Sclerotinia Sclerotiorum Research Articles

In vitro antifungal activity of Datura discolor aqueous extracts obtained by High Pressure Processing

Background/Objective. The present work reports the in vitro effect of aqueous extracts (2, 4 and 6% w/v) of root, seed and leaf of Datura discolor obtained in two times (3 and 6 minutes) at High Pressure Processing, against Sclerotium rolfsii, Sclerotinia sclerotiorum and Colletotrichum gloeosporioides. Materials and Methods. Extracts of roots, seeds and leaves of D. discolor were prepared in a 1:10 w/v ratio with distilled water. Two continuous treatments of high pressure (600 MPa) with pressure maintained for 3 min and another with pressure (600 MPa) maintained for 6 min were considered. The extracts were evaluated against S. rolfsii, S. sclerotiorum and C. gloeosporioides. The experiments were performed in Petri dishes with PDA medium. The efficiency of the extracts was evaluated by obtaining the percentage of inhibition. Results. The results show variable percentages of inhibition of the extracts in the different anatomical parts of the plant and concentrations; The leaf extracts at 6%, regardless of the extraction time, show effectiveness against the three pathogens, with inhibition of 99 and 100%, 55 and 56%, and 43 and 36% for S. rolfsii, S. sclerotiorum and C. gloeosporioides at 3 and 6 minutes respectively. Conclusion. The effectiveness of leaf extract at 6%, six months after its preparation, is similar to the observed with fresh extracts. These results pave the way for future research focused on the sustainable management of phytopathogens. Studies on the biological effectiveness of the extracts in the greenhouse and field are suggested.

Baseline sensitivity and physiological characteristics of natural product hinokitiol against Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum, a pathogenic fungus of oilseed rape, poses a severe threat to the oilseed rapeseed industry. In this study, we evaluated the potential of the natural compound hinokitiol against S. sclerotiorum by determining its biological activity and physiological characteristics. Our results showed that hinokitiol strongly inhibited the hyphae expansion of S. sclerotiorum, and its effective concentration of hyphae growing inhibition by 50% (EC50) against 103 S. sclerotiorum strains varied from 0.36 to 3.45 μg/mL, with an average of 1.23 μg/mL. Hinokitiol possessed better protective efficacy than therapeutic effects, and it exhibited no cross-resistance between carbendazim. After treatment with hinokitiol, many vesicular protrusions developed on the mycelium with rough surface and thickened cell wall. Moreover, the cell membrane permeability and glycerol content increased, while the oxalic acid declined after hinokitiol treatment. In addition, hinokitiol induced membrane lipid peroxidation and improved the production of reactive oxygen species (ROS) in S. sclerotiorum. Importantly, real-time quantitative polymerase chain reaction showed that cell wall and ROS synthesis-related genes were significantly up-regulated after hinokitiol treatment. This study revealed that hinokitiol has good biological activity against S. sclerotiorum and could be considered as an alternative bio-fungicide for the resistance management in controlling sclerotinia stem rot infected by S. sclerotiorum. These investigations provided new insights into understanding the toxic action of hinokitiol against pathogenic fungi. © 2024 Society of Chemical Industry.

Growth Kinetics Modeling and Evaluation of Antiphytopathogenic Activity of Newly Isolated Fungicolous Epicoccum nigrum Associated with Dryad’s Saddle (Polyporaceae)

In the present study, an unknown fungal strain was isolated from the fruiting body of a local Dryad’s Saddle mushroom (Polyporaceae). The molecular identification of the isolate was performed by amplification of the ITS1-5.8S-ITS2 region and the strain was identified with 100.00% confidence as Epicoccum nigrum. The morphological characteristics, including the distinctive colony pigmentation, conidiophore structure, and conidial shape, were determined to ensure comprehensive characterization of the fungus. The modeling of the kinetics of the growth process was conducted with the applying the logistic curve model and the reverse autocatalytic growth model, and the concentrations of the compounds in the nutrient medium required for the E. nigrum development were established. Controlled submerged cultivation was carried out for cultural liquid obtaining, which was further used for the evaluation of the biological activities. The untreated cultural liquid demonstrated antimicrobial activity against Sclerotinia sclerotiorum where the minimal inhibitory concentration was 1.25 mg/mL. Antimicrobial activity was also detected toward Botrytis cinerea (2.5 mg/mL) and Aspergillus flavus (2.5 mg/mL). The direct utilization of crude cultural liquid for phytopathogenic control is a sustainable approach that will provide the opportunity for the development of an environmentally friendly manufacturing process.

Synthesis and Fungicidal Activity Evaluation of Novel Triazole Thione/Thioether Derivatives Containing a Pyridylpyrazole Moiety.

Compounds containing N-pyridylpyrazole motif have aroused interest and brought about research hotspots due to their highly-efficient insecticidal activity. The fungicidal potential of N-pyridylpyrazole derivatives has gradually been disclosed in recent years. To discover new agrochemicals with poly-heterocyclic features, a series of novel triazole thione/thioether derivatives containing pyridylpyrazole motif (8-11) was synthesized. The new compounds were identified by melting point, 1H-NMR, 13C NMR, 19F NMR, HRMS, and elemental analysis. The bioassays showed that most of the pyridylpyrazole-containing triazole thione Mannich bases possessed favorable in vitro fungicidal activity toward pathogenic fungi, such as Magnaporthe oryzae, Sclerotinia sclerotiorum, Botrytis cinerea and Fusarium verticillioides, and were comparable with those of the contrast compounds A and triadimefon. Some of them exhibited moderate to good in vivo fungicidal activity against S. sclerotiorum at 0.2 mg/mL (e. g. 8f control efficacy: 60.9±3.2 %). The SEM observation displayed that 8f might cause disruption of cell membrane and wall of S. sclerotiorum. Compounds 8a, 8c, 8f-8h, 8p and 9b can serve as promising new fungicidal agents to make further structural optimization. The findings in this article provide useful clue and guidance for the design and development of new poly-heterocyclic agrochemicals.

Genetic diversity and virulence variability of Sclerotinia sclerotiorum in Eastern and Northeastern India.

Sclerotinia sclerotiorum, the necrotrophic cosmopolitan fungus, has become an emerging and re-emerging pathogen in the subtropical regions. Genetic diversity of 36 isolates of the fungus isolated from infected samples collected from the eastern and North eastern states was carried out using UP-PCR and SSR. Virulence variability was analysed based on four different measures. Among the eight UP-PCR primers and various combinations used, L-21, 3-2 and AA2M2-AS4 generated maximum number of fingerprints (13, 13 and 12, respectively) ranging from 100bp to 1kb. The isolates exhibited varied level of aggressiveness; majority (77.78%) were moderately virulent, 8.33% (22.22% of Assam and 6.67% of West Bengal) isolates were highly virulent, and 13.89% were less virulent. Several amplification products viz., 500bp generated by AA2M2-AS4, 150bp by AA2M2-L-21 and 100bp by L-21-3-2 were positively correlated with disease severity grading at 5% level of significance, whereas, 600bp band generated by AA2M2-3-2 was correlated at 1% level of significance. This indicates presence of these bands in highly virulent isolates. Out of the eight SSR primers, TATG9 did not generate any amplification and the isolates were divided into two major groups; the group II contained single isolate from Nagaland (NG4) indicating it to be genetically diverse from rest of the isolates. The subgroup A of the major group I was the largest and most diverse group with 11 members indicating genetic admixture within different geographic populations with different levels of similarity (70-100%). Genetic diversity based on SSR banding pattern showed highest value of Nei's gene diversity and Shannon's index of diversity (%pb = 61.11; h = 0.219; I = 0.330) for the Nagaland population with 9 members followed by West Bengal population with 15 members. Nei's genetic distance of all the tested populations was low, ranging from 0.0014 to 0.2350; however, genetic identity was high ranging from 0.7905 to 0.9986. The findings suggest that the pathogen populations of eastern and North eastern region were predominantly clonal with some evidence of infrequent out crossing.

Machine learning-based identification of general transcriptional predictors for plant disease.

This study investigated the generalizability of Arabidopsis thaliana immune responses across diverse pathogens, including Botrytis cinerea, Sclerotinia sclerotiorum, and Pseudomonas syringae, using a data-driven, machine learning approach. Machine learning models were trained to predict disease development from early transcriptional responses. Feature selection techniques based on network science and topology were used to train models employing only a fraction of the transcriptome. Machine learning models trained on one pathosystem where then validated by predicting disease development in new pathosystems. The identified feature selection gene sets were enriched for pathways related to biotic, abiotic, and stress responses, though the specific genes involved differed between feature sets. This suggests common immune responses to diverse pathogens that operate via different gene sets. The study demonstrates that machine learning can uncover both established and novel components of the plant's immune response, offering insights into disease resistance mechanisms. These predictive models highlight the potential to advance our understanding of multigenic outcomes in plant immunity and can be further refined for applications in disease prediction.

Environment, plant genetics, and their interaction shape important aspects of sunflower rhizosphere microbial communities.

Associations with soil microorganisms are crucial for plants' overall health and functioning. While much work has been done to understand drivers of rhizosphere microbiome structure and function, the relative importance of geography, climate, soil properties, and plant genetics remains unclear, as results have been mixed and comprehensive studies across many sites and genotypes are limited. Rhizosphere microbiomes are crucial for crop resistance to pathogens, stress tolerance, nutrient availability, and ultimately yield. Here, we quantify the relative roles of plant genotype, environment, and their interaction in shaping soil rhizosphere communities, using 16S and ITS gene sequencing of rhizosphere soils from 10 genotypes of cultivated sunflower (Helianthus annuus) at 15 sites across the Great Plains of the United States. While site generally outweighed genotype overall in terms of effects on archaeal, bacterial, and fungal richness, community composition, and taxa relative abundances, there was also a significant interaction such that genotype exerted a significant influence on archaeal, bacterial, and fungal microbiomes in certain sites. Site effects were attributed to a combination of spatial distance and differences in climate and soil properties. Microbial taxa that were previously associated with resistance to the fungal necrotrophic pathogen Sclerotinia were present in most sites but differed significantly in relative abundance across sites. Our results have implications for plant breeding and agronomic microbiome manipulations for agricultural improvement across different geographic regions.IMPORTANCEDespite the importance of plant breeding in agriculture, we still have a limited understanding of how plant genetic variation shapes soil microbiome composition across broad geographic regions. Using 15 sites across the Great Plains of North America, we show that cultivated sunflower rhizosphere archaeal, bacterial, and fungal communities are driven primarily by site soil and climatic differences, but genotype can interact with site to influence the composition, especially in warmer and drier sites with lower overall microbial richness. We also show that all taxa that were previously found to be associated with resistance to the fungal pathogen Sclerotinia sclerotiorum were widespread but significantly affected by site, while a subset was also significantly affected by genotype. Our results contribute to a broader understanding of rhizosphere archaeal, bacterial, and fungal community assembly and provide foundational knowledge for plant breeding efforts and potential future microbiome manipulations in agriculture.

Effect of Various pH Levels on the Growth and Sporulation of Trichoderma viride Isolates and Assessing their Antagonistic Activity against Soil-borne Pathogens

Trichoderma viride strains, which are filamentous fungi commonly found in soil, possess the ability to parasitize various fungi harmful to plants. In this study, ten strains of T. viride were isolated from different locations in Uttar Pradesh, India, and examined for their cultural, physiological, morphological, and antagonistic characteristics against soil-borne pathogens. The T. viride isolates were assessed at different pH levels for their growth, sporulation, and antagonistic efficacy under in vitro conditions using the dual culture technique against five major soil-borne pathogens that cause significant diseases in cereal and pulse crops. Among the ten isolates tested, the 49CP isolate from Sultanpur exhibited the maximum growth and sporulation at a pH of 6.5 as well as the highest inhibition percentages of mycelial growth in the pathogens: 63.23% against Fusarium oxysporum f. sp. ciceri, 65.85% against Sclerotium rolfsii, 53.33% against Sclerotinia sclerotiorum, 53.84% against Pythium sp., and 48.00% against Rhizoctonia bataticola. Trichoderma viride is also recognized for its effectiveness as a biocontrol agent against soil-borne pathogens, which are responsible for significant crop losses.

Novel flavonoid derivatives containing 1,2,4-triazole Schiff bases as potential antifungal agents: design, synthesis, and biological evaluation

A series of flavonol derivatives containing 1,2,4-triazole Schiff base was designed, synthesized and tested for their biological activities. The results of the biological activity test showed that compounds exhibited the obvious antifungal activities against Sclerotinia sclerotiorum (S.s), Rhizoctonia solani (R.s), Botrytis cinerea (B.c) and Phomopsis sp (P.s). Among them, K14 showed excellent antimicrobial activity against B.c with the half maximal effective concentration (EC50) of 7.6 µg/mL as compared to azoxystrobin (18.0 µg/mL). Additionally, the in vivo protective and therapeutic activities of K14 on blueberry leaves were 94.1 and 88.7 % respectively, surpassing than that of the control drug azoxystrobin (91.6 and 74.4 %) at 200 µg/mL. The results of SEM showed that the mycelium appeared wrinkled, folded and changed in morphology after being treated with K14. In addition, fluorescence microscopy (FM) and cytoplasmic leakage assays showed that the cell membrane of B.c was disrupted. Further study of malondialdehyde (MDA) and relative conductivity measurements indicated that the normal function of cells is affected by K14 by increasing cell membrane permeability and promoting membrane lipid peroxidation. These results indicate that flavonol derivatives containing 1,2,4-triazole Schiff bases are expected to provide a new prospect for the development of novel fungicides.

Progress in the study of pathogenic factors of Sclerotinia sclerotiorum

Abstract. Sclerotinia sclerotiorum is a devastating soil-borne plant fungal pathogen that can infect over 600 plant species, including important economic crops such as rapeseed, soybeans, and peanuts. Sclerotinia-induced plant diseases are distributed worldwide, and the economic losses caused by sclerotinia fruiting bodies are considerable every year. This article combines relevant research results to discuss the research on Sclerotinia sclerotiorum from four aspects: the biological characteristics and harm of the fungus, the "two-stage" infection model, the roles of oxalic acid, hydrolytic enzymes, and other five pathogenic factors in the pathogenesis of Sclerotinia, and the prevention and control measures of sclerotinia fruiting body disease using traditional methods and HIGS technology.

Development and Biological Evaluation of New Diphenyl Ether Formylhydrazide Compounds as Potent Inhibitors of Succinate Dehydrogenase.

Succinate dehydrogenase (SDH), also recognized as succinate ubiquinone oxidoreductase (SQR), is considered one of the most promising targets for fungicide development, garnering significant international interest. We have focused on the development of highly effective, broad-spectrum-targeted SDH inhibitors. Using an active scaffold combining strategy, we designed and synthesized a series of novel diphenyl ether formylhydrazine derivatives, and most compounds have demonstrated broad-spectrum antifungal activity. Notably, compound M8 exhibited antifungal activity of more than 93% against four tested pathogen types at a concentration of 10 μg/mL, with an EC50 value below 0.3 μg/mL for each pathogen, outperforming boscalid. Additionally, compound M8 exhibited a control efficacy of 83% against Sclerotinia sclerotiorum on rapeseed leaves at a concentration of 200 μg/mL and demonstrated an 87% efficacy in controlling Fusarium graminearum on wheat ears when applied at 400 μg/mL. Structure-activity relationship research suggested that para-substituted benzene rings are more effective, offering stronger and more extensive antifungal potency. Further investigation, including enzyme inhibition assays, mycelial morphology observations, and molecular docking studies, suggests that the antifungal potency of M8 is due to the inhibition of its SDH activity. Therefore, our research positions compound M8 as a highly promising lead compound with broad-spectrum antifungal properties, potentially introducing a new class of fungicide.

Antifungal Activity of Novel Isoindoline-2-Yl Putrescines as Potential Autophagy-Activated Fungicide.

The exacerbation of plant fungal diseases necessitates the development of new fungicides to prevent outbreaks. In this study, five novel isoindoline-2-yl putrescines (ISPs) were synthesized, and their synthetic procedures and gram-scale preparation were explored. When tested at 50 μg mL-1, ISPs did not significantly inhibit mycelial growth on agar plates. However, at 100 μg mL-1, they demonstrated remarkable in vivo efficacy in mitigating Botrytis cinerea infection, especially ISP3 showed curative and protective activities of 91.9 % and 92.6 %, respectively. Moreover, ISP3 also effectively halted lesion expansion of gray mold, Sclerotic rot, and Fusarium scabs, while inducing excessive malformed top mycelial branches of B. cinerea and Sclerotinia sclerotiorum, suppressing sclerotia formation in S. sclerotiorum, and triggering autophagic vacuolization with numerous autophagosomes in the mycelia of these fungi. Molecular docking revealed that ISP3 effectively bound to the active site of BcAtg3, forming hydrogen bonds with Ser279, Gly343, Asp370, and Asp13, along with establishing a stable salt bridge with Asp13. Furthermore, ISP3 possessed favorable ADMET properties. These findings highlight ISP3 as a promising antifungal candidate through autophagy activation.

Zinc finger transcription factors BnaSTOP2s regulate sulfur metabolism and confer Sclerotinia sclerotiorum resistance in Brassica napus.

Rapeseed (Brassica napus L.) exhibits high-sulfur requirements to achieve optimal growth, development, and pathogen resistance. Despite the importance of sulfur, the mechanisms regulating its metabolism and disease resistance are not fully understood. In this study, we found that the zinc finger transcription factors BnaSTOP2s play a pivotal role in sulfur metabolism and Sclerotinia sclerotiorum resistance. Our findings indicate that BnaSTOP2s are involved in sulfur metabolism, as evidenced by extensive protein interaction screening. BnaSTOP2s knockout reduced the content of essential sulfur-containing metabolites, including glucosinolate and glutathione, which is consistent with the significantly lowered transcriptional levels of BnaMYB28s and BnaGTR2s, key factors involved in glucosinolate synthesis and transportation, respectively. Comprehensive RNA-seq analysis revealed the substantial effect of BnaSTOP2s on sulfur metabolism from roots to siliques, which serve as pivotal sources and sinks for sulfur metabolism, respectively. Furthermore, we found that leaf lesion size significantly decreased and increased in the BnaSTOP2-OE and Bnastop2 mutants, respectively, compared with the wild-type during S. sclerotiorum infection, suggesting a vital role of BnaSTOP2s in plant defense response. In conclusion, BnaSTOP2s act as global regulators of sulfur metabolism and confer resistance to S. sclerotiorum infection in B. napus. Thus, they have potential implications for improving crop resilience.

Characterisation of the Phenotypic Reaction of Brazilian Soybean Genotypes to Sclerotinia sclerotiorum Under Controlled Conditions

ABSTRACTWhite mould is a disease caused by the fungus Sclerotinia sclerotiorum, and it is considered one of the most devastating diseases in soybean crops, causing huge losses in productivity. In this study, we aimed to contribute to the genetic control of this disease by characterising the phenotypic reaction of 67 Brazilian soybean genotypes to S. sclerotiorum under controlled conditions. Plants were artificially inoculated with mycelium discs when they reached the four‐node phenological stage. Symptoms of white mould developed in all soybean genotypes. The resistance reaction was characterised by measuring the length of lesions on the main stem at 7 days after inoculation. Of the 67 genotypes evaluated, nine showed greater resistance to S. sclerotiorum, including 17S‐01443‐L8, 16S‐00630‐L4, GER_00003, 13S‐00001‐L2/FPS 2457 RR, BMX Torque I2X, P95Y02 IPRO, 17S‐00842‐L5, HO Pirapó IPRO and TMG 2359 IPRO. Twenty‐three genotypes showed an intermediate response, while 35 genotypes showed greater susceptibility to S. sclerotiorum. Further studies should be conducted under field conditions with the soybean genotypes that showed greater resistance response to S. sclerotiorum under controlled conditions.

The Role of Oxalic Acid in Clarireedia jacksonii Virulence and Development on Creeping Bentgrass.

Dollar spot is a destructive foliar disease of amenity turfgrass caused by Clarireedia spp. fungi, mainly C. jacksonii, on the Northern United States region's cool-season grass. Oxalic acid (OA) is an important pathogenicity factor in related fungal plant pathogens such as Sclerotinia sclerotiorum; however, the role of OA in the pathogenic development of C. jacksonii remains unclear due to its recalcitrance to genetic manipulation. To overcome these challenges, a CRISPR/Cas9-mediated homologous recombination approach was developed. Using this novel approach, the oxaloacetate acetylhydrolase (oah) gene that is required for the biosynthesis of OA was deleted from a C. jacksonii wild-type (WT) strain. Two independent knockout mutants, ΔCjoah-1 and ΔCjoah-2, were generated and inoculated on potted creeping bentgrass along with a WT isolate and a genome sequenced isolate LWC-10. After 12 days, bentgrass inoculated with the mutants ΔCjoah-1 and ΔCjoah-2 exhibited 59.41% lower dollar spot severity compared with the WT and LWC-10 isolates. OA production and environmental acidification were significantly reduced in both mutants when compared with the WT and LWC-10. Surprisingly, stromal formation was also severely undermined in the mutants in vitro, suggesting a critical developmental role of OA independent of plant infection. These results demonstrate that OA plays a significant role in C. jacksonii virulence and provide novel directions for future management of dollar spot. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Evidence of white mold disease caused by Neonectria candida on Morchella importuna

Morels (Morchella sp. pl.) are valuable mushrooms, and their applications in the pharmaceutical and food industries has steadily increased in China.White mold disease is a common and severe disease in the culturing of morels, which is mainly manifested as white villous mycelial infection on the fruiting bodies of these mushrooms. However, the causal agent is not yet known. Therefore, this study aims to identify, at the species level, the causal pathogen of this disease via morphological and molecular methods and then to confirm its pathogenicity through Koch’s postulates. The pathogen was identified as Neonectria candida. Healthy ascocarps were inoculated with N. candida, which produced the initial disease symptoms with white mold appearing at the inoculation sites. The same pathogen was then isolated again from diseased ascocarps. To our knowledge, this is the first report of Morchella importuna ascocarps with white mold disease caused by N. candida in China. Moreover, this report will inform the establishment of sustainable management strategies for white mold disease in morels.

Structure and Fungicidal Activity of Secondary Metabolites Isolated from Trichoderma hamatum b-3.

Two new harziane diterpenes (1-2), five undescribed cyclonerane sesquiterpenes (3-7), and three known compounds, 11-cycloneren-3, 7, 10-triol (8), harziandione (9), and dehydroacetic acid (10), were isolated from Trichoderma hamatum b-3. Their structures were elucidated via comprehensive inspection of spectral evidence in HRESIMS and 1D and 2D NMR, and the absolute configuration of 1-8 was confirmed by NMR, ECD calculation, as well as Mosher's method. In vitro fungicidal activity showed that some compounds showed great inhibitory activity against pathogenic fungi, including Fusarium graminearum, Sclerotinia sclerotiorum, Botrytis cinerea, and Rhizoctonia solani, among which compound 10 showed 100% inhibition of S. sclerotiorum and B. cinerea. The in vivo activity test showed that compound 10 was 65.8% effective against B. cinerea and compound 10 can be used as a lead compound for the development of biopesticides that inhibit B. cinerea. This study elucidated the bioactivity of secondary metabolites of T. hamatum and indicated the direction for the subsequent development of the biological control activity of T. hamatum.

Intrinsic Natural Resistance of Various Plant Pathogens to Ipflufenoquin, a New DHODH (Dihydroorotate Dehydrogenase)-inhibiting Fungicide, in Relation to Unaltered Amino Acid Sequence of the Target Site.

In recent years, increasingly stringent pesticide regulations have made the development of new chemistries challenging. Under these regulations, the new fungicide ipflufenoquin (FRAC Code 52) was first released in Japan. Its mode of action is new; it inhibits dihydroorotate dehydrogenase (DHODH), a key enzyme in the biosynthesis of pyrimidine-based nucleotides. However, because it is a single-site inhibitor, the risk of resistance developing in pathogens must be carefully considered. The risk for dual use of DHODH inhibitors in agriculture and medicine has also become a great concern because a new antifungal olorofim is under development against human pathogens now and cross-resistance has recently been reported between ipflufenoquin and olorofim in Aspergillus fumigatus. In this study, the sensitivity to ipflufenoquin was examined in culture and in plants using "baseline" isolates, which had never been exposed to DHODH inhibitors. Isolates of Alternaria alternata, Botrytis cinerea, B. elliptica, Colletotrichum fioriniae, C. fructicola, C. nymphaeae, C. orbiculare, C. siamense, C. tropicale, C. truncatum, and Sclerotinia sclerotiorum were highly sensitive to ipflufenoquin in culture, but isolates of Coniella vitis, Corynespora cassiicola, Pseudocercospora fuligena, and Rhizoctonia solani were inherently resistant. Ipflufenoquin had low efficacy against C. cassiicola and C. vitis after inoculation of cucumber and grapevine leaves, respectively. To understand the mechanism of natural resistance, we analyzed the partial sequence of pyrE genes, which encode the DHODH enzyme, but did not find any differences in the deduced amino acids that were thought to be associated with resistance. Thus, mechanisms other than target-site mutations might be involved in the intrinsic resistance.

Design, synthesis and antifungal activity of arylhydrazine analogs containing diphenyl ether fragments.

Succinate dehydrogenase (SDH) represents a critical target in the development of novel fungicides. To address the growing issue of resistance and safeguard the economic viability of agricultural production, the pursuit of new succinate dehydrogenase inhibitors (SDHIs) has emerged as a significant focus of contemporary research. In this project, 32 arylhydrazine derivatives containing diphenyl ether structural units were synthesized and evaluated for their fungicidal activities against Rhizoctonia solani, Sclerotinia sclerotiorum, Alternaria alternata, Gibberella zeae, Alternaria solani and Colletotrichum gloeosporioides. In an in vitro fungicidal activity assay, compound D6 showed significant inhibitory activity against R. solani with a half-maximum effective concentration (EC50) of 0.09 mg L-1. The in vivo fungicidal activity demonstrated that compound D6 inhibited R. solani by 95.39% in rice leaves, which was significantly better than that of boscalid (85.76%). The results of SDH enzyme assay, molecular docking simulation, mitochondrial membrane potential assay, cytoplasmic release studies and morphological observations demonstrated that the target compound D6 not only had significant SDH inhibitory activity, but also affected the membrane integrity of mycelium. Bioactivity screening and validation of the mechanism of action indicated that compound D6 was a potentially unique SDHI, acting on SDH while also affecting cell membrane permeability, which deserved further study. © 2024 Society of Chemical Industry.

Exploration of the Sclerotinia sclerotiorum-Brassica pathosystem: advances and perspectives in omics studies.

The polyphagous phytopathogen Sclerotinia sclerotiorum causing Stem rot disease is a major biotic stress in Brassica, and affects the yield and quality in various crops of agricultural significance. It affects the crop at pre-maturity which causes a reduction in the seed yield and deteriorates the oil quality in rapeseeds and Indian mustard globally. The hemibiotrophic nature and long persistence in the soil as sclerotia have made this pathogen difficult to manage through conventional agronomical practices. Hence, for alternative strategies, it is important to understand the basic aspects of the pathogen and the pathogenesis processes in the host. The current developments in technologies for omics studies including whole-genomes, transcriptomes, proteomes, and metabolomes have deciphered various genes, transcription factors, effectors and their target molecules involved in interaction, disease establishment and pathogen progress in the host tissues. The current review encompasses the studies that were conducted to decipher the Brassica-S. sclerotiorum pathosystem and the molecular factors identified through multi-omics studies for their application in building resistance to Sclerotinia stem rot disease in the susceptible cultivars of oilseed Brassica.