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This review covers, for the first time, all methods based on the use of Aspergillus strains as biocontrol agents for the management of plant diseases caused by fungi and oomycetes. Atoxigenic Aspergillus strains have been screened in a variety of hosts, such as peanuts, maize kernels, and legumes, during the preharvest and postharvest stages. These strains have been screened against a wide range of pathogens, such as Fusarium, Phytophthora, and Pythium species, suggesting a broad applicability spectrum. The highest efficacies were generally observed when using non-toxigenic Aspergillus strains for the management of mycotoxin-producing Aspergillus strains. The modes of action included the synthesis of antifungal metabolites, such as kojic acid and volatile organic compounds (VOCs), secretion of hydrolytic enzymes, competition for space and nutrients, and induction of disease resistance. Aspergillus strains degraded Sclerotinia sclerotiorum sclerotia, showing high control efficacy against this pathogen. Collectively, although two Aspergillus strains have been commercialized for aflatoxin degradation, a new application of Aspergillus strains is emerging and needs to be optimized. [ABSTRACT FROM AUTHOR]

Abstract Background Leaf rust (LR) is among the most destructive fungal diseases of rye (Secale cereale L.). Despite intensive research using various analytical and methodological approaches, such as quantitative trait locus (QTL) mapping, candidate gene expression analysis, and transcriptome sequencing, the genetic basis of the rye immune response to LR remains unclear. Results A genome-wide association study was employed to detect QTLs controlling the immune response to LR of rye. A mapping population, G38A, was constructed by crossing two inbred lines: 723 (susceptible to LR) and JKI-NIL-Pr3 (a donor of the LR resistance gene Pr3). For genotyping, SNP-DArT and silico-DArT markers were used. Resistance phenotyping was conducted by visual assessment of the infection severity in detached leaf segments inoculated with two isolates of Puccinia recondita f. sp. secalis, namely, 60/17/2.1 (isolate S) in the main experiment and 86/n/2.1_5x (isolate N) in the validation experiment, at 10 and 17 days post-infection (dpi), respectively. In total, 42,773 SNP-DArT and 105,866 silico-DArT markers were included in the main analysis including isolate S, of which 129 and 140 SNP-DArTs and 767 and 776 silico-DArTs were significantly associated (p ≤ 0.001; − log10(p) ≥ 3.0) with the immune response to LR at 10 and 17 dpi, respectively. Most significant markers were mapped to chromosome 1R. The number of common markers from both systems and at both time points occupying common chromosomal positions was 37, of which 21 were positioned in genes, comprising 18 markers located in exons and three in introns. This gene pool included genes encoding proteins with a known function in response to LR (e.g., a NBS-LRR disease resistance protein-like protein and carboxyl-terminal peptidase). Conclusion This study has expanded and supplemented existing knowledge of the genetic basis of rye resistance to LR by (1) detecting two QTLs associated with the LR immune response of rye, of which one located on the long arm of chromosome 1R is newly detected, (2) assigning hundreds of markers significantly associated with the immune response to LR to genes in the ‘Lo7’ genome, and (3) predicting the potential translational effects of polymorphisms of SNP-DArT markers located within protein-coding genes.

Abstract Background Pathogens have evolved diverse lifestyles and adopted pivotal new roles in both natural ecosystems and human environments. However, the molecular mechanisms underlying their adaptation to new lifestyles are obscure. Comparative genomics was adopted to determine distinct strategies of plant ascomycete fungal pathogens with different lifestyles and to elucidate their distinctive virulence strategies. Results We found that plant ascomycete biotrophs exhibited lower gene gain and loss events and loss of CAZyme-encoding genes involved in plant cell wall degradation and biosynthesis gene clusters for the production of secondary metabolites in the genome. Comparison with the candidate effectome detected distinctive variations between plant biotrophic pathogens and other groups (including human, necrotrophic and hemibiotrophic pathogens). The results revealed the biotroph-specific and lifestyle-conserved candidate effector families. These data have been configured in web-based genome browser applications for public display ( http://lab.malab.cn/soft/PFPG ). This resource allows researchers to profile the genome, proteome, secretome and effectome of plant fungal pathogens. Conclusions Our findings demonstrated different genome evolution strategies of plant fungal pathogens with different lifestyles and explored their lifestyle-conserved and specific candidate effectors. It will provide a new basis for discovering the novel effectors and their pathogenic mechanisms.

This review covers, for the first time, all methods based on the use of Aspergillus strains as biocontrol agents for the management of plant diseases caused by fungi and oomycetes. Atoxigenic Aspergillus strains have been screened in a variety of hosts, such as peanuts, maize kernels, and legumes, during the preharvest and postharvest stages. These strains have been screened against a wide range of pathogens, such as Fusarium , Phytophthora , and Pythium species, suggesting a broad applicability spectrum. The highest efficacies were generally observed when using non-toxigenic Aspergillus strains for the management of mycotoxin-producing Aspergillus strains. The modes of action included the synthesis of antifungal metabolites, such as kojic acid and volatile organic compounds (VOCs), secretion of hydrolytic enzymes, competition for space and nutrients, and induction of disease resistance. Aspergillus strains degraded Sclerotinia sclerotiorum sclerotia, showing high control efficacy against this pathogen. Collectively, although two Aspergillus strains have been commercialized for aflatoxin degradation, a new application of Aspergillus strains is emerging and needs to be optimized., Competing Interests: The authors declare no conflict of interest.

Biotrophic plant pathogenic fungi are widely distributed and are among the most damaging pathogenic organisms of agriculturally important crops responsible for significant losses in quality and yield. However, the pathogenesis of obligate parasitic pathogenic microorganisms is still under investigation because they cannot reproduce and complete their life cycle on an artificial medium. The successful lifestyle of biotrophic fungal pathogens depends on their ability to secrete effector proteins to manipulate or evade plant defense response. By integrating genomics, transcriptomics, and effectoromics, insights into how the adaptation of biotrophic plant fungal pathogens adapt to their host populations can be gained. Efficient tools to decipher the precise molecular mechanisms of rust–plant interactions, and standardized routines in genomics and functional pipelines have been established and will pave the way for comparative studies. Deciphering fungal pathogenesis not only allows us to better understand how fungal pathogens infect host plants but also provides valuable information for plant diseases control, including new strategies to prevent, delay, or inhibit fungal development. Our review provides a comprehensive overview of the efforts that have been made to decipher the effector proteins of biotrophic fungal pathogens and demonstrates how rapidly research in the field of obligate biotrophy has progressed. [ABSTRACT FROM AUTHOR]

Biotrophic plant pathogenic fungi are widely distributed and are among the most damaging pathogenic organisms of agriculturally important crops responsible for significant losses in quality and yield. However, the pathogenesis of obligate parasitic pathogenic microorganisms is still under investigation because they cannot reproduce and complete their life cycle on an artificial medium. The successful lifestyle of biotrophic fungal pathogens depends on their ability to secrete effector proteins to manipulate or evade plant defense response. By integrating genomics, transcriptomics, and effectoromics, insights into how the adaptation of biotrophic plant fungal pathogens adapt to their host populations can be gained. Efficient tools to decipher the precise molecular mechanisms of rust–plant interactions, and standardized routines in genomics and functional pipelines have been established and will pave the way for comparative studies. Deciphering fungal pathogenesis not only allows us to better understand how fungal pathogens infect host plants but also provides valuable information for plant diseases control, including new strategies to prevent, delay, or inhibit fungal development. Our review provides a comprehensive overview of the efforts that have been made to decipher the effector proteins of biotrophic fungal pathogens and demonstrates how rapidly research in the field of obligate biotrophy has progressed.

Fungal pathogens can invade not only the fruit peel but also the outer part of the fruit mesocarp, limiting the efficacy of fungicides. In this study, the relationships between fungicide structure, diffusion capacity and in vivo efficacy were evaluated for the first time. The diffusion capacity from pear peel to mesocarp of 11 antifungal compounds, including p-aminobenzoic acid, carbendazim, difenoconazole, dipicolinic acid, flusilazole, gentamicin, kojic acid, prochloraz, quinolinic acid, thiophanate methyl and thiram was screened. The obtained results indicated that size and especially polarity were negatively correlated with the diffusion capacity. Although some antifungal compounds, such as prochloraz and carbendazim, were completely degraded after a few days in peel and mesocarp, other compounds, such as p-aminobenzoic acid and kojic acid, showed high stability. When applying the antifungal compounds at the EC50 concentrations, it was observed that the compounds with high diffusion capacity showed higher in vivo antifungal activity against Alternaria alternata than compounds with low diffusion capacity. In contrast, there was no relationship between stability and in vivo efficacy. Collectively, the obtained results indicated that the diffusion capacity plays an important role in the efficacy of fungicides for the control of pear fruit diseases. [ABSTRACT FROM AUTHOR]

Fungal pathogens can invade not only the fruit peel but also the outer part of the fruit mesocarp, limiting the efficacy of fungicides. In this study, the relationships between fungicide structure, diffusion capacity and in vivo efficacy were evaluated for the first time. The diffusion capacity from pear peel to mesocarp of 11 antifungal compounds, including p-aminobenzoic acid, carbendazim, difenoconazole, dipicolinic acid, flusilazole, gentamicin, kojic acid, prochloraz, quinolinic acid, thiophanate methyl and thiram was screened. The obtained results indicated that size and especially polarity were negatively correlated with the diffusion capacity. Although some antifungal compounds, such as prochloraz and carbendazim, were completely degraded after a few days in peel and mesocarp, other compounds, such as p-aminobenzoic acid and kojic acid, showed high stability. When applying the antifungal compounds at the EC50 concentrations, it was observed that the compounds with high diffusion capacity showed higher in vivo antifungal activity against Alternaria alternata than compounds with low diffusion capacity. In contrast, there was no relationship between stability and in vivo efficacy. Collectively, the obtained results indicated that the diffusion capacity plays an important role in the efficacy of fungicides for the control of pear fruit diseases.

Chemicals are often used in attempts to control diseases caused by plant pathogenic fungi during food production. However, chemicals can have adverse effects not just on food, but they also remain active for a long time within ecosystems, and thus are not environmentally friendly. Therefore, development of bio-treatment and avoiding use of chemicals are urgently needed. With the aim of studying and developing new environmentally-friendly treatments, we tested extracts from selected bryophyte species (Porella platyphylla, Cinclidotus fontinaloides and Anomodon viticulosus) on five plant pathogenic fungi under controlled conditions. The fungi (Botryosphaeria dothidea, Phomopsis viticola, Calosphaeria sp., Colletotrichum acutatum and Monilinia laxa) were selected based on common diseases they cause on fruits and grapevine. They were isolated in cultures and treated with bryophyte extracts. Bryophyte extracts were shown to be effective in suppression of certain plant pathogenic fungi growth and to have a huge potential in development of novel biotechnological treatments and biofungicides. The best results were achieved in inhibition of B. dothidea, P. viticola and Calosphaeria sp.

Four fungi isolated from trunks and branches of European hazelnut (Corylus avellana L.) from commercial orchards in the Willamette Valley, Oregon were characterized and pathogenicity was tested on potted hazelnut trees. The acreage of hazelnuts in Oregon has expanded greatly in recent years in response to the availability of Eastern filbert blight resistant cultivars. Fungi were characterized using the BLASTn algorithm and the GenBank database with multiple partial gene sequence(s). If BLASTn and GenBank were not sufficient for species-level identification, then a multilocus sequence analysis (MLSA) was performed. The four pathogens were identified as Diplodia mutilla (Fr.) Mont., Dothiorella omnivora B.T. Linaldeddu, A. Deidda & B. Scanu, Valsa cf. eucalypti Cooke & Harkn., and Diaporthe eres Nitschke. All pathogens but D. omnivora have not been previously reported from European hazelnut in the literature. All four pathogens caused lesions on trunks bare root hazelnut trees cv. 'Jefferson' planted in pots in the greenhouse and fungi were re-isolated from inoculated trees. D. mutilla appeared particularly aggressive in repeated inoculation experiments. [ABSTRACT FROM AUTHOR]

Since the discovery that entomopathogenic fungi can live inside plants as endophytes, researchers have been trying to understand how this affects mainly plants and herbivores. We studied how inoculation of Vicia faba L. (Fabales: Fabaceae) plants with Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Ascomycota: Hypocreales) (strain GHA) either via the seeds or leaves influenced the nymph production of two successive generations of Aphis fabae Scopoli (Hemiptera: Aphididae). While we did not find any difference in nymph production for the first generation of aphids, second-generation aphids on both seed- and spray inoculated plants produced significantly higher numbers of nymphs than aphids on uninoculated plants. This emphasizes the importance of two (or multi-) generational experimentation. Beauveria bassiana was recovered from 26.0, 68.8 and 6.3% of respectively seed-, spray inoculated and control plants, thus, demonstrating its ability to live as an endophyte in V. faba. The confirmation that plants inoculated with entomopathogenic fungi can have a positive effect on pest insects makes careful consideration of these multi-trophic interactions imperative. [ABSTRACT FROM AUTHOR]

The reduction of synthetic fungicides in agriculture is necessary to guarantee a sustainable production that protects the environment and consumers’ health. Downy mildew caused by the oomycete Plasmopara viticola is the major pathogen in viticulture worldwide and responsible for up to 60% of pesticide treatments. Alternatives to reduce fungicides are thus utterly needed to ensure sustainable vineyard-ecosystems, consumer health and public acceptance. Essential oils (EOs) are amongst the most promising natural plant protection alternatives and have shown their antibacterial, antiviral and antifungal properties on several agricultural crops. However, the efficiency of EOs highly depends on timing, application method and the molecular interactions between the host, the pathogen and EO. Despite proven EO efficiency, the underlying processes are still not understood and remain a black box. The objectives of the present study were: a) to evaluate whether a continuous fumigation of a particular EO can control downy mildew in order to circumvent the drawbacks of direct application, b) to decipher molecular mechanisms that could be triggered in the host and the pathogen by EO application and c) to try to differentiate whether essential oils directly repress the oomycete or act as plant resistance primers. To achieve this a custom-made climatic chamber was constructed that enabled a continuous fumigation of potted vines with different EOs during long-term experiments. The grapevine (Vitis vinifera) cv Chasselas was chosen in reason of its high susceptibility to Plasmopara viticola. Grapevine cuttings were infected with P. viticola and subsequently exposed to continuous fumigation of different EOs at different concentrations, during 2 application time spans (24 hours and 10 days). Experiments were stopped when infection symptoms were clearly observed on the leaves of the control plants. Plant physiology (photosynthesis and growth rate parameters) were recorded and leaves were sampled at different time points for subsequent RNA extraction and transcriptomics analysis. Strikingly, the Oregano vulgare EO vapour treatment during 24h post-infection proved to be sufficient to reduce downy mildew development by 95%. Total RNA was extracted from leaves of 24h and 10d treatments and used for whole transcriptome shotgun sequencing (RNA-seq). Sequenced reads were then mapped onto the V. vinifera and P. viticola genomes. Less than 1% of reads could be mapped onto the P. viticola genome from treated samples, whereas up to 30% reads from the controls mapped onto the P. viticola genome, thereby confirming the visual observation of P. viticola absence in the treated plants. On average, 80% of reads could be mapped onto the V. vinifera genome for differential expression analysis, which yielded 4800 modulated genes. Transcriptomic data clearly showed that the treatment triggered the plant’s innate immune system with genes involved in salicylic, jasmonic acid and ethylene synthesis and signaling, activating Pathogenesis-Related-proteins as well as phytoalexin synthesis. These results elucidate EO-host-pathogen interactions for the first time and indicate that the antifungal efficiency of EO is mainly due to the triggering of resistance pathways inside the host plants. This is of major importance for the production and research on biopesticides, plant stimulation products and for resistance-breeding strategies. [ABSTRACT FROM AUTHOR]

Strawberry powdery mildew (Podosphaera aphanis Wallr.) is a pathogen which infects the leaves, fruit, stolon and flowers of the cultivated strawberry (Fragaria ×ananassa), causing major yield losses, primarily through unmarketable fruit. The primary commercial control of the disease is the application of fungicidal sprays. However, as the use of key active ingredients of commercial fungicides is becoming increasingly restricted, interest in developing novel strawberry cultivars exhibiting resistance to the pathogen is growing rapidly. In this study, a mapping population derived from a cross between two commercial strawberry cultivars (‘Sonata’ and ‘Babette’) was genotyped with single nucleotide polymorphism (SNP) markers from the Axiom iStraw90k genotyping array and phenotyped for powdery mildew susceptibility in both glasshouse and field environments. Three distinct, significant QTLs for powdery mildew resistance were identified across the two experiments. Through comparison with previous studies and scrutiny of the F. vesca genome sequence, candidate genes underlying the genetic control of this trait were identified. [ABSTRACT FROM AUTHOR]

Newly emerged wheat blast disease is a serious threat to global wheat production. Wheat blast is caused by a distinct, exceptionally diverse lineage of the fungus causing rice blast disease. Through sequencing a recent field isolate, we report a reference genome that includes seven core chromosomes and mini-chromosome sequences that harbor effector genes normally found on ends of core chromosomes in other strains. No mini-chromosomes were observed in an early field strain, and at least two from another isolate each contain different effector genes and core chromosome end sequences. The mini-chromosome is enriched in transposons occurring most frequently at core chromosome ends. Additionally, transposons in mini-chromosomes lack the characteristic signature for inactivation by repeat-induced point (RIP) mutation genome defenses. Our results, collectively, indicate that dispensable mini-chromosomes and core chromosomes undergo divergent evolutionary trajectories, and mini-chromosomes and core chromosome ends are coupled as a mobile, fast-evolving effector compartment in the wheat pathogen genome. [ABSTRACT FROM AUTHOR]

Fusarium head blight (FHB) caused by Fusarium graminearum is a disease that results in yield loss and mycotoxin contamination in wheat globally. This study assessed the effect of a plant biostimulant prepared from a brown macroalga Ascophyllum nodosum (Liquid Seaweed Extract; LSE) alone and in combination with chitosan in controlling Fusarium. Wheat seedlings drenched with LSE and chitosan in combination showed reduced severity of F. graminearum infection on leaves as evidenced by a significant reduction in necrotic area and fewer number of conidia produced in the necrotic area. Gene expression studies showed that the combination of LSE and chitosan amplified the response of pathogenesis-related genes (TaPR1.1, TaPR2, TaPR3, TaGlu2) in wheat seedlings infected with Fusarium spores above that observed for the individual treatments. The combination treatments were more effective in enhancing the activity of various defense related enzymes such as peroxidase and polyphenol oxidase. FHB studies on adult plants showed a reduction of bleached spikes in wheat heads treated with the combination of LSE and chitosan. Mycotoxin content appeared to be correlated with FHB severity. Combination treatments of LSE and chitosan reduced the levels of mycotoxins deoxynivalenol and sambucinol in wheat grains. Systemic disease resistance appears to be induced by LSE and chitosan in response to F. graminearum in wheat by inducing defense genes and enzymes. [ABSTRACT FROM AUTHOR]

Trichophyton rubrum is a human pathogenic fungus. As a dermatophyte it causes athlete's foot, fungal infection of nails, jock itch and ringworm. The pigmentation of T. rubrum is variable and can range from white or yellow to wine-red. We demonstrate that the pigmentation is strongly influenced by pH. Under alkaline conditions, T. rubrum has a red pigmentation, whereas at acid conditions, T. rubrum has a yellow pigmentation. Moreover, the color change immediately from yellow to red by adding NaOH and reverse immediately from red to yellow by adding HCl. We suggest that the chemical compound Xanthomegnin is responsible for red as well for yellow pigmentation in T. rubrum. To figure out, why T. rubrum has red pigmentation on Trichophyton medium, adjust to alkaline, but not on Synthetic-Complete medium, also adjusted to alkaline, we measure the pH of liquid media, adjusted to pH 3.5, 6 and 8, over a period of four weeks. The pH of both cultivation media changes significantly, with a maximum of five pH levels. Whereas the Trichophyton medium, initially adjusted to pH 8, stays alkaline, the pH of the Synthetic-Complete medium drops to acid conditions. The acidification of the SC medium and the alkalization of the Trichophyton medium explains the different pigment color of the T. rubrum colonies. [ABSTRACT FROM AUTHOR]

Melanin is a natural pigment that is produced by filamentous fungi. In this study, the endophytic species, Spissiomyces endophytica (strain SDBR-CMU319), produced a brown-black pigment in the mycelia. Consequently, the pigment was extracted from the dried fungal biomass. This was followed by pigment purification, characterization and identification. Physical and chemical characteristics of the pigment showed acid precipitation, alkali solubilization, decolorization with oxidizing agents, and insolubility in most organic solvents and water. The pigment was confirmed as melanin based on ultraviolet-visible spectroscopy, Fourier-transform infrared, and electron paramagnetic resonance spectra analyses. The analyses of the elemental composition indicated that the pigment possessed a low percentage of nitrogen, and therefore, was not 3,4-dihydroxyphenylalanine melanin. Inhibition studies involving specific inhibitors, both tricyclazole and phthalide, and suggest that fungal melanin could be synthesized through the 1,8-dihydroxynaphthalene pathway. The optimum conditions for fungal pigment production from this species were investigated. The highest fungal pigment yield was observed in glucose yeast extract peptone medium at an initial pH value of 6.0 and at 25°C over three weeks of cultivation. This is the first report on the production and characterization of melanin obtained from the genus Spissiomyces. [ABSTRACT FROM AUTHOR]

Emerging fungal phytodiseases are a food security threat and novel fungicides are in an urgent need. Herein, a series of isobutyrophenone derivatives were designed and synthesized. The derivatives exhibited excellent fungicidal activities against seven fungi. The structure-activity relationship (SAR) study indicated that the introduction of a bromo group at the position 3 or 5 of the phenyl ring, as well as esterification of the 4-hydroxy with a chloroacetyl group, could substantially increase the antifungal activity and spectrum of the compounds. Among all 23 compounds, 2-bromo-3-hydroxy-4-isobutyryl-6-methylphenyl 2-chloroacetate (12b) showed the highest fungicidal activity against all seven tested fungal pathogens with EC 50 values ranging from 1.22 to 39.94 μg/mL and exhibited the most potent inhibition against class II fructose-1,6-bisphosphate aldolase with an IC 50 of 3.63 μM. The lead compounds were proven to be safe to NIH3T3/293 T cells and silkworm larvae, and relatively stable under different harsh conditions. Detached fruit tests showed the practical potential of lead compounds for fruit (or plant) protection. Taken together, our results indicated that the isobutyrophenone derivatives could be further optimized and developed as advanced leads for new fungicides. Unlabelled Image • Novel isobutyrophenone analogs were designed and synthesized. • 2-bromo-3-hydroxy-4-isobutyryl-6-methylphenyl 2-chloroacetate (12b) showed potent broad-spectrum antifungal activity. • Compound 12b exhibited relative stable and non-toxic properties. • Compound 12b could control C. gloeosporioides infection on detached fruit. [ABSTRACT FROM AUTHOR]

The infection of Aspergillus flavus and its aflatoxin production pose a severe threat to humans, animals as well as plants life. Their inhibition using green techniques are considered as one of the important challenges. The present study outlines the antifungal activity of the ZnO nanoparticles (NPs) synthesized from lemongrass leaf extract and their effect on the mycelial growth of Aspergillus flavus and its aflatoxins production. The qualitative and quantitative analyses of aflatoxins were determined, respectively using thin-layer chromatography and spectrophotometric methods. The X-ray diffraction as well as scanning and transmission electron microscopy studies indicated the formations of hexagonal ZnO NPs having the sizes ranged between 7 and 14 nm. FTIR spectrum confirmed the formation of ZnO NPs. The ZnO NPs displayed 92.25% inhibition of the growth of A. flavus and 100% inhibition of the aflatoxins production at the concentrations of 200 μl/mL and 150 μl/mL respectively. The present biosynthetic method is a simple, cost-effective, eco-friendly, high yield, green and handy protocol capable of synthesizing ZnO NPs, which might have accomplished due to the activities of plant metabolites and phytochemicals available in the lemongrass leaves parenchyma. This study revealed that ZnO NPs have the potential to forbid the growth of A. flavus and its aflatoxins production. Hence, ZnO NPs could be used in the plant protection and as a preservative for safe storage of food commodities to prevent A. flavus contamination and aflatoxins poisoning in coming future. [ABSTRACT FROM AUTHOR]

Chitin is an important component of the fungal cell wall with a family of chitin synthases mediating its synthesis. Here, we report on the genetic characterization of the full suite of seven chitin synthases (MaChsI-VII) identified in the insect pathogenic fungus, Metarhizium acridum. Aberrant distribution of chitin was most evident in targeted gene knockouts of MaChsV and MaChsVII. Mutants of MaChsI, MaChsIII, MaChsIV showed delayed conidial germination, whereas ΔMaChsII and ΔMaChsV mutants germinated more rapidly when compared to the wild-type parent. All MaChs genes impacted conidial yield, but differentially affected stress tolerances. Inactivation of MaChsIII, MaChsV, MaChsVII resulted in cell wall fragility, and ΔMaChsV and ΔMaChsVII mutants showed high sensitivity to Congo red and calcofluor white, suggesting that the three genes are required for cell wall integrity. In addition, ΔMaChsIII and ΔMaChsVII mutants showed the highest sensitivities to heat and UV-B stress. Three of seven chitin synthase genes, MaChsIII, MaChsV, MaChsVII, were found to contribute to fungal virulence. Compared with the wild-type strain, ΔMaChsIII and ΔMaChsV mutants were reduced in virulence by topical inoculation, while the ΔMaChsVII mutant showed more severe virulence defects. Inactivation of MaChsIII, MaChsV, or MaChsVII impaired appressorium formation, affected growth of in insecta produced hyphal bodies, and altered the surface properties of conidia and hyphal bodies, resulting in defects in the ability of the mutant strains to evade insect immune responses. These data provide important links between the physiology of the cell wall and the ability of the fungus to parasitize insects and reveal differential functional consequences of the chitin synthase family in M. acridum growth, stress tolerances, cell wall integrity and virulence. [ABSTRACT FROM AUTHOR]

Biological control as a promising method to combat plant disease has gained public attention in recent years. In the present study, we isolated 12 strains resistant to Magnaporthe oryzae from western Sichuan subalpine soil. Among them, CQ07 exhibited remarkable activity against M. oryzae. The result of 16S rRNA sequence analysis revealed that CQ07 is approximately 99% similar to Bacillus australimaris. The sterilized culture filtrate of CQ07 inhibited the growth of M. oryzae, which motivated us to deduce the influence of CQ07 on the pathogenicity of M. oryzae. As shown by experimentation, sterilized culture filtrate (10 μl/ml) of CQ07 can delay and even suppress the germination of conidia and prevent the formation of appressorium in vitro and in vivo. In addition, by simulative field tests, the spraying of conidia suspension diluted with sterilized culture filtrate of CQ07 reduced infection of rice blast. To better control rice blasts, understanding the infection mechanism of M. oryzae and inhibiting the mechanism of the antagonistic strain is of great importance. [ABSTRACT FROM AUTHOR]

In many plant species, conflicts between divergent elements of the immune system, especially nucleotide-binding oligomerization domain-like receptors (NLR), can lead to hybrid necrosis. Here, we report deleterious allele-specific interactions between an NLR and a non-NLR gene cluster, resulting in not one, but multiple hybrid necrosis cases in Arabidopsis thaliana. The NLR cluster is RESISTANCE TO PERONOSPORA PARASITICA 7 (RPP7), which can confer strain-specific resistance to oomycetes. The non-NLR cluster is RESISTANCE TO POWDERY MILDEW 8 (RPW8) / HOMOLOG OF RPW8 (HR), which can confer broad-spectrum resistance to both fungi and oomycetes. RPW8/HR proteins contain at the N-terminus a potential transmembrane domain, followed by a specific coiled-coil (CC) domain that is similar to a domain found in pore-forming toxins MLKL and HET-S from mammals and fungi. C-terminal to the CC domain is a variable number of 21- or 14-amino acid repeats, reminiscent of regulatory 21-amino acid repeats in fungal HET-S. The number of repeats in different RPW8/HR proteins along with the sequence of a short C-terminal tail predicts their ability to activate immunity in combination with specific RPP7 partners. Whether a larger or smaller number of repeats is more dangerous depends on the specific RPW8/HR autoimmune risk variant. [ABSTRACT FROM AUTHOR]

The article offers information related to the biology and applications of Endophytic Insect-Pathogenic Fungi. Topics include occurrence of interactions which lead to the demise of plant insect pests; the nature of plant–insect–fungus relationships; and overview of EIPF by reviewing the knowledge about their evolution, ecology, and mechanisms of insect and plant colonization.

Wide crosses between genetically diverged parents may reveal novel loci for crop improvement that are not apparent in crosses between elite cultivars. The landrace Chevallier was a noted malting barley first grown in 1820. To identify potentially novel alleles for agronomic traits, Chevallier was crossed with the modern malting cultivar NFC Tipple generating two genetically diverse recombinant inbred line populations. Genetic maps were produced using genotyping-by-sequencing and 384-SNP genotyping, and the populations were phenotyped for agronomic traits to allow the identification of quantitative trait loci (QTL). Within the semi-dwarf 1 (sdw1) region on chromosome 3H Chevallier conferred increased plant height and reduced tiller number, with QTL for these traits explaining 79.4% and 35.2% of the phenotypic variance observed, respectively. Chevallier was also associated with powdery mildew susceptibility, with a QTL on 1H accounting for up to 19.1% of the variance and resistance at this locus most likely resulting from an Mla variant from Tipple. Two novel QTL for physiological leaf spotting were identified on 3H and 7H, explaining up to 17.1% of the variance and with the Chevallier allele reducing symptom severity on 7H. Preliminary micromalting analysis was also undertaken to compare the malting characteristics of Chevallier and Tipple. Chevallier malt contained significantly lower levels of both α-amylase and wort β-glucan than Tipple malt, however no significant differences were observed for the remaining malting parameters measured. This suggests that the most obvious improvements in barley since the introduction of Chevallier are for agronomic traits such as height, yield and lodging resistance rather than for malting characteristics. Overall, our results demonstrate that this wide cross between Chevallier and Tipple may provide a source of novel QTL for barley breeding. [ABSTRACT FROM AUTHOR]

The intracellular accommodation structures formed by plant cells to host arbuscular mycorrhiza fungi and biotrophic hyphal pathogens are cytologically similar. Therefore we investigated whether these interactions build on an overlapping genetic framework. In legumes, the malectin-like domain leucine-rich repeat receptor kinase SYMRK, the cation channel POLLUX and members of the nuclear pore NUP107-160 subcomplex are essential for symbiotic signal transduction and arbuscular mycorrhiza development. We identified members of these three groups in Arabidopsis thaliana and explored their impact on the interaction with the oomycete downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa). We report that mutations in the corresponding genes reduced the reproductive success of Hpa as determined by sporangiophore and spore counts. We discovered that a developmental transition of haustorial shape occurred significantly earlier and at higher frequency in the mutants. Analysis of the multiplication of extracellular bacterial pathogens, Hpa-induced cell death or callose accumulation, as well as Hpa- or flg22-induced defence marker gene expression, did not reveal any traces of constitutive or exacerbated defence responses. These findings point towards an overlap between the plant genetic toolboxes involved in the interaction with biotrophic intracellular hyphal symbionts and pathogens in terms of the gene families involved. [ABSTRACT FROM AUTHOR]

Bacterial Panicle Blight (BPB), caused by Burkholderia glumae, is a bacterial disease in rice (Oryza sativa) that reduces rice yield and quality for producers and consequently creates higher market prices for consumers. BPB is caused by the simultaneous occurrence of high daily minimum temperatures (~22°C) and relative humidity (~77%), which may increase under the current scenario of global warming. This study hypothesized that the economic damage from warming may cause an increase in economic losses, though at a decreasing rate per degree. Thus, this study estimates the yield losses associated with BPB occurrences at the county level in the Mid-South United States (US) for annual rice production in 2003–2013 and under +1–3°C warming scenarios using daily weather information with appropriate thresholds. From the estimated losses, the total production potential of a BPB-resistant rice was quantified using a spatial equilibrium trade model to further estimate market welfare changes with the counterfactual scenario that all US county-level rice production were BPB resistant. Results from the study indicate that the alleviation of BPB would represent a $69 million USD increase in consumer surplus in the US and a concomitant increase in rice production that would feed an additional 1.46 million people annually assuming a global average consumption of 54 Kg per person. Under the 1°C warming scenario, BPB occurrences and production losses would cause price increases for rice and subsequently result in a $112 million USD annual decrease in consumer surplus in the US and a loss of production equivalent to feeding 2.17 million people. Under a 3°C warming scenario, production losses due to BPB cause an annual reduction of $204 million USD in consumer surplus in the US, and a loss in production sufficient to feed 3.98 million people a year. As global warming intensifies, BPB could become a more common and formidable rice disease to combat, and breeding for BPB resistance would be the primary line-of-defense as currently no effective chemical options are available. The results of this study inform agriculturalists, policymakers, and economists about the value of BPB-resistance in the international rice market and also help support efforts to focus future breeding toward climate change impact resilience. [ABSTRACT FROM AUTHOR]

Summary: Soil plant‐pathogenic (PF) and mycorrhizal fungi (MF) are both important in maintaining plant diversity, for example via host‐specialized effects. However, empirical knowledge on the degree of host specificity and possible factors affecting the fungal assemblages is lacking.We identified PF and MF in fine roots of 519 individuals across 45 subtropical tree species in southern China in order to quantify the importance of host phylogeny (including via its effects on functional traits), habitat and space in determining fungal communities. We also compared host specificity in PF and MF at different host‐phylogenetic scales.In both PF and MF, host phylogeny independently accounted for > 19% of the variation in fungal richness and composition, whereas environmental and spatial factors each explained no more than 4% of the variation. Over 77% of the variation explained by phylogeny was attributable to covariation in plant functional traits. Host specificity was phylogenetically scale‐dependent, being stronger in PF than in MF at low host‐phylogenetic scales (e.g. within genus) but similar at larger scales.Our study suggests that host‐phylogenetic effects dominate the assembly of both PF and MF communities, resulting from phylogenetically clustered plant traits. The scale‐dependent host specificity implies that PF were specialized at lower‐level and MF at higher‐level host taxa. [ABSTRACT FROM AUTHOR]

Over the last decades, endophytic fungi represent a new source of pharmacologically active secondary metabolites based on the underlying assumption that they live symbiotically within their plant host. In the present study, a new endophytic fungus was isolated from Rauwolfia macrophylla, a medicinal plant from Cameroon. The fungus showed a highest homology to Curvularia sp. based on complete nucleotide sequence data generated from the internal transcribed spacer (ITS) of ribosomal DNA region. Large scale fermentation, working-up and separation of the strain extract using different chromatographic techniques afforded three bioactive compounds: 2'-deoxyribolactone (1), hexylitaconic acid (2) and ergosterol (3). The chemical structures of compounds 1–3 were confirmed by 1 and 2D NMR spectroscopy and mass spectrometry, and comparison with corresponding literature data. Biologically, the antimicrobial, antioxidant activities and the acetylcholinesterase inhibitory of the isolated compounds were studied. [ABSTRACT FROM AUTHOR]

Plant seed exudates are composed of complex mixtures of chemicals with potential for bioactive compounds with antimicrobial properties. This study focused on kochia (Kochia scoparia), one of many weedy plant species considered invasive in many agricultural systems. Extraction of compounds in water yielded an exudate mass equivalent to 7% of the original seed mass used. Water-soluble exudates were tested against 16 known plant pathogens in disk diffusion assays and kochia exudates were found to inhibit Colletotrichum graminicola, the fungal causative agent of anthracnose and stalk rot in maize. The narrow range of fungi found as targets suggested the mechanism of inhibition may be specific rather than broadly antifungal. A decline in viability of cells over four orders of magnitude occurred within six hours of exposure to exudate. The minimum inhibitory concentration was 3.125 mg L-1. Hyphae formation in C. graminicola appeared inhibited following exposure to the exudate. Small molecular weight compounds as determined by GC/MS analysis showed high relative amounts of the sugars fructose, galactopyranose, glucose, and sorbitol, along with moderate proportions of organic acids and amino acids. Protein content averaged 0.7% in the standard concentration (100 mg mL-1) used for inhibition assays. Size fractionation of the exudate and subsequent disk diffusion assays revealed bioactive fractions with compounds in the MW range <5 kDa. To the best of our knowledge, this study is the first to show promising bioactivity against C. graminicola that was associated with water-extractable compounds from a common weed species. The results suggest that seeds of persistent plant species with long-lived seed banks like kochia may have potential for use in the discovery of compounds active in inhibiting fungal pathogens. [ABSTRACT FROM AUTHOR]

Diverse fungal endophytes live in plants and are shaped by some abiotic and biotic stresses. Plant disease as particular biotic stress possibly gives an impact on the communities of fungal endophytes. In this study, clubroot disease caused by an obligate biotroph protist, Plasmodiophora brassicae, was considered to analyze its influence on the fungal endophyte community using an internal transcribed spacer (ITS) through high-throughput sequencing and culture-dependent methods. The results showed that the diversity of the endophyte community in the healthy roots was much higher than the clubroots. Ascomycota was the dominant group of endophytes (Phoma, Mortierella, Penicillium, etc.) in the healthy roots while P. brassicae was the dominant taxon in the clubroots. Hierarchical clustering, principal component analysis (PCA), principal coordinates analysis (PCoA) and analysis of similarities (ANOSIM) indicated significant differences between the endophyte communities in the healthy roots and clubroots. Linear discriminant analysis effect size (LefSe) analysis showed that the dominant genera could be regarded as potential biomarkers. The endophyte community in the healthy roots had a more complex network compared with the clubroots. Also, many plant pathogenic Fusarium were isolated from the clubroots by the culture-dependent method. The outcome of this study illustrates that P. brassicae infection may change the fungal endophyte community associated with the roots of tumourous stem mustard and facilitates the entry of soil pathogen into the roots. [ABSTRACT FROM AUTHOR]

Outbreaks of emerging plant diseases and insect pests are increasing at an alarming rate threatening the food security needs of a booming world population. The role of plant pathologists in addressing these threats to plant health is critical. Here, we share our personal experience with the appearance in Bangladesh of a destructive new fungal disease called wheat blast and stress the importance of open-science platforms and crowdsourced community responses in tackling emerging plant diseases. Benefits of the open-science approach include recruitment of multidisciplinary experts, application of cutting-edge methods, and timely replication of data analyses to increase the robustness of the findings. Based on our experiences, we provide some general recommendations and practical guidance for responding to emerging plant diseases. [ABSTRACT FROM AUTHOR]

It has been proposed that in wild ecosystems viruses are often plant mutualists, whereas agroecosystems favour pathogenicity. We seek evidence for virus pathogenicity in wild ecosystems through the analysis of plant-virus coevolution, which requires a negative effect of infection on the host fitness. We focus on the interaction between Arabidopsis thaliana and Cucumber mosaic virus (CMV), which is significant in nature. We studied the genetic diversity of A. thaliana for two defence traits, resistance and tolerance, to CMV. A set of 185 individuals collected in 76 A. thaliana Iberian wild populations were inoculated with different CMV strains. Resistance was estimated from the level of virus multiplication in infected plants, and tolerance from the effect of infection on host progeny production. Resistance and tolerance to CMV showed substantial genetic variation within and between host populations, and depended on the virus x host genotype interaction, two conditions for coevolution. Resistance and tolerance were co-occurring independent traits that have evolved independently from related life-history traits involved in adaptation to climate. The comparison of the genetic structure for resistance and tolerance with that for neutral traits (QST/FST analyses) indicated that both defence traits are likely under uniform selection. These results strongly suggest that CMV infection selects for defence on A. thaliana populations, and support plant-virus coevolution. Thus, we propose that CMV infection reduces host fitness under the field conditions of the wild A. thaliana populations studied. [ABSTRACT FROM AUTHOR]

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is an airborne fungal disease which always destructs leaf and leads to stagnation of grain filling, decreasing of kernel weight, thin seed and yield loss. Winter wheat Huixianhong is a special germplasm with special characteristics of tolerance or resistance against stripe rust. In order to understand the effect on Huixianhong from stripe rust, we designed two kinds of treatment, inoculation of stripe rust fungi (IH) and artificial immune by bactericide (CK) to study the dynamic of disease process, the grain filling and the thousand-kernel weight (TKW). Our results showed that the incubation period of Hongxinahui was 13.5 days. The prevalence increased from 32.9% at 15 days after jointing to 80.0% at 9 days after booting, and reached to 97.0% at the heading stage. The infection type (IT) was 7 to 9 at the beginning of anthesis. The severity, leaf withered area ratio and disease index at the 15th day after anthesis were 67.17%, 98.17% and 0.6717, respectively. The IH maximum increasing rate of leaf necrosis and chlorosis area was from heading beginning stage to anthesis beginning stage, which increased from 18.66 mm2·d-1 to 21.04 mm2·d-1. The maximum rate of grain filling was 1.25 mg·d-1 at the 18th day after anthesis, which was earlier than that of CK by 3.3 days. The IH thousand-kernel weight Loss (TKWL) was more than that of CK by 6.19%, the stage of heading and amature were 3.0 days and 4.5 days earlier than CK, respectively. The stripe rust infection seriously destructed the photosynthetic function of leaf at the earlier stage of grain filling, i.e. at the beginning of anthesis, which led to the most important biomass loss and the grain filling rate decrease. As far as stripe rust is concerned, Huixianhong is a high susceptible, easily been infected, seriously showing symptoms and most quickly epidemic type but can successfully complete grain filling in high quality. It is a very useful germplasm for creating and selecting special breeding materials against stripe rust. [ABSTRACT FROM AUTHOR]

Pathogenic yeasts and fungi are an increasing global healthcare burden, but discovery of novel antifungal agents is slow. The mycoparasitic yeast Saccharomycopsis schoenii was recently demonstrated to be able to kill the emerging multi-drug resistant yeast pathogen Candida auris. However, the molecular mechanisms involved in the predatory activity of S. schoenii have not been explored. To this end, we de novo sequenced, assembled and annotated a draft genome of S. schoenii. Using proteomics, we confirmed that Saccharomycopsis yeasts have reassigned the CTG codon and translate CTG into serine instead of leucine. Further, we confirmed an absence of all genes from the sulfate assimilation pathway in the genome of S. schoenii, and detected the expansion of several gene families, including aspartic proteases. Using Saccharomyces cerevisiae as a model prey cell, we honed in on the timing and nutritional conditions under which S. schoenii kills prey cells. We found that a general nutrition limitation, not a specific methionine deficiency, triggered predatory activity. Nevertheless, by means of genome-wide transcriptome analysis we observed dramatic responses to methionine deprivation, which were alleviated when S. cerevisiae was available as prey, and therefore postulate that S. schoenii acquired methionine from its prey cells. During predation, both proteomic and transcriptomic analyses revealed that S. schoenii highly upregulated and translated aspartic protease genes, probably used to break down prey cell walls. With these fundamental insights into the predatory behavior of S. schoenii, we open up for further exploitation of this yeast as a biocontrol yeast and/or source for novel antifungal agents. [ABSTRACT FROM AUTHOR]

Fusarium Head Blight (FHB) is the number one floral disease of cereals and poses a serious health hazard by contaminating grain with the harmful mycotoxin deoxynivalenol (DON). Fungi adapt to fluctuations in their environment, coordinating development and metabolism accordingly. G-protein coupled receptors (GPCRs) communicate changes in the environment to intracellular G-proteins that direct the appropriate biological response, suggesting that fungal GPCR signalling may be key to virulence. Here we describe the expansion of non-classical GPCRs in the FHB causing pathogen, Fusarium graminearum, and show that class X receptors are highly expressed during wheat infection. We identify class X receptors that are required for FHB disease on wheat, and show that the absence of a GPCR can cause an enhanced host response that restricts the progression of infection. Specific receptor sub-domains are required for virulence. These non-classical receptors physically interact with intracellular G-proteins and are therefore bona fide GPCRs. Disrupting a class X receptor is shown to dysregulate the transcriptional coordination of virulence traits during infection. This amounts to enhanced wheat defensive responses, including chitinase and plant cell wall biosynthesis, resulting in apoplastic and vascular occlusions that impede infection. Our results show that GPCR signalling is important to FHB disease establishment. [ABSTRACT FROM AUTHOR]

The pathogenic fungus Sclerotinia sclerotiorum infects over 600 species of plant. It is present in numerous environments throughout the world and causes significant damage to many agricultural crops. Fragmentation and lack of gene flow between populations may lead to population sub-structure. Within discrete recombining populations, positive selection may lead to a ‘selective sweep’. This is characterised by an increase in frequency of a favourable allele leading to reduction in genotypic diversity in a localised genomic region due to the phenomenon of genetic hitchhiking. We aimed to assess whether isolates of S. sclerotiorum from around the world formed genotypic clusters associated with geographical origin and to determine whether signatures of population-specific positive selection could be detected. To do this, we sequenced the genomes of 25 isolates of S. sclerotiorum collected from four different continents–Australia, Africa (north and south), Europe and North America (Canada and the northen United States) and conducted SNP based analyses of population structure and selective sweeps. Among the 25 isolates, there was evidence for two major population clusters. One of these consisted of 11 isolates from Canada, the USA and France (population 1), and the other consisted of nine isolates from Australia and one from Morocco (population 2). The rest of the isolates were genotypic outliers. We found that there was evidence of outcrossing in these two populations based on linkage disequilibrium decay. However, only a single candidate selective sweep was observed, and it was present in population 2. This sweep was close to a Major Facilitator Superfamily transporter gene, and we speculate that this gene may have a role in nutrient uptake from the host. The low abundance of selective sweeps in the S. sclerotiorum genome contrasts the numerous examples in the genomes of other fungal pathogens. This may be a result of its slow rate of evolution and low effective recombination rate due to self-fertilisation and vegetative reproduction. [ABSTRACT FROM AUTHOR]

Epicoccum is a genus of ascomycetes often associated with the mycobiome of grapevines (Vitis vinifera). Epicoccum spp. are found in the soil, phyllosphere, as well as in the wood, where they interact both with the plant and with other endophytes and pathogens. Wood pathogens involved in the esca disease complex, a grapevine trunk disease, are particularly concerning in viticulture, as current control strategies have proven unsatisfactory. This study investigated the interaction among Epicoccum spp. and three esca-associated fungi, with the aim of establishing whether they are suitable candidates for biological control.A screening conducted in vitro, by means of dual culture, revealed that all tested Epicoccum spp. inhibited the growth of pathogens Phaeomoniella chlamydospora and Fomitiporia mediterranea, while only some of them inhibited Phaeoacremonium minimum. Epicoccum layuense E24, identified as the most efficient antagonist, was tested in rooted grapevine cuttings of cultivars Cabernet Sauvignon and Touriga Nacional, under greenhouse conditions, against P. chlamydospora and P. minimum. This study revealed that the inoculation of E. layuense E24 produced a successful colonization of the wood of grapevines; in addition it did not impair the growth of the plants or induce the appearance of symptoms in leaves or in wood. Moreover, grapevines colonized by E. layuense E24 showed a considerable decrease in the wood symptomatology caused by the inoculated pathogens (by 31–82%, depending on the pathogen/grapevine cultivar), as well as a reduction in their frequency of re-isolation (60–74%).Our findings suggest that E. layuense E24 is a promising candidate for its application in biological control, due to its antagonistic interaction with some esca-associated fungal pathogens. [ABSTRACT FROM AUTHOR]

Hyperspectral imaging has proved its potential for evaluating complex plant-pathogen interactions. However, a closer link of the spectral signatures and genotypic characteristics remains elusive. Here, we show relation between gene expression profiles and specific wavebands from reflectance during three barley—powdery mildew interactions. Significant synergistic effects between the hyperspectral signal and the corresponding gene activities has been shown using the linear discriminant analysis (LDA). Combining the data sets of hyperspectral signatures and gene expression profiles allowed a more precise differentiation of the three investigated barley-Bgh interactions independent from the time after inoculation. This shows significant synergistic effects between the hyperspectral signal and the corresponding gene activities. To analyze this coherency between spectral reflectance and seven different gene expression profiles, relevant wavelength bands and reflectance intensities for each gene were computed using the Relief algorithm. Instancing, xylanase activity was indicated by relevant wavelengths around 710 nm, which are characterized by leaf and cell structures. HvRuBisCO activity underlines relevant wavebands in the green and red range, elucidating the coherency of RuBisCO to the photosynthesis apparatus and in the NIR range due to the influence of RuBisCO on barley leaf cell development. These findings provide the first insights to links between gene expression and spectral reflectance that can be used for an efficient non-invasive phenotyping of plant resistance and enables new insights into plant-pathogen interactions. [ABSTRACT FROM AUTHOR]

Extracts of many plant species have substantial antifungal activity, therefore the use of plant extracts with good activity against plant fungal pathogens could lead to the development of inexpensive and environmentally acceptable fungicides based on locally available natural products. Because large quantities of invasive weeds are available we decided to determine the antifungal activity of acetone extracts of seven invasive weeds (Aristolochia elegans, Chromolaena odorata, Ipomoea alba, Passiflora suberosa, Passiflora subpeltata, Solanum seaforthianum and Tecoma stans). The activity was determined against eight plant fungal pathogens viz Rhizoctonia solani, Fusarium oxysporium, Penicillium janthinellum, Penicillium expansum, Aspergillus parasiticus, Aspergillus niger, Pythium ultimum and Phytophthora nicotiana. Extracts of some invasive plant species had better activity against some fungal pathogens than some commercial fungicides. P. suberosa had promising antifungal activity with an average minimum inhibitory concentration (MIC) of 0.09 mg/ml. Tecoma stans extracts were not as active (average MIC 0.55 mg/ml). This extract, however contained compounds that yielded clear inhibition zones in bioautography making it easy to isolate the active compound by bioassay guided fractionation. • There is an abundance of invasive plant material available. • Invasive plants may have good antifungal activity as a competitive advantage. • Determined activity of seven invasive plant species against eight fungal pathogens. • The number of active compounds were determined by bioautography. • Some extracts sufficiently active to protect plant crops against fungal pathogens. [ABSTRACT FROM AUTHOR]

Salicylic acid (SA) is an effective elicitor to increase taxol production in Pestalotiopsis microspora. Addition of SA at the concentration of 300 μM yielded taxol 625.47 μg L-1, 45- fold higher than that of the control. Elicitation of the role of SA in the fungal taxol biosynthetic pathway revealed that SA enhanced reactive oxygen species and lipid peroxidation of unsaturated fatty acids of P. microspora mycelia. This oxidative process stimulates isoprene biosynthetic pathway by triggering expression of the geranylgeranyl pyrophosphate synthase gene leading to improved biosynthesis of taxol in P. microspora. [ABSTRACT FROM AUTHOR]

Disease prediction tools improve management efforts for many plant diseases. Prediction and downstream prevention demand information about disease etiology, which can be complicated for some diseases, like those caused by soilborne microorganisms. Fortunately, the availability of machine learning methods has enabled researchers to elucidate complex relationships between hosts and pathogens without invoking difficult-to-satisfy assumptions. The etiology of a destructive plant disease, Verticillium wilt of mint, caused by the fungus Verticillium dahliae was reevaluated with several supervised machine learning methods. Specifically, the objective of this research was to identify drivers of wilt in commercial mint fields, describe the relationships between these drivers, and predict wilt. Soil samples were collected from commercial mint fields. Wilt foci, V. dahliae, and plant-parasitic nematodes that can exacerbate wilt were quantified. Multiple linear regression, a generalized additive model, random forest, and an artificial neural network were fit to the data, validated with 10-fold cross-validation, and measures of explanatory and predictive performance were compared. All models selected nematodes within the genus Pratylenchus as the most important predictor of wilt. The fungus after which this disease is named, V. dahliae, was the fourth most important predictor of wilt, after crop age and cultivar. All models explained around 50% of the total variation (R2 ≤ 0.46), and exhibited comparable predictive error (RMSE ≤ 1.21). Collectively, these models revealed that the quantitative relationships between two pathogens, mint cultivars and age are required to explain wilt. The ascendance of Pratylenchus spp. in predicting symptoms of a disease assumed to primarily be caused by V. dahliae exposes the underestimated contribution of these nematodes to wilt. This research provides a foundation on which predictive forecasting tools can be developed for mint growers and reminds us of the lessons that can be learned by revisiting assumptions about disease etiology. [ABSTRACT FROM AUTHOR]

Biosurveillance is a proactive approach that may help to limit the spread of invasive fungal pathogens of trees, such as rust fungi which have caused some of the world’s most damaging diseases of pines and poplars. Most of these fungi have a complex life cycle, with up to five spore stages, which is completed on two different hosts. They have a biotrophic lifestyle and may be propagated by asymptomatic plant material, complicating their detection and identification. A bioinformatics approach, based on whole genome comparison, was used to identify genome regions that are unique to the white pine blister rust fungus, Cronartium ribicola, the poplar leaf rust fungi Melampsora medusae and Melampsora larici-populina or to members of either the Cronartium and Melampsora genera. Species- and genus-specific real-time PCR assays, targeting these unique regions, were designed with the aim of detecting each of these five taxonomic groups. In total, twelve assays were developed and tested over a wide range of samples, including different spore types, different infected plant parts on the pycnio-aecial or uredinio-telial host, and captured insect vectors. One hundred percent detection accuracy was achieved for the three targeted species and two genera with either a single assay or a combination of two assays. This proof of concept experiment on pine and poplar leaf rust fungi demonstrates that the genome-enhanced detection and identification approach can be translated into effective real-time PCR assays to monitor tree fungal pathogens. [ABSTRACT FROM AUTHOR]

Understanding of genetic diversity is important to explore existing gene in any crop breeding program. Most of the diversity preserved in the landraces which are well–known reservoirs of important traits for biotic and abiotic stresses. In the present study, the genetic diversity at twenty-four most significant blast resistance gene loci using twenty-eight gene specific markers were investigated in landraces originated from nine diverse rice ecologies of India. Based on phenotypic evaluation, landraces were classified into three distinct groups: highly resistant (21), moderately resistant (70) and susceptible (70). The landraces harbour a range of five to nineteen genes representing blast resistance allele with the frequency varied from 4.96% to 100%. The cluster analysis grouped entire 161 landraces into two major groups. Population structure along with other parameters was also analyzed to understand the evolution of blast resistance gene in rice. The population structure analysis and principal coordinate analysis classified the landraces into two sub–populations. Analysis of molecular variance showed maximum (93%) diversity within the population and least (7%) between populations. Five markers viz; K3957, Pikh, Pi2–i, RM212and RM302 were strongly associated with blast disease with the phenotypic variance of 1.4% to 7.6%. These resistant landraces will serve as a valuable genetic resource for future genomic studies, host–pathogen interaction, identification of novel R genes and rice improvement strategies. [ABSTRACT FROM AUTHOR]

Pigments and phytotoxins are crucial for the survival and spread of plant pathogenic fungi. The genome of the tomato biotrophic fungal pathogen Cladosporium fulvum contains a predicted gene cluster (CfPKS1, CfPRF1, CfRDT1 and CfTSF1) that is syntenic with the characterized elsinochrome toxin gene cluster in the citrus pathogen Elsinoë fawcettii. However, a previous phylogenetic analysis suggested that CfPks1 might instead be involved in pigment production. Here, we report the characterization of the CfPKS1 gene cluster to resolve this ambiguity. Activation of the regulator CfTSF1 specifically induced the expression of CfPKS1 and CfRDT1, but not of CfPRF1. These co-regulated genes that define the CfPKS1 gene cluster are orthologous to genes involved in 1,3-dihydroxynaphthalene (DHN) melanin biosynthesis in other fungi. Heterologous expression of CfPKS1 in Aspergillus oryzae yielded 1,3,6,8-tetrahydroxynaphthalene, a typical precursor of DHN melanin. Δcfpks1 deletion mutants showed similar altered pigmentation to wild type treated with DHN melanin inhibitors. These mutants remained virulent on tomato, showing this gene cluster is not involved in pathogenicity. Altogether, our results showed that the CfPKS1 gene cluster is involved in the production of DHN melanin and suggests that elsinochrome production in E. fawcettii likely involves another gene cluster. [ABSTRACT FROM AUTHOR]

The WRKY proteins constitute a large family of transcription factors that have been known to play a wide range of regulatory roles in multiple biological processes. Over the past few years, many reports have focused on analysis of evolution and biological function of WRKY genes at the whole genome level in different plant species. However, little information is known about WRKY genes in melon (Cucumis melo L.). In the present study, a total of 56 putative WRKY genes were identified in melon, which were randomly distributed on their respective chromosomes. A multiple sequence alignment and phylogenetic analysis using melon, cucumber and watermelon predicted WRKY domains indicated that melon WRKY proteins could be classified into three main groups (I-III). Our analysis indicated that no recent duplication events of WRKY genes were detected in melon, and strong purifying selection was observed among the 85 orthologous pairs of Cucurbitaceae species. Expression profiles of CmWRKY derived from RNA-seq data and quantitative RT-PCR (qRT-PCR) analyses showed distinct expression patterns in various tissues, and the expression of 16 CmWRKY were altered following powdery mildew infection in melon. Besides, we also found that a total of 24 WRKY genes were co-expressed with 11 VQ family genes in melon. Our comparative genomic analysis provides a foundation for future functional dissection and understanding the evolution of WRKY genes in cucurbitaceae species, and will promote powdery mildew resistance study in melon. [ABSTRACT FROM AUTHOR]

Human activities including those in crop gene banks are subject to errors, especially during seed multiplication and maintenance of seed germination. Therefore, the most serious problem of gene banks is authenticity of the accessions and their genotypic purity. There are many methods for determining the identity of varieties, but comparisons between current data and past records are not easy since the latter are often missing. Breeding barley resistant to powdery mildew caused by Blumeria graminis f. sp. hordei (Bgh) was traditionally based on incorporating major genes into new varieties and the results have been published. Our goal was to identify resistance genes to powdery mildew in accessions of the Czech spring barley core collection and compare these data with earlier information to establish the authenticity of the accessions. Two hundred and twenty-three accessions of the collection including 665 single plant progenies were tested. Sixty-four selected reference isolates of Bgh representing the world diversity of the pathogen were used for resistance tests. Twenty-two known resistance genes were postulated either separately or in combinations. In the collection, 151 homogeneous accessions were found, but the resistances of nine of them were inconsistent with published data and in 12 accessions their authenticity is doubtful. The remaining 72 accessions were heterogeneous and comprised 176 resistance genotypes, 54 of which were probably mechanical admixtures of other varieties. There are several pathogens of cereals, e.g. rusts and mildews, against which many resistance genes in host crops have also been exploited. Knowledge of these resistances can assist in maintaining pure and genuine stocks in gene banks. Seed purity and the authenticity of accessions can subsequently be checked with more advanced methods. [ABSTRACT FROM AUTHOR]

The present study explores the insect toxicity and antifungal activity of 2, 3-dimethylmaleic anhydride against mixed-age cultures of several stored product insects namely: the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae); the pulse beetle, Callosobruchus chinensis Fab (Coleoptera: Bruchidae) and the rust-red flour beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) and plant fungal pathogens namely: Fusarium oxysporum f. sp. cepa (Hypocreales:Nectriaceae) and Sclerotium oryzae Cattaneo (Magnaporthales: Magnaporthaceae), respectively. The study also revealed that the mixed-age-cultures of C. chinensis were slightly tolerant to 2, 3-dimethylmaleic anhydride, showing 80-90% mortality in 72-h exposure at 100 µg/L dose only. Whereas mixed-age-population of S. oryzae and T. castaneum were fairly susceptible, attaining 100% population extinction at 100 µg/L doses of 2, 3-dimethylmaleic anhydride in 24, 48 or 72 h of exposure. Further, the isolated compound also inhibits mycelia growth of the two filamentous fungi under study at 5 mg/plate and inhibition was dose-dependent and species-specific. This is first to report showing the antifungal activities of 2, 3-dimethylmaleic anhydride. Finally, results reveal that 2, 3-dimethylmaleic anhydride could be potential biopesticides for plant fungal pathogens and stored product beetles. [ABSTRACT FROM AUTHOR]