Compounds Released by the Biocontrol Yeast Hanseniaspora opuntiae Protect Plants Against Corynespora cassiicola and Botrytis cinerea

Bacteria from the skin of amphibians promote growth of Arabidopsis thaliana and Solanum lycopersicum by modifying hormone-related transcriptome response

Plants and microorganisms establish beneficial associations that can improve their development and growth. Recently, it has been demonstrated that bacteria isolated from the skin of amphibians can contribute to plant growth and defense. However, the molecular mechanisms involved in the beneficial effect for the host are still unclear. In this work, we explored whether bacteria isolated from three tropical frogs species can contribute to plant growth. After a wide screening, we identified three bacterial strains with high biostimulant potential, capable of modifying the root structure of Arabidopsis thaliana plants. In addition, applying individual bacterial cultures to Solanum lycopersicum plants induced an increase in their growth. To understand the effect that these microorganisms have over the host plant, we analysed the transcriptomic profile of A. thaliana during the interaction with the C32I bacterium, demonstrating that the presence of the bacteria elicits a transcriptional response associated to plant hormone biosynthesis. Our results show that amphibian skin bacteria can function as biostimulants to improve agricultural crops growth and development by modifying the plant transcriptomic responses.

Amphibian skin bacteria display antifungal activity and induce plant defense mechanisms against Botrytis cinerea

Botrytis cinerea is the causal agent of gray mold, which affects a wide variety of plant species. Chemical agents have been used to prevent the disease caused by this pathogenic fungus. However, their toxicity and reduced efficacy have encouraged the development of new biological control alternatives. Recent studies have shown that bacteria isolated from amphibian skin display antifungal activity against plant pathogens. However, the mechanisms by which these bacteria act to reduce the effects of B. cinerea are still unclear. From a diverse collection of amphibian skin bacteria, three proved effective in inhibiting the development of B. cinerea under in vitro conditions. Additionally, the individual application of each bacterium on the model plant Arabidopsis thaliana, Solanum lycopersicum and post-harvest blueberries significantly reduced the disease caused by B. cinerea. To understand the effect of bacteria on the host plant, we analyzed the transcriptomic profile of A. thaliana in the presence of the bacterium C32I and the fungus B. cinerea, revealing transcriptional regulation of defense-related hormonal pathways. Our study shows that bacteria from the amphibian skin can counteract the activity of B. cinerea by regulating the plant transcriptional responses.

Exploring future applications of the apiculate yeast Hanseniaspora

As a metaphor, lemons get a bad rap; however the proverb 'if life gives you lemons, make lemonade' is often used in a motivational context. The same could be said of Hanseniaspora in winemaking. Despite its predominance in vineyards and grape must, this lemon-shaped yeast is underappreciated in terms of its contribution to the overall sensory profile of fine wine. Species belonging to this apiculate yeast are known for being common isolates not just on grape berries, but on many other fruits. They play a critical role in the early stages of a fermentation and can influence the quality of the final product. Their deliberate addition within mixed-culture fermentations shows promise in adding to the complexity of a wine and thus provide sensorial benefits. Hanseniaspora species are also key participants in the fermentations of a variety of other foodstuffs ranging from chocolate to apple cider. Outside of their role in fermentation, Hanseniaspora species have attractive biotechnological possibilities as revealed through studies on biocontrol potential, use as a whole-cell biocatalyst and important interactions with Drosophila flies. The growing amount of 'omics data on Hanseniaspora is revealing interesting features of the genus that sets it apart from the other Ascomycetes. This review collates the fields of research conducted on this apiculate yeast genus.

Melatonin as a master regulatory hormone for genetic responses to biotic and abiotic stresses in model plant Arabidopsis thaliana: a comprehensive review

Melatonin is a naturally occurring biologically active amine produced by plants, animals and microbes. This review explores the biosynthesis of melatonin in plants, with a particular focus on its diverse roles in Arabidopsis thaliana , a model species. Melatonin affects abiotic and biotic stress resistance in A. thaliana . Exogenous and endogenous melatonin is addressed in association with various conditions, including cold stress, high light stress, intense heat and infection with Botrytis cinerea or Pseudomonas , as well as in seed germination and lateral root formation. Furthermore, melatonin confers stress resistance in Arabidopsis by initiating the antioxidant system, remedying photosynthesis suppression, regulating transcription factors involved with stress resistance (CBF, DREB, ZAT, CAMTA, WRKY33, MYC2, TGA) and other stress-related hormones (abscisic acid, auxin, ethylene, jasmonic acid and salicylic acid). This article additionally addresses other precursors, metabolic components, expression of genes (COR , CBF , SNAT , ASMT , PIN , PR1 , PDF1.2 and HSFA ) and proteins (JAZ, NPR1) associated with melatonin and reducing both biological and environmental stressors. Furthermore, the future perspective of melatonin rich agri-crops is explored to enhance plant tolerance to abiotic and biotic stresses, maximise crop productivity and enhance nutritional worth, which may help improve food security.

A biostimulant yeast, Hanseniaspora opuntiae, modifies Arabidopsis thaliana root architecture and improves the plant defense response against Botrytis cinerea

MAIN CONCLUSION

The biostimulant Hanseniaspora opuntiae regulates Arabidopsis thaliana root development and resistance to Botrytis cinerea. Beneficial microbes can increase plant nutrient accessibility and uptake, promote abiotic stress tolerance, and enhance disease resistance, while pathogenic microorganisms cause plant disease, affecting cellular homeostasis and leading to cell death in the most critical cases. Commonly, plants use specialized pattern recognition receptors to perceive beneficial or pathogen microorganisms. Although bacteria have been the most studied plant-associated beneficial microbes, the analysis of yeasts is receiving less attention. This study assessed the role of Hanseniaspora opuntiae, a fermentative yeast isolated from cacao musts, during Arabidopsis thaliana growth, development, and defense response to fungal pathogens. We evaluated the A. thaliana-H. opuntiae interaction using direct and indirect in vitro systems. Arabidopsis growth was significantly increased seven days post-inoculation with H. opuntiae during indirect interaction. Moreover, we observed that H. opuntiae cells had a strong auxin-like effect in A. thaliana root development during in vitro interaction. We show that 3-methyl-1-butanol and ethanol are the main volatile compounds produced by H. opuntiae. Subsequently, it was determined that A. thaliana plants inoculated with H. opuntiae have a long-lasting and systemic effect against Botrytis cinerea infection, but independently of auxin, ethylene, salicylic acid, or jasmonic acid pathways. Our results demonstrate that H. opuntiae is an important biostimulant that acts by regulating plant development and pathogen resistance through different hormone-related responses.

Risk assessment for resistance to fludioxonil in Corynespora cassiicola in Liaoning China

Cucumber corynespora leaf spot, caused by Corynespora cassiicola, is the primary disease of cucumber leaves in greenhouses in China. Fludioxonil is a phenylpyrrole fungicide that inhibits C. cassiicola growth. We studied the sensitivity of 170 isolates of C. cassiicola to fludioxonil and evaluated resistance risk. All of the isolates were sensitive to fludioxonil. The EC50 values ranged from 0.082 to 0.539 μg/mL with a mean of 0.207 ± 0.0053 μg/mL. Laboratory-created mutants with a high resistance factor to fludioxonil were genetically stable after 10 transfers and showed positive cross-resistance to iprodione and procymidone but not to azoxystrobin, carbendazim, pydiflumetofen, and prochloraz. There was no significant difference in mycelial growth and temperature adaptation between the mutant s and the sensitive isolates, except for pathogenicity and sporulation. The resistant isolates accumulated less glycerol than their parental isolates and were more sensitive to osmotic stress. The histidine kinase activity of the sensitive isolates was significantly inhibited compared to that of the resistant mutants. Sequence alignment of the histidine kinase gene CCos revealed that the mutants RTL4, RXM5, and RFS102 had point mutations at different sites that resulted in amino acid changes at G934E, S739F, and A825P in the CCos protein. The mutant RFS102 had an alanine deletion at site 824. After fludioxonil treatment, CCos expression by RFS20 was significantly lower than that of the parental isolate. Our findings demonstrate that C. cassiicola exhibits moderate resistance to fludioxonil.

Aspergillus ochraceus biocontrol by Hanseniaspora opuntiae in vitro and on coffee fruits

Aspergillus ochraceus is an ochratoxin-producing fungus which contaminates coffee. In this study the antifungal effect of the yeast Hanseniaspora opuntiae on three Aspergillus ochraceus strains (IOC 4417, IOC 4462, Ao 14) was evaluated in vitro and on coffee fruits. H. opuntiae (106 and 107 cells mL-1) reduced in vitro fungal growth from 82% to 87%, when co-cultivated with A. ochraceus. The yeast cell free supernatant (CFS) inhibited conidial germination from 76.5% to 92.5%, and hyphal growth from 54% to 78%. The yeast (107 and 109 cells mL-1) applied on coffee fruits delayed fruit decay by A. ochraceus (IOC 4417 and Ao 14) until the 9th day, and was significantly different (p < 0.05) from the controls. Furthermore, the ultrastructure of the yeast-fungus interaction on the coffee fruit surface showed yeast attachment to A. ochraceus hyphae, and morphological alterations in fungal structures, with hyphal abnormalities, such as tortuous hyphae with irregular, non-uniform surface compared to the control without yeast. H. opuntiae showed efficacy as biocontrol agent and, to the best of our knowledge, this is the first study on the antifungal activity of H. opuntiae against A. ochraceus on coffee fruits Nevertheless, application of H. opuntiae to the crop in the field requires further studies.

The Metabolite Profiling and Microbial Community Dynamics during Pineapple By-Product Fermentation Using Co-Inoculation of Lactic Acid Bacteria and Yeast

Value-added utilization of pineapple waste is very import for the food industry and environmental protection. In this study, whey protein (2.6%, w/w) was added to pineapple waste in order to make up for the protein deficiency of the raw material and give the final products better flavor characteristics. Autochthonous Lactococcus lactis LA5 and Hanseniaspora opuntiae SA2 were used for the co-inoculation of pineapple by-products; during fermentation, the metabolite profiling and microbial community dynamics were investigated. Results showed that the contents of organic acids, total FAAs, total phenolic compounds and flavonoids significantly increased with fermentation, and 152 kinds of peptides were identified in the final products. Relevant analyses demonstrated that dominant strains including Lactococcus lactis, Hanseniaspora and Saccharomyces not only significantly promoted the accumulation of organic acids, total phenols and other active substances, but also inhibited the growth of pathogenic bacteria and further influenced the fermentation process of pineapple waste.

Ecology and functional potential of phyllosphere yeasts

The phyllosphere (i.e., the aerial parts of plants) harbors a rich microbial life, including bacteria, fungi, viruses, and yeasts. Current knowledge of yeasts stems primarily from industrial and medical research on Saccharomyces cerevisiae and Candida albicans, both of which can be found on plant tissues. For most other yeasts found in the phyllosphere, little is known about their ecology and functions. Here, we explore the diversity, dynamics, interactions, and genomics of yeasts associated with plant leaves and how tools and approaches developed for model yeasts can be adopted to disentangle the ecology and natural functions of phyllosphere yeasts. A first genomic survey exemplifies that we have only scratched the surface of the largely unexplored functional potential of phyllosphere yeasts.

The immunity priming effect of the Arabidopsis phyllosphere resident yeast Protomyces arabidopsidicola strain C29

The phyllosphere is a complex habitat for diverse microbial communities. Under natural conditions, multiple interactions occur between host plants and phyllosphere resident microbes, such as bacteria, oomycetes, and fungi. Our understanding of plant associated yeasts and yeast-like fungi lags behind other classes of plant-associated microbes, largely due to a lack of yeasts associated with the model plant Arabidopsis, which could be used in experimental model systems. The yeast-like fungal species Protomyces arabidopsidicola was previously isolated from the phyllosphere of healthy wild-growing Arabidopsis, identified, and characterized. Here we explore the interaction of P. arabidopsidicola with Arabidopsis and found P. arabidopsidicola strain C29 was not pathogenic on Arabidopsis, but was able to survive in its phyllosphere environment both in controlled environment chambers in the lab and under natural field conditions. Most importantly, P. arabidopsidicola exhibited an immune priming effect on Arabidopsis, which showed enhanced disease resistance when subsequently infected with the fungal pathogen Botrytis cinerea. Activation of the mitogen-activated protein kinases (MAPK), camalexin, salicylic acid, and jasmonic acid signaling pathways, but not the auxin-signaling pathway, was associated with this priming effect, as evidenced by MAPK3/MAPK6 activation and defense marker expression. These findings demonstrate Arabidopsis immune defense priming by the naturally occurring phyllosphere resident yeast species, P. arabidopsidicola, and contribute to establishing a new interaction system for probing the genetics of Arabidopsis immunity induced by resident yeast-like fungi.

Exploring biotechnological and functional characteristics of probiotic yeasts: A review

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In this review, the probiotic attributes of yeasts other than Saccharomyces boulardii and the various applications of probiotic yeast in biotechnology have been explored.

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This review comprises of the probiotic attributes, antagonistic activity against pathogens, plant growth promoting attributes, industrial application and their biotherapeutic potentials.

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Advanced and additional studies on non-Saccharomyces yeasts are necessary prior to administer these yeasts as potential probiotics for health and wellbeing.

Probiotics are vital and beneficial organisms which offers the health benefits to the host organisms. The fungal probiotic field is one of the developing fields nowadays. Yeast has an enormous and diverse group of microorganisms that is attracting and expanding the attention from researchers and industries. Saccharomyces boulardii, the only patented strain belonging to yeast genera for the human use, has been broadly evaluated for its probiotic effect. Yeasts belonging to the genera Debaryomyces, Pichia, Yarrowia, Meyerozyma, Kluyveromyces etc.., have attained more interest because of their beneficial and probable probiotic features. These yeast probiotics produce VOCs (Volatile organic compounds), mycocins and antimicrobials which shows the antagonistic effect against pathogenic fungi and bacteria. Additionally, those yeasts have been recorded as good plant growth promoting microorganisms. Yeast has an important role in environmental applications such as bioremediation and removal of metals like chromium, mercury, lead etc., from waste water. Probiotic yeasts with their promising antimicrobial, antioxidant, anticancer properties, cholesterol assimilation and immunomodulatory effects can also be utilized as biotherapeutics. In this review article we have made an attempt to address important yeast probiotic attributes.

Isolation and Identification of Wild Yeast from Malaysian Grapevine and Evaluation of Their Potential Antimicrobial Activity against Grapevine Fungal Pathogens

Pathogenic fungi belonging to the genera Botrytis, Phaeomoniella, Fusarium, Alternaria and Aspergillus are responsible for vines diseases that affect the growth, grapevine yield and organoleptic quality. Among innovative strategies for in-field plant disease control, one of the most promising is represented by biocontrol agents, including wild epiphytic yeast strains of grapevine berries. Twenty wild yeast, isolated and molecularly identified from three different Malaysian regions (Perlis, Perak and Pahang), were evaluated in a preliminary screening test on agar to select isolates with inhibition against Botrytis cinerea. On the basis of the results, nine yeasts belonging to genera Hanseniaspora, Starmerella, Metschnikowia, Candida were selected and then tested against five grape berry pathogens: Aspergillus carbonarius, Aspergillus ochraceus, Fusarium oxysporum, Alternaria alternata and Phaeomoniella chlamydospora.Starmerella bacillaris FE08.05 and Metschnikowia pulcherrima GP8 and Hanseniaspora uvarum GM19 showed the highest effect on inhibiting mycelial growth, which ranged between 15.1 and 4.3 mm for the inhibition ring. The quantitative analysis of the volatile organic compound profiles highlighted the presence of isoamyl and phenylethyl alcohols and an overall higher presence of low-chain fatty acids and volatile ethyl esters. The results of this study suggest that antagonist yeasts, potentially effective for the biological control of pathogenic moulds, can be found among the epiphytic microbiota associated with grape berries.

Endophytic bacteria from strawberry plants control gray mold in fruits via production of antifungal compounds against Botrytis cinerea L

Botrytis cinerea causes the gray mold disease in a wide range of plant hosts, especially in post-harvest periods. The control of this phytopathogen has been accomplished through the application of fungicides. However, this practice can cause environmental problems and increase fruit production costs. In addition, this fungus species has developed resistance to conventional synthetic fungicides. In this context, plant growth-promoting bacteria have shown potential for application in agricultural production because they are able to stimulate plant growth through different mechanisms, including the biological control of phytopathogens (indirect growth promotion mechanism). The aim of this work was to evaluate in vitro and in fruits the potential for indirect plant growth-promotion of bacteria isolated from strawberry leaves and roots. Dual plate method and inverted plate method were used to verify the ability of controlling in vitro the growth of Botrytis cinerea via the production of diffusible and volatile antifungal compounds, respectively. The effect of six bacterial isolates that showed greater potential for biological control in vitro was evaluated by scanning electron microscopy. Antifungal compounds produced by these bacterial isolates were identified by liquid chromatography coupled with mass spectrometry. Six bacterial strains were tested on strawberry pseudofruits. Five selected strains belong to the genus Bacillus and one to the genus Pantoea sp. Selected strains were able to inhibit more than 80 % of the mycelial growth of B. cinerea by the production of diffusible compounds and 90 % by volatile antifungal compounds production. Scanning electron microscopy showed the intense degradation of fungal hyphae caused by the presence of all bacterial strains. Bioactive compounds (salycilamide, maculosin, herniarin, lauroyl diethanolamide, baptifoline, undecanedioic acid, botrydial, 8 3-butylidene-7-hydroxyphthalide and N-(3-oxo-henoyl)-homoserine lactone) were obtained from liquid culture of these strains and extraction with ethyl acetate. All six isolates tested in vivo reduced the incidence of gray mold in strawberry pseudofruits in postharvest. It is concluded that isolates 26, 29, 65, 69, 132 (Bacillus sp.) and MQT16M1 (Pantoea sp.) have potential application for the biological control of Botrytis cinerea in strawberry via the production of diffusible and volatile antifungal compounds.

Gadolinium Protects Arabidopsis thaliana against Botrytis cinerea through the Activation of JA/ET-Induced Defense Responses

Plant food production is severely affected by fungi; to cope with this problem, farmers use synthetic fungicides. However, the need to reduce fungicide application has led to a search for alternatives, such as biostimulants. Rare-earth elements (REEs) are widely used as biostimulants, but their mode of action and their potential as an alternative to synthetic fungicides have not been fully studied. Here, the biostimulant effect of gadolinium (Gd) is explored using the plant-pathosystem Arabidopsis thaliana–Botrytis cinerea. We determine that Gd induces local, systemic, and long-lasting plant defense responses to B. cinerea, without affecting fungal development. The physiological changes induced by Gd have been related to its structural resemblance to calcium. However, our results show that the calcium-induced defense response is not sufficient to protect plants against B. cinerea, compared to Gd. Furthermore, a genome-wide transcriptomic analysis shows that Gd induces plant defenses and modifies early and late defense responses. However, the resistance to B. cinerea is dependent on JA/ET-induced responses. These data support the conclusion that Gd can be used as a biocontrol agent for B. cinerea. These results are a valuable tool to uncover the molecular mechanisms induced by REEs.

Selection and application of antifungal VOCs-producing yeasts as biocontrol agents of grey mould in fruits

Rotting caused by grey mould (Botrytis cinerea) is a concerning disease for numerous crops both pre- and postharvest stages. Application of antagonistic yeasts is a promising strategy for controlling grey mould incidence which could mitigate undesirable consequences of using synthetic fungicides. In this work, a screening for detection of yeasts isolated from figs producers of antifungal volatile organic compounds (VOCs) were performed by confrontation in double dishes systems. Eleven out of 34 yeasts confronted reduced B. cinerea growth parameter in vitro. This reduction was correlated (p ≤ 0.050) with the production of 10 volatile compounds: two acids (acetic acid and octanoic acid), 7 esters (Ethyl propionate, n-Propyl acetate, Isobutyl acetate, 2-methylbutyl acetate, furfuryl acetate, phenylmethyl acetate, 2-phenylethyl acetate) and one ketone (Heptan-2-one). In bases on in vitro assay, Hanseniaspora uvarum 793 was applied to in vivo assays with strawberries and cherries. The reduction of incidence of B. cinerea in strawberries at 7 °C and 25 °C was 54.9 and 72.1% after 6 and 3 days, respectively. The reduction of incidence of B. cinerea in cherries at 7 °C and 25 °C was 48.9 and 45.6% after 5 and 4 days, respectively. These results showed that VOCs produced by Hanseniaspora uvarum 793 are effective in the control of incidence of Botrytis cinerea in fruits, being a potential alternative to chemical fungicide.

Endophytes from Wild Rubber Trees as Antagonists of the Pathogen Corynespora cassiicola

The Corynespora leaf fall disease of rubber trees, caused by the necrotrophic fungus Corynespora cassiicola, is responsible for important yield losses in Asian and African plantations, whereas its impact is negligible in South America. The objective of this study was to identify potential antagonists of C. cassiicola among fungal endophytes (i.e., Pestalotiopsis, Colletotrichum, and Trichoderma spp.) isolated from wild and cultivated rubber trees distributed in the Peruvian Amazon. We first tested the endophytes in dual in vitro confrontation assays against a virulent C. cassiicola isolate (CCP) obtained from diseased rubber trees in the Philippines. All Trichoderma isolates overran the CCP colony, suggesting some antagonistic mechanism, while species from the other genera behaved as mutual antagonists. Trichoderma isolates were then tested through antibiosis assays for their capacity to produce growth-inhibiting molecules. One isolate (LA279), recovered as an endophyte from a wild Hevea guianensis specimen and identified as Trichoderma koningiopsis, showed significant antibiosis capacity. We demonstrated that LA279 was also able to endophytically colonize the cultivated rubber tree species (H. brasiliensis). Under controlled laboratory conditions, rubber plants were inoculated with three Trichoderma strains, including LA279, in combination with the pathogenic CCP. Results showed that 1 week preinoculation with the endophytes differentially reduced CCP mycelial development and symptoms. In conclusion, this study suggests that T. koningiopsis isolate LA279-and derivate compounds-could be a promising candidate for the biological control of the important rubber tree pathogen C. cassiicola.

Plant evolution and environmental adaptation unveiled by long-read whole-genome sequencing of Spirodela

Aquatic plants have to adapt to the environments distinct from where land plants grow. A critical aspect of adaptation is the dynamics of sequence repeats, not resolved in older sequencing platforms due to incomplete and fragmented genome assemblies from short reads. Therefore, we used PacBio long-read sequencing of the Spirodela polyrhiza genome, reaching a 44-fold increase of contiguity with an N50 (a median of contig lengths) of 831 kb and filling 95.4% of gaps left from the previous version. Reconstruction of repeat regions indicates that sequentially nested long terminal repeat (LTR) retrotranspositions occur early in monocot evolution, featured with both prokaryote-like gene-rich regions and eukaryotic repeat islands. Protein-coding genes are reduced to 18,708 gene models supported by 492,435 high-quality full-length PacBio complementary DNA (cDNA) sequences. Different from land plants, the primitive architecture of Spirodela's adventitious roots and lack of lateral roots and root hairs are consistent with dispensable functions of nutrient absorption. Disease-resistant genes encoding antimicrobial peptides and dirigent proteins are expanded by tandem duplications. Remarkably, disease-resistant genes are not only amplified, but also highly expressed, consistent with low levels of 24-nucleotide (nt) small interfering RNA (siRNA) that silence the immune system of land plants, thereby protecting Spirodela against a wide spectrum of pathogens and pests. The long-read sequence information not only sheds light on plant evolution and adaptation to the environment, but also facilitates applications in bioenergy and phytoremediation.

A bioactivity and biochemical analysis of iminoctadine tris (albesilate) as a fungicide against Corynespora cassiicola

Iminoctadine tris (albesilate) is a bis-guazatine fungicide, and its specific modes of action and efficacy against C. cassiicola are not yet clear. In this study, baseline sensitivity data for mycelial growth showed that the frequency distribution curve of iminoctadine tris (albesilate) EC₅₀ values is unimodal. The EC₅₀ values ranged from 0.1151 to 1.2101 μg/mL, with a mean of 0.5775 ± 0.2677 μg/mL. Iminoctadine tris (albesilate) affected the morphological development of C. cassiicola, causing increased branching of the mycelium. The significant increase in membrane permeability and malondialdehyde content after iminoctadine tris (albesilate) treatment indicated that this fungicide caused severe damage to the membrane structure. Furthermore, 0.4 μg/mL iminoctadine tris (albesilate) could decrease the spore density of C. cassiicola from 2.6200 × 10⁴ to 1.4967 × 10⁴/cm² on average in vitro, indicating that the fungicide had great potential to reduce secondary infection with C. cassiicola in the field. Additionally, 120 μg/mL iminoctadine tris (albesilate) provided over 95% curative efficacy and 81.17% preventative efficacy on detached cucumber leaves inoculated with C. cassiicola. In field trials, iminoctadine tris (albesilate) at a dose of 120 g a.i./ha exhibited 72.92% and 80.92% control efficacy in 2017 and 2018, respectively. However, the efficacy supplied by the reference fungicide azoxystrobin at 250 g a.i./ha was only approximately 50% due to the development of fungicide resistance in C. cassiicola. Taken together, the findings above provide a solid foundation for the exploration of the action mechanisms of iminoctadine tris (albesilate) against C. cassiicola and provide overwhelming evidence for the use of iminoctadine tris (albesilate) as an excellent potential alternative fungicide in the management of cucumber Corynespora leaf spot.