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The article "Supplementary Materials" in Frontiers in Microbiology discusses pathogenicity assays of Fusarium phalaenopsidis isolates on Phalaenopsis 'V3' leaves and stems. It includes phylogenetic analysis of the isolates and non-target isolates of Fusarium solani species complex. The document also covers primer specificity assays on non-Fusarium isolates and sensitivity assays of specific primers. The study provides valuable insights into the characteristics and behavior of these fungal pathogens. [Extracted from the article]

Orchids are among the most cultivated flowers in the world. Plants of Dendrobium thyrsiflorum (DT) and Cattleya wittigiana (CW), cultivated at the Botanic Garden of Bauru in São Paulo, Brazil, presented black rot symptoms. The causal organism was identified as P. palmivora on DT and P. nicotianae on CW orchids based on its morphological and molecular characterization. Inoculation caused disease symptoms and Koch's postulates were fulfilled by re-isolation of the pathogen. [ABSTRACT FROM AUTHOR]

Summary: Phytophthora parasitica causes diseases on a broad range of host plants. It secretes numerous effectors to suppress plant immunity. However, only a few virulence effectors in P. parasitica have been characterized.Here, we highlight that PpE18, a conserved RXLR effector in P. parasitica, was a virulence factor and suppresses Nicotiana benthamiana immunity. Utilizing luciferase complementation, co‐immunoprecipitation, and GST pull‐down assays, we determined that PpE18 targeted NbAPX3‐1, a peroxisome membrane‐associated ascorbate peroxidase with reactive oxygen species (ROS)‐scavenging activity and positively regulates plant immunity in N. benthamiana. We show that the ROS‐scavenging activity of NbAPX3‐1 was critical for its immune function and was hindered by the binding of PpE18. The interaction between PpE18 and NbAPX3‐1 resulted in an elevation of ROS levels in the peroxisome.Moreover, we discovered that the ankyrin repeat‐containing protein NbANKr2 acted as a positive immune regulator, interacting with both NbAPX3‐1 and PpE18. NbANKr2 was required for NbAPX3‐1‐mediated disease resistance. PpE18 competitively interfered with the interaction between NbAPX3‐1 and NbANKr2, thereby weakening plant resistance.Our results reveal an effective counter‐defense mechanism by which P. parasitica employed effector PpE18 to suppress host cellular defense, by suppressing biochemical activity and disturbing immune function of NbAPX3‐1 during infection. [ABSTRACT FROM AUTHOR]

In this study, KGMOS (DP, 2-13), derived from KGM (Konjac glucomannan), was applied to elucidate plant immunity in a Nicotiana benthamiana Phytophthora nicotianae model. Application of KGMOS (25–100 mg/L) notably inhibited P. nicotianae, resulting in reduced disease indices and a significant accumulation of defense molecules such as H2O2 and callose. Transcriptomic analysis revealed that genes shared between KGMOS-treated and control plants are involved in signaling pathways, transcription regulation, hydrogen peroxide catabolism, and oxidative stress response. This suggests that KGMOS triggers H2O2 accumulation, callose deposition, and activation of the salicylic acid (SA) and jasmonic acid/ethylene (JA/ET) pathways after pathogen inoculation. Upregulated defense-response genes in the KGMOS group included SA-related late blight-resistant, pathogenesis-related (PR), and JA/ET-related ethylene response factor (ERF) genes. Heatmap analysis showed more upregulated defense genes (PR and NPR) related to SA in the KGMOS-treated group than in controls. RT-qPCR validation revealed significant upregulation of SA and JA/ET pathway genes in KGMOS-treated plants. Higher SA content in these plants suggests enhanced disease resistance. This study concludes that KGMOS pre-treatment induced resistance against P. nicotianae, especially at a lower concentration (25 mg/L). These findings could offer valuable insights for the future application of KGMOS in controlling plant diseases for sustainable agriculture and postharvest management. [ABSTRACT FROM AUTHOR]

Small secreted peptides (SSPs), serving as signaling molecules for intercellular communication, play significant regulatory roles in plant growth, development, pathogen immunity, and responses to abiotic stress. Despite several SSPs, such as PIP, PSK, and PSY having been identified to participate in plant immunity, the majority of SSPs remain understudied, necessitating the exploration and identification of SSPs regulating plant immunity from vast genomic resources. Here we systematically characterized 756 putative SSPs across the genome of Nicotiana tabacum. 173 SSPs were further annotated as established SSPs, such as nsLTP, CAPE, and CEP. Furthermore, we detected the expression of 484 putative SSP genes in five tissues, with 83 SSPs displaying tissue‐specific expression. Transcriptomic analysis of tobacco roots under plant defense hormones revealed that 46 SSPs exhibited specific responsiveness to salicylic acid (SA), and such response was antagonistically regulated by methyl jasmonate. It's worth noting that among these 46 SSPs, 16 members belong to nsLTP family, and one of them, NtLTP25, was discovered to enhance tobacco's resistance against Phytophthora nicotianae. Overexpression of NtLTP25 in tobacco enhanced the expression of ICS1, subsequently stimulating the biosynthesis of SA and the expression of NPR1 and pathogenesis‐related genes. Concurrently, NtLTP25 overexpression activated genes associated with ROS scavenging, consequently mitigating the accumulation of ROS during the subsequent phases of pathogenesis. These discoveries indicate that these 46 SSPs, especially the 16 nsLTPs, might have a vital role in governing plant immunity that relies on SA signaling. This offers a valuable source for pinpointing SSPs involved in regulating plant immunity. [ABSTRACT FROM AUTHOR]

To prevent threats from pathogens such as Phytophthora species from international plant trade, molecular identification techniques are needed for rapid, accurate quarantine inspection. Here, for quarantine control in Japan, we developed a simple DNA extraction for plants and a practical detection method that combines multiplexed PCR using primers specific for Phytophthora species, for P. nicotianae, which is the only non-quarantine Phytophthora species, and as internal controls, for plants. For the new genus-level primer set, we modified previously reported genus-specific primers to improve detectability. The new primers were able to detect mycelial DNA of 155 taxa among Phytophthora clades 1–10, with a sensitivity of 100 fg/µL for three representative species, P. ramorum, P. kernoviae and P. nicotianae. In the PCRs using DNA from non-target species, amplification was observed for only three taxa, and for some strains, four taxa in a closely related genus. Duplex and triplex PCR of the genus-specific primers combined with previously reported plant primers verified the success of DNA extraction and PCR detection from diseased plant samples, and in the triplex PCR, whether the pathogen was diagnosed as P. nicotianae or not by the species-specific primer. The new method detected the pathogen in naturally infected and inoculated plants. The amplicons using the genus-specific primer have enough variation to be sequenced to identify the species. This new method can be used immediately for detecting Phytophthora species and for quarantine control in Japan. [ABSTRACT FROM AUTHOR]

Tobacco (Nicotiana tabacum L.) is a significant cash crop in China. In this study, we investigated the effect of microbial agent application with different rates and application periods on tobacco diseases and soil microorganisms. During the tobacco growing process, the doses of 0, 30 and 60 kg hm-1 were applied at the time of ridging, transplanting and resettling, respectively. 16S rRNA and ITS gene sequencing techniques were utilized to analyze the microbial communities in tobacco fields. The results indicated that the application of microbials significantly decreased the incidence rate and disease index of Ralstonia solanacearum and Phytophthora nicotianae. Moreover, the application of microbial agents resulted in an increase in the abundance of specific fungi (Basidiomycota) and bacteria (Nitrospirae), while reducing the abundance of other fungi (Blastocladiomycota) and bacteria (Spirochaetes). The optimum application dose of microbial agents at the budding stage was recommended as 60 kg.hm-2 for improving tobacco production and soil health, as well as for increasing the economic value of the tobacco leaves of roasted cigarettes significantly. This study emphasizes soil organic matter and pH as key factors influencing tobacco root microbiota. After microbial fertilizer treatment, the relative abundance of various microorganisms in tobacco rhizosphere soil positively correlated with soil enzyme activity and negatively correlated with soil nutrients, which reflected that tobacco rhizosphere microorganisms were regulated by the combination of soil nutrients and enzyme activity. [ABSTRACT FROM AUTHOR]

Seven Phytophthora isolates were recovered from roots and rhizosphere soil of different plants of the Bajaur, a newly merged district in Khyber Pakhtunkhwa province of Pakistan. These isolates were characterized morphologically as well as molecularly using internal transcribed spacer (ITS) sequences and of them identified are Phytophthora lacustris, Phytophthora capsici, Phytophthora citrophthora and Phytophthora nicotianae. P. lacustris appeared to be a new record from Pakistan not hitherto reported. P. nicotianae and P. citrophthora are reported for the first time from the rhizosphere of Isodon rugosus and Cajanus cajan in Pakistan. [ABSTRACT FROM AUTHOR]

Phytophthora nicotianae is a global and polyphagous pathogen with a wide host range. P. nicotianae can infect Areca catechu, Durio zibethinus L., Psidium guajava L., Hevea brasiliensis, and other tree species. The pathogen is capable of inducing butt rot and affecting aerial parts, including stems, leaves, and fruits. Compared to other Phytophthora species, P. nicotianae is more adaptable to abiotic stress. In this study, recombinase polymerase amplification (RPA) in combination with the CRISPR/Cas12a system was used for the detection of P. nicotianae, and achieved rapid and efficient detection of P. nicotianae. The assay was highly specific to P. nicotianae. All 4 tested isolates of P. nicotianae yielded positive results, whereas 30 isolates belonging to 17 other Phytophthora species, 8 fungal species, and 4 Bursaphelenchus xylophilus vermicules lacked detection. Under the conditions of 37 °C, after 20 min of RPA reaction and 25 min of Cas12a cleavage, a DNA concentration as low as 10 pg·μL−1 could be detected. In addition, it detected P. nicotianae from artificially inoculated leaves of Fatsia japonica. In this study, a novel method was established for the efficient and accurate detection of P. nicotianae based on the combination of RPA and the CRISPR/Cas12a system. [ABSTRACT FROM AUTHOR]

Tobacco black shank (TBS), caused by Phytophthora nicotianae, is a severe disease. Plant root exudates play a crucial role in mediating plant-pathogen interactions in the rhizosphere. However, the specific interaction between key secondary metabolites present in root exudates and the mechanisms of disease resistance remains poorly understood. This study conducted a comprehensive comparison via quasi-targeted metabolomic analysis on the root exudate metabolites from the tobacco cultivar Yunyan87 and K326, both before and after inoculation with P. nicotianae. The results showed that the root exudate metabolites changed after P. nicotianae inoculation, and the root exudate metabolites of different tobacco cultivar was significantly different. Furthermore, homovanillic acid, lauric acid, and isoliquiritigenin were identified as potential key compounds for TBS resistance based on their impact on the mycelium growth of the pathogens. The pot experiment showed that isoliquiritigenin reduced the incidence by 55.2%, while lauric acid reduced it by 45.8%. This suggests that isoliquiritigenin and lauric acid have potential applications in the management of TBS. In summary, this study revealed the possible resistance mechanisms of differential metabolites in resistance of commercial tobacco cultivar, and for the first time discovered the inhibitory effects of isoliquiritigenin and homovanillic acid on P. nictianae, and attempt to use plants secondary metabolites of for plant protection.

Castor bean (Ricinus communis) is a crop of great economic importance in Brazil. It is used for producing oil used in the manufacture of cosmetics and biodiesel. The genus Phytophthora contains pathogens with a wide range of host plants, including ornamentals, fruit and vegetable crops. Among the symptoms induced by Phytophthora species are collar and root rot. This study aimed to identify Phytophthora species causing collar and root rot in castor bean seedlings in the Federal District and test their pathogenicity. Samples of symptomatic plants were collected in four satellite cities in Distrito Federal, Brazil. Fourteen isolates were obtained, and they were initially identified through the morphology of reproductive structures. The isolates were subjected to molecular characterization using phylogeny of the sequences from the ITS region and the Cytochrome Oxidase II gene. Ten isolates of the pathogen were tested for pathogenicity on seedlings of two castor bean accessions and species known to be hosts of P. nicotianae. The isolates were identified as P. nicotianae (12 isolates) and P. palmivora (two isolates). In the pathogenicity test, all isolates were capable of causing disease in castor beans. The isolates of P. nicotianae and P. palmivora varied in pathogenicity to other plant species. This is the first report of P. nicotianae causing collar and root rot in castor bean in the Central‐West Region of Brazil. It is also the first report of P. palmivora causing diseases in castor beans in South America. [ABSTRACT FROM AUTHOR]

Tobacco black shank (TBS) and tobacco root black rot (TRBR) are two of the most devastating tobacco soil‐borne diseases that threaten sustainable tobacco planting. This study investigated the effects of Trichoderma sp. and a resistance inducer (RI) extracted from traditional Chinese medicine, individually or in combination, on the control of TBS and TRBR. The results showed that the application of Trichoderma sp. and RI, individually or in combination, significantly controlled the two soil‐borne diseases by significantly affecting the bacterial, but not fungal, Shannon and Simpson diversity indexes. The disease indexes of TBS and TRBR in integrated application management were the lowest, resulting in the highest potassium contents in the tobacco leaves. The control efficacies of TBS and TRBR in the integrated application treatment were 71.52 ± 1.43% and 68.33 ± 0.69%, respectively. The integrated treatment altered the composition of the rhizosphere soil microbial community. The bacterial community, but not the fungal community, of the control treatment was separated from those of other treatments. The relative abundance of bacteria involved in chemoheterotrophy and fermentation in the control treatment increased, whereas that of bacteria involved in nitrification and aerobic ammonia oxidation decreased compared with the other treatments. Importantly, the application of Trichoderma sp. and RI, individually or in combination, clearly increased the relative abundance of saprotrophic fungi in contrast to the control treatment, while decreasing that of pathotrophic fungi. Our study suggests that a suitable integrated application of bioagents and RI has synergistic effects on the suppression of two tobacco soil‐borne diseases by altering the rhizosphere microbiome composition in the field. [ABSTRACT FROM AUTHOR]

Background: Plant pathogens secrete effector proteins into host cells to suppress immune responses and manipulate fundamental cellular processes. One of these processes is autophagy, an essential recycling mechanism in eukaryotic cells that coordinates the turnover of cellular components and contributes to the decision on cell death or survival. Results: We report the characterization of AVH195, an effector from the broad-spectrum oomycete plant pathogen, Phytophthora parasitica. We show that P. parasitica expresses AVH195 during the biotrophic phase of plant infection, i.e., the initial phase in which host cells are maintained alive. In tobacco, the effector prevents the initiation of cell death, which is caused by two pathogen-derived effectors and the proapoptotic BAX protein. AVH195 associates with the plant vacuolar membrane system and interacts with Autophagy-related protein 8 (ATG8) isoforms/paralogs. When expressed in cells from the green alga, Chlamydomonas reinhardtii, the effector delays vacuolar fusion and cargo turnover upon stimulation of autophagy, but does not affect algal viability. In Arabidopsis thaliana, AVH195 delays the turnover of ATG8 from endomembranes and promotes plant susceptibility to P. parasitica and the obligate biotrophic oomycete pathogen Hyaloperonospora arabidopsidis. Conclusions: Taken together, our observations suggest that AVH195 targets ATG8 to attenuate autophagy and prevent associated host cell death, thereby favoring biotrophy during the early stages of the infection process. [ABSTRACT FROM AUTHOR]

Induced resistance is considered an eco-friendly disease control strategy, which can enhance plant disease resistance by inducing the plant's immune system to activate the defense response. In recent years, studies have shown that lactic acid can play a role in plant defense against biological stress; however, whether lactic acid can improve tobacco resistance to Phytophthora nicotianae, and its molecular mechanism remains unclear. In our study, the mycelial growth and sporangium production of P. nicotianae were inhibited by lactic acid in vitro in a dose-dependent manner. Application of lactic acid could reduce the disease index, and the contents of total phenol, salicylic acid (SA), jasmonic acid (JA), lignin and H2O2, catalase (CAT) and phenylalanine ammonia–lyase (PAL) activities were significantly increased. To explore this lactic acid-induced protective mechanism for tobacco disease resistance, RNA-Seq analysis was used. Lactic acid enhances tobacco disease resistance by activating Ca2+, reactive oxygen species (ROS) signal transduction, regulating antioxidant enzymes, SA, JA, abscisic acid (ABA) and indole-3-acetic acid (IAA) signaling pathways, and up-regulating flavonoid biosynthesis-related genes. This study demonstrated that lactic acid might play a role in inducing resistance to tobacco black shank disease; the mechanism by which lactic acid induces disease resistance includes direct antifungal activity and inducing the host to produce direct and primed defenses. In conclusion, this study provided a theoretical basis for lactic acid-induced resistance and a new perspective for preventing and treating tobacco black shank disease. [ABSTRACT FROM AUTHOR]

The natural pesticide phenazine-1-carboxylic acid (PCA) is known to lack phloem mobility, whereas Metalaxyl is a representative phloem systemic fungicide. In order to endow PCA with phloem mobility and also enhance its antifungal activity, thirty-two phenazine-1-carboxylic acid-N-phenylalanine esters conjugates were designed and synthesized by conjugating PCA with the active structure N-acylalanine methyl ester of Metalaxyl. All target compounds were characterized by 1H NMR, 13C NMR and HRMS. The antifungal evaluation results revealed that several target compounds exhibited moderate to potent antifungal activities against Sclerotinia sclerotiorum, Bipolaris sorokiniana, Phytophthora parasitica, Phytophthora citrophthora. In particular, compound F7 displayed excellent antifungal activity against S. sclerotiorum with an EC50 value of 6.57 µg/mL, which was superior to that of Metalaxyl. Phloem mobility study in castor bean system indicated good phloem mobility for the target compounds F1–F16. Particularly, compound F2 exhibited excellent phloem mobility; the content of compound F2 in the phloem sap of castor bean was 19.12 μmol/L, which was six times higher than Metalaxyl (3.56 μmol/L). The phloem mobility tests under different pH culture solutions verified the phloem translocation of compounds related to the "ion trap" effect. The distribution of the compound F2 in tobacco plants further suggested its ambimobility in the phloem, exhibiting directional accumulation towards the apical growth point and the root. These results provide valuable insights for developing phloem mobility fungicides mediated by exogenous compounds. [ABSTRACT FROM AUTHOR]

The understanding of how solitary and combined use of covercrop species and seeding rates influences soilborne diseases is lacking. Cover crops (crimson clover, triticale and crimson clover + triticale) were seeded in the field plots in September 2019 (Trial 1) and September 2021 (Trial 2) at two seeding rates (low and high) and a no cover cropped fallow served as a control. The soil was collected from all the plots in the following June. Red maple rooted cuttings were planted in nursery containers filled with those soils and plant health was evaluated with and without inoculation with Phytophthora nicotianae, Phytopythium vexans and Rhizoctonia solani. Plant height and fresh weight were measured, and plant roots were assessed for root rot severity (0–100% roots affected) and pathogen recovery. The number of fluorescent Pseudomonads present in soil samples was counted. Root rot severity and pathogen recovery were less with plants grown in cover cropped soil compared to non-cover cropped soil. Root rot severity caused by all three pathogens was least with the plants grown in the crimson clover and mixed cover cropped soil with the mixture being better than crimson clover. Moreover, plants grown in the high rate of cover cropped soil had less root rot severity compared to plants grown in low seeding rate cover cropped soil. Plant fresh weight was greater for plants grown in the high rate of crimson clover cover cropped soil and, in the mixture, compared to the non-cover cropped soil, whereas height was least affected. The Pseudomonad population was greatest in mixed cover cropped as well as in the high rate of cover cropped soil. Our findings suggest that a mixture of cover crop species and high seeding rate provides better service in suppressing root rot diseases likely associated with biological processes and nutrient availability. [ABSTRACT FROM AUTHOR]

Phytophthora cactorum is the most common causal agent of Phytophthora crown rot and leather rot of strawberry, but P. nicotianae is also responsible for the disease in Florida. Studies of P. nicotianae populations have suggested that different groups of genotypes are associated with different hosts; however, it is not yet clear how many lineages exist globally and how they are related to different production systems. The aim of this study was to determine the genetic relationships of P. nicotianae isolates from Florida strawberry with genotypes reported from other hosts, quantify the genetic variation on strawberry, and test for an association with nursery source. A total of 49 isolates of P. nicotianae were collected from strawberry plants originating from multiple nursery sources during six seasons of commercial fruit production in Florida. Microsatellite genotyping identified 28 multilocus genotypes on strawberry that were distinct among 208 isolates originating from various hosts and locations. Based on STRUCTURE analysis, two genetic groups were identified: one consisting of isolates from strawberry, and the other comprising samples from different hosts. Multilocus genotypes were shared among nursery sources, and populations defined by nursery were not differentiated. Both mating types were found among the isolates from North Carolina- and California-origin plants and in most strawberry seasons; however, a predominance of A1 was observed, and regular sexual reproduction was not supported by the data. This study reveals a unique genetic population of P. nicotianae associated with strawberry and emphasizes the vital role of nursery monitoring in mitigating disease spread. [ABSTRACT FROM AUTHOR]

Phytophthora parasitica is an oomycete pathogen that infects a broad range of crops of worldwide economic interest; among them are citrus species. In general, some Citrus and the rootstocks of related genera offer considerable resistance against P. parasitica; therefore, understanding the mechanisms involved in the virulence of this pathogen is crucial. In this work, P. parasitica secondary metabolite production was studied using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) and ultrahigh-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC/ESI-Q-TOF-MS) combined with chemometric tools, and its metabolic profile was evaluated under the influence of Citrus sunki (a highly susceptible host) and Poncirus trifoliata (a resistant genotype) extracts. The root extracts of Citrus sunki had an influence on the growth and hyphae morphology, and the root extracts of P. trifoliata had an influence on the zoospore behavior. In parallel, the spatial distribution of several metabolites was revealed in P. parasitica colonies using MALDI-MSI, and the metabolite ion of m/z 246 was identified as the protonated molecule of Arg-Ala. The MALDI-MSI showed variations in the surface metabolite profile of P. parasitica under the influence of the P. trifoliata extract. The P. parasitica metabolome analysis using UHPLC-ESI-Q-TOF-MS resulted in the detection of Arg-Gln (m/z 303.1775), as well as L-arginine (m/z 175.1191) and other unidentified metabolites. Significant variations in this metabolome were detected under the influence of the plant extracts when evaluated using UHPLC-ESI-Q-TOF-MS. Both techniques proved to be complementary, offering valuable insights at the molecular level when used to assess the impact of the plant extracts on microbial physiology in vitro. The metabolites identified in this study may play significant roles in the interaction or virulence of P. parasitica, but their functional characterization remains to be analyzed. Overall, these data confirm our initial hypotheses, demonstrating that P. parasitica has the capabilities of (i) recognizing host signals and altering its reproductive programing and (ii) distinguishing between hosts with varying responses in terms of reproduction and the production of secondary metabolites. [ABSTRACT FROM AUTHOR]

Anton de Bary first coined the genus, Phytophthora, which means "plant destroyer", viewing its devastating nature on potatoes. Globally plants have faced enormous threat from Phytophthora since its occurrence. In fact, a century ago, Phytophthora palmivora was first reported on Dendrobium maccarthiae in Sri Lanka. Since then, members of beautiful flowering crops of the family Orchidaceae facing the destructive threat of Phytophthora. Several Phytophthora species have been recorded to infect orchids with economic loss worldwide. To date, orchids are attacked by 12 species of Phytophthora. Five Phytophthora species (P. palmivora, P. nicotianae, P. cactorum, P. multivesiculata, P. meadii) are the major pathogenic Oomycetous Chromista" rather than true fungi frequently occurred on Orchidaceae. Phytophthora palmivora (having ~32 orchid host genera in 15 countries), Phytophthora nicotianae (having ~15 orchid host genera in 16 countries), Phytophthora cactorum (having ~43 orchid host genera in 6 countries), Phytophthora multivesiculata (having 2 orchid host genera in 5 countries) and Phytophthora capsici (having 2 orchid host genera in all Vanilla growing countries) are potential destroyers of Orchidaceae. Most of them are water loving Oomycetes cause disease in moist environments (> 80% RH) at 16-28°C. In artificially constructed orchidaria, anthropogenic factors are mostly contributed to the dissemination Phytophthora diseases in addition to many other factors. Water management, clean cultivation, and agro-chemicals are the major options for effective management of orchid Phytophthora, as the eco-friendly management options like development of resistant hybrids/cultivars, biological disease management, transgenic approaches, RNAi technology remained in the infant stage. In this review, we intended to highlight the insight of Phytophthora diseases associated with the orchid disease with reference to the historical aspect of the diseases, symptoms and signs, the pathogens, taxonomy, geographic distribution, host range within the Orchidaceae, pathogen identification, molecular diagnostics, mating types and races, management options and strategies and future perspectives. [ABSTRACT FROM AUTHOR]

Botryosphaeria dothidea infects hundreds of woody plants and causes a severe economic loss to apple production. In this study, we characterized BdLM1, a protein from B. dothidea that contains one LysM domain. BdLM1 expression was dramatically induced at 6 h post-inoculation in wounded apple fruit, strongly increased at 7 d post-inoculation (dpi), and peaked at 20 dpi in intact shoots. The knockout mutants of BdLM1 had significantly reduced virulence on intact apple shoots (20%), wounded apple shoots (40%), and wounded apple fruit (40%). BdLM1 suppressed programmed cell death caused by the mouse protein BAX through Agrobacterium-mediated transient expression in Nicotiana benthamiana, reduced H2O2 accumulation and callose deposition, downregulated resistance gene expression, and promoted Phytophthora nicotianae infection in N. benthamiana. Moreover, BdLM1 inhibited the active oxygen burst induced by chitin and flg22, bound chitin, and protected fungal hyphae against degradation by hydrolytic enzymes. Taken together, our results indicate that BdLM1 is an essential LysM effector required for the full virulence of B. dothidea and that it inhibits plant immunity. Moreover, BdLM1 could inhibit chitin-triggered plant immunity through a dual role, i.e., binding chitin and protecting fungal hyphae against chitinase hydrolysis. [ABSTRACT FROM AUTHOR]

Since the summer of 2020, severe decline and gummosis were observed on 20‐ to 30‐year‐old grapefruit trees cv. Star Ruby in Antalya province in the Western Mediterranean region of Türkiye. Grapefruit trees were examined in affected commercial orchards in Aksu, Manavgat, Muratpaşa and Serik counties, located near the coast of the Mediterranean Sea. Symptomatic trees exhibited leaf discoloration, defoliation and severe dieback, as well as dark, water‐soaked lesions with gum exudates, characteristic of Phytophthora infections, formed on the bark of the main stem and major limbs. No Phytophthora species could be isolated from these bark tissues, while two were obtained from soil samples taken from around symptomatic trees. Based on morphological characteristics, isolates were identified as P. citrophthora and P. nicotianae. Identifications were confirmed by sequencing of the internal transcribed spacer (ITS) and the cytochrome oxidase I (cox1) gene regions. Pathogenicity tests, carried out by inoculations of the main stems and branches of grapefruit seedlings cv. Star Ruby indicated that both species were pathogenic. All P. citrophthora and P. nicotianae isolates obtained in this work were sensitive to mefenoxam. EC50 values of P. citrophthora isolates were between 0.284 and 0.285 μg mL−1, whereas those of P. nicotianae were between 0.288 and 0.291 μg mL−1. Phytophthora citrophthora was previously known to cause disease on citrus in Türkiye, but this is the first report of P. nicotianae causing citrus gummosis in the country. Because P. nicotianae is more widespread than P. citrophthora, it should be considered a threat to citrus cultivation in this region of Türkiye. [ABSTRACT FROM AUTHOR]

Plantations of avocado (Persea americana), a high-demand crop in Thailand are severely affected by Phytophthora spp. A severe avocado root rot disease of avocado that has recently been observed in the Chiang Dao district of Chiang Mai province causes dieback and root rot. A potential pathogen isolated from symptomatic plant material was identified as P. nicotianae based on morphology and ITS and COX1 sequences. Pathogenicity assay on detached leaves and seedling roots confirmed the pathogenicity of P. nicotianae. The report is the first of P. nicotianae causing avocado root rot in Thailand. [ABSTRACT FROM AUTHOR]

SUMMARY: We investigated the basis for better performance of transgenic Nicotiana tabacum plants with G6PDH‐isoenzyme replacement in the cytosol (Xanthi::cP2::cytRNAi, Scharte et al., 2009). After six generations of selfing, infiltration of Phytophthora nicotianae zoospores into source leaves confirmed that defence responses (ROS, callose) are accelerated, showing as fast cell death of the infected tissue. Yet, stress‐related hormone profiles resembled susceptible Xanthi and not resistant cultivar SNN, hinting at mainly metabolic adjustments in the transgenic lines. Leaves of non‐stressed plants contained twofold elevated fructose‐2,6‐bisphosphate (F2,6P2) levels, leading to partial sugar retention (soluble sugars, starch) and elevated hexose‐to‐sucrose ratios, but also more lipids. Above‐ground biomass lay in between susceptible Xanthi and resistant SNN, with photo‐assimilates preferentially allocated to inflorescences. Seeds were heavier with higher lipid‐to‐carbohydrate ratios, resulting in increased harvest yields ‐ also under water limitation. Abiotic stress tolerance (salt, drought) was improved during germination, and in floated leaf disks of non‐stressed plants. In leaves of salt‐watered plants, proline accumulated to higher levels during illumination, concomitant with efficient NADP(H) use and recycling. Non‐stressed plants showed enhanced PSII‐induction kinetics (upon dark–light transition) with little differences at the stationary phase. Leaf exudates contained 10% less sucrose, similar amino acids, but more fatty acids – especially in the light. Export of specific fatty acids via the phloem may contribute to both, earlier flowering and higher seed yields of the Xanthi‐cP2 lines. Apparently, metabolic priming by F2,6P2—combined with sustained NADP(H) turnover—bypasses the genetically fixed growth–defence trade‐off, rendering tobacco plants more stress‐resilient and productive. [ABSTRACT FROM AUTHOR]

Introduction: Tobacco black shank is a devastating soil-borne disease caused by the oomycete Phytophthora nicotianae, severely hamper tobacco production worldwide. However, the synergistic effect of biocontrol bacteria and marine polysaccharides/ oligosaccharides on tobacco black shank control was few documented. Methods: In this study, Bacillus amyloliquefaciens CAS02 (CAS02) and chitooligosaccharide (COS) were screened firstly, and their synergistic antagonistic effect against P. nicotianae and the underlying mechanism were investigated in vitro and in vivo. Results: In vitro experiments showed that, compared with the application of CAS02 or COS alone, co-application of CAS02 and COS significantly increased the inhibition rate against P. nicotianae by 11.67% and 63.31%, respectively. Furthermore, co-application of CAS02 and COS disrupted the structure of mycelia to a greater extent. The co-application of CAS02 and COS showed synergistic effect, with the relative control effect maintained above 60% during the 60-day pot experiment, significantly higher than that of application CAS02 or COS alone. The combined application of CAS02 and COS reduced the relative abundance of P. nicotianae in the rhizosphere soil and increased the relative abundance of bacterial taxa potentially involved in disease suppression, such as Nocardioides, Devosia and Bradyrhizobium. Meanwhile, CAS02 and COS synergistically activated salicylic acid (SA), ethylene (ET), and hypersensitive response (HR) defense signaling pathways in tobacco plants. Discussion: Our findings demonstrate that co-application of CAS02 and COS remarkably improve the relative control effect against tobacco black shank through multiple pathways and provide a promising strategy for the efficient green control of tobacco black shank. [ABSTRACT FROM AUTHOR]

Tobacco black shank induced by Phytophthora nicotianae causes significant yield losses in tobacco plants. MicroRNAs (miRNAs) play a pivotal role in plant biotic stress responses and have great potential in tobacco breeding for disease resistance. However, the roles of miRNAs in tobacco plants in response to P. nicotianae infection has not been well characterized. In this study, we found that Nta-miR6155, a miRNA specific to Solanaceae crops, was significantly induced in P. nicotianae infected tobacco. Some of predicted target genes of Nta-miR6155 were also observed to be involved in disease resistance. To further investigate the function of miR6155 in tobacco during P. nicotianae infection, Nta-miR6155 overexpression plants (miR6155-OE) were generated in the Honghua Dajinyuan tobacco variety (HD, the main cultivated tobacco variety in China). We found that the Nta-miR6155 overexpression enhanced the resistance in tobacco towards P. nicotianae infections. The level of reactive oxygen species (ROS) was significantly lower and antioxidant enzyme activities were significantly higher in miR6155-OE plants than those in control HD plants during P. nicotianae infection. In addition, we found that the accumulation of salicylic acid and the expression of salicylic acid biosynthesis and signal transduction-related genes is significantly higher in miR6155-OE plants in comparison to the control HD plants. Furthermore, we found that Nta-miR6155 cleaved target genes NtCIPK18 to modulate resistance towards P. nicotianae in tobacco plants. Additionally, phenotypic analysis of miR6155-OE plants showed that Nta-miR6155 could inhibit the growth of tobacco by suppressing nitrogen uptake and photosynthesis. In conclusion, our findings indicated that miR6155 plays a crucial role in the regulation of growth and resistance against P. nicotianae infections in tobacco plants. [ABSTRACT FROM AUTHOR]

As the main cause of destructive plant diseases, pathogenic oomycete in plant rhizosphere brings about enormous losses to agricultural production. Although chemical pesticides are still one of the most important prevention and control methods for phytopathogens, the usage of chemical pesticides was limited by the 3R (resistance, residue, and rampant) problem. In the early stage of our research, analysis and comparison of the metabolome of resistance to Phytophthora nicotianae and common strain suggested that naringenin might be a highly efficient potential biogenic antimicrobial agent to prevent and control soil rhizosphere diseases. Unfortunately, the bioactivity and absorption capacity of active ingredients in the environment made it unsuitable for field application; thus, for efficient field application of naringenin, the 24 nm-sized naringenin-loaded nano- star -shaped polymerized (NSPs) were prepared with good loading efficiency 37.3% for naringenin. The soil mobility test indicated that NSPs could effectively reduce the adsorption of active ingredients and enhance the mobility of active ingredients in soil. The bacteriostatic test proved that these NSPs had better antimicrobial activity than the naringenin used alone and could efficiently induce the expression of plant resistance phenylpropanoid compounds. Finally, pot and field experiments showed improved control efficiency of NSPs 41% loaded with naringenin. Transcriptome analysis found that a large number of energy-related genes were downregulated in NSPs nematodes, suggesting that disturbed energy-related genes might lead to the disturbance of energy synthesis and metabolism. Naringenin-loaded nano-carriers were used to prevent and control plant disease-causing pathogens in the rhizosphere, which is of great significance to improve the prevention and control effect and reduce the environmental load of these anti-pathogenic agents. [Display omitted] • The mechanism of biopesticide naringenin improving plant disease resistance was clarified. • Preparation of a low-cost nano-pesticide that can significantly improve the control effect of naringenin. • Nanocarriers improve the mobility of naringenin in soil and protect the active ingredient from degradation. • Nano-pesticides have good control effects on soil root diseases in the greenhouse or field. [ABSTRACT FROM AUTHOR]

Phytophthora nicotianae merupakan patogen yang mampu memusnahkan tanaman tembakau pada tahap awal sehingga menyebabkan penyakit lanas dan menyebabkan kematian tanaman hampir 100%. Serangan dimulai dari dalam jaringan akar dan berlanjut hingga menghancurkan pembuluh pengangkut sehingga menyebabkan bibit tembakau layu. Kebijakan pengendalian penyakit harus menerapkan konsep pengendalian hama dan penyakit terpadu (PHT) secara bijaksana dan selaras dengan strategi PHT. Efektivitas bahan aktif fungisida dalam mengendalikan P. nicotianae harus diuji melalui uji khasiat yang meliputi pengujian dosis. Oleh karena itu, perlu dilakukan uji efikasi fungisida Trivia 73 WP (fluopikolid 6% dan propineb 67%). Pengujian dilakukan di Desa Sumberpucung Kabupaten Malang dengan menggunakan metode RAK (Rancangan Acak Lengkap) dengan 5 perlakuan dan 5 ulangan. Hasil penelitian menunjukkan bahwa fungisida Trivia 73 WP yang mengandung bahan aktif fluopikolid (6%) dan propineb (67%) dengan dosis 3 gram per liter efektif menurunkan angka kematian tanaman tembakau akibat patogen P. nicotianae.

This document, titled "PP 1/122 (3) Phytophthora nicotianae var. parasitica and other Phytophthora species causing canker on citrus," provides guidelines for conducting trials to evaluate the efficacy of fungicides against Phytophthora species that cause canker on citrus trees. The document outlines the experimental conditions, trial conditions, design and layout of the trial, application of treatments, mode of assessment, recording and measurements, and reporting of results. It emphasizes the importance of following good experimental practices and provides references to other relevant standards. The document does not provide specific results or conclusions, but rather serves as a guide for researchers conducting trials on this topic. [Extracted from the article]

In this study, KGMOS (DP, 2-13), derived from KGM (Konjac glucomannan), was applied to elucidate plant immunity in a Nicotiana benthamiana Phytophthora nicotianae model. Application of KGMOS (25–100 mg/L) notably inhibited P. nicotianae, resulting in reduced disease indices and a significant accumulation of defense molecules such as H2O2 and callose. Transcriptomic analysis revealed that genes shared between KGMOS-treated and control plants are involved in signaling pathways, transcription regulation, hydrogen peroxide catabolism, and oxidative stress response. This suggests that KGMOS triggers H2O2 accumulation, callose deposition, and activation of the salicylic acid (SA) and jasmonic acid/ethylene (JA/ET) pathways after pathogen inoculation. Upregulated defense-response genes in the KGMOS group included SA-related late blight-resistant, pathogenesis-related (PR), and JA/ET-related ethylene response factor (ERF) genes. Heatmap analysis showed more upregulated defense genes (PR and NPR) related to SA in the KGMOS-treated group than in controls. RT-qPCR validation revealed significant upregulation of SA and JA/ET pathway genes in KGMOS-treated plants. Higher SA content in these plants suggests enhanced disease resistance. This study concludes that KGMOS pre-treatment induced resistance against P. nicotianae, especially at a lower concentration (25 mg/L). These findings could offer valuable insights for the future application of KGMOS in controlling plant diseases for sustainable agriculture and postharvest management.

BACKGROUND: To find more effective agricultural antibiotics, a class of new 2‐aminothiazole derivatives containing the 4‐aminoquinazoline moiety were synthesized and evaluated for their antimicrobial properties against phytopathogenic bacteria and fungi of agricultural importance. RESULTS: All the target compounds were fully characterized by 1H NMR, 13C NMR, and high‐resolution mass spectrometry. The bioassay results showed that compound F29 with a 2‐pyridinyl substituent exhibited an outstanding antibacterial effect against Xanthomonas oryzae pv. oryzicola (Xoc) in vitro, having an half‐maximal effective concentration (EC50) value as low as 2.0 μg/mL (over 30‐fold more effective than the commercialized agrobactericide bismerthiazol, with an EC50 value of 64.3 μg/mL). In addition, compound F8 with a 2‐fluorophenyl group demonstrated a good inhibitory activity toward the bacterium Xanthomonas axonopodis pv. citri (Xac), around twofold more active than bismerthiazol in terms of their EC50 values (22.8 versus 71.5 μg/mL). Interestingly, this compound also demonstrated a notable fungicidal effect against Phytophthora parasitica var. nicotianae, with an EC50 value largely comparable with that of the commercialized fungicide carbendazim. Finally, mechanistic studies revealed that compound F29 exerted its antibacterial effects by increasing the permeability of bacterial membranes, reducing the release of extracellular polysaccharides, and triggering morphological changes of bacterial cells. CONCLUSION: Compound F29 has promising potential as a lead compound for developing more efficient bactericides to fight against Xoc. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The Periconia fungal genus belongs to the phylum Ascomycota, order Pleosporales, family Periconiaceae. Periconia are found in many habitats, but little is known about their ecology. Several species from this genus produce bioactive molecules. Periconia digitata extracts were shown to be deadly active against the pine wilt nematode. Furthermore, P. digitata was shown to inhibit the plant pathogenic oomycete Phytophthora parasitica. Because P. digitata has great potential as a biocontrol agent and high quality genomic resources are still lacking in the Periconiaceae family, we generated long-read genomic data for P. digitata. Using PacBio Hifi sequencing technology, we obtained a highly-contiguous genome assembled in 13 chromosomes and totaling ca. 39 Mb. In addition, we produced a reference transcriptome, based on 12 different culture conditions, and proteomic data to support the genome annotation. Besides representing a new reference genome within the Periconiaceae, this work will contribute to our better understanding of the Eukaryotic tree of life and opens new possibilities in terms of biotechnological applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Phytophthora nicotianae is a global and polyphagous pathogen with a wide host range. P. nicotianae can infect Areca catechu, Durio zibethinus L., Psidium guajava L., Hevea brasiliensis, and other tree species. The pathogen is capable of inducing butt rot and affecting aerial parts, including stems, leaves, and fruits. Compared to other Phytophthora species, P. nicotianae is more adaptable to abiotic stress. In this study, recombinase polymerase amplification (RPA) in combination with the CRISPR/Cas12a system was used for the detection of P. nicotianae, and achieved rapid and efficient detection of P. nicotianae. The assay was highly specific to P. nicotianae. All 4 tested isolates of P. nicotianae yielded positive results, whereas 30 isolates belonging to 17 other Phytophthora species, 8 fungal species, and 4 Bursaphelenchus xylophilus vermicules lacked detection. Under the conditions of 37 °C, after 20 min of RPA reaction and 25 min of Cas12a cleavage, a DNA concentration as low as 10 pg·μL−1 could be detected. In addition, it detected P. nicotianae from artificially inoculated leaves of Fatsia japonica. In this study, a novel method was established for the efficient and accurate detection of P. nicotianae based on the combination of RPA and the CRISPR/Cas12a system.

Nursery growers rely on fungicides to manage root rot disease of boxwood caused by Phytophthora nicotianae and P. cinnamomi. Repeated use of the same fungicide may lead to the fungicide resistance. In this study, fungicides pyraclostrobin + cyazofamid (Empress + Segway), ametoctradin + dimethomorph (Orvego), ametoctradin + dimethomorph alternated with pyraclostrobin (Orvego alt Empress), ametoctradin + dimethomorph alternated with fluxapyroxad + pyraclostrobin (Orvego alt Orkestra), and oxathiapiprolin (Segovis) were evaluated for their efficacy in managing Phytophthora root rot under greenhouse conditions in Tennessee. One-year-old container-grown boxwood 'Green Velvet' plants were inoculated with P. nicotianae or P. cinnamomi. The first applications of fungicide treatments were made preventatively as a drench 48 h before pathogen inoculation. Following inoculation, four applications of fungicide treatments were performed on a 14-day intervals. Initial and final plant height and width were measured. Total plant fresh weight and root fresh weight were measured at the end of the trials, and plants were evaluated for root rot severity (0% to 100% roots affected) and pathogen recovery. All fungicides significantly reduced root rot severity and pathogen recovery of P. nicotianae and P. cinnamomi. Ametoctradin + dimethomorph alternated with pyraclostrobin (Orvego alt Empress) provided similar protection against P. cinnamomi to that of a single application of ametoctradin + dimethomorph (Orvego) or oxathiapiprolin (Segovis). For P. nicotianae, ametoctradin + dimethomorph alternated with pyraclostrobin + fluzapyroxad (Orvego alt Orkestra) was found to be as effective as a single application of either ametoctradin + dimethomorph (Orvego) or oxathiapiprolin (Segovis) in one of the two trials. Effects of fungicides on plant growth such as height, width, total, and root fresh weight were not significant. These findings will be useful to nursery growers in selecting the right fungicide program for the management of root rot disease of boxwood caused by P. nicotianae and P. cinnamomi. [ABSTRACT FROM AUTHOR]

Samples from potato fields with lesions with late blight-like symptoms were collected from eastern North Carolina in 2017 and the causal agent was identified as Phytophthora nicotianae. We have identified P. nicotianae in potato and tomato samples from North Carolina, Virginia, Maryland, Pennsylvania, and New York. Ninety-two field samples were collected from 46 fields and characterized for mefenoxam sensitivity, mating type, and simple sequence repeat genotype using microsatellites. Thirty-two percent of the isolates were the Al mating type, while 53% were the A2 mating type. In six cases, both A1 and A2 mating types were detected in the same field in the same year. All isolates tested were sensitive to mefenoxam. Two genetic groups were discerned based on STRUCTURE analysis: one included samples from North Carolina and Maryland, and one included samples from all five states. The data suggest two different sources of inoculum from the field sites sampled. Multiple haplotypes within a field and the detection of both mating types in close proximity suggests that P. nicotianae may be reproducing sexually in North Carolina. There was a decrease in the average number of days with weather suitable for late blight, from 2012 to 2016 and 2017 to 2021 in all of the North Carolina counties where P. nicotianae was reported. P. nicotianae is more thermotolerant than P. infestons and grows at higher temperatures (25 to 35°C) than P. infestons (18 to 22°C). Late blight outbreaks have decreased in recent years and first reports of disease are later, suggesting that the thermotolerant P. nicotianae may cause more disease as temperatures rise due to climate change. [ABSTRACT FROM AUTHOR]

Antalya province is the main center of vegetable production in Türkiye. Tomato comes first in terms of crops cultivated under greenhouse. Phytophthora species causing root and crown rot are among the factors negatively affecting tomato yield and quality. This research aimed to determine the prevalence of root and crown rot of tomatoes grown in Antalya province and to identify Phytophthora species causing disease. During surveys performed in 170 tomato greenhouses, plant and soil samples were taken from the areas where root and crown rot, stem blight, and drying symptoms were observed. Disease prevalence and incidence in the investigated greenhouses were 25.88% and 4.87%, respectively. Phytophthora symptoms were not observed in the greenhouses in Demre and Kepez districts, while the highest disease prevalence was found in Elmalı district with 75%. Eighty of 84 Phytophthora isolates were identified as P. nicotianae and four as P. capsici, according to their cultural, morphological and molecular characterisation. Virulence of 18 selected isolates were determined by using stem inoculation technique and all isolates caused lesions with different lengths on tomato stems. The reactions of 22 tomato genotypes in the gene pool of BATEM against P. nicotianae were also investigated and the genotype DT-15 was found as the most susceptible genotype with the largest lesions, while A-286 was the most resistant genotype. This study formed the basis for further studies on tomato breeding and integrated disease management. [ABSTRACT FROM AUTHOR]

Root rot and gummosis caused by Phytophthora spp. are considered one of the most important citrus diseases in Brazil. Symptoms of Phytophthora spp. infection in citrus plants are associated with lesions on the bark at the base of the plant, roots, and even lower branches. Inappropriately performed cultural practices, such as excessive irrigation and practices that result in reduced aeration and soil drainage, favor the disease. The objective of this study was to evaluate the effect of Urochloa ruziziensis mulching provided by an ecological mower on the severity of Phytophthora nicotianae root rot and the development of citrus plants and their root system. The experiments were carried out under controlled conditions on Rangpur lime seedlings kept in pots containing soil from 'Hamlin' orange orchards with the use of an ecological mower or a conventional mower in the management of inter-row vegetation for six years. Urochloa ruziziensis mulching (9 t ha−1) was added or not to the pots. The inoculation of P. nicotianae in the roots occurred through infection of the soil with a solution containing mycelium and sporangia of the pathogen. A 2 × 2 × 2 factorial scheme was used, with the following factors A: soil type, B: inoculation of P. nicotianae and C: mulching of U. ruziziensis. The attributes of plant development, such as root growth, average number of leaves, leaves and dry mass of shoots and roots, in addition to assessments of the severity of disease in the roots, were evaluated. The mulch of U. ruziziensis did not promote an increase in root rot. The soil resulting from this management promoted the better development of Rangpur lime plants. Therefore, vegetation management of inter-row with an ecological mower is not associated with increased symptoms of Phytophthora root rot. [ABSTRACT FROM AUTHOR]

Black shank disease incited by Phytophthora nicotianae is one of the most devastating soil-borne diseases of tobacco (Nicotiana tabacum L.). Crop rotation is an effective strategy for the management of this disease. However, the efficacy of rotation with different crops in controlling tobacco black shank remains obscure. In this study, 10 different preceding crops, including rape, wheat, barley, broad bean, pea, garlic, ryegrass, cow vetch, alfalfa, and milk vetch, were selected in fields with an history of severe tobacco black shank. The effectiveness of crop rotation on tobacco black shank disease control was quantitatively determined as amount of Phytophthora nicotianae using (1) fluorescence quantitative Polymerase Chain Reaction (qPCR), (2) tobacco leaf disk assays, and (3) soil dilution plating assays. In addition, the bacterial assemblage associated with rhizosphere of different crops was analyzed by Terminal Restriction Fragment Length Polymorphism (T-RFLP). Results showed that ryegrass, garlic, and barley can effectively reduce the levels of P. nicotianae in the soil, with a consequent decrease of both morbidity and disease index. The rhizosphere bacterial community assemblages changed depending on the different preceding crops. [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 Ɓ-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. [ABSTRACT FROM AUTHOR]

Sanhua plum (Prunus salicina), native to Guangdong Province, China, is a highly valued fruit tree because of the fruit's characteristic taste and excellent nutritional properties. A severe blighting of shoots of Sanhua plum was observed at local Sanhua orchards in Guangdong Province from 2019 to 2021, which weakens the tree vigour and reduces the fruit yield. This study aimed to characterize the symptoms of Sanhua plum leaf blight and shoot dieback, evaluate the incidence and impact, and identify the causal agent and evaluate its pathogenicity. The disease was present in all three Sanhua orchards surveyed (a total of 29 hectares), but incidence varied with locations and years, ranging from 0.4% to 3.7%. An oomycete species was isolated from symptomatic shoots collected from the surveyed fields. Based on morphological and cultural characteristics and combined phylogenetic analysis of two molecular markers, including the internal transcribed spacer regions (ITS) of rDNA and Ras-related Ypt1 gene, 15 isolates were identified as belonging to the species Phytophthora nicotianae. The isolates were pathogenic to Sanhua plum plants in nursery experiments, and symptoms identical to that observed in the fields were reproduced. The pathogen was isolated consistently from the inoculated plants, confirming Koch's postulates. Shoot blight caused by P. nicotianae represents a new threat to Sanhua plum productivity and longevity in southern China. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Eicosatetraenoic acid (ETA, 20:4, ω-3) is the desaturation product of dihomo-gamma linolenic acid (DGLA, 20:3, ω-6) catalyzed by delta-17 desaturase, which is considered as a healthy product that helps to lower risk of heart diseases. The oleaginous filamentous fungus, Mucor circinelloides, has been used for a long time as a model micro-organism for GLA production at industrial scales. However, M. circinelloides lacks the key enzymes to synthesize C20 polyunsaturated fatty acids (PUFAs). M. circinelloides could produce DGLA by overexpressing the D6E(GLELO) gene, which could be a useful tool to produce ETA due to the availability of established genetic manipulation tools. Therefore, in this study, delta-17 desaturase (PpD17 and PaD17) genes from Phytophthora parasitica and Pythium aphanidermatum, respectively, were introduced into M. circinelloides to construct an ETA-producing cell factory. Our results showed that the PaD17 and PpD17 overexpression strains' biomass increased by 25.98 and 23.34 g/L (39.98 and 25.75%), respectively, compared with the control strain. Meanwhile, the lipid contents of the recombinant strains also increased and reached up to 28.88% in Mc-PaD17 and 30.95% in Mc-PpD17, respectively, compared with the control strain (23.38% in Mc-2076). The RT-qPCR results showed that overexpression of delta-17 desaturase genes promoted the expression of cme2, fas2, and D6E, thereby contributing to lipid biosynthesis in M. circinelloides. Meanwhile, the content of ETA reached up to 1.95%, and the yield of ETA was up to 114.69 mg/L in PpD17 overexpression mutants at 96 h. This study provided the first report on the construction of an ETA-producing cell factory by heterologous overexpression of the PpD17 gene in M. circinelloides, which established a new scope for further research in the production of ETA in oleaginous fungi. [ABSTRACT FROM AUTHOR]

Phytophthora nicotianae causes substantial economic losses in most countries where tobacco is produced. At present, the control of P. nicotianae mainly depends on chemical methods, with considerable environmental and health issues. We investigated the effects of ethanol extracts from Scutellaria baicalensis Georgi (SBG) and Magnolia officinalis (MO). On mycelial growth, sporangium formation, and zoospore release of P. nicotianae. Both extracts inhibited the growth of P. nicotianae, with mycelial growth inhibition rates of 88.92% and 93.92%, respectively, at 40 mg/mL, and EC50 values of 5.39 and 5.74 mg/mL, respectively. The underlying mechanisms were the inhibition of sporangium formation, the reduction of zoospore number, and the destruction of the mycelium structure. At an SBG extract concentration of 16.17 mg/mL, the inhibition rates for sporangia and zoospores were 98.66% and 99.39%, respectively. At an MO extract concentration of 2.87 mg/mL, the production of sporangia and zoospores was completely inhibited. The hyphae treated with the two plant extracts showed different degrees of deformation and damage. Hyphae treated with SBG extract showed adhesion and local swelling, whereas treatment with MO extract resulted in broken hyphae. Mixture of the extracts resulted in a good synergistic effect. [ABSTRACT FROM AUTHOR]

AbstractOomycete 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.

Black shank, a devastating disease affecting tobacco production worldwide, is caused by Phytophthora nicotianae. However, few genes related to Phytophthora resistance have been reported in tobacco. Here, we identified NpPP2-B10, a gene strongly induced by P. nicotianae race 0, with a conserved F-box motif and Nictaba (tobacco lectin) domain, in the highly resistant tobacco species Nicotiana plumbaginifolia. NpPP2-B10 is a typical F-box-Nictaba gene. When it was transferred into the black shank-susceptible tobacco cultivar 'Honghua Dajinyuan', it was found to promote resistance to black shank disease. NpPP2-B10 was induced by salicylic acid, and some resistance-related genes (NtPR1, NtPR2, NtCHN50, and NtPAL) and resistance-related enzymes (catalase and peroxidase) were significantly upregulated in the overexpression lines after infection with P. nicotianae. Furthermore, we showed that NpPP2-B10 actively regulated the tobacco seed germination rate, growth rate, and plant height. The erythrocyte coagulation test of purified NpPP2-B10 protein showed that NpPP2-B10 had plant lectin activity, and the lectin content in the overexpression lines was significantly higher than that in the WT, which could lead to accelerated growth and improved resistance of tobacco. SKP1 is an adaptor protein of the E3 ubiquitin ligase SKP1, Cullin, F-box (SCF) complex. We demonstrated that NpPP2-B10 could interact with the NpSKP1-1A gene in vivo and in vitro through yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC), indicating that NpPP2-B10 likely participates in the plant immune response by mediating the ubiquitin protease pathway. In conclusion, our study provides some important insights concerning NpPP2-B10-mediated regulation of tobacco growth and resistance. [ABSTRACT FROM AUTHOR]

As a fungicide, oxathiapiprolin has excellent effects on diseases caused by oomycetes. Fungicides generally protect crops by inhibiting pathogens, but little research has addressed the effects of fungicides on crops. This study combined transcriptomic and metabolomic analyses to systematically analyze the physiological regulatory mechanisms of oxathiapiprolin on tobacco under Phytophthora nicotianae infection. The results showed that under P. nicotianae infection, tobacco's photosynthetic rate and antioxidant enzyme activity increased after the application of oxathiapiprolin. Omics results showed that the genes related to carbon metabolism, disease‐resistant proteins, and amino acid synthesis were highly expressed, and the amino acid content increased in tobacco leaves. This study is the first comprehensive investigation of the physiological regulatory effects of oxathiapiprolin on tobacco in response to P. nicotianae infection. These findings provide a basis for the balance between regulating tobacco growth and development and enhancing disease resistance under the stimulation of oxathiapiprolin and provide new research and development opportunities for identifying new disease‐resistance genes and the development of high‐yielding disease‐resistant crop varieties. [ABSTRACT FROM AUTHOR]