Search Results (22)

Foliar diseases caused by various fungi severely affect the yield and quality of banana crops. This study was conducted to clarify the biological characteristics of Bipolaris oryzae (teleomorph: Cochliobolus miyabeanus), a pathogen reported in 2023 as a new etiological agent of leaf spot in the banana variety ‘Pisang Mas’ (Musa acuminata, AA group) in Hainan Province, China, and to screen effective fungicides for its control. The results indicated that banana leaf extract agar (BLEA) and cornmeal agar (CMA) were the best media for the growth and sporulation of the pathogen, respectively. The pathogen grew best on a Czapek’s agar (CZA) medium with sucrose as a carbon source and yeast extract as a nitrogen source, while the optimal carbon and nitrogen sources for sporulation were lactose and beef extract, respectively. The pathogen could grow within a temperature range from 5 °C to 35 °C, and the optimal temperatures for growth and sporulation were 30 °C and 25 °C, respectively. Exposure to 50 °C for 10 min was lethal. Additionally, the pathogen could grow and sporulate within pH ranges of 4 to 10 and 4 to 9, respectively, and the optimal pH values for growth and sporulation were 5 and 8, respectively. The optimal photoperiods for growth and sporulation were 16 h light/8 h dark and 24 h light, respectively. Among the 12 tested fungicides, 500 g/L of iprodione SC showed the highest toxicity against B. oryzae, with an EC₅₀ value of 0.08 μg/mL, followed by 30% difenoconazole-azoxystrobin SC and 125 g/L of epoxiconazole SC, with EC₅₀ values of 0.13 μg·mL⁻¹ and 0.20 μg/mL, respectively. A fungicide containing 40% chlorothalonil SC had the poorest fungicidal activity, with an EC₅₀ value of 155.98 μg/mL. An artificial inoculation pot experiment showed that 125 g/L of epoxiconazole SC at 250 μg/mL, 500 g/L of iprodione SC at 1667 μg/mL, and 30% difenoconazole-azoxystrobin SC at 250 μg/mL provided a protective control efficacy of 100% against B. oryzae, while 125 g/L of epoxiconazole SC at 250 μg/mL and 500 g/L of iprodione SC at 1667 μg/mL provided a curative control efficacy of greater than 60%. This study clarified the optimal conditions for the mycelial growth and sporulation of B. oryzae isolated from banana and screened out fungicides with effective inhibitory activities. These results can provide guidance for field applications and the management of leaf spot caused by B. oryzae in banana. Full article

Rice brown spot disease, caused by Bipolaris oryzae, is a significant fungal disease that poses a major threat to global rice production. Despite its widespread impact, genomic studies of B. oryzae remain limited, particularly those involving high-quality genomic data. In this study, we performed whole-genome sequencing of the B. oryzae strain RBD1, which was isolated from the demonstration field for upland rice cultivation in Haozhiba Village, Lancang County, Pu’er City, Yunnan Province, China, using a combination of second-generation Illumina sequencing and third-generation Single-Molecule Real-Time (SMRT) sequencing. The assembled genome was 37.5 Mb in size with a G + C content of 49.39%, containing 42 contigs with a contig N50 of 2.0 Mb. Genomic analysis identified genes related to carbon, nitrogen, and lipid metabolism, highlighting the strain’s metabolic flexibility under diverse environmental conditions and host interactions. Additionally, we identified pathogenicity-related genes involved in MAPK signaling, G protein signaling, and oxidative stress responses. Under 1.2 M sorbitol-induced osmotic stress, we observed significant differences in growth responses between RBD1 and the rice blast fungus Magnaporthe oryzae H7. Transcriptomic analysis using Illumina sequencing revealed that RBD1 responds to osmotic stress by enhancing carbohydrate metabolism, fatty acid degradation, and amino acid synthesis, while H7 primarily relies on protein synthesis to enhance growth tolerance. This study provides a valuable foundation for understanding the pathogenic mechanisms of rice brown spot and future disease control strategies. Full article

Pleosporales represents the largest order within the class Dothideomycetes (Fungi), comprising phytopathogenic, saprobic, and endophytic taxa with a widespread presence in terrestrial and aquatic environments. Rice (Oryza sativa) is a primary economic crop in numerous tropical countries, particularly in Thailand. Studying fungal species associated with rice holds the potential to enhance our understanding of fungal diversity, lifestyles, and biology of rice, offering valuable insights for future research aimed at disease management and yield improvement. Thirty-nine pleosporalean isolates were obtained from various parts of rice plants collected across diverse regions in Chiang Rai Province, Thailand. Species identification involved a combination of morphology and molecular phylogeny, utilizing multi-locus sequence analyses of the ITS, LSU, SSU, gapdh, rpb2, tef1, and tub2 genes. The isolates were identified in 18 taxa distributed across five families and ten genera, including five new species (Bipolaris chiangraiensis, Ophiosphaerella oryzae, Paraphaeosphaeria oryzae, Pyrenochaetopsis oryzicola, and Setophoma oryzicola). Additionally, six new host records and two new geographical records are documented. Photoplates, detailed morphological descriptions, and phylogenetic trees are provided to elucidate the placement of both known and novel taxa. Full article

Magnaporthe oryzae, one of the most destructive rice pathogens, causes significant losses during the rice harvest every year. Bacillus amyloliquefaciens has been explored in many crops as a potential biocontrol agent. However, the mechanisms of B. amyloliquefaciens controled rice blast are not fully understood. Here, a biocontrol strain LM-1, isolated from a contaminated medium, was identified as B. amyloliquefaciens using morphological observation, physiological and biochemical tests, and 16S rDNA sequencing. LM-1 inhibited the growth and pathogenicity of M. oryzae and Bipolaris oryzae (Breda de Haan) Shoem. The mycelia of M. oryzae co-cultured with LM-1 were enlarged and broken by fluorescence microscopy using calcofluor white. LM-1 inhibited the mycelia of M. oryzae from producing conidia. Genes itu, srf, and fenB were detected in LM-1. Furthermore, the supernatant of LM-1 interfered with the appressorium formation of M. oryzae, blocked conidial cell death, and reduced autophagy degradation but did not affect the normal germination of rice seeds and seeding growth. Additionally, we observed hypersensitivity reactions, reactive oxygen species, and iron accumulation reduction in rice cells inoculated with supernatant. Our study reveals that LM-1 has a control effect on rice blast and affects cell wall integrity, sporulation, appressorium formation, cell death, and autophagy. Full article

Crop fungal diseases pose a serious threat to global crop production and quality. Developing new and efficient fungicides is an important measure to control crop diseases. Phenylthiazole was found to be an excellent antifungal skeleton based on our previous study on the structural optimization and biological activity of the natural product thiasporine A. To find new fungicides, 45 phenylthiazole derivatives containing an acylhydrazone moiety were designed and synthesized by the principle of active substructure splicing. Forty-two of the forty-five compounds are novel, except for compounds E1, E14, and E33. Their structures were structurally characterized by ¹H NMR, ¹³C NMR, and HRMS. The antifungal activities of the target compounds against Magnaporthe oryzae Colletotrichum camelliaet, Bipolaris maydis, and Sclerotinia sclerotiorum were evaluated at 25 μg/mL. The bioassay results revealed that most of these compounds exhibited excellent antifungal activities against M. oryzae and C. camelliaet at 25 μg/mL. In particular, compounds E4, E10, E14, E17, E23, E26, and E27 showed the inhibition rate of more than 80% against M. oryzae, with EC₅₀ values of 1.66, 2.01, 2.26, 1.45, 1.50, 1.29, and 2.65 μg/mL, respectively, which were superior to that of the commercial fungicides Isoprothiolane (EC₅₀ = 3.22 μg/mL) and Phenazine-1-carboxylic acid (EC₅₀ = 27.87 μg/mL). The preliminary structure–activity relationship (SAR) results suggested that introducing methyl, halogen, or methoxy at the ortho-position of R¹ and the para-position of R² can endow the final structure with excellent antifungal activity against M. oryzae. The current results provide useful data for developing phenylthiazole derivatives as new fungicides for controlling rice blast caused by M. oryzae. Full article

The ability of microorganisms to promote plant growth and mitigate abiotic and biotic stresses makes them an interesting tool for sustainable agriculture. Numerous studies aim to identify new, promising bacteria isolates. Traditional culture-based methods, which focus on selecting microorganisms with plant-growth-promoting traits, such as hormone production, nutrient solubilization, and antifungal properties, are widely used. This study aims to investigate the role of plant-growth-promoting properties in bacteria-mediated stress mitigation and the suitability of traditional culture-based methods as a screening tool for the identification of beneficial bacteria. To this end, we tested three endophytic Bacillus isolates, which have previously been shown to affect tolerance against iron toxicity in lowland rice, (a) for their effect on the resistance against brown spot disease, and (b) for plant-growth-promoting traits using common culture-based methods. Both B. pumilus isolates inhibited fungal growth in vitro and reduced brown spot disease in two of three rice cultivars in planta, although they tested negative for all plant-growth-promoting traits. While B. megaterium was negative for ACC deaminase activity and nutrient solubilization, it exhibited auxin production. Nevertheless, B. megaterium did not suppress brown spot disease in any of the three rice cultivars. This study shows that bacteria do not necessarily have to possess classical plant-growth-promoting properties in order to be beneficial to plants, and it emphasizes the limitation of common culture-based methods in effectively identifying beneficial bacteria. Moreover, our results highlight the significance of the interaction between bacteria and plant cultivars in determining the beneficial effects of Bacillus spp. on plants under biotic or abiotic stresses. Full article

Dirty panicle disease is one of the most important diseases that can cause yield losses in rice production. Despite the severity of the disease, the molecular basis of resistance to the pathogen is poorly understood. Using QTL-seq with an F₂ population, we identified three genomic regions on chromosomes 1, 9, and 10, namely qDP1, qDP9, and qDP10. These regions are significantly associated with resistance to dirty panicle disease caused by two fungal pathogens, Bioplaris oryzae and Cirvularia lunata. qDP1 was significantly associated only with resistance to B. oryzae, whereas qDP9 and qDP10 were significantly associated with both B. oryzae and C. lunata. We also developed KASP markers for each QTL detected and validated them in the F₂ population. The markers were able to explain phenotypic variation in a range of 5.87–15.20%. Twelve potential candidate genes with annotated functions as resistance-related genes were proposed. These candidate genes include those encoding RLK, MATE, WAK, NBS-LRR, subtilisin-like protease, and ankyrin repeat proteins. The results of this study provide insights into the genetic mechanism of dirty panicles in rice and will be useful for future breeding programs for dirty panicle resistance. This is the first report of QTLs associated with resistance to dirty panicle disease in rice. Full article

Five undescribed pentaketide derivatives, (R)-6,8-dihydroxy-4,5-dimethyl-3-methylidene-3,4-dihydro-1H-2-benzopyran-1-one (1), [(3S,4R)-3,8-dihydroxy-6-methoxy-4,5-dimethyl-1-oxo-3,4-dihydro-1H-isochromen-3-yl]methyl acetate (2), (R)-5, 7-dimethoxy-3-((S)-(1-hydroxyethyl)-3,4-dimethylisobenzofuran-1(3H)-one (4b), (S)-7-hydroxy-3-((S)-1-hydroxyethyl)-5-methoxy-3,4-dimethylisobenzofuran 1(3H)-one (5), and a p-hydroxyphenyl-2-pyridone derivative, avellaneanone (6), were isolated together with the previously reported (R)-3-acetyl-7-hydroxy-5-methoxy-3,4-dimethylisobenzofuran-1(3H)-one (3), (R)-7-hydroxy-3-((S)-1-hydroxyethyl)-5-methoxy-3,4-dimethylisobenzofuran-1(3H)-one (4a) and isosclerone (7), from the ethyl acetate extract of a culture of a marine sponge-derived fungus, Hamigera avellanea KUFA0732. The structures of the undescribed compounds were elucidated using 1D and 2D NMR, as well as high-resolution mass spectral analyses. The absolute configurations of the stereogenic carbons in 1, 4b, 5, and 6 were established by X-ray crystallographic analysis. The absolute configurations of C-3 and C-4 in 2 were determined by ROESY correlations and on the basis of their common biosynthetic origin with 1. The crude fungal extract and the isolated compounds 1, 3, 4b, 5, 6, and 7 were assayed for their growth inhibitory activity against various plant pathogenic fungi viz. Alternaria brassicicola, Bipolaris oryzae, Colletotrichum capsici, C. gloeosporiodes, Curvularia oryzae, Fusarium semitectum, Lasiodiplodia theobromae, Phytophthora palmivora, Pyricularia oryzae, Rhizoctonia oryzae and Sclerotium rolfsii. Full article

The infection biology of Bipolaris oryzae and the defence responses of its host rice were studied using the rice cv. MTL 189 inoculated with two isolates of B5 (highly compatible with MTL 189) and K2 (less compatible). In the former interaction, the hyphal progress was accompanied by tissue degradation and extensive sporulation after 8 days, whereas in the latter interaction, only very limited tissue degradation and sporulation was observed. Quantitative microscopy of the infection showed that the percentages of conidia and appressoria causing penetration and fluorescent epidermal cells (FEC) were lower for isolate K2 than for isolate B5 at 12 and 24 hours after inoculation (hai). Fluorescent papillae (FP) were only seen in the less compatible interaction and the percentage of conidia causing single FEC was highest in the less compatible interaction at 12 hai, but not at 24 hai. Qualitative examination of other defence responses showed that H₂O₂ started to accumulate at 4 hai in the less compatible interaction, whereas it appeared in the compatible interaction only at 12 hai. The level of H₂O₂ was generally higher in the less compatible than in the compatible interaction. Cross sections of leaves showed that H₂O₂ accumulated in the outer walls of epidermal cells. Likewise, accumulation of callose and polyphenolic substances was most pronounced in the less compatible interaction and occurred at the same places as H₂O₂. To our knowledge, this is the first report implicating H₂O₂ as an early defence response against the hemibiotrophic pathogen B. oryzae during early infection stages in rice. Understanding defence reactions may aid in resistance breeding. Full article

A gene encoding a protein similar to germin-like proteins (GLPs) was obtained from maize (Zea mays) and designated as ZmGLP1. Based on the ZmGLP1 conserved domain and phylogenetic status, ZmGLP1 was grouped into GLP subfamily b and has high similarity to OsGLP8-14 from Oryza sativa. ZmGLP1 is expressed in different maize tissues during different growth stages and is mainly expressed in the stems and leaves. The induced expression patterns confirmed that ZmGLP1 is differentially expressed under abiotic and hormone stress; it had an early response to jasmonic acid (JA) and ethephon (ET) but a late response to salicylic acid (SA) and was significantly upregulated under Bipolaris maydis infection. The overexpression of ZmGLP1 in Arabidopsis improved the resistance to biotrophic Pseudomonas syringae pv. tomato DC3000 (PstDC3000) and necrotrophic Sclerotinia sclerotiorum by inducing the expression of JA signaling-related genes. Moreover, the hydrogen peroxide (H₂O₂) content increased due to the overexpression of ZmGLP1 in Arabidopsis after pathogen infection. Compared to the wild-type control, the H₂O₂ content of ZmGLP1-overexpressing Arabidopsis infected by PstDC3000 increased significantly but was lower in transgenic plants infected with S. sclerotiorum. Furthermore, high-performance liquid chromatography–tandem mass (HPLC-MS/MS) spectrometry showed that the JA contents of ZmGLP1-overexpressing Arabidopsis markedly increased after pathogen infection. However, the improved resistance of ZmGLP1-overexpressing Arabidopsis pretreated with the JA biosynthetic inhibitor, sodium diethyldithiocarbamate trihydrate (DIECA), was suppressed. Based on these findings, we speculate that ZmGLP1 plays an important role in the regulation of Arabidopsis resistance to biotrophic PstDC3000 and necrotrophic S. sclerotiorum; the regulatory effects are achieved by inducing plant oxidative burst activity and activation of the JA signaling pathway. Full article

Rhizoctonia cerealis is the causal agent of sharp eyespot, a devastating disease of cereal crops including wheat. Several metalloproteases have been implicated in pathogenic virulence, but little is known about whole-genome metalloproteases in R. cerealis. In this study, a total of 116 metalloproteases-encoding genes were identified and characterized from the R. cerealis Rc207 genome. The gene expression profiles and phylogenetic relationship of 11 MEP36/fungalysin metalloproteases were examined during the fungal infection to wheat, and function of an upregulated secretory MEP36 named RcFL1 was validated. Of 11 MEP36 family metalloproteases, ten, except RcFL5, were predicted to be secreted proteins and nine encoding genes, but not RcFL5 and RcFL2, were expressed during the R. cerealis infection process. Phylogenetic analysis suggested that MEP36 metalloproteases in R. cerealis were closely related to those of Rhizoctonia solani but were remote to those of Bipolaris sorokiniana, Fusarium graminearum, F. pseudograminearum, and Pyricularia oryzae. Expression of RcFL1 was significantly upregulated during the infection process and induced plant cell death in wheat to promote the virulence of the pathogen. The MEP36 domain was necessary for the activities of RcFL1. Furthermore, RcFL1 could repress the expression of wheat genes coding for the chitin elicitor receptor kinase TaCERK1 and chitinases. These results suggest that this MEP36 metalloprotease RcFL1 may function as a virulence factor of R. cerealis through inhibiting host chitin-triggered immunity and chitinases. This study provides insights on pathogenic mechanisms of R. cerealis. RcFL1 likely is an important gene resource for improving resistance of wheat to R. cerealis through host-induced gene silencing strategy. Full article

Switchgrass (Panicum virgatum L.), a northern native perennial grass, suffers from yield reduction from Bipolaris leaf spot caused by Bipolaris oryzae (Breda de Haan) Shoemaker. This study aimed to determine the resistant populations via multiple phenotyping approaches and identify potential resistance genes from genome-wide association studies (GWAS) in the switchgrass northern association panel. The disease resistance was evaluated from both natural (field evaluations in Ithaca, New York and Phillipsburg, Philadelphia) and artificial inoculations (detached leaf and leaf disk assays). The most resistant populations based on a combination of three phenotyping approaches—detached leaf, leaf disk, and mean from two locations—were ‘SW788’, ‘SW806’, ‘SW802’, ‘SW793’, ‘SW781’, ‘SW797’, ‘SW798’, ‘SW803’, ‘SW795’, ‘SW805’. The GWAS from the association panel showed 27 significant SNPs on 12 chromosomes: 1K, 2K, 2N, 3K, 3N, 4N, 5K, 5N, 6N, 7K, 7N, and 9N. These markers accumulatively explained the phenotypic variance of the resistance ranging from 3.28 to 26.52%. Within linkage disequilibrium of 20 kb, these SNP markers linked with the potential resistance genes included the genes encoding for NBS-LRR, PPR, cell-wall related proteins, homeostatic proteins, anti-apoptotic proteins, and ABC transporter. Full article

Kazakhstan is the fourteenth largest wheat producer in the world. Despite this fact, there has not been a comprehensive survey of wheat root and crown rot. A quantitative survey was conducted for the purpose of establishing the distribution of fungi associated with root and crown rot on wheat (Triticum spp.). During the 2019 growing season, samples were taken from the affected plants’ roots and stem bases. A total of 1221 fungal isolates were acquired from 65 sites across the central (Karagandy region), eastern (East Kazakhstan region), and southeastern (Almaty region) parts of the country and identified using morphological and molecular tools. The internal transcribed spacer (ITS), translation elongation factor 1-alpha (EF1-α), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) sequences were successfully used to identify the species of fungal isolates. It was found that Bipolaris sorokiniana (44.80%) and Fusarium acuminatum (20.39%) were the most predominant fungal species isolated, which were present in 86.15 and 66.15% of the fields surveyed, respectively, followed by F. equiseti (10.16%), Curvularia spicifera (7.62%), F. culmorum (4.75%), F. oxysporum (4.10%), F. redolens (2.38%), Rhizoctonia solani AG2-1 (1.06%), Nigrospora oryzae (0.98%), C. inaequalis (0.90%), F. pseudograminearum (0.74%), F. flocciferum (0.74%), Macrophomina phaseolina (0.66%), F. cf. incarnatum (0.33%), Fusarium sp. (0.25%), and F. torulosum (0.16%). A total of 74 isolates representing 16 species were tested via inoculation tests on the susceptible Triticum aestivum cv. Seri 82 and the results revealed that F. culmorum and F. pseudograminearum, B. sorokiniana, Fusarium sp., R. solani, F. redolens, C. spicifera, C. inaequalis, and N. oryzae were virulent, whereas others were non-pathogenic. The findings of this investigation demonstrate the presence of a diverse spectrum of pathogenic fungal species relevant to wheat crown and root rot in Kazakhstan. To the best of our knowledge, this is the first report of F. pseudograminearum, Fusarium sp., C. spicifera, and C. inaequalis as pathogens on wheat in Kazakhstan. Full article

Composition of phytopathogens—causal agents of “black point” was studied in 2018–2019. Investigations were carried out at the Institute of Plant Protection of National Academy of Agrarian Sciences of Ukraine. Seed samples were taken from different locations in the Forest-Steppe and Polissya zones of Ukraine. The results obtained showed that fungi from the genus Alternaria Nees dominated in the pathogen complex. They were isolated from 76.5–83.1% of seeds from the Forest-Steppe of Ukraine. Less often they were found in samples from the Polissya zone (59.0–69.4%). Alternaria tenuissima тa Alternaria infectoria were isolated in an almost equal proportion. In addition, seeds with “black point” were colonized by fungi from genera Fusarium Link, Curvularia Boed, Bipolaris Shoem., Aspergillus P.Micheli, Nigrospora Zimm., Cladosporium Link, Acremoniella Sacc., Stemphillium Walr., Sordaria Ces. & De Not, Epicoccum Link, Aureobasidium Viala at Boy. It should be noted that the causal agent of nigrospora dry rot of maize Nigrospora oryzae (Berk & Broom) Petch was isolated from nearly 6% of seeds from the Polissya zone. In addition, saprophitic fungi Stemphillium spp. and Sordaria spp. were found. The majority of isolated fungi produce mycotoxins which are harmful for people and animals. Thus, the monitoring of species composition of pathogens on wheat seeds, in particular causal agents of “black point”, is essential for obtaining a high-quality wheat grain. Full article

A series of tetrahydro-ß-carbolines substituted with an alkyl or acyl side chain was synthesized and screened for its antifungal activity against plant pathogenic fungi (Bipolaris oryzae, Curvularia lunata, Fusarium semitectum, and Fusarium fujikuroi). The structure activity relationship revealed that the substituent at the piperidine nitrogen plays an important role for increasing antifungal activities. In this series, 2-octyl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole (3g) displayed potent antifungal activities with a minimum inhibitory concentration of 0.1 μg/mL, including good inhibitory activity to the radial growth of fungus at a concentration of 100 μg/mL compared to amphotericin B. Full article