obligate fungus Phakopsora pachyrhizi mostly relies on the use of synthetic fungicides, especially in areas where the disease inflicts serious yield losses. The reliance on synthetic fungicides to manage this disease has resulted in resistance of P. pachyrhizi populations to most fungicides. In this study, bacteria isolated from diverse environments were evaluated for their biocontrol potential against P. pachyrhizi using soybean detached-leaf method and on-plant in the growth chamber, greenhouse, and field. Among 998 bacterial isolates evaluated using the detached-leaf method; 58% were isolated from plant-related materials, 27% from soil, 10% from insects, and 5% from other environments. Of the isolates screened, 73 were active (they had ⪖ 75% rust reduction) with an active rate of 7.3%. From the active isolates, 65 isolates were re-tested on-plant in the growth chamber for activity confirmation. In the confirmation test, 49 bacteria isolated from plant-related materials maintained their activity with a confirmation rate of 75%. The majority of bacteria with confirmed activity belonged to the taxonomic classes Bacilli and Gammaproteobacteria (70%). Active isolates were prioritized for greenhouse and field testing based on activity in the initial screen and confirmation test. Six bacterial isolates AFS000009 (Pseudomonas_E chlororaphis), AFS032321 (Bacillus subtilis), AFS042929 (Bacillus_C megaterium), AFS065981 (Bacillus_X simplex_A), AFS090698 (Bacillus_A thuringiensis_S), and AFS097295 (Bacillus_A toyonensis) were selected from those bacteria that maintained activity in the confirmation test and were evaluated in the greenhouse, and five among them were evaluated in the field. From the Alabama field evaluation, all bacterial isolates reduced rust infection as well as azoxystrobin (Quadris^® at 0.3 L/ha) used as the fungicide control (P > 0.05). Moreover, the scanning electron micrographs demonstrated evidence of antagonistic activity of AFS000009 and AFS032321 against P. pachyrhizi urediniospores. Bacterial isolates that consistently showed activity comparable to that of azoxystrobin can be improved through fermentation and formulation optimization, developed, and deployed. These bacteria strains would provide a valuable alternative to the synthetic fungicides and could play a useful role in integrated disease management programs for this disease.

A Comparative Study on Fungal Diversity in Organic and Conventionally Cultivated Lemons During Accelerated Storage

There has been a growing interest in organic farming as a countermeasure to the environmental burden caused by chemical pesticides. We analyzed and compared the fungal diversity of lemon fruits from organic and conventional cultivation by automated rRNA intergenic spacer analysis (ARISA), accompanied by isolation of cultured colonies and metagenomic analysis. Lemon peels were cut out and subjected to the analyses at purchase and after accelerated storage at 28 °C. The organic lemons did not decay even after 14 weeks, while most of the conventional lemons did decay. The fungal colony counts were not significantly different, although the number of fungal species together with the Shannon index, considering the abundance of each species, clearly showed more diversity in organic lemons than in conventional lemons (p = 0.011). Fusarium sp. (putative F. solani) accounted for as much as 90% of the relative abundance in the decayed conventional lemons. Metagenomic analysis also supported the lack of fungal diversity in conventional lemons. These results may suggest that organic cultivation maintains the diversity of native fungal flora in lemon fruit and could contribute to preventing decay during ambient storage.

Antifungal Activity and Biocontrol Potential of Simplicillium lamellicola JC-1 against Multiple Fungal Pathogens of Oilseed Rape

A fungal strain (JC-1) of Simplicillium was isolated from a pod of oilseed rape (Brassica napus) infested with the blackleg pathogen Leptosphaeria biglobosa. This study was done to clarify its taxonomic identity using morphological and molecular approaches, to characterize its antifungal activity through bioassays and genome-based identification of antifungal metabolites, and to determine its efficacy in inducing systemic resistance (ISR) in oilseed rape. The results showed that JC-1 belongs to Simplicillium lamellicola. It displayed a strong antagonistic relationship with L. biglobosa, Botrytis cinerea (gray mold) and Sclerotinia sclerotiorum (stem rot). The cultural filtrates of JC-1 showed a high efficacy in suppressing infection by S. sclerotiorum on detached leaves of oilseed rape. Genome analysis indicated that JC-1 has the capability of producing multiple antifungal metabolites, including aureobasidin A1, squalestatin S1 and verlamelin. Inoculation of JC-1 on seeds of oilseed rape caused a suppressive effect on infection by L. biglobosa on the cotyledons of the resulting seedlings, suggesting that JC-1 can trigger ISR. Endophytic growth, accumulation of anthocyanins, up-regulated expression of CHI (for chalcone isomerase) and PR1 (for pathogenesis-related protein 1), and down-regulated expression of NECD3 (for 9-cis-epoxycarotenoid dioxygenase) were detected to be associated with the ISR. This study provided new insights into the biocontrol potential and modes of action of S. lamellicola.

Evaluating the Utility of Simplicillium lanosoniveum, a Hyperparasitic Fungus of Puccinia graminis f. sp. tritici, as a Biological Control Agent against Wheat Stem Rust

Wheat stem rust is one of the wheat diseases caused by Puccinia graminis Pers. f. sp. tritici (Pgt). This disease has been responsible for major losses to wheat production worldwide. Currently used methods for controlling this disease include fungicides, the breeding of stem rust-resistant cultivars, and preventive agricultural measures. However, the excessive use of fungicides can have various deleterious effects on the environment. A hyperparasitic fungus with white mycelia and oval conidia, Simplicillium lanosoniveum, was isolated from the urediniospores of Pgt. When Pgt-infected wheat leaves were inoculation with isolates of S. lanosoniveum, it was found that S. lanosoniveum inoculation inhibited the production and germination of urediniospores, suggesting that S. lanosoniveum could inhibit the growth and spread of Pgt. Scanning electron microscopy revealed that S. lanosoniveum could inactivate the urediniospores by inducing structural damage. Overall, findings indicate that S. lanosoniveum might provide an effective biological agent for the control of Pgt.

New Approaches to Manage Asian Soybean Rust (Phakopsora pachyrhizi) Using Trichoderma spp. or Their Antifungal Secondary Metabolites

Attempts have been made to determine the in vitro and in planta suppressive potential of particular Trichoderma strains (T16 and T23) and their secondary metabolites (SMs) against Asian soybean rust (ASR) incited by Phakopsora pachyrhizi. Aside from the previously identified SMs 6-pentyl-α-pyrone (6PAP) and viridiofungin A (VFA), the chemical structures of harzianic acid (HA), iso-harzianic acid (iso-HA), and harzianolide (HZL) were characterized in this study. Our results indicate that exposure of urediospores to 200 ppm 6PAP completely inhibits germination. A slightly higher dosage (250 ppm) of HZL and VFA reduces germination by 53.7% and 44%, respectively. Germ tube elongation seems more sensitive to 6PAP than urediospore germination. On detached leaves, application of conidia of T16 and T23 results in 81.4% and 74.3% protection, respectively. Likewise, 200 ppm 6PAP recorded the highest ASR suppression (98%), followed by HZL (78%) and HA (69%). Treatment of undetached leaves with 6PAP, HA, or HZL reduces ASR severity by 84.2%, 65.8%, and 50.4%, respectively. Disease reduction on the next, untreated trifoliate by T23 (53%), T16 (41%), HZL (42%), and 6PAP (32%) suggests a translocation or systemic activity of the SMs and their producers. To our knowledge, this study provides the first proof for controlling ASR using antifungal SMs of Trichoderma. Our findings strongly recommend the integration of these innovative metabolites, particularly 6PAP and/or their producers in ASR management strategies.

An efficient Agrobacterium tumefaciens-mediated transformation method for Simplicillium subtropicum (Hypocreales: Cordycipitaceae)

Filamentous fungi are the organisms of choice for most industrial biotechnology. Some species can produce a variety of secondary metabolites and enzymes of commercial interest, and the production of valuable molecules has been enhanced through different molecular tools. Methods for genetic manipulation and transformation have been essential for the optimization of these organisms. The genus Simplicillium has attracted increased attention given several potential biotechnological applications. The Simplicillium genus harbors several entomopathogenic species and some isolates have been explored for bioremediation of heavy metal contaminants. Furthermore, the myriad of secondary metabolites isolated from Simplicillium spp. render these organisms as ideal targets for deep exploration and further biotechnological mining possibilities. However, the lack of molecular tools hampered the exploration of this genus. Thus, an Agrobacterium tumefaciens-mediated transformation method was established for Simplicillium subtropicum, employing the far-red fluorescent protein TURBOFP635/Katushka, as a visual marker, and the selection marker SUR gene, that confers resistance to chlorimuron ethyl. Notably, one round of transformation using the established method yielded almost 400 chlorimuron resistant isolates. Furthermore, these transformants displayed mitotic stability for, at least, five generations. We anticipate that this method can be useful for deep molecular exploration and improvement of strains in the Simplicillium genus.

Taxonomic and phylogenetic characterizations reveal four new species of Simplicillium (Cordycipitaceae, Hypocreales) from Guizhou, China

Simplicillium species are commonly found from soil, seawater, rock surface, decayed wood, air and as symbiotic, endophytic, entomopathogenic and mycoparasitic fungi. Minority insect-associated species was reported. Simplicillium coccinellidae, S. hymenopterorum, S. neolepidopterorum and S. scarabaeoidea were introduced as the newly insect-associated species. The phylogenetic analyses of two combined datasets (LSU + RPB1 + TEF and SSU + ITS + LSU) revealed that S. coccinellidae and S. hymenopterorum were both nested in an independent clade. S. neolepidopterorum and S. scarabaeoidea have a close relationship with S. formicidae and S. lepidopterorum, respectively. S. neolepidopterorum can be easily distinguished from S. formicidae by ellipsoidal to cylindrical, solitary conidia which occasionally gather in short imbricate chains. S. scarabaeoidea could be easily distinguished from S. lepodopterorum by having longer phialides and larger conidia. Based on the morphological and phylogenetic conclusion, we determine the four newly generated isolates as new species of Simplicillium and a new combination is proposed in the genus Leptobacillium.

Diversity, Ecological Role and Biotechnological Potential of Antarctic Marine Fungi

The Antarctic Ocean is one of the most remote and inaccessible environments on our planet and hosts potentially high biodiversity, being largely unexplored and undescribed. Fungi have key functions and unique physiological and morphological adaptations even in extreme conditions, from shallow habitats to deep-sea sediments. Here, we summarized information on diversity, the ecological role, and biotechnological potential of marine fungi in the coldest biome on Earth. This review also discloses the importance of boosting research on Antarctic fungi as hidden treasures of biodiversity and bioactive molecules to better understand their role in marine ecosystem functioning and their applications in different biotechnological fields.

Cork Oak Endophytic Fungi as Potential Biocontrol Agents against Biscogniauxia mediterranea and Diplodia corticola

An increase in cork oak diseases caused by Biscogniauxia mediterranea and Diplodia corticola has been reported in the last decade. Due to the high socio-economic and ecologic importance of this plant species in the Mediterranean Basin, the search for preventive or treatment measures to control these diseases is an urgent need. Fungal endophytes were recovered from cork oak trees with different disease severity levels, using culture-dependent methods. The results showed a higher number of potential pathogens than beneficial fungi such as cork oak endophytes, even in healthy plants. The antagonist potential of a selection of eight cork oak fungal endophytes was tested against B. mediterranea and D. corticola by dual-plate assays. The tested endophytes were more efficient in inhibiting D. corticola than B. mediterranea growth, but Simplicillium aogashimaense, Fimetariella rabenhorstii, Chaetomium sp. and Alternaria alternata revealed a high potential to inhibit the growth of both. Simplicillium aogashimaense caused macroscopic and microscopic mycelial/hyphal deformations and presented promising results in controlling both phytopathogens' growth in vitro. The evaluation of the antagonistic potential of non-volatile and volatile compounds also revealed that A. alternata compounds could be further explored for inhibiting both pathogens. These findings provide valuable knowledge that can be further explored in in vivo assays to find a suitable biocontrol agent for these cork oak diseases.

Effect of Substrate Characteristics on the Growth and Sporulation of Two Biocontrol Microorganisms during Solid State Cultivation

Biocontrol agents are a group of naturally occurring organisms capable of interrupting the lifespan and suppressing the propagation of disease organisms. The use of biocontrol agents offers an environment-friendly and sustainable solution to the synthetic agrochemicals. In this study, we investigated parboiled rice and millets as substrates for spore production of two model biocontrol microorganisms (Bacillus pumilus and Streptomyces griseus) under solid state cultivation (SSC) conditions. The effects of cultivation parameters such as initial moisture content, water activity, and cultivation time on microbial growth and spore production were studied. Furthermore, texture profile analysis was performed to test the stress and strain curve and the hardness and stickiness of the substrates. The greatest spore production occurred at 50% moisture content with millets as a substrate, yielding a count of 1.34 × 108 spores/g-wet-substrate enumerated with plate count analysis and 1.70 × 108 events/g-wet-substrate using flow cytometry analysis. Substrate texture profile was highly correlative to the initial moisture content and substrate type and all proved to be essential process variables in controlling the bacterial growth and sporulation during SSC processes.

Draft Genome Sequence of Simplicillium aogashimaense 72-15.1, a Putative Endophyte of Brachiaria brizantha

Here, we report a 29-Mb draft genome sequence of strain 72-15.1 of Simplicillium aogashimaense (Cordycipitaceae, Hypocreales). Strain 72-15.1 was a unique fungal isolate obtained from asymptomatic tillers of the tropical grass Brachiaria brizantha.

Here, we report a 29-Mb draft genome sequence of strain 72-15.1 of Simplicillium aogashimaense (Cordycipitaceae, Hypocreales). Strain 72-15.1 was a unique fungal isolate obtained from asymptomatic tillers of the tropical grass Brachiaria brizantha.

Identification of a Hyperparasitic Simplicillium obclavatum Strain Affecting the Infection Dynamics of Puccinia striiformis f. sp. tritici on Wheat

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most serious threats to wheat production worldwide. Changes of Pst virulence may circumvent resistance in wheat varieties, and application of fungicides may cause environmental problems. Parasites of Pst can be used to develop biological agents for environmentally friendly control of this fungal disease. Here, we report a hyperparasitic fungus isolated from Pst and identified it as Simplicillium obclavatum through molecular and morphological characterizations. We demonstrated that inoculation of Pst-infected wheat leaves with S. obclavatum reduced the production and germination rate of Pst urediniospores. Therefore, S. obclavatum has the potential to be developed into a biological control agent for managing wheat stripe rust.

The genus Simplicillium

Simplicillium species have a wide host range and an extensive distribution. Some species are associated with rusts, as well as other plant pathogenic fungi and play an important role in biological control. In this study, two specimens of Simplicillium were collected from Chiang Mai Province, Thailand. Simplicilliumformicae sp. nov. was isolated from an infected ant and S.lanosoniveum from Ophiocordycepsunilateralis which is a new host record. Species were initially identified using ITS gene sequences and confirmed using morphology coupled with phylogenetic analyses of a combined nrLSU, nrSSU, TEF and RPB1 dataset. Simplicilliumformicae differs from other species in the genus by the presence of flask-shaped synnemata and phialides with intercalary nodes. Simplicilliumlanosoniveum resembles other collections of the species by its completely solitary, tapering phialides and globose to ellipsoidal conidia which adhere in a slimly head. A key to species of Simplicillium is also provided.

Three novel insect-associated species of Simplicillium (Cordycipitaceae, Hypocreales) from Southwest China

In this paper, we introduce three new species of Simplicillium, viz. S. cicadellidae, S. formicidae and S. lepidopterorum, which were isolated from an infected leafhopper, ant and carpenterworm, respectively. Morphological comparisons and phylogenetic analyses based on multigene datasets (LSU+RPB1+RPB2+TEF and ITS+LSU) support the establishment of the three new species. Simplicillium cicadellidae was distinguished from other species in morphological characteristics by having smaller phialides and ellipsoidal conidia, and lacking octahedral crystals. The reverse of colonies were yellowish (#FFBF00), especially in the middle, and radially sulcate. Simplicillium formicidae was morphologically distinguished from other by having longer phialides and filiform to fusoid conidia, and by lacking octahedral crystals. Simplicillium lepidopterorum was morphologically distinguished from other species by having smaller, ellipsoidal to fusiform conidia, and by lacking octahedral crystals. The reverse of the colony was pale white. The three new species are likely to be nourished by plant to animal (especially insect) nutrients based on the evolutionary pattern of the Hypocreales, and they are described herein as being clearly distinct from other species in Simplicillium.

Effect of Selected Biopesticides in Reducing Soybean Rust (Phakopsora pachyrhizi) Development

The intensive use of fungicides in controlling soybean rust (SBR), a damaging foliar fungal disease of soybean caused by the obligate fungus Phakopsora pachyrhizi, may have accelerated the insensitivity of P. pachyrhizi populations to fungicides. The objective of this study was to determine the effect of selected biopesticides and their application time on reducing SBR infection. There were differences (P < 0.05) in percent rust reduction values for application times, biopesticide treatments, and their interaction in detached-leaf and whole-plant greenhouse experiments. All application times and nearly all biopesticide treatments reduced (α = 0.05) fungal infection compared with the nonfungicide control. Among the treatments, Bacillus subtilis QST 713 and acibenzolar-S-methyl often reduced fungal sporulation more than the other treatments in detached-leaf and whole-plant greenhouse experiments. The identification of biopesticides effective to P. pachyrhizi may be a valuable alternative or complement to synthetic fungicides and may be useful in integrated pest management programs for SBR control.

Taxonomy, phylogeny and ecology of cultivable fungi present in seawater gradients across the Northern Antarctica Peninsula

Thirty-six seawater samples collected at different depths of the Gerlache and Bransfield Straits in the Northern Antarctic Peninsula were analyzed, and the average of the total fungal counts ranged from 0.3 to >300 colony forming units per liter (CFU/L) in density. The fungal were purified and identified as 15 taxa belonged to the genera Acremonium, Aspergillus, Cladosporium, Cystobasidium, Exophiala, Glaciozyma, Graphium, Lecanicillium, Metschnikowia, Penicillium, Purpureocillium and Simplicillium. Penicillium chrysogenum, Cladosporium sphaerospermum, and Graphium rubrum were found at high densities in at least two different sites and depths. Our results show at the first time that in the seawater of Antarctic Ocean occur diverse fungal assemblages despite extreme conditions, which suggests the presence of a complex aquatic fungi food web, including species reported as barophiles, symbionts, weak and strong saprobes, parasites and pathogens, as well as those found in the polluted environments of the world. Additionally, some taxa were found in different sites, suggesting that the underwater current might contribute to fungal (and microbial) dispersal across the Antarctic Ocean, and nearby areas such as South America and Australia.

A new antibiotic produced by the cyanobacterium-symbiotic fungus Simplicillium lanosoniveum

The culture broth of the cyanobacterium-symbiotic fungus Simplicillium lanosoniveum var. Tianjinienss Q. L. Dong exhibited unanticipated antibacterial activities against the Gram-positive bacteria, particularly the pathogenic bacterium Staphylococcus aureus, indicating the secretion of antibiotic-like metabolite, for which the modified Sabouraud medium was the suitable medium. The antibiotic-like metabolite was separated with macroporous resins CT-12 (absorption) and 95% ethanol (desorption), purified by ion-exchange resins D301T and displayed a characteristic absorption peak at 228 nm, suggesting the presence of nitrogen. The negative biuret and ninhydrin tests confirmed the absence of -NH₂ and -COOH groups. Further, HPLC and mass spectrometry analyses showed that the retention time and molecular weight of the antibiotic-like metabolite were 4.1031 min and 163.0182 (Δ ± 2.3 ppm), respectively. Taking together, we speculated that the antibiotic-like metabolite was a new antibiotic structurally similar to alkaloid, which was the first one isolated from the species of Simplicillium genus.

Fighting Asian Soybean Rust

Phakopsora pachyrhizi is a biotrophic fungus provoking SBR disease. SBR poses a major threat to global soybean production. Though several R genes provided soybean immunity to certain P. pachyrhizi races, the pathogen swiftly overcame this resistance. Therefore, fungicides are the only current means to control SBR. However, insensitivity to fungicides is soaring in P. pachyrhizi and, therefore, alternative measures are needed for SBR control. In this article, we discuss the different approaches for fighting SBR and their potential, disadvantages, and advantages over other measures. These encompass conventional breeding for SBR resistance, transgenic approaches, exploitation of transcription factors, secondary metabolites, and antimicrobial peptides, RNAi/HIGS, and biocontrol strategies. It seems that an integrating approach exploiting different measures is likely to provide the best possible means for the effective control of SBR.

Antimicrobial activities of novel mannosyl lipids isolated from the biocontrol fungus Simplicillium lamellicola BCP against phytopathogenic bacteria

The antagonistic fungus Simplicillium lamellicola BCP has been developed as a microbial biopesticide that effectively controls the development of various plant diseases caused by both pathogenic bacteria and pathogenic fungi. Antibacterial bioassay-directed fractionation was used to isolate mannosyl lipids from S. lamellicola BCP, and the structures of these compounds were elucidated using spectral analysis and chemical degradation. Three novel mannosyl lipids were characterized and identified as halymecins F and G and (3R,5R)-3-O-β-D-mannosyl-3,5-dihydrodecanoic acid. Massoia lactone and (3R, 5R)-3-hydroxydecan-5-olide were also isolated from S. lamellicola BCP. The three novel compounds inhibited the growth of the majority of phytopathogenic bacteria that were tested, and halymecin F displayed the strongest antibacterial activity. Agrobacterium tumefaciens was the most sensitive to the three novel compounds, with IC₅₀ values ranging from 1.58 to 24.8 μg/mL. The ethyl acetate extract of the fermentation broth from the antagonistic fungus effectively reduced the bacterial wilt caused by Ralstonia solanacearum on tomato seedlings. These results indicate that S. lamellicola BCP suppresses the development of plant bacterial diseases through the production of antibacterial metabolites.