Species Diversity and Virulence Potential of the Beauveria bassiana Complex and Beauveria scarabaeidicola Complex

Wang Y., Wang Y., Fan Q., Duan D., Zhang G., Dai R., Dai Y., Zeng W., Chen Z., Li D., Tang D., Xu Z., Sun T., Nguyen T., Tran N., et. al.

The phylogeny and systematics of cordycipitoid fungi have been extensively studied in the last two decades. However, systematic positions of some taxa in the family Cordycipitaceae have not yet been thoroughly resolved. In this study, a new phylogenetic framework of Cordycipitaceae is reconstructed using multigene (nrSSU, nrLSU, tef-1α, rpb1 and rpb2) sequence data with large-scale taxon sampling. In addition, ITS sequence data of species belonging to the Lecanicillium lineage in the family Cordycipitaceae are used to further determine their phylogenetic placements. Based on molecular phylogenetic data together with morphological evidence, two new genera (Flavocillium and Liangia), 16 new species and four new combinations are introduced. In the new genus Flavocillium, one new species F. bifurcatum and three new combinations previously described as Lecanicillium, namely F. acerosium, F. primulinium and F. subprimulinium, are proposed. The genus Liangia is built by the new species Lia. sinensis with Lecanicillium-like asexual morph, isolated from an entomopathogenic fungus Beauveria yunnanensis. Due to the absence of Paecilomyces hepiali, an economically and medically significant fungus, in the earlier phylogenetic analyses, its systematic position has been puzzling in both business and academic communities for a long time. Here, P. hepiali is recharacterized using the holotype material along with seven additional samples. It is assigned to the genus Samsoniella (Cordycipitaceae, Hypocreales) possessing Cordyceps-like sexual morph and Isaria-like asexual morph, and thus a new combination, namely S. hepiali is proposed. An additional nine new species in Samsoniella are described: S. alpina, S. antleroides, S. cardinalis, S. cristata, S. lanmaoa, S. kunmingensis, S. ramosa, S. tortricidae and S. yunnanensis. Four new species in Cordyceps are described: C. chaetoclavata, C. cocoonihabita, C. shuifuensis and C. subtenuipes. Simplicillium yunnanense, isolated from synnemata of Akanthomyces waltergamsii, is described as a new species.

Wang Y., Tang D., Duan D., Wang Y., Yu H.

Beauveria pseudobassiana has great potential for use in the management of various insect pests. In the present study, we aimed to explore the the virulence of B. pseudobassiana isolated from a diversity of hosts to Bombyx mori and Tenebrio molitor larvae. To this end, 15B. pseudobassiana isolates from 10 different geographical locations were identified based on morphological characteristics and molecular data. The phylogenetic positions of the isolates were evaluated according to morphological features and phylogenetic inferences based on six loci (nrSSU, nrLSU, TEF, RPB1, RPB2 and Bloc). In addition to growth in soil, the B. pseudobassiana isolates in our study were isolated from a wide host range that extended to 5 orders, 11 families, and 14 species. Moreover, anamorphically typified B. pseudobassiana was grown for the first time from teleomorph stromata. Pathogenicity of the B. pseudobassiana isolates from the different hosts was determined with two bioassays using B. mori and T. molitor larvae. The results indicated that mortality of B. mori caused by the lepidopteran isolates was significantly higher than that of isolates from other hosts, and virulence of the coleopteran isolates to T. molitor was significantly higher than that of isolates from other hosts. The host specificity of B. pseudobassiana should be studied in more detail before future consideration of isolates for use in biological control of pests.

Khonsanit A., Luangsa-ard J.J., Thanakitpipattana D., Noisripoom W., Chaitika T., Kobmoo N.

Thailand has rich natural resources and diverse ecosystems. From our surveys of entomopathogenic fungi in Thailand over the last decade, 66 Beauveria strains in BIOTEC Culture Collection (BCC) were studied to account for the diversity of this genus in Thailand. Examination of morphological characteristics from various media and phylogenetic analyses based on partial sequence of ITS, TEF, RBP1, RPB2, and the nuclear intergenic region Bloc, were realized. Among the strains from Thailand, we described here a new species, namely B. mimosiformis sp. nov., isolated from Coleoptera larva in the North of Thailand. This new species has a unique characteristic of phialides and conidia forming an ensemble similar to plant leaves of the genus Mimosa; it has pale yellow to light yellow stromata, cylindrical with rounded apices or oblong conidia, cylindrical part-ascospores. We also found a teleomorph linked to B. asiatica and documented new hosts (Lepidoptera larva and adult beetle) of B. gryllotalpidicola, as well as reported B. malawiensis for the first time in Thailand. Beside those species, B. bassiana and B. loeiensis were also identified, adding up to six species from Thailand. Through molecular phylogenetic analyses, we revealed (1) diverging lineages within B. asiatica and B. bassiana which, despite lack of support to be erected as any higher taxonomical unit, demonstrated complex intra-specific molecular diversity undergoing differentiation and (2) ambiguous relations between certain known species, particularly for B. majiangensis that we synonymized as B. asiatica.

Bustamante D.E., Oliva M., Leiva S., Mendoza J.E., Bobadilla L., Angulo G., Calderon M.S.

The genusBeauveriais considered a cosmopolitan anamorphic and teleomorphic genus of soilborne necrotrophic arthropod-pathogenic fungi that includes ecologically and economically important species. Species identification inBeauveriais difficult because of its structural simplicity and the lack of distinctive phenotypic variation. Therefore, the use of multi-locus sequence data is essential to establish robust species boundaries in addition to DNA-based species delimitation methods using genetic distance, coalescent, and genealogical concordance approaches (polyphasic approaches). In this regard, our study used multilocus phylogeny and five DNA-based methods to delimit species inBeauveriausing three molecular makers. These polyphasic analyses allowed for the delimitation of 20–28 species inBeauveria, confirming cryptic diversity in five species (i.e.B. amorpha,B. bassiana,B. diapheromeriphila, andB. pseudobassiana) and supporting the description ofB. peruviensisas a new taxon from northeastern Peru. The other five species were not evaluated as they did not have enough data (i.e.B. araneola,B. gryllotalpidicola,B. loeiensis,B. medogensis, andB. rudraprayagi). Our results demonstrate that the congruence among different methods in a polyphasic approach (e.g. genetic distance and coalescence methods) is more likely to show reliably supported species boundaries. Among the methods applied in this study, genetic distance, coalescent approaches, and multilocus phylogeny are crucial when establishing species boundaries inBeauveria.

Chen Z., Chen K., Dai Y., Zheng Y., Wang Y., Yang X., Yu H., Yang Y., Xu L.

The Gaoligong Mountains accommodate diverse ecosystems and biological resources. Beauveria species diversity is inventoried in seven vegetation types of the Gaoligong Mountains along an elevation gradient from 600 to 3800 m. Strains were isolated from soil by using Tenebrio molitor larvae as baits and from naturally occurring insect cadavers carrying anamorphic or teleomorphic fruiting structures of Beauveria spp. The 231 isolated Beauveria strains were identified based on molecular phylogenetic analyses inferred from Bloc, nrSSU, nrLSU, TEF, RPB1, and RPB2 sequences. Eleven species were identified as Beauveria asiatica, B. bassiana, B. brongniartii, B. caledonica, B. medogensis, B. pseudobassiana, and B. sinensis, previously recorded in other Chinese environments, and B. baoshanensis sp. nov., B. malawiensis, B. rudraprayagi, and B. yunnanensis sp. nov., encountered in China for the first time. Species phylogenies are presented and morphological characters of the new species are described. Most isolates were identified as B. bassiana and B. pseudobassiana (86.1%), while the other nine species were isolated rarely. Beauveria was widely distributed in six vegetation types, but not in the vegetation type of the highest altitude. More than four species were encountered in vegetation types with moderate elevation, and these environments also showed highest diversity of plants and insects.

Luo Z., Zhang T., Liu P., Bai Y., Chen Q., Zhang Y., Keyhani N.O.

Little is known about adaptations required for growth at high (>9) pH. Here, we show that a specific fungal membrane-remodeling β-1,3-glucanosyltransferase gene ( Bbgas3 ) regulated by the pH-responsive PacC transcription factor forms a critical aspect of the ability of the insect-pathogenic fungus Beauveria bassiana to grow at extreme pH. The loss of Bbgas3 resulted in a unique decreased ability to grow at high pH, with little to no effects seen with respect to other stress conditions, i.e., cell wall integrity and osmotic and oxidative stress. However, pH-dependent alternations in cell wall properties and virulence were noted for the Δ Bbg as3 mutant. These data provide a mechanistic insight into the importance of the specific cell wall structure required to stabilize the cell at high pH and link it to the PacC/Pal/Rim pH-sensing and regulatory system.

McKinnon A.C., Glare T.R., Ridgway H.J., Mendoza-Mendoza A., Holyoake A., Godsoe W.K., Bufford J.L.

Entomopathogenic fungi from the genus Beauveria (Vuillemin) play an important role in controlling insect populations and have been increasingly utilized for the biological control of insect pests. Various studies have reported that B. bassiana (Bals.), Vuill. also has the ability to colonize a broad range of plant hosts as endophytes without causing disease but while still maintaining the capacity to infect insects. Beauveria is often applied as an inundative spore application, but little research has considered how plant colonization may alter the ability to persist in the environment. The aim of this study was to investigate potential interactions between B. bassiana and Zea mays L. (maize) in the rhizosphere following inoculation, in order to understand the factors that may affect environmental persistence of the fungi. The hypothesis was that different isolates of B. bassiana have the ability to colonize maize roots and/or rhizosphere soil, resulting in effects to the plant microbiome. To test this hypothesis, a two-step nested PCR protocol was developed to find and amplify Beauveria in planta or in soil; based on the translation elongation factor 1-alpha (ef1α) gene. The nested protocol was also designed to enable Beauveria species differentiation by sequence analysis. The impact of three selected B. bassiana isolates applied topically to roots on the rhizosphere soil community structure and function were consequently assessed using denaturing gradient gel electrophoresis (DGGE) and MicroResp™ techniques. The microbial community structure and function were not significantly affected by the presence of the isolates, however, retention of the inocula in the rhizosphere at 30 days after inoculation was enhanced when plants were subjected to intensive wounding of foliage to crudely simulate herbivory. The plant defense response likely changed under wound stress resulting in the apparent recruitment of Beauveria in the rhizosphere, which may be an indirect defensive strategy against herbivory and/or the result of induced systemic susceptibility in maize enabling plant colonization.

CHEN W., LIU M., HUANG Z., YANG G., HAN Y., LIANG J., LIANG Z.

Beauveria majiangensis sp. nov., a fungal grub parasite, isolated from a blueberry farm in Guizhou Province, China, is herein described based on morphological and phylogenetic evidence. Beauveria majiangensis differs from other Beauveria species based on its indeterminate, denticulate rachis, cylindrical or sometimes subspherical conidiogenous cells, and ellipsoidal conidia. Phylogenetic analyses based on four loci (TEF, RPB1, Bloc, and ITS) strongly support that this strain is distinct within Beauveria.

Kepler R.M., Luangsa-ard J.J., Hywel-Jones N.L., Quandt C.A., Sung G., Rehner S.A., Aime M.C., Henkel T.W., Sanjuan T., Zare R., Chen M., Li Z., Rossman A.Y., Spatafora J.W., Shrestha B.

The ending of dual nomenclatural systems for pleomorphic fungi in 2011 requires the reconciliation of competing names, ideally linked through culture based or molecular methods. The phylogenetic systematics of Hypocreales and its many genera have received extensive study in the last two decades, however resolution of competing names in Cordycipitaceae has not yet been addressed. Here we present a molecular phylogenetic investigation of Cordycipitaceae that enables identification of competing names in this family, and provides the basis upon which these names can be maintained or suppressed. The taxonomy presented here seeks to harmonize competing names by principles of priority, recognition of monophyletic groups, and the practical usage of affected taxa. In total, we propose maintaining nine generic names, Akanthomyces, Ascopolyporus, Beauveria, Cordyceps, Engyodontium, Gibellula, Hyperdermium, Parengyodontium, and Simplicillium and the rejection of eight generic names, Evlachovaea, Granulomanus, Isaria, Lecanicillium, Microhilum, Phytocordyceps, Synsterigmatocystis, and Torrubiella. Two new generic names, Hevansia and Blackwellomyces, and a new species, Beauveria blattidicola, are described. New combinations are also proposed in the genera Akanthomyces, Beauveria, Blackwellomyces, and Hevansia.

CHEN W., HAN Y., LIANG Z., JIN D.

Beauveria araneola sp. nov., a fungus parasitic on spiders, was isolated from a spider at the Experimental Farm of the Institute of Entomology, Guizhou University, China; and described with morphological and phylogenetic evidences. This species differs morphologically from other species in the genus by its long slender denticulate rachis, cylindrical to ellipsoid conidiogenous cells, and ellipsoidal to globose conidia. Phylogenetic analyses based on three-locus (TEF, RPB1 and Bloc) data strongly support the distinction of this fungus within the genus. Based on the phylogenetic results, B. araneola shares some pleiomorphic traits with soil-borne or entomogenous members of the genus, and is likely to have jumped from soil or insect hosts to spider.

Imoulan A., Wu H., Lu W., Li Y., Li B., Yang R., Wang W., Wang X., Kirk P.M., Yao Y.

Beauveria is among the most ubiquitous genera of entomopathogenic fungi throughout the world. A previously unknown species of the genus was recently discovered from a soil sample collected from Tibetan Plateau, China and is here described as new to science, B. medogensis sp. nov. The new species is distinguished from its closest relatives based on both morphological characterization and molecular phylogenetic analyses. Beauveria medogensis is characterized by globose to subglobose conidia, morphologically similar to some other species of in the genus, but was conclusively separated from those species in the phylogenetic analyses including sequences of four nuclear genes (RPB1, RPB2, TEF1 and Bloc). The new species was clustered in the analyses in a single terminal lineage which was grouped with B. australis sequences together as a sister clade to the B. brongniartii terminal clade. Although molecularly closely related, the new species is distinct morphologically from its closest sisters, B. australis and B. brongniartii, in producing globose to subglobose conidia rather than subglobose, broadly ellipsoid to ellipsoid conidia or ellipsoidal to cylindrical conidia. As isolated from a soil sample, the entomopathogenicity of the new species has been confirmed using Helicoverpa armigera and Tenebrio molitor larvae.

Keyser C.A., De Fine Licht H.H., Steinwender B.M., Meyling N.V.

Knowledge of the natural occurrence and community structure of entomopathogenic fungi is important to understand their ecological role. Species of the genus Metarhizium are widespread in soils and have recently been reported to associate with plant roots, but the species M. flavoviride has so far received little attention and intra-specific diversity among isolate collections has never been assessed. In the present study M. flavoviride was found to be abundant among Metarhizium spp. isolates obtained from roots and root-associated soil of winter wheat, winter oilseed rape and neighboring uncultivated pastures at three geographically separated locations in Denmark. The objective was therefore to evaluate molecular diversity and resolve the potential population structure of M. flavoviride. Of the 132 Metarhizium isolates obtained, morphological data and DNA sequencing revealed that 118 belonged to M. flavoviride, 13 to M. brunneum and one to M. majus. Further characterization of intraspecific variability within M. flavoviride was done by using amplified fragment length polymorphisms (AFLP) to evaluate diversity and potential crop and/or locality associations. A high level of diversity among the M. flavoviride isolates was observed, indicating that the isolates were not of the same clonal origin, and that certain haplotypes were shared with M. flavoviride isolates from other countries. However, no population structure in the form of significant haplotype groupings or habitat associations could be determined among the 118 analyzed M. flavoviride isolates. This study represents the first in-depth analysis of the molecular diversity within a large isolate collection of the species M. flavoviride. The AFLP analysis confirmed a high level of intra-specific diversity within the species and lack of apparent association patterns with crop or location indicates limited ecological specialization. The relatively infrequent isolation of M. flavoviride directly from crop roots suggests low dependence of root association for the species.

Robene-Soustrade I., Jouen E., Pastou D., Payet-Hoarau M., Goble T., Linderme D., Lefeuvre P., Calmes C., Reynaud B., Nibouche S., Costet L.

Wang Y., Yu H., Dai Y., Wu C., Zeng W., Yuan F., Liang Z.

A new species, Polycephalomyces agaricus, which is parasitic on Ophiocordyceps sp., a pathogen of melolonthid larvae in southwestern China, is described using morphological and phylogenetic evidence. This species differs morphologically from other species in the genus by its agaric-shaped synnemata, pileus-like slimy masses on short stipes, globose to subglobose α-conidia, and plenty of laterally or apically proliferating phialides. The phylogenetic analyses based on 5-locus (nrSSU, nrLSU, tef-1α, rpb1, and rpb2) data strongly support that this fungus is a distinct species in the genus.

Shrestha B., Hyun M.W., Oh J., Han J., Lee T.H., Cho J.Y., Kang H., Kim S.H., Sung G.

A teleomorph of Beauveria sungii S.A. Rehner & Humber is identified as Cordyceps scarabaeicola Y. Kobayasi based on the teleomorphic material of the B. sungii isolate used in the recent phylogenetic study. Cordyceps Fr. 1818 is an older generic name than Beauveria Vuill. 1912 in Cordyceps sensu stricto. Here, C. scarabaeicola is suggested to be adopted for B. sungii on the priority basis of both generic name and species epithet in compliance with the recent revision of Article 59 of the Melbourne Code (recently changed to the 'International Code of Nomenclature for algae, fungi, and plant' or ICN). The pros and cons of a unified nomenclature for pleomorphic fungi are briefly discussed with reference to Beauveria.

Ding M., Wu L., Yu H., Fan H., Guo Z., Xu S., Chun J., Wang Y., Zheng S.

The banana pseudostem weevil (BPW), Odoiporus longicollis (Oliver), is one of the most destructive pests of bananas that is seriously affecting the yield and quality of bananas. We isolated pathogens from banana pseudostem weevils in Xishuangbanna and Dongchuan, Yunnan, China, and explored their biological characteristics. The pathogenicity of the strains was verified through laboratory and greenhouse inoculation experiments. The results showed that four strains of fungi were identified and confirmed as Beauveria caledonica (Bc) via ITS-rDNA sequencing. Optimal in vitro culture conditions were found to be a photoperiod of 24 h light, 25 °C temperature, and 18 days on potato dextrose agar (PDA) medium with insect meal. Under these conditions, the Cs-1 strain achieved a colony diameter of 65.17 ± 0.74 mm and spore production of 1.24 × 108 cfu/cm2. The Cs-1 strain had the shortest lethal time (LT50) of 9.36 days at an inoculum of 1.00 × 109 cfu/mL, with a lethality of 86.67% after 20 days. The Cs-3 strain showed 77.78% lethality at 1.00 × 108 cfu/mL after 20 days. Despite variations in virulence, lethality did not correlate with major cuticle-degrading enzymes. The Cs-3 strain demonstrated effective biocontrol in greenhouse tests. Banana plants suffered significant damage without Bc-treated BPW, while the treated plantlets thrived. The mortality rate reached 82.78% after 35 days. This study marks the first identification of these entomopathogenic fungi (EPF) in Yunnan, China, highlighting B. caledonica’s potential for biocontrol application.

Kumar D., Roy S., Babu A., Pandey A.K.

ABSTRACTPests and diseases have a significant impact on crop health and yields, posing a serious threat to global agriculture. Effective management strategies, such as integrated pest management (IPM), including crop rotation, use of synthetic pesticides, biological control, and resistant/tolerant crop varieties, are essential to mitigate these risks and ensure sustainable agricultural practices. Fungal bioagents play an important role in managing phytopathogens and insect pests by acting as biological agents. They promote healthy plant growth by enhancing the uptake of nutrients and combating systemic resistance in plants. Furthermore, fungal bioagents are environmentally friendly, reducing application of fungicides and insecticides and minimizing their negative impact on the crops and environment. Their use in IPM promotes sustainable agriculture and ensures high‐quality crops while maintaining soil health and microbial biodiversity. These fungal bioagents are rich sources of volatile organic compounds (VOCs), which play an important role in biological communication during interaction with insect pests and phytopathogens. In pest management, VOC production by beneficial fungi is accountable for their efficacy against pests and pathogens. Thus, this review discusses the important fungal bioagents producing VOCs, extraction methods of VOC, and the use of VOC‐producing fungi in pest and disease management, knowledge gaps, and future research areas.

St Leger R.J.

Metarhizium species interact with plants, insects, and microbes within a diffuse coevolutionary framework that benefits soil health, biodiversity, and plant growth. The insect host ranges of these fungi vary greatly. Specialization to a narrow host range usually occurs in the tropics with its stable insect populations, and is characterized by the rapid evolution of existing protein sequences, sexual recombination, and small genomes. Host-generalists are associated with temperate regions and ephemeral insect populations. Their mutualistic plant-colonizing lifestyle increases survival when insects are rare, while facultative entomopathogenicity feeds both the fungi and plants when insects are common. Generalists have lost meiosis and associated genome defense mechanisms, enabling gene duplications to diversify functions related to plant colonization and host exploitation. Horizontal gene transfer events via transposons have also contributed to host range changes, while parasexuality combines beneficial mutations within individual clones of generalists. There is also a lot of genetic variation in insect populations and both pathogen virulence and insect immunity are linked with variations in stress responses. Thus, susceptibility to generalists can vary due to non-specific resistance to multiple stressors, multipurpose physical and chemical barriers, and heterogeneity in physiological and behavioral factors, such as sleep.

Bhattacharyya P.N., Baishya B., Borgohain D.J., Sarma B., Bhattacharyya L.H., Garganese F., Barman T.S.

Rapid usage of agrochemicals in tea is prohibitive because it has several negative consequences. The current review unveils the biocontrol potential of entomopathogenic fungi, Beauveria bassiana, as a sustainable and non-chemical pest management tactic in tea. Multifarious action mechanisms are highlighted to explore B. bassiana-dependent pest management in tea. Different climatological and physiological factors, such as humidity, moisture, temperature, pH, atmospheric CO2, fungal spore load, spore viability, types of enzymes, host plant chemistry and related interactions including insect life stages possess significant impacts on B. bassiana-mediated pest management in tea. Scientometrics is employed to augment the global recognition of research by quantifying and examining the scientific outcomes associated with using B. bassiana-mediated pest control. Furthermore, biopesticide registration and patenting, improved microbial mass production and standardization, and the commercialization of quality microbial bioformulations demonstrate the significance of these entomopathogenic fungi in sustainable tea pest management.

Vermelho A.B., Moreira J.V., Akamine I.T., Cardoso V.S., Mansoldo F.R.

Pesticide use in crops is a severe problem in some countries. Each country has its legislation for use, but they differ in the degree of tolerance for these broadly toxic products. Several synthetic pesticides can cause air, soil, and water pollution, contaminating the human food chain and other living beings. In addition, some of them can accumulate in the environment for an indeterminate amount of time. The agriculture sector must guarantee healthy food with sustainable production using environmentally friendly methods. In this context, biological biopesticides from microbes and plants are a growing green solution for this segment. Several pests attack crops worldwide, including weeds, insects, nematodes, and microorganisms such as fungi, bacteria, and viruses, causing diseases and economic losses. The use of bioproducts from microorganisms, such as microbial biopesticides (MBPs) or microorganisms alone, is a practice and is growing due to the intense research in the world. Mainly, bacteria, fungi, and baculoviruses have been used as sources of biomolecules and secondary metabolites for biopesticide use. Different methods, such as direct soil application, spraying techniques with microorganisms, endotherapy, and seed treatment, are used. Adjuvants like surfactants, protective agents, and carriers improve the system in different formulations. In addition, microorganisms are a tool for the bioremediation of pesticides in the environment. This review summarizes these topics, focusing on the biopesticides of microbial origin.

Ranesi M., Vitale S., Staropoli A., Di Lelio I., Izzo L.G., De Luca M.G., Becchimanzi A., Pennacchio F., Lorito M., Woo S.L., Vinale F., Turrà D.

Beauveria bassiana (Bb) is a widespread entomopathogenic fungus widely used in agriculture for crop protection. Other than pest control, fungi belonging to the B. bassiana complex represent an important microbial resource in agroecosystems, considering their multiple interactions with other microorganisms as antagonists of phytopathogens, or with plants as endophytic colonizers and growth promoters. Here, we characterised field collected or commercial isolates of B. bassiana relative to the environmental factors that affect their growth. We further compared the metabolome, the entomopathogenic potential and biocontrol activity of the tested isolates respectively on the insect pest Spodoptera littoralis or against the fungal plant pathogen Fusarium oxysporum. Our analysis revealed that the B. bassiana complex is characterised by a high level of inter-isolate heterogeneity in terms of nutritional requirements, establishment of intra- or inter-kingdom interactions, and the nature of metabolites produced. Interestingly, certain B. bassiana isolates demonstrated a preference for low nutrient plant-derived media, which hints at their adaptation towards an endophytic lifestyle over a saprophytic one. In addition, there was a noticeable variation among different B. bassiana isolates in their capacity to kill S. littoralis larvae in a contact infection test, but not in an intrahaemocoelic injection experiment, suggesting a unique level of adaptability specific to the host. On the other hand, most B. bassiana isolates exhibited similar biocontrol efficacy against the soil-dwelling ascomycete F. oxysporum f. sp. lycopersici, a pathogen responsible for vascular wilt disease in tomato plants, effectively averting wilting. Overall, we show that the effectiveness of B. bassiana isolates can greatly vary, emphasising the importance of isolate selection and nutritional adaptability consideration for their use in sustainable agriculture.

Cao W., Yu C., Zhao Y., Lin Q., Deng C., Li C.

In this study, one strain of Beauveria caledonica was isolated from wild fruiting bodies collected from Guizhou Province, China, and its species identification, biological characteristics, domestication, and cultivation methods were studied along with polysaccharide and adenosine content analysis. The mycelia were identified by ITS sequencing, and the fruiting bodies of B. caledonica were domestically cultivated for the first time using wheat and rice as basic cultivation media. The carbon sources, nitrogen sources, cultivation temperatures, and pH for mycelial growth were optimized through single-factor experiments and response surface methodology (RSM) experiments. The polysaccharide content was detected by the phenol–sulfuric acid method, and the adenosine content was measured by high-performance liquid chromatography (HPLC). The results confirmed that the identified mycelia were B. caledonica. The optimum medium for solid culture was 25.8 g/L glycerol, 10.9 g/L yeast extract, 1 g/L MgSO4·7H2O, 1 g/L KH2PO4, 10 mg/L vitamin B1, and 20 g/L agar; the optimum pH was 6.5, and the optimum culture temperature was 25 °C. The optimal liquid culture medium was 26.2 g/L glycerol, 11.1 g/L yeast extract, 1 g/L MgSO4·7H2O, 1 g/L KH2PO4, and 10 mg/L vitamin B1; the mycelia grew well at pH 6.6 and 25 °C. The average biological efficiencies of fruiting bodies on wheat and rice as culture media were 1.880% and 2.115%, respectively; the polysaccharide contents of fruiting bodies on the two media were 6.635% and 9.264%, respectively, while the adenosine contents were 0.145% and 0.150%, respectively. This study provides a valuable reference for further artificial cultivation and utilization of B. caledonica by investigating its biological characteristics, cultivation conditions for artificial domestication, and polysaccharide and adenosine contents in cultivated fruiting bodies.

Deng S., Li N., Yang X., Lu H., Liu J., Peng Z., Wang L., Zhang M., Zhang C., Chen C.

ABSTRACT The entomopathogenic fungus Beauveria bassiana provides an eco-friendly substitute to chemical insecticides for mosquito control. Nevertheless, its widespread application has been hindered by its comparatively slow efficacy in eliminating mosquitoes. To augment the potency of B. bassiana against Aedes mosquitoes, a novel recombinant strain, Bb -Cyt1Aa, was developed by incorporating the Bacillus thuringiensis toxin gene Cyt1Aa into B. bassiana . The virulence of Bb -Cyt1Aa was evaluated against Aedes aegypti and Aedes albopictus using insect bioassays. Compared to the wild-type (WT) strain, the median lethal time (LT 50 ) for A. aegypti larvae infected with Bb -Cyt1Aa decreased by 33.3% at a concentration of 1 × 10 8 conidia/mL and by 22.2% at 1 × 10 7 conidia/mL. The LT 50 for A. aegypti adults infected with Bb -Cyt1Aa through conidia ingestion was reduced by 37.5% at 1 × 10 8 conidia/mL and by 33.3% at 1 × 10 7 conidia/mL. Likewise, the LT 50 for A. aegypti adults infected with Bb -Cyt1Aa through cuticle contact decreased by 33.3% and 30.8% at the same concentrations, respectively. Furthermore, the Bb -Cyt1Aa strain also demonstrated increased toxicity against both larval and adult A. albopictus , when compared to the WT strain. In conclusion, our study demonstrated that the expression of B. thuringiensis toxin Cyt1Aa in B. bassiana enhanced its virulence against Aedes mosquitoes. This suggests that B. bassiana expressing Cyt1Aa has potential value for use in mosquito control. IMPORTANCE Beauveria bassiana is a naturally occurring fungus that can be utilized as a bioinsecticide against mosquitoes. Cyt1Aa is a delta-endotoxin protein produced by Bacillus thuringiensis that exhibits specific and potent insecticidal activity against mosquitoes. In our study, the expression of this toxin Cyt1Aa in B. bassiana enhances the virulence of B. bassiana against Aedes aegypti and Aedes albopictus , thereby increasing their effectiveness in killing mosquitoes. This novel strain can be used alongside chemical insecticides to reduce dependence on harmful chemicals, thereby minimizing negative impacts on the environment and human health. Additionally, the potential resistance of B. bassiana against mosquitoes in the future could be overcome by acquiring novel combinations of exogenous toxin genes. The presence of B. bassiana that expresses Cyt1Aa is of significant importance in mosquito control as it enhances genetic diversity, creates novel virulent strains, and contributes to the development of safer and more sustainable methods of mosquito control.

Sain S.K., Kranthi S., Kranthi K.R., Monga D., Paul D., Prasad Y.G.

Abstract Beauveria bassiana (Bal.-Criv.) is an important entomopathogenic fungus being used for the management of various agricultural pests worldwide. However, all strains of B. bassiana may not be effective against whitefly, Bemisia tabaci, or other pests, and strains show diversity in their growth, sporulation, virulence features, and overall bioefficacy. Thus, to select the most effective strain, a comprehensive way needs to be devised. We studied the diversity among the 102 strains of B. bassiana isolated from 19 insect species based on their physiological features, virulence, and molecular phylogeny, to identify promising ones for the management of B. tabaci. Strains showed diversity in mycelial growth, conidial production, and their virulence against B. tabaci nymphs. The highest nymphal mortality (2nd and 3rd instar) was recorded with MTCC-4511 (95.1%), MTCC-6289 (93.8%), and MTCC-4565 (89.9%) at a concentration of 1 × 106 conidia ml−1 under polyhouse conditions. The highest bioefficacy index (BI) was in MTCC-4511 (78.3%), MTCC-4565 (68.2%), and MTCC-4543 (62.1%). MTCC-4511, MTCC-4565, and MTCC-4543 clustered with positive loading of eigenvalues for the first two principal components and the cluster analysis also corresponded well with PCA (principal component analysis) (nymphal mortality and BI). The molecular phylogeny could not draw any distinct relationship between physiological features, the virulence of B. bassiana strains with the host and location. The BI, PCA, and square Euclidean distance cluster were found the most useful tools for selecting potential entomopathogenic strains. The selected strains could be utilized for the management of the B. tabaci nymphal population in the field through the development of effective formulations. Key points • 102 B. bassiana strains showed diversity in growth and virulence against B. tabaci. • Bioefficacy index, PCA, and SED group are efficient tools for selecting potential strains. • MTCC-4511, 4565, and 4543 chosen as the most virulent strains to kill whitefly nymphs.

Memela N.S., Rutherford R.S., Schmidt S.

AbstractEldana saccharina Walker is a problematic sugarcane stalk borer pest in South Africa. Twenty-eight sugarcane genotypes (Saccharum spp. hybrids) and seven different species of host plants of E. saccharina were surveyed for the presence of endophytic Beauveria bassianasensu lato (s.l.). Collectively, 326 plant samples (roots, stems, or leaves) were collected from five locations in sugarcane-producing areas (KwaZulu-Natal; South Africa). Following plant surface disinfection, 128 fungal colonies morphologically resembling Beauveria spp. were isolated from internal plant tissues. The sequence analysis of the internal transcribed spacer region confirmed that 13 representative isolates were B. bassiana.s.l. Eight B. bassiana isolates were recovered from E. saccharina natural host plants, and 120 from different sugarcane stem parts (top node, top internodes, bottom node, and bottom internode). Endophytic B. bassiana isolates were recovered from 22 of 28 sugarcane genotypes surveyed. The number of B. bassiana isolates obtained from different sugarcane parts differed significantly, with more B. bassiana isolates obtained from the top than the bottom internodes. Furthermore, sugarcane genotypes N31 and N41 yielded B. bassiana from all plant parts sampled, while five sugarcane genotypes harbored no B. bassiana isolates. This study demonstrates for the first time the natural occurrence of endophytic B. bassiana strains in sugarcane plants and E. saccharina host plants in South Africa.

Pastirčáková K., Baková K., Adamčíková K., Barta M., Lalík M., Pavlík M., Kunca A., Galko J., Pastirčák M.

AbstractThe black timber bark beetle (Xylosandrus germanus) is a strongly invasive ambrosia beetle and an important forest pest in Slovakia. This pest is closely associated with symbiotic fungi used as its food source. We investigated the fungi associated with X. germanus adults in Slovakia. In this study, Beauveria bassiana, B. pseudobassiana, Clonostachys rosea, Fusarium oxysporum, Ophiostoma quercus, Phaeoacremonium scolyti, and Talaromyces amestolkiae were isolated and identified by morphological and molecular analyses. The fungus Ophiostoma quercus was most frequently isolated from living beetles, while the entomopathogenic Beauveria bassiana was the most commonly isolated from dead beetles. The morphological descriptions of fungi based on isolates from the surface of X. germanus adults are provided.

Zeng J., Bai J., Wang H., Su X., Wang X., Fu N., Li H.

One common biocontrol strategy employed to combat the wood borer Semanotus bifasciatus Motschulsky (the Chinese fir borer, CFB) is the release of parasitic wasps, specifically Sclerodermus guani Xiao et Wu. However, the rate of parasitism of these wasps is not sufficient to meet the increasing demand for effective control. To address this issue, the present study explored the potential of releasing parasitic wasps carrying spores of the entomopathogen Beauveria bassiana. Vuill. BD01 (Bb@Sg) to enhance the control efficacy against CFB. Administering spore powder on the wasp bodies retained more spores compared with using spore suspensions. Releasing parasitic wasps in a CFB to S. guani ratio of 1:3 resulted in higher rates of parasitism compared with ratios of 1:2 or 1:4. In addition, the Bb@Sg strategy resulted in a mortality rate of 91.55% at day 90 against CFB in a laboratory biocontrol experiment using cypress (Juniperus chinensis L.), being 16.24–19.30% more effective than using only S. guani. Promising results were also observed in the field, where the mortality of CFB in cypress trunks reached 83.36%, 11.62% higher than the rate obtained solely from S. guani release. This study introduces a novel biocontrol strategy for CFB and advances our understanding and application of joint strategies against longhorned beetles and other wood borers.

Manfrino R., Gutierrez A., Ben Gharsa H., Schuster C., López Lastra C., Leclerque A.

It has been the aim of this study to molecular-taxonomically identify 15 Beauveria isolates collected from different geographical regions and insect hosts in Argentina and to investigate the levels of inter- and intra-specific diversity across this set of isolates. Based on phylogenetic analyses of EF1A-RPB1-RPB2 concatenated genes and BLOC markers, all Beauveria strains were identify as B. bassiana. Within the B. bassiana clades of both phylogenies, isolates from Argentina were not clustered according to geographic origin or host. The 15 fungal isolates were further analyzed by PCR amplification of the intron insertion hot spot region of the nuclear 28S rRNA encoding sequence. By intron sequence and position, seven different group-I intron combinations termed variants A, B1, B2, C, D, E and F were found in the 15 isolates under study. Variants B1/B2 consisting of a single 28Si2 intron were found in ten isolates, whereas variant A occurred twice and variants C through F were unique across the set of isolates under study. The determination of the different introns and intron combinations in the 28S rRNA gene is a powerful tool for achieving infraspecific differentiation of B. bassiana isolates from Argentina.

Ferreira J.R., Bitencourt R.D., Angelo I.D., Tondo L.A., Lima P.P., Golo P.S., Matos R.D., Ubiali D.G., Bittencourt V.R.

Rajab L., Ahmad M., Gazal I.

Abstract Background The genus Beauveria (Bals.) Vuill. includes many species, some of which are limited to specific regions while others are distributed worldwide. The diversity of Beauveria species is poorly investigated in Syria and most studies lack proper diagnosis of species. Entomopathogenic isolates of this genus were obtained using the Galleria Bait Method. This study aimed to identify these isolates based on morphological characterizations combined with molecular data, using nuclear ribosomal internal transcribed spacer (ITS) and elongation factor 1-alpha (EF1-α) sequences. The diversity of this genus in Syria has also been evaluated using a phylogenetic analysis of available ITS sequences of Syrian isolates in the GenBank. Results Two entomopathogenic isolates, B195 and B243, were detected in the soil of agro-ecosystems in the Syrian coastal region. Morphological and molecular information revealed that these two isolates belong to Beauveria bassiana (Bals.) Vuill. (Hypocreales: Cordycipitaceae) with 514 bp and 284 bp for the sequences of each isolate for ITS and EF1-α, respectively. Pathogenicity test showed 100% mortality of Galleria mellonella L. larvae 2–3 days post-fungal exposure for both isolates. The phylogenetic tree showed that all Syrian sequences of Beauveria clustered within the species B. bassiana, with a considerable intraspecific diversity, except for two isolates previously identified as B. bassiana, which are closely related to Beuveria pseudobassiana S.A. Rehner and Humber. Conclusions This study presents a morpho-molecular characterization of two Syrian soil-sourced B. bassiana isolates highly pathogenic to G. mellonella larvae and clarifies their phylogenetic placement. Depending on our findings, further exploration studies of the genus Beauveria in Syria are still needed to better our understanding of the diversity and distribution of this entomopathogen in Syria.