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Cembranoids produced by tobacco glandular trichomes have bioactivities in resistance to insect pests and pathogens. Cembratrien-ol synthase (CBTS) plays a key role in the biosynthesis of cembranoids and directly determines the cembranoid content in tobacco. This study examined the effect of changing CBTS1 expression on tobacco resistance to the insect pest Spodoptera frugiperda and oomycete pathogen Phytophthora nicotianae. The CDS sequence of CBTS1 was cloned into gene overexpression and silencing vectors and introduced into tobacco (Nicotiana tabacum L. cv. TN90) to obtain CBTS1-overexpression plants (CBTS1-OE) and CBTS1-silenced plants (CBTS1-RI). Compared with control plants, the content of cembratrien-ol (CBT-ol) was increased 4.48 times in the CBTS1-OE plants but decreased by 68% in the CBTS1-RI plants, while that of cembratrien-diol (CBT-diol) was increased 3.17 times in the CBTS1-OE plants but decreased by 76% in the CBTS1-RI plants. The S. frugiperda resistance of transgenic tobacco plants was evaluated by in vitro toxicity test, and the results showed that the resistance of CBTS1-OE plants to S. frugiperda was significantly improved but that of CBTS1-RI plants was reduced. The P. nicotianae resistance of transgenic tobacco plants was assessed by the detached leaf assay, and the results showed that the resistance of CBTS1-OE plants to P. nicotianae was enhanced, while that of CBTS1-RI plants was attenuated. Further gene expression analysis showed that overexpression of CBTS1 increased the expression of the pathogen-related gene PR-1a, while silencing of CBTS1 decreased its expression. This study demonstrated that manipulating the expression of CBTS1 could change the cembranoid content in tobacco plants and alter their resistance to both insect pests and oomycete pathogens. [ABSTRACT FROM AUTHOR]

From the rice fermentation product of a new record fungus, Neohelicosporium griseum, two new polyketides, neogrisphenol A (1) and neogrisphenol B (2), one new isochroman-1-one, (S)-6-hydroxy-7-methoxy-3,5-dimethylisochroman-1-one (3), and four known compounds (4–7) were isolated. Their structures were determined using 1D- and 2D-NMR, mass spectrometry, and chemical calculations. The C-3~C-2′ polymerization mode between the two α-naphthalenone derivative moieties is uncommon in compounds 1 and 2. Meanwhile, compounds 1–2 and 5 exhibited antibacterial activity against Bacillus subtilis, Clostridium perfringens, Staphylococcus aureus, and Staphylococcus aureus, with MIC values ranging between 16 and 31 µg/mL. In addition, compound 5 showed antifungal activity against Sclerotinia sclerotiorum and Phytophthora nicotianae var. nicotianae, with respective IC50 values of 88.14 ± 2.21 µg/mL and 52.36 ± 1.38 µg/mL. Compound 1 showed significant cytotoxicity against A2780, PC-3, and MBA-MD-231 cell lines with respective IC50 values of 3.20, 10.68, and 16.30 µM, and the cytotoxicity against A2780 cells was even higher than that of cisplatin (CDDP). With an IC50 value of 10.13 µM, compound 2 also exhibited cytotoxicity against A2780. The in vitro results showed that compound 1 inhibited A2780 cell proliferation, induced apoptosis, and arrested the cell cycle at the S-phase in a concentration-dependent manner. [ABSTRACT FROM AUTHOR]

Tobacco black shank (TBS), caused by Phytophthora nicotianae, is one of the most harmful diseases of tobacco. There are many studies have examined the mechanism underlying the induction of disease resistance by arbuscular mycorrhizal fungi (AMF) and β-aminobutyric acid (BABA) alone, but the synergistic effects of AMF and BABA on disease resistance have not yet been studied. This study examined the synergistic effects of BABA application and AMF inoculation on the immune response to TBS in tobacco. The results showed that spraying BABA on leaves could increase the colonization rate of AMF, the disease index of tobacco infected by P.nicotianae treated with AMF and BABA was lower than that of P.nicotianae alone. The control effect of AMF and BABA on tobacco infected by P.nicotianae was higher than that of AMF or BABA and P.nicotianae alone. Joint application of AMF and BABA significantly increased the content of N, P, and K in the leaves and roots, in the joint AMF and BABA treatment than in the sole P. nicotianae treatment. The dry weight of plants treated with AMF and BABA was 22.3% higher than that treated with P.nicotianae alone. In comparison to P. nicotianae alone, the combination treatment with AMF and BABA had increased Pn, Gs, Tr, and root activity, while P. nicotianae alone had reduced Ci, H2O2 content, and MDA levels. SOD, POD, CAT, APX, and Ph activity and expression levels were increased under the combined treatment of AMF and BABA than in P.nicotianae alone. In comparison to the treatment of P.nicotianae alone, the combined use of AMF and BABA increased the accumulation of GSH, proline, total phenols, and flavonoids. Therefore, the joint application of AMF and BABA can enhance the TBS resistance of tobacco plants to a greater degree than the application of either AMF or BABA alone. In summary, the application of defense-related amino acids, combined with inoculation with AMF, significantly promoted immune responses in tobacco. Our findings provide new insights that will aid the development and use of green disease control agents.

Extracts from plants used in Chinese medicine can be good sources of fungicides for agricultural applications. In this study, we separated and identified antifungal compounds from four traditional Chinese medicine extracts and evaluated their antifungal activities in vitro and in vivo. In vitro, honokiol extracted from Artemisia argyi showed broad-spectrum antimicrobial and mycelial inhibitory activity with EC50 in the range 3.56 − 33.85 μg/mL against eight plant pathogens. q-PCR indicated that honokiol might induce cell cancerisation and inhibit cellular respiration, which provided significant insights into honokiol function in tobacco resistance to molecular mechanisms of the phytopathogenic fungus Phytophthora nicotianae. In vivo, honokiol significantly decreased the rate of fungal infection in eggplants, potatoes, grapes, cherry tomatoes, and cucumbers, and enhanced disease resistance in tobacco. Overall, our results indicate that honokiol has the potential to control a variety of fungal and oomycete diseases, and A. argyi could be a source of honokiol. [ABSTRACT FROM AUTHOR]

Pythium oligandrum is known as an important biological control agent against fungal plant pathogens. The commercial formulations of this oomycete could reduce the application of the chemical fungicides and lessen the environmental impact of treatments. This study aimed to investigate the antagonistic ability of Iranian isolates of P. oligandrum to select proper and efficient candidates as native biocontrol agents using a previously characterized collection of forty-five isolates from fields of different regions of Iran. The antagonistic effects of native P. oligandrum isolates were evaluated against two soil-borne fungal pathogens, Fusarium oxysporum f. sp. lycopersici and Phytophthora parasitica, causing diseases on tomato. Pythium oligandrum isolates K29, K48, and K87 were recognized as the most effective isolates based also on previously published in vitro antagonistic assays, oligandrin production, and the ability of root colonization. The oospores of the selected candidates were formulated as seed-coating, kaolin dust mixture, and perlite-coating and compared with common fungicides in greenhouse tests. The results of greenhouse studies revealed that all selected P. oligandrum isolates and chemical fungicides significantly reduced disease severity but the efficacy of P. oligandrum isolates varied according to the type of formulation. Seed-coating formulation with oospores exhibited better performance than other formulations. The results showed that the application of formulated P. oligandrum selected isolates had the same performance (40–50% reduction in disease severity) as compared to the chemical fungicide treatments for controlling soil-borne pathogens. These results make it possible to consider in the near future the use of isolates of P. oligandrum as biocontrol agents to protect vegetable crops, in particular tomato, from soil-borne pathogens. [ABSTRACT FROM AUTHOR]

The objective of the work was to evaluate the resistance of new tobacco (Nicotiana tabacum L.) hybrids to Phytophthora nicotianae Breda de Haan by incorporating resistance genes from 'Beinhart-1000-1'. Two hundred plants per genotype were included in seedbed experiments, where a randomized block design with three replicates was used. The percentage of plants affected by the disease was evaluated until the susceptible control 'KY-14' reached 100% of diseased plants. For the plantation experiment, 45 day old plants were transplanted from another developed seedbed, and a completely randomized design with two replications was used. Each cultivar occupied a plot with five furrows of 20 plants each. The data on the percentage of diseased plants in both experiments allowed determining the Area Under the Disease Progress Curve (AUDPC) to subsequently perform a Simple Ranked Analysis of Variance, Fixed Effects Model. The AUDPC values were higher (less resistant) at the seedling stage than at the planting stage in both experiments, and it was observed that the hybrids and 'Beinhart-1000-1' showed the lowest AUDPCvalues in the two years of research. The female parents achieved higher AUDPC values (less resistant) and differed from their respective F1 offspring. All five tobacco hybrids showed high levels of resistance to P. nicotianae, exceeding the resistance of the female parents, but not that of the male parent 'B-1000-1'. [ABSTRACT FROM AUTHOR]

Aims The soil-borne oomycete pathogen Phytophthora parasitica can cause black shank disease in tobacco plants. The use of resistant varieties can be used to control black shank disease. The potential relationships of the composition of the rhizosphere microbiome to resistance to black shank disease are poorly understood. This work aims to compare the rhizosphere microbial community and network of the tobacco resistant variety HB202 with the susceptible variety XY3. Methods and Results Rhizospheric soils were collected from tobacco plants of HB202 and XY3 in the fields with same soil types and agricultural operations. The compositions of the rhizosphere microbial communities were revealed by Illumina sequencing of bacterial 16S rRNA genes and fungal spacer (ITS) sequences and analysed with molecular ecological network pipeline. The alpha diversity of fungal communities of the two varieties was significantly different. The structure and composition of bacterial and fungal communities in the resistant variety in the rhizosphere was different from the susceptible variety. Relative abundances of beneficial genera in the HB202 microbiota were higher than in the XY3. Conversely, the XY3 microbiota exhibited a higher abundance of deleterious genera compared to the HB202 microbiota. The resistant variety influences the topological properties and microbial interactions in the rhizosphere against the disease. The network of the HB202 was more complex and had higher connectivity compared to the XY3 network. Conclusions The rhizosphere microbial communities and networks of two tobacco varieties are very different. These changes in the microbial communities and their interactions may play an important role in tobacco resistance to black shank disease. [ABSTRACT FROM AUTHOR]

A new method for the synthesis of α-trifluoromethylated tertiary alcohols bearing coumarins is described. The reaction of 3-(trifluoroacetyl)coumarin and pyrrole provided the target compounds with high yields under catalyst-free, mild conditions. The crystal structure of compound 3fa was investigated by X-ray diffraction analysis. The biological activities, such as in vitro antifungal activity of the α-trifluoromethylated tertiary alcohols against Fusarium graminearum, Fusarium oxysporum, Fusarium moniliforme, Rhizoctonia solani Kuhn, and Phytophthora parasitica var nicotianae, were investigated. The bioassay results indicated that compounds 3ad, 3gd, and 3hd showed broad-spectrum antifungal activity in vitro. Compound 3cd exhibited excellent fungicidal activity against Rhizoctonia solani Kuhn, with an EC50 value of 10.9 μg/mL, which was comparable to that of commercial fungicidal triadimefon (EC50 = 6.1 μg/mL). Furthermore, molecular docking study suggested that 3cd had high binding affinities with 1W9U, like argifin. [ABSTRACT FROM AUTHOR]

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Chrysanthemum is an important flower crop grown in different parts of the world. Apparently there are new reports of chrysanthemum collar rot and root rot caused by Phytophthora sp. around the world. In recent years there has been increase in incidence of Phytophthora root and collar rot in chrysanthemum and no information is available about this disease in India. Therefore the aim of the present study is to isolate and characterize the pathogen causing collar rot and root rot disease of chrysanthemum. During year 2021, the plants exhibiting collar rot and root rot disease symptoms were received from the local farmers. Based on initial micro-morphological observation it was identified as Phytophthora sp. Further the pure culture of pathogen was isolated and confirmed its identity through cultural, morphological and amplification of the three regions/genes (ITS, tef-1α and β-tubulin) of Phytophthora sp. Phylogenetic analysis of concatenated sequence derived from ITS, tef-1 and β-tubulin sequences of five Phytophthora isolates (PhN1, PhN2, PhN3, PhN4 and PhN5) showed close clustering of these isolates with Phytophthora nicotianae isolates infecting different crops. This is first detailed characterization of Phytophthora nicotianae causing collar rot and root rot in chrysanthemum in India. [ABSTRACT FROM AUTHOR]

Heterotrimeric G proteins, comprising Gα, Gβ, and Gγ subunits, are key regulators of eukaryotic intracellular signaling. Extra-large G (XLG) proteins are a subfamily of plant-specific Gα proteins interacting with plasma membrane-localized receptors to regulate multiple biological processes. The Nicotiana benthamiana genome encodes seven XLG proteins, NbXLG1–7, whose functions in disease resistance and underlying mechanisms are unknown. In this study, we silenced all the seven genes and found that disease susceptibility was enhanced when both NbXLG3 and NbXLG5 or NbXLG4 was silenced. Then, we generated N. benthamiana xlg3xlg5 double- and xlg4 single-mutant lines using the CRISPR-Cas9 approach. All the mutants showed reduced resistance to the bacterial pathogen Pseudomonas syringae pv. tomato DC3000, the fungal pathogen Sclerotinia sclerotiorum, and a series of oomycete pathogens, including Phytophthora capsici, Phytophthora infestans, and Phytophthora parasitica. We further demonstrated that NbXLG3/4/5 positively regulated microbial pattern-induced reactive oxygen species burst and defense gene expression by directly coupling to the tested plant immune receptors. In addition, we examined the role of NbXLG3/4/5 in abiotic stress tolerance and observed that NbXLG3 and NbXLG5 negatively regulated plant resistance to high-salt, mannitol, and PEG. Our study demonstrates the possible role of NbXLG3/4/5 in response to biotic and abiotic stresses and provides insights for the improvement of plant resistance to environmental changes. [ABSTRACT FROM AUTHOR]

Tobacco black shank caused by Phytophthora nicotianae is a devastating disease that causes huge losses to tobacco production across the world. Investigating the regulatory mechanism of tobacco resistance to P. nicotianae is of great importance for tobacco resistance breeding. The jasmonate (JA) signaling pathway plays a pivotal role in modulating plant pathogen resistance, but the mechanism underlying JA-mediated tobacco resistance to P. nicotianae remains largely unclear. This work explored the P. nicotianae responses of common tobacco cultivar TN90 using plants with RNAi-mediated silencing of NtCOI1 (encoding the perception protein of JA signal), and identified genes involved in this process by comparative transcriptome analyses. Interestingly, the majority of the differentially expressed bHLH transcription factor genes, whose homologs are correlated with JA-signaling, encode AtBPE-like regulators and were up-regulated in NtCOI1-RI plants, implying a negative role in regulating tobacco response to P. nicotianae. A subsequent study on NtbHLH49, a member of this group, showed that it’s negatively regulated by JA treatment or P. nicotianae infection, and its protein was localized to the nucleus. Furthermore, overexpression of NtbHLH49 decreased tobacco resistance to P. nicotianae, while knockdown of its expression increased the resistance. Manipulation of NtbHLH49 expression also altered the expression of a set of pathogen resistance genes. This study identified a set of genes correlated with JA-mediated tobacco response to P. nicotianae, and revealed the function of AtBPE-like regulator NtbHLH49 in regulating tobacco resistance to this pathogen, providing insights into the JA-mediated tobacco responses to P. nicotianae. [ABSTRACT FROM AUTHOR]

Tobacco black shank caused by Phytophthora nicotianae is a serious disease in tobacco cultivation. We found that naringenin is a key factor that causes different sensitivity to P. nicotianae between resistant and susceptible tobacco. The level of basal flavonoids in resistant tobacco was distinct from that in susceptible tobacco. Of all flavonoids with different content, naringenin showed the best antimicrobial activity against mycelial growth and sporangia production of P. nicotianae in vitro. However, naringenin showed very low or no antimicrobial activity to other plant pathogens. We found that naringenin induced not only the accumulation of reactive oxygen species, but also the expression of salicylic acid biosynthesis‐related genes. Naringenin induced the expression of the basal pathogen resistance gene PR1 and the SAR8.2 gene that contributes to plant resistance to P. nicotianae. We then interfered with the expression of the chalcone synthase (NtCHS) gene, the key gene of the naringenin synthesis pathway, to inhibit naringenin biosynthesis. NtCHS‐RNAi rendered tobacco highly sensitive to P. nicotianae, but there was no change in susceptibility to another plant pathogen, Ralstonia solanacearum. Finally, exogenous application of naringenin on susceptible tobacco enhanced resistance to P. nicotianae and naringenin was very stable in this environment. Our findings revealed that naringenin plays a core role in the defence against P. nicotianae and expanded the possibilities for the application of plant secondary metabolites in the control of P. nicotianae. [ABSTRACT FROM AUTHOR]

An experiment was conducted to standardize the isolation and screening protocol Phytophthora nicotianae on betel vine to identify the resistance source. The artificial inoculation was carried out by detached leaf assay (pin prick method) and drenching with spore suspension for the root. The result showed that carrot agar was suitable for active culture subsistence, and the pin prick method was the best method for inoculation and screening. Among the inter-specific hybrids used in the present investigation, IIHRPBIH9 recorded significant resistance to Phytophthora foot rot compared to the susceptible check IIHRBV170. Thus, screening of inter-specific hybrids for this disease through artificial inoculation helps to identify resistance sources for the breeding programme, thereby meeting the demand for superior quality, disease-free planting materials and effective disease management. This is the first report for identifying the resistance source in betel vine against P. nicotianae. [ABSTRACT FROM AUTHOR]

Effector proteins secreted by plant pathogens are essential for infection. Cytoplasmic RXLR effectors from oomycetes are characterized by the presence of RXLR and EER motifs that are frequently linked to WY- and/or LWY-domains, folds that are exclusive to this effector family. A related family of secreted candidate effector proteins, carrying WY-domains and the EER motif but lacking the canonical RXLR motif, has recently been described in oomycetes and is mainly found in downy mildew pathogens. Plasmopara viticola is an obligate biotrophic oomycete causing grapevine downy mildew. Here we describe a conserved Pl. viticola secreted candidate non-RXLR effector protein with cell death-inducing activity in Nicotiana species. A similar RXLR effector candidate from the broad host range oomycete pathogen Phytophthora parasitica also induces cell death in Nicotiana. Through comparative tertiary structure modelling, we reveal that both proteins are predicted to carry WY- and LWY-domains. Our work supports the presence of LWY-domains in non-RXLR effectors and suggests that effector candidates with similar domain architecture may exert similar activities. [ABSTRACT FROM AUTHOR]

Nitric oxide (NO) is involved not only in the regulation of plant growth, development, and stress responses but also in the regulation of plant-microbe interactions. Here, we demonstrate that Piriformospora indica can induce tobacco nitrate reductase to produce a NO signal in roots which enhances nitrogen uptake capacity by inducing the expression of ammonium and nitrate transporter genes and the development of lateral root and root hair, thereby promoting tobacco growth. In addition, the NO signal induced by P. indica is significantly different from that induced by the pathogen Phytophthora nicotianae. Inoculation with P. indica did not produce H2O2 and maintained high expression of Phytoglobin 1 in roots, resulting in a significantly lower NO level than in the roots inoculated with P. nicotianae. These findings suggest that an appropriate NO level is the likely basis of plant-P. indica symbiosis, which promotes the growth of host plants. [ABSTRACT FROM AUTHOR]

Black shank caused by Phytophthora nicotianae has become a destructive soil-borne disease to different flue-cured tobacco cultivars in Southwest China. The use of biochar amendments for microorganism synergy is a promising effective strategy for P. nicotianae development control. In this study, biochar samples were prepared from tamarisk with different pyrolization temperatures (300–500 °C). The effect of pyrolytic temperatures on the bacteria immobilization efficiency of biochar was investigated. B. subtilis Tpb55 was successfully loaded on different biochars as biocontrol composites. The survival investigation of the inoculum suggested that biochar pyrolized at 300 °C (BC300), with a large pore opening diameter; a greater pore volume exhibited a better Tpb55 immobilization. A pot experiment indicated that Tpb55-loaded BC300 had a more pronounced decrease in the disease severity index of black shank disease and an increase in the soil pH, alkali-hydrolyzable nitrogen, soil-available phosphorus, and available potassium. BC300 inoculated with Tpb55 showed the highest control effect (79.60%) against tobacco black shank in the pot experiments, with the lowest copy number of P. nicotianae DNA. In conclusion, biochar-immobilized Tpb55 may provide a new strategy for preventing and controlling tobacco black shank. [ABSTRACT FROM AUTHOR]

Abstract Background Black shank disease caused by Phytophthora nicotianae is a serious threat to flue-cured tobacco production. Whole-plant resistance is characterized by the expression of a number of pathogenesis-related proteins, genes, and the activity of different defense-related enzymes. In this study, we investigated the activity of defense-related enzymes and expression of differentially expressed proteins through the iTRAQ technique across two flue-cured tobacco cultivars, i.e., K326 and Hongda, in response to the black shank pathogen. Results Results showed that the highest disease incidence was recorded in flue-cured tobacco cultivar Hongda compared with K326, which shows that Hongda is more susceptible to P. nicotianae than K326. A total of 4274 differentially expressed proteins were detected at 0 h and after 24 h, 72 h of post-inoculation with P. nicotianae. We found that 17 proteins induced after inoculation with P. nicotianae, including pathogenesis (5), photosynthesis (3), oxidative phosphorylation (6), tricarboxylic acid cycle (1), heat shock (1), and 14–3-3 (1) and were involved in the resistance of flue-cured tobacco against black shank disease. The expression of 5 pathogenesis-related proteins and the activities of defense-related enzymes (PPO, POD, SOD, and MDA) were significantly higher in the leaves of K326 than Hongda after inoculation with P. nicotianae. Conclusion These results provide new molecular insights into flue-cured tobacco responses to P. nicotianae. It is concluded that differences in protein expressions and defense-related enzymes play an important role in developing resistance in flue-cured tobacco cultivars against black shank disease.

• According to the structure of existing amide SDHI fungicides, 40 new coumarin-quinoline amide derivatives were designed and synthesized reasonably. The structures of the compounds were confirmed and characterized by 1H NMR, 13C NMR, FT-IR, and HRMS. • The compound 11g was confirmed by single-crystal X-ray diffraction. • Through a series of in vitro activity tests, compounds 11t and 12t were found to have good antifungal activity against Rice sheath blight, which provides theoretical support for further study of SDHI antifungal drugs. • The molecular docking studies of the representative compounds were performed. Succinate dehydrogenase inhibitors (SDHI) are widely used in plant antifungal agents. To break the barrier of resistance, a series of new coumarin-quinolinamide SDHI derivatives containing monocyclic monoterpenes were designed and synthesized using natural camphor or natural menthol as lead compounds, and their structures were characterized by FT-IR, 1H NMR, 13C NMR and HRMS. In vitro antifungal activity test results showed that the target compounds had inhibitory activity against most plant pathogenic fungi, especially against Rhizoctonia solani and Phytophthora nicotianae var. nicotianae , which was superior to other fungi. Among them, compounds 11t and 12t showed better inhibitory effects on Rhizoctonia solani than the commercial fungicide tricyclazole, with EC 50 of 16.90 mg/L and 27.09 mg/L, respectively. Based on this, the detached leaf assay was used to further explore the in vivo therapeutic and preventive effects of compounds 11t and 12t on rice sheath blight in plants. The results of the antifungal activity test in vivo showed that compound 11t was slightly better than the positive control, while compound 12t was close to the control effect of azoxystrobin. More importantly, the more bioactive compounds 11t and 12t did not affect the germination of cowpea seeds and also did not affect the growth of normal human hepatocytes and kidney cells. Molecular docking experiments showed that the introduction of the diethylamino group could promote the formation of hydrogen bonds between the hydrogen atom on the amide bond of the target compound and residue Tyr91, and compounds 11t and 12t had smaller free energy between the amino acid residue, which would enhance the antifungal activity of the compounds. These studies proved the potential value of this series of compounds for the study of novel amide-based SDHI fungicides. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) and Chitooligosaccharide (COS) can increase the resistance of plants to disease. COS can also promote the symbiosis between AMF and plants. However, the effects of AMF & COS combined application on the rhizosphere soil microbial community of tobacco and the improvement of tobacco's resistance to black shank disease are poorly understood.·We treated tobacco with AMF, COS, and combined application of AMF & COS (AC), respectively. Then studied the incidence, physio-biochemical changes, root exudates, and soil microbial diversity of tobacco seedling that was inoculated with Phytophthora nicotianae. The antioxidant enzyme activity and root vigor of tobacco showed a regular of AC > AMF > COS > CK, while the severity of tobacco disease showed the opposite regular. AMF and COS enhance the resistance to black shank disease by enhancing root vigor, and antioxidant capacity, and inducing changes in the rhizosphere microecology of tobacco. We have identified key root exudates and critical soil microorganisms that can inhibit the growth of P. nicotianae. The presence of caprylic acid in root exudates and Bacillus (WdhR-2) in rhizosphere soil microorganisms is the key factor that inhibits P. nicotianae growth. AC can significantly increase the content of caprylic acid in tobacco root exudates compared to AMF and COS. Both AMF and COS can significantly increase the abundance of Bacillus in tobacco rhizosphere soil, but the abundance of Bacillus in AC is significantly higher than that in AMF and COS. This indicates that the combined application of AMF and COS is more effective than their individual use. These findings suggest that exogenous stimuli can induce changes in plant root exudates, regulate plant rhizosphere microbial community, and then inhibit the growth of pathogens, thereby improving plant resistance to diseases. [Display omitted] • AMF & COS can enhance the resistance of tobacco to black shank. • Co-application of AMF & COS increased caprylic acid in tobacco root exudates. • Caprylic acid can effectively inhibit the growth of P. nicotianae. • AMF & COS can increase the abundance of Bacillus in tobacco rhizosphere soil. • Bacillus has a significantly negative effect on the growth of P. nicotianae. [ABSTRACT FROM AUTHOR]

Five novel imidazole-functionalized chitosan derivatives 3a-3e were synthesized via addition reactions of chitosan with imidazole derivatives. The partial incorporation of imidazole moiety in chitosan were confirmed by FTIR, UV, 1H NMR, XRD, SEM and GPC. Meanwhile, the antifungal activity against three common plant pathogenic fungi: Phytophthora nicotianae (P. nicotianae), Fusarium graminearum (F. graminearum) and Rhizoctonia solani (R. solani), was assayed in vitro at 0.5 and 1.0 mg/mL by hyphal measurement, and the introduction of imidazole group can influence the antifungal activity. At 0.5 mg/mL, 3e inhibited P. nicotianae growth by 42 % and had an inhibitory index against R. solani of 50 %. Derivative 3e was more effective than unmodified chitosan whose antifungal index was 17 % against P. nicotianae and 22 % against R. solani. To our surprise, at 1.0 mg/mL, the inhibition rate of 3e against R. solani can reach 99 %, while the inhibition rate of chitosan is only 38 %. These results indicated that some imidazole chitosan derivatives with enhanced antifungal activities could serve as potential biomaterial for antifungal application. [Display omitted] [ABSTRACT FROM AUTHOR]

Phytophthora nicotianae is a devastating pathogen in citrus and tolerant rootstocks are required for its management. Seven Jatti Khatti (JK, a rough lemon strain; susceptible) × Poncirus trifoliata (PT; tolerant) hybrids were screened against P. nicotianae. In feeder root rot based evaluation, three hybrids were found moderately tolerant (MT) while four were moderately susceptible (MS). The H 2 O 2 in plant pathogen interactions contributes in resistance/susceptibility to the biotrophic/necrotrophic pathogens. To comprehend its role in citrus against Phytophthora (a hemi-biotrophic pathogen), H 2 O 2 , lipid peroxidation, and peroxidase (POD) activity were determined in Phytophthora inoculated and non-inoculated roots of JK, PT, three MT and one MS hybrids at 10, 20 and 30 days post inoculation (dpi). The tolerant parent, PT and MT hybrids exhibited lower or stable H 2 O 2 content in Phytophthora inoculated plants at 20 or 30-dpi. Their POD activity increased at 10-dpi, depicting its role in H 2 O 2 homoeostasis. At 30-dpi, JK and MS hybrid showed significantly higher H 2 O 2 content (4.10 and 3.62 μmol g−1 FW), compared to 1.88 μmol g−1 FW in PT. The lipid peroxidation content significantly increased in JK or MS hybrid at 20 or 30-dpi. The susceptible or MS individuals displayed significantly higher (18–25 % higher) electrolyte leakage than their control. A strong positive association (r = 0.89) was found between electrolytes leakage and H 2 O 2 accumulation at 30-dpi. The POD activity and H 2 O 2 at 10-dpi showed strong negative correlation (r = −0.86). Results infer that high H 2 O 2 causes cellular death and contributes to Phytophthora susceptibility in citrus. It can serve as a biomarker for predicting relative sensitivity to Phytophthora. • Three citrus hybrids with moderate tolerance to Phytophthora nicotianae identified. • Oxidative stress (H 2 O 2 , MDA, peroxidase activity) examined in citrus under P. nicotianae infection. • Susceptible genotypes showed higher H 2 O 2 accumulation than tolerant ones. • Tolerant genotype recorded initial higher peroxidase activity. [ABSTRACT FROM AUTHOR]

Chrysanthemum is an important flower crop grown in different parts of the world. Apparently there are new reports of chrysanthemum collar rot and root rot caused by Phytophthora sp. around the world. In recent years there has been increase in incidence of Phytophthora root and collar rot in chrysanthemum and no information is available about this disease in India. Therefore the aim of the present study is to isolate and characterize the pathogen causing collar rot and root rot disease of chrysanthemum. During year 2021, the plants exhibiting collar rot and root rot disease symptoms were received from the local farmers. Based on initial micro-morphological observation it was identified as Phytophthora sp. Further the pure culture of pathogen was isolated and confirmed its identity through cultural, morphological and amplification of the three regions/genes (ITS, tef-1α and β-tubulin) of Phytophthora sp. Phylogenetic analysis of concatenated sequence derived from ITS, tef-1 and β-tubulin sequences of five Phytophthora isolates (PhN1, PhN2, PhN3, PhN4 and PhN5) showed close clustering of these isolates with Phytophthora nicotianae isolates infecting different crops. This is first detailed characterization of Phytophthora nicotianae causing collar rot and root rot in chrysanthemum in India.

Highlights: The endophytic community in apple leaves relates to geographic locations, apple varieties, and environment, providing the basis to explain the mechanisms underlying the establishment of apple endophytic communities and may help to devise apple disease management strategies. The dominant culturable endophytic bacteria Bacillus velezensis and B. subtilis successfully inhibit not only apple pathogens Alternaria alternata, Botryosphaeria dothidea, Valsa mali, Fusarium oxysporum, F. solani, and Rosellinia necatrix, but also F. oxysporum f. sp. cubense (banana Fusarium wilt) and Phytophthora nicotianae (tobacco black shank). The endophytic bacteria in apple leaves from apple-producing areas of Yunnan, China were isolated and identified on the basis of bacterial colony morphology and nucleotide sequences of 16S rRNA and rpoB genes. The endophytic bacterial isolates with nitrogen, phosphorus, and potassium utilization abilities were screened by culturing on functional media. A total of 5709 isolates of culturable endophytic bacteria (CEB) were isolated from 30 apple leaf samples collected from different regions. A total of 39 CEB representative isolates were identified as Bacillus velezensis, B. subtilis, B. licheniformis, B. safensis, B. pumilus, and Priestia megaterium. Among them, B. velezensis and B. subtilis were the main CEB, accounting for 55.00% and 34.37%, respectively, which exhibited potential inhibition on not only the main apple disease pathogens of Alternaria alternata, Valsa mali, Fusarium oxysporum, and Rosellinia necatrix, but also some important and uncontrollable phytopathogens, including F. oxysporum f. sp. cubense that causes banana Fusarium wilt, and Phytophthora nicotianae that causes tobacco black shank. Among these isolated endophytic bacteria species, a total of 10 strains, including b3, b4, b16, b17, b20, and b23 of B. subtilis, b7, b24, and b28 of B. licheniformis, and b38 of B. velezensis, can fix nitrogen; 8 strains, including b7 and b28 of B. licheniformis, b5, b10, and b23 of B. subtilis, b8 of B. safensis, and b6 of Priestia megaterium, could dissolve inorganic phosphorus; 11 strains, including b9, b12, b14, b30, b34, and b43 of B. velezensis, b6 of Priestia megaterium, and b17, b18, b20, and b26 of B. subtilis, could degrade organic phosphorus; and 5 strains, including b4, b5, and b26 of B. subtilis, and b7 and b28 of B. licheniformis could dissolve potassium. These strains are valuable resources of endophytic bacteria that have adapted to the ecological environment of the Cold Plateau apple-production area and could be used as plant disease biocontrol agents and biofertilizers of crops. The culturable phyllosphere endophytes in apple leaves relate to geographic locations, apple varieties, and environment, providing the basis to explain the mechanisms underlying the establishment of apple endophyte diversity and may help to devise apple disease management strategies. [ABSTRACT FROM AUTHOR]

Plant health is of utmost importance for optimal agricultural production and sustainability. Unfortunately, biotic and abiotic factors put a major constraint on crop safety and productivity. Plant diseases caused by oomycetes inflict serious damage to various crops. Moreover, the injudicious use of chemical pesticides poses threats related to pesticide resistance development in pathogens and environmental pollution. Biocontrol offers an effective solution for disease control; however, research on biocontrol of oomycete-related diseases is scarce. Thus, this study undertakes the screening of biocontrol resources for the effective management of oomycete-related plant diseases. In this regard, 86 isolates of Trichoderma spp. were assessed against Phytophthora nicotianae, P. capsici, Pythium vexans, P. ultimum, and P. dissotocum through dual culture assay. Furthermore, the antagonistic effect of selected isolates was studied against tobacco black shank disease and damping-off of cucumber seedlings in the greenhouse. The relative control effect of the three antagonistic Trichoderma strains AR-4, Tv-1, and ST4-1 on tobacco black shank was more than 60%, which was not significantly different from 6.88 gl-1 fluopicolide-propamocarb. Whereas, the relative control effect of Trichoderma AR-4 and ST4-1 on damping-off of cucumber seedlings was 80.33% and 82.67%, respectively, which were significantly higher than Trichoderma Tv-1 (35.49%) and fluopicolide-propamocarb (47.82%). According to the morphological and molecular characterization, the fungal strains AR-4, Tv-1, and ST4-1 were identified as Trichoderma koningiopsis, T. asperellum, and T. gamsii, respectively. In conclusion, the strains exhibited a strong antagonistic effect against oomycete pathogens and can be integrated into disease management strategies. [ABSTRACT FROM AUTHOR]

Black shank disease caused by Phytophthora nicotianae is one of the most important diseases in tobacco worldwide and can result in a devastating loss in tobacco cultivation. Many efforts have been carried out to identify the chromosome segment from Nicotiana plumbaginifolia containing a resistance locus carrying a gene named Php; however, the Php gene has not been cloned, and knowledge of the potential mechanism of the Php gene in the resistant lines is limited. To further characterize the resistance mechanism of the Php gene, we first used the resistant line "RBST" and the susceptible cultivar "Honghuadajinyuan" (HD) to obtain the near-isogenic line RBS89 containing the Php gene from RBST. RBS89 showed high resistance to black shank disease. Transcriptomic and iTRAQ analyses were applied to explore the potential defense mechanisms in RBS89 plants in comparison with HD plants with or without inoculation. Many differentially expressed genes (DEGs) and proteins were identified, and some pathogenesis-related (PR) proteins were extensively abundant in the RBS89 plants when compared with the HD plants in response to black shank disease. Importantly, overexpression of the PR gene NtPR-1B in HD plants improved the resistance of tobacco plants to black shank disease, indicating that NtPR-1B and Php genes might have similar roles in protecting tobacco from black shank disease. However, the relationship between NtPR-1B and Php genes requires further analysis. Therefore, our study provides valuable information for breeding tobacco cultivars with black shank disease resistance and sheds light on the defense mechanism of black shank disease in tobacco for enhancing Phytophthora resistance in other Solanaceae crops. [ABSTRACT FROM AUTHOR]

A series of novel indole Schiff base derivatives (2a–2t) containing a 1,3,4-thiadiazole scaffold modified with a thioether group were synthesized, and their structures were confirmed using FT-IR, 1H NMR, 13C NMR, and HR-MS. In addition, the antifungal activity of synthesized indole derivatives was investigated against Fusarium graminearum (F. graminearum), Fusarium oxysporum (F. oxysporum), Fusariummoniliforme (F.moniliforme), Curvularia lunata (C. lunata), and Phytophthora parasitica var. nicotiana (P. p. var. nicotianae) using the mycelium growth rate method. Among the synthesized indole derivatives, compound 2j showed the highest inhibition rates of 100%, 95.7%, 89%, and 76.5% at a concentration of 500 μg/mL against F. graminearum, F. oxysporum, F.moniliforme, and P. p. var. nicotianae, respectively. Similarly, compounds 2j and 2q exhibited higher inhibition rates of 81.9% and 83.7% at a concentration of 500 μg/mL against C. lunata. In addition, compound 2j has been recognized as a potential compound for further investigation in the field of fungicides. [ABSTRACT FROM AUTHOR]

Oomycete pathogens that belong to the genus Phytophthora cause devastating diseases in solanaceous crops such as pepper, potato, and tobacco, resulting in crop production losses worldwide. Although the application of fungicides efficiently controls these diseases, it has been shown to trigger negative side effects such as environmental pollution, phytotoxicity, and fungicide resistance in plant pathogens. Therefore, biological control of Phytophthora-induced diseases was proposed as an environmentally sound alternative to conventional chemical control. In this review, progress on biological control of the soilborne oomycete plant pathogens, Phytophthora capsici, Phytophthora infestans, and Phytophthora nicotianae, infecting pepper, potato, and tobacco is described. Bacterial (e.g., Acinetobacter, Bacillus, Chryseobacterium, Paenibacillus, Pseudomonas, and Streptomyces) and fungal (e.g., Trichoderma and arbuscular mycorrhizal fungi) agents, and yeasts (e.g., Aureobasidium, Curvibasidium, and Metschnikowia) have been reported as successful biocontrol agents of Phytophthora pathogens. These microorganisms antagonize Phytophthora spp. via antimicrobial compounds with inhibitory activities against mycelial growth, sporulation, and zoospore germination. They also trigger plant immunity-inducing systemic resistance via several pathways, resulting in enhanced defense responses in their hosts. Along with plant protection, some of the microorganisms promote plant growth, thereby enhancing their beneficial relations with host plants. Although the beneficial effects of the biocontrol microorganisms are acceptable, single applications of antagonistic microorganisms tend to lack consistent efficacy compared with chemical analogues. Therefore, strategies to improve the biocontrol performance of these prominent antagonists are also discussed in this review. [ABSTRACT FROM AUTHOR]

Phytophthora nicotianae and Rhizoctonia solani are the well-described soilborne pathogens of concern causing Phytophthora and Rhizoctonia root rot, respectively, of red maple plants (Acer rubrum L.), resulting in substantial economic losses to nursery growers. The management of root and crown rot disease of red maple is a big challenge. The objective of this study was to test the efficacy of several fungicide and biofungicide products to control Phytophthora and Rhizoctonia root rot on red maple plants in greenhouse conditions. Treatments, including fungicides and biofungicides, and nontreated and inoculated and nontreated and noninoculated as controls were arranged in a completely randomized design with six replications. Red maples planted in number 1 nursery containers were artificially inoculated with P. nicotianae or R. solani. Plant height, plant width, total fresh weight, and root fresh weight were measured and roots were assessed for root rot disease severity based on a scale of 0% to 100% root damaged. The pathogen recovery percentage of plant roots was determined by culturing ten randomly selected root pieces (≈1 cm long) cut from the root tips on Phytophthora selective medium (PARPH-V8) or Rhizoctonia semi-selective medium. All tested fungicides and biofungicides reduced Phytophthora and Rhizoctonia root rot on red maple plants compared with the nontreated and inoculated control. Likewise, pathogen recovery was lower for fungicide-treated and biofungicide-treated plants. Fungicides, such as mefenoxam, oxathiapiprolin, pyraclostrobin plus boscalid, and pyraclostrobin provided the most effective control of Phytophthora root rot. Pyraclostrobin plus boscalid and pyraclostrobin followed by biofungicides Bacillus amyloliquefaciens strain F727 and Trichoderma harzianum Rifai strain T-22 plus T. virens strain G-41 were most effective for suppressing Rhizoctonia root rot. There were no differences in plant height, plant width, plant fresh weight, and root fresh weight among the treatments. These findings will help nursery producers make decisions while formulating soilborne disease management strategies for red maple production. [ABSTRACT FROM AUTHOR]

Plant immunity is activated upon perception of pathogens and often affects growth when it is constitutively active. It is still a challenge to balance plant immunity and growth in disease resistance breeding. Here, we demonstrated that soybean (Glycine max) polyamine oxidase (GmPAO) confers resistance to multiple Phytophthora pathogens, but has no obvious adverse impact on agronomic traits. GmPAO produces H2O2 by oxidizing spermidine and spermine. Phytophthora sojae induces an increase in these two substrates, and thus promotes GmPAO-mediated polyamine catabolism specifically during infection. Interestingly, we found that the two substrates showed higher accumulation in transgenic soybean lines overexpressing GmPAO than in WT and CK after inoculation with P. sojae to ensure H2O2 production during infection, rather than directly inhibit P. sojae. In these transgenic soybean plants, the significantly enhanced resistance to different P. sojae isolates was achieved; PAMP-induced H2O2 accumulation was enhanced by GmPAO overexpression. Moreover, transient expression of GmPAO also significantly improved Nicotiana benthamiana resistance to Phytophthora capsici and Phytophthora parasitica in agroinfiltration assays. Our results provide a novel approach to allow rapid defense responses in plants upon pathogen infection while minimizing growth penalties under normal conditions, with a clear mechanism in which plant promotes H2O2 production via pathogen-activated substrates. [ABSTRACT FROM AUTHOR]

Tobacco (Nicotiana tabacum) is one of the most important economic crops in China; however, black shank caused by Phytophthora parasitica is major threat to its cultivation. So far, little is known regarding potential antagonistic effects of endophytes on plant pathogens. A total of 109 culturable endophytic fungal strains were recovered from various tissues of six tobacco cultivars that are commonly cultivated in southwestern China. Morphological and molecular identification showed that these isolates belonged to 18 different genera, including Aspergillus, Chaetomium, Gibellulopsis and Penicillium as predominant genera, which were frequently observed in stem, leaf and root tissues. Among them, only 17 endophytic fungal strains exerted antagonistic effects on P. parasitica in the dual‐culture test, and the highest inhibition rate of 73% was produced by a Penicillium janthinellum strain isolated from stem tissue of a cultivar HD. Nevertheless, a field trial revealed that Shannon–Wiener indices were negatively correlated with the disease index and with the incidence of tobacco blank shank in cultivars K326, YUN85, D101 and GUI1, which was further supported by the evaluation of endophytic community similarity. Our results contribute to the understanding of functions and diversity of endophytic fungi, and culturable endophytic fungal strains may be considered potential libraries for screening novel bioactive and effective metabolites to control P. parasitica in crops which requires further research. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• The roots of non-host plant interfere infection of Phytophthora nicotianae.• Vanillin and other compounds play key roles in antimicrobial activity of fennel roots.• ROS accumulation is the potentially mechanism involved in inhibition of antimicrobial compounds on P. nicotianae.Crop rotations are widely used because they can significantly reduce the incidence of pests and diseases. The interactions between non-host roots and pathogens may be key in the inhibition of soilborne pathogens in crop rotations. Interactions between fennel (Foeniculum vulgare) roots/root exudates and Phytophthora nicotianae were investigated because of the known allelopathy between fennel and tobacco (Nicotiana tabacum). The effects of the key compounds in the fennel rhizosphere on the mycelial growth and zoospore behavior of P. nicotianae were assessed. The roots of fennel attracted P. nicotianae zoospores and inhibited their motility and the germination of cystospores, with some cystospores rupturing. 4-ethylacetophenone, vanillin and N-formylpiperidine were consistently identified in the fennel rhizosphere and were found to interfere with the infection of P. nicotianae, especially vanillin. Hyphae treated with these compounds produced more abnormal branches and accumulated reactive oxygen species. These interspecific interactions between non-host roots and pathogens were found to be an important factor in the inhibition by fennel of infection by P. nicotianae.

Phytophthora nicotianae and Rhizoctonia solani are the well-described soilborne pathogens of concern causing Phytophthora and Rhizoctonia root rot, respectively, of red maple plants (Acer rubrum L.), resulting in substantial economic losses to nursery growers. The management of root and crown rot disease of red maple is a big challenge. The objective of this study was to test the efficacy of several fungicide and biofungicide products to control Phytophthora and Rhizoctonia root rot on red maple plants in greenhouse conditions. Treatments, including fungicides and biofungicides, and nontreated and inoculated and nontreated and noninoculated as controls were arranged in a completely randomized design with six replications. Red maples planted in number 1 nursery containers were artificially inoculated with P. nicotianae or R. solani. Plant height, plant width, total fresh weight, and root fresh weight were measured and roots were assessed for root rot disease severity based on a scale of 0% to 100% root damaged. The pathogen recovery percentage of plant roots was determined by culturing ten randomly selected root pieces (≈1 cm long) cut from the root tips on Phytophthora selective medium (PARPH-V8) or Rhizoctonia semi-selective medium. All tested fungicides and biofungicides reduced Phytophthora and Rhizoctonia root rot on red maple plants compared with the nontreated and inoculated control. Likewise, pathogen recovery was lower for fungicide-treated and biofungicide-treated plants. Fungicides, such as mefenoxam, oxathiapiprolin, pyraclostrobin plus boscalid, and pyraclostrobin provided the most effective control of Phytophthora root rot. Pyraclostrobin plus boscalid and pyraclostrobin followed by biofungicides Bacillus amyloliquefaciens strain F727 and Trichoderma harzianum Rifai strain T-22 plus T. virens strain G-41 were most effective for suppressing Rhizoctonia root rot. There were no differences in plant height, plant width, plant fresh weight, and root fresh weight among the treatments. These findings will help nursery producers make decisions while formulating soilborne disease management strategies for red maple production.

Citrus is an important economic plant in Thailand. The infection of citrus roots by Phytophthora nicotianae leads to root rot, reduced growth, and branch death. Although fosetyl aluminum and metalaxyl are commonly employed to address citrus root rot, they possess limitations in terms of their ability to diffuse to the root of citrus. Vernonia amygdalina leaf ethyl acetate extract (VLE) has been demonstrated to effectively inhibit Pythium deliense, a fungus closely related to Phytophthora nicotianae. This study aimed to investigate the anti-fungus activity of fractions obtained from the ethyl acetate extract of Vernonia amygdalina leaf against Phytophthora nicotianae, identify the most effective fraction, and formulate it into polymeric micro/nanoparticles using the electrospray process. The findings revealed that the VLE fraction eluted with ethanol:chloroform 1:1 had a high alkaloid content from metabolomic study and exhibited the potential to inhibit Phytophthora nicotianae at a concentration of 200 µg/mL. Consequently, this fraction was selected for incorporation into polymer blends of Poly Vinyl Alcohol/cellulose acetate to generate electrosprayed particles with a diameter of 0.97 ± 0.55 microns. These particles effectively suppressed in vitro Phytophthora nicotianae, thereby suggesting that VLE-containing electrosprayed particles have the potential to be applied and their in vivo performance in the treatment of citrus root rot evaluated in future experiments.

As an ornamental plant, Fatsia japonica has been widely used in gardens. From April 2021 to 2022, a disease that caused the wilting and root rot of F. japonica in a large area was observed, which eventually led to the plants wilting and dying, while the leaves did not fall off. This disease greatly reduced the landscape effect of plants. An oomycete species was isolated from the roots of the infected plants. This colony morphology was slightly radial to stellate, and the aerial mycelium was flocculent. Oval sporangia with papillae, apical chlamydospores and zoospores formed in sporangia were observed. The morphological characteristics were consistent with Phytophthora. For accurate identification, the internal transcribed spacer (ITS), cytochrome oxidase subunit II (COXII) and large ribosomal subunit (LSU) genes were amplified and sequenced. The species was identified as Phytophthora nicotianae using phylogenetic analysis. Finally, the disease was reproduced by inoculating healthy F. japonica with a zoospore suspension; the symptoms were consistent with those of natural infections, and the isolate obtained from artificially infected plants had the same morphological characteristics as the inoculated isolate. The results demonstrated that P. nicotianae is the pathogenic factor of root rot. of F. japonica. This is the first report of root rot on F. japonica caused by P. nicotianae in China.

In this study, an oomycete strain FQ01 of Phytophthora nicotianae, which could cause destructive postharvest disease, was isolated. At present, chemical fungicides are themain reagents used for controlling Phytophthora diseases. It is necessary to find new control techniques that are environmentally friendly. The biocontrol activity of Hanseniaspora uvarumMP1861 against P. nicotianae FQ01 was therefore investigated. Our results revealed that the volatile organic compounds (VOCs) released by the yeast strain MP1861 could inhibit the development of P. nicotianae FQ01. The major component of the VOCs produced by the yeast strainMP1861 was identified to be ethyl acetate (70.8%). Biocontrol experiments showed that Phytophthora disease in tomato fruit could be reduced by 95.8% after the yeast VOCs treatment. Furthermore, ethyl acetate inhibited the mycelial growth of the oomycete strain FQ01, and damaged the pathogen cell membrane. This paper describes the pioneering utilization of the yeast strain MP1861 for biocontrol of postharvest fruit rot in tomato caused by P. nicotianae. [ABSTRACT FROM AUTHOR]

Phytophthora root rot, caused by Phytophthora nicotianae Breda de Haan, is one of the destructive diseases of boxwood (Buxus sempervirens L.) and can affect all growth stages of field- and container-grown boxwood plants. Management is a problem and is only possible through an integrated approach. In this study, the efficacy of fungicides, biofungicides, host-plant defense inducers, and fertilizer were evaluated to manage Phytophthora root rot of boxwood. The objective of this experiment was to develop fungicide and biofungicide recommendations for Phytophthora root rot management in boxwood production. Field and greenhouse experiments were conducted in 2019 (Trial 1) and 2020 (Trial 2). The field experiment was arranged in a completely randomized design with four plots per treatment with five single 'Green Velvet' boxwood plants per plot. The greenhouse experiment was arranged in a completely randomized design with five single 'Green Velvet' container-grown boxwood plants per treatment. Plots/containers were inoculated with P. nicotianae grown on rice grains. Plant growth data such as height and average width were recorded at the beginning and end of the experiments. Total plant fresh weight and root fresh weight were recorded at the end of the experiments. Roots were assessed for root rot disease severity using a scale of 0% to 100% roots affected. Treatments used in both experiments were fungicides--ametoctradin + dimethomorph, fluzapyroxad, mefenoxam, oxathiapiprolin, pyraclostrobin, pyraclostrobin + boscalid; host-plant defense inducers--aluminum tris-drench, aluminum tris-foliar, potassium salts of phosphoric acid; biofungicides--Trichoderma harzianum Rifai strain T-22 + Trichoderma virens strain G-41, Bacillus amyloliquefaciens Priest; fertilizer--water-soluble nitrogen (nitrogen 5%) and soluble potash; and combination of water-soluble nitrogen, soluble potash, and T. harzianum Rifai strain T-22 + T. virens strain G-41. All treatments were drench applied except one of the aluminum tris, which was applied as foliar. The controls were nontreated, inoculated and nontreated, and noninoculated boxwood plants. In the greenhouse experiments, treatments that effectively reduced disease severity were pyraclostrobin, ametoctradin + dimethomorph, and oxathiapiprolin. In the field experiments, treatments such as pyraclostrobin, oxathiapiprolin, mefenoxam, fluzapyroxad, and combination of water-soluble nitrogen (nitrogen 5%), soluble potash, and T. harzianum Rifai strain T-22 + T. virens strain G-41 effectively reduced Phytophthora root rot severity. Oxathiapiprolin and pyraclostrobin are the chemical fungicides that were effective in both field and greenhouse experiments. [ABSTRACT FROM AUTHOR]

Copyright of Mycosystema is the property of Mycosystema Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

SUMMARY: Oomycetes are diploid eukaryotic microorganisms that seriously threaten sustainable crop production. MicroRNAs (miRNAs) and corresponding natural antisense transcripts (NATs) are important regulators of multiple biological processes. However, little is known about their roles in plant immunity against oomycete pathogens. In this study, we report the identification and functional characterization of miR398b and its cis‐NAT, the core‐2/I‐branching beta‐1,6‐N‐acetylglucosaminyltransferase gene (AtC2GnT), in plant immunity. Gain‐ and loss‐of‐function assays revealed that miR398b mediates Arabidopsis thaliana susceptibility to Phytophthora parasitica by targeting Cu/Zn‐Superoxidase Dismutase1 (CSD1) and CSD2, leading to suppressed expression of CSD1 and CSD2 and decreased plant disease resistance. We further showed that AtC2GnT transcripts could inhibit the miR398b–CSDs module via inhibition of pri‐miR398b expression, leading to elevated plant resistance to P. parasitica. Furthermore, quantitative reverse transcription PCR, RNA ligase‐mediated 5′‐amplification of cDNA ends (RLM‐5′ RACE), and transient expression assays indicated that miR398b suppresses the expression of AtC2GnT. We generated AtC2GnT‐silenced A. thaliana plants by CRISPR/Cas9 or RNA interference methods, and the Nicotiana benthamiana NbC2GnT‐silenced plants by virus‐induced gene silencing. Pathogenicity assays showed that the C2GnT‐silenced plants were more susceptible, while AtC2GnT‐overexpressing plants exhibited elevated resistance to P. parasitica. AtC2GnT encodes a Golgi‐localized protein, and transient expression of AtC2GnT enhanced N. benthamiana resistance to Phytophthora pathogens. Taken together, our results revealed a positive role of AtC2GnT and a negative regulatory loop formed by miR398b and AtC2GnT in regulating plant resistance to P. parasitica. [ABSTRACT FROM AUTHOR]

Lower bed single-row pineapple cultivation could protect pineapple from soil erosion during the rainy season and drought period; however, disease problems could arise as a result of water logging. Two experiments were conducted in Ultisol soil using a lower bed single row to investigate the ability of gypsum to provide soil calcium (Ca) to the pineapple plant, plant resistance to heart rot disease, and provide a better effect on crop growth and fruit quality. In the first trial, four levels of gypsum (0, 1.0, 1.5 and 2.0 Mg·ha-1) and dolomite (2 Mg·ha-1) were spread and incorporated into soil that had been saturated with Phytophthora nicotianae inoculums. In the second trial, gypsum treatments (0, 1.0, 1.5, 2.0 and 2.5 Mg·ha-1) were used as a basic fertiliser in the row between the single beds. P. nicotianae attacked all treatments at 6 weeks after planting (WAP), and at 10 WAP, the mortality of the dolomite treatment reached 63.8%, significantly higher than that of the gypsum treatments (3.3%-14.3%). In the second experiment, gypsum significantly increased plant weight from 3 to 9 months after planting (MAP), especially when applied at 1.5-2.5 Mg·ha-1. Fruit texture, total soluble solids (TSS), and titratable acidity (TA) were not significantly different between treatments, but they all met the standards for canned pineapple grades. The results showed that soil-applied gypsum before planting provides soil calcium, meets the plant Ca requirement during an early and fast growth stage, and is free of heart rot disease. [ABSTRACT FROM AUTHOR]

Tobacco black shank is a kind of soil-borne disease caused by the Oomycete Phytophthora parasitica. This disease is one of the most destructive diseases to tobacco (Nicotiana tabacum L.) growth worldwide. At present, various measures have been taken to control this disease, but they still have different challenges and limitations. Studies have shown that β-aminobutyric acid (BABA), a nonprotein amino acid, can enhance disease resistance in plants against different varieties of pathogens. However, it is unclear whether BABA can induce plants to resist Phytophthora parasitica infection. Therefore, this study aims to explore the effect and related mechanism of BABA against tobacco black shank. Our results showed that 5 mmol.L-1 BABA had an obvious anti-inducing effect on the pathogenic fungus and could effectively inhibit the formation of dark spots in the stems. The results also showed that a large amount of callose deposition was observed in BABA-treated tobacco. Furthermore, the application of BABA induced the accumulation of H2O2 in tobacco and effectively regulated the homeostasis of reactive oxygen in tobacco plants, reducing the toxicity of H2O2 to plants while activating the defense system. In addition, BABA spray treatment could induce an increase in the concentrations of salicylic acid (SA) and jasmonic acid-isoleucine (JA-Ile) in tobacco, and the gene expression results confirmed that BABA upregulated the expression of SA-related genes (PR1, PR2 and PR5), JA-related genes (PDF1.2) and ET-related genes (EFE26 and ACC oxidase) in tobacco plants. Taken together, BABA could activate tobacco resistance to black shank disease by increasing H2O2 accumulation, callose deposition, plant hormone (SA and JA-Ile) production, and SA-, JA-, and ET- signaling pathways. [ABSTRACT FROM AUTHOR]

Cover crops represent a potential tool for suppression of soil borne diseases in woody ornamental nursery production, which can cause significant economic losses. Field experiments were conducted in 2019 and 2020 to explore the effects of a cover crop and the timing of cover crop disturbance on soilborne disease suppression. Soils from red maple (Acer rubrum 'October Glory') plantations grown with or without a cover crop [crimson clover (Trifolium incarnatum)] were sampled following senescence of the cover crop. Greenhouse bioassays were conducted using red maple cuttings on inoculated (with Rhizoctonia solani, Phytopythium vexans or Phytophthora nicotianae) and non-inoculated field soils. Plant height, total and root fresh weight were measured, and the roots were assessed for disease severity on a 0 to 100% root damage scale. Pathogen recovery was assessed by culturing root pieces (~1 cm length) on oomycetes or Rhizoctonia semi-selective media. Soil samples were analyzed for organic matter, nitrogen, phosphorus, potassium, pH and Pseudomonad population count. A minimal effect of cover crop disturbance timing (late fall or early spring) was found on disease suppression. Cover crop usage reduced disease severity and pathogen recovery in red maple field soils. Plants grown in cover cropped soil had greater total, root and aboveground fresh weight compared with those from non-cover cropped soil, but plant height was not affected. Cover crops increased soil organic matter and total nitrogen in 2020. Pseudomonad populations were higher when cover crops were used. The results suggest that cover crops can reduce soilborne disease in woody ornamentals. [ABSTRACT FROM AUTHOR]

Chitosan is a polymer of glucosamine with antimicrobial properties and an elicitor of plant defence responses. In this study, different chitosan concentrations were assessed for impact on the life cycle of Phytophthora nicotianae Breda de Haan, an oomycete pathogen of tomato and tobacco crops. Reduced mycelial growth was observed when chitosan was added to solid media, and this inhibitory activity was amplified with increasing chitosan concentrations from 0.5 g L−1 to 2.5 g L−1. Colony morphology and hyphal diameter were unaffected by the polymer; however, the number of oospores (sexual reproductive structures) was reduced at the lowest chitosan concentration (0.5 g L−1) tested. Mycelia plugs imbibed with 0.5 g L−1 chitosan were prone to increased sporangium formation, but the effect was subdued with higher chitosan concentrations. The length/width ratio of the sporangia did not change in the presence of the polymer. Indirect germination of the sporangia was particularly sensitive to this compound, and 1.5 g L−1 completely abolished this process. The zoospores treated with chitosan formed cysts that did not germinate and were unable to infect tomato plant roots. Chitosan was also found to prime tomato plantlets for P. nicotianae resistance; a foliar application of 0.1 and 1 g L−1 of chitosan 72 h before inoculation induced host resistance, which was concurrent with increased activity of phenylpropanoid pathway markers. The results presented herein show the potential of chitosan as a tool to control P. nicotianae inoculum and increase tomato crop resistance against this pathogen. [ABSTRACT FROM AUTHOR]

Mitochondrial function depends on the RNA processing of mitochondrial gene transcripts by nucleus-encoded proteins. This posttranscriptional processing involves the large group of nuclear-encoded pentatricopeptide repeat (PPR) proteins. Mitochondrial processes represent a crucial part in animal immunity, but whether mitochondria play similar roles in plants remains unclear. Here, we report the identification of RESISTANCE TO PHYTOPHTHORA PARASITICA 7 (AtRTP7), a P-type PPR protein, in Arabidopsis thaliana and its conserved function in immunity to diverse pathogens across distantly related plant species. RTP7 affects the levels of mitochondrial reactive oxygen species (mROS) by participating in RNA splicing of nad7, which encodes a critical subunit of the mitochondrial respiratory chain Complex I, the largest of the four major components of the mitochondrial oxidative phosphorylation system. The enhanced resistance of rtp7 plants to Phytophthora parasitica is dependent on an elevated mROS burst, but might be independent from the ROS burst associated with plasma membrane-localized NADPH oxidases. Our study reveals the immune function of RTP7 and the defective processing of Complex I subunits in rtp7 plants resulted in enhanced resistance to both biotrophic and necrotrophic pathogens without affecting overall plant development. [ABSTRACT FROM AUTHOR]

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Introduction: Phytophthora nicotianae is a destructive plant pathogen with a worldwide distribution that causes root, fruit, leaf, and crown rot. Phytophthora species are the main reason for various diseases in a wide range of plant species including vegetables. Symptoms include fruit, stem, crown, and root rot. They lead to plant host death and in most cases, the economic losses caused by P. nicotianae are very high due to the diversity of the host range and its damage, therefore, controlling this pathogen is a constant challenge. Materials and methods: In order to biologically control the disease, three Streptomyces isolates including M6, M8, and M215 were selected from a large number of soil-inhabitant actinomycetes isolated from Kerman province, which showed effective anti-Oomycete activity against P. nicotianae. To better understand the inhibitory mechanism of these isolates, in vitro dual-culture assay, plant growth promotion, and pathogen control effects were investigated through the application of antagonists under laboratory and greenhouse conditions. Molecular identification of the most promising isolate was also achieved. Results: The antagonistic activity of three isolates including M8, M6, and M215 against P. nicotianae in tomato plants (super chef variety) was evaluated. Among all, based on the statistical analysis under both laboratory and glasshouse conditions, the M8 isolate had an inhibitory effect on the crown and root rot of tomato. The comparison of the effects of antagonists on the tomato plant yield indices revealed that M8 isolate had the greatest effect on increasing the growth indices of the tomato plant (super chef cultivar) including plant height, the number of flowers, shoot, and root dry weight. The M8 isolate was identified by the sequence analysis of a small ribosomal RNA subunit (16S rRNA). Based on the results of the present study, Streptomyces venetus CMU-AB225T strain had the highest similarity (96.08%) with the M8 isolate. Discussion and conclusion: The results showed that M8 isolate can be considered as a beneficial microorganism to produce some useful biofertilizers and bioactive materials to control tomato crown and root rot biologically. Some biocontrol agents such as T. harzianum and T. asperellum within composts can be effective in reducing the symptoms of Ph. nicotianae in pepper seedlings. The production of any product based on the S. venetus (M8) requires fulfilling further research steps such as the interaction of the bacterium with other beneficial soil microorganisms and its impact on the population of beneficial soil microbes, evaluation of the antimicrobial activity of M8 against other plant pathogenic fungi, fungal-like microorganisms and bacteria. Moreover, biosafety considerations and measures have to be investigated.