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Abstract Background Secretome analysis is a valuable tool to study host-pathogen protein interactions and to identify new proteins that are important for plant health. Microbial signatures elicit defense responses in plants, and by that, the plant immune system gets triggered prior to pathogen infection. Functional properties of secretory proteins from Xanthomonas axonopodis pv. dieffenbachiae (Xad1) involved in priming plant immunity was evaluated. Results In this study, the secretome of Xad1 was analyzed under host plant extract-induced conditions, and mass spectroscopic analysis of differentially expressed protein was identified as plant-defense-activating protein viz., flagellin C (FliC). The flagellin and Flg22 peptides both elicited hypersensitive reaction (HR) in non-host tobacco, activated reactive oxygen species (ROS) scavenging enzymes, and increased pathogenesis-related (PR) gene expression viz., NPR1, PR1, and down-regulation of PR2 (β-1,3-glucanase). Protein docking studies revealed the Flg22 epitope of Xad1, a 22 amino acid peptide region in FliC that recognizes plant receptor FLS2 to initiate downstream defense signaling. Conclusion The flagellin or the Flg22 peptide from Xad1 was efficient in eliciting an HR in tobacco via salicylic acid (SA)-mediated defense signaling that subsequently triggers systemic immune response epigenetically. The insights from this study can be used for the development of bio-based products (small PAMPs) for plant immunity and health.

Copyright of Jurnal Fitopatologi Indonesia is the property of IPB University 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.)

Background: Secretome analysis is a valuable tool to study host-pathogen protein interactions and to identify new proteins that are important for plant health. Microbial signatures elicit defense responses in plants, and by that, the plant immune system gets triggered prior to pathogen infection. Functional properties of secretory proteins from Xanthomonas axonopodis pv. dieffenbachiae (Xad1) involved in priming plant immunity was evaluated. Results: In this study, the secretome of Xad1 was analyzed under host plant extract-induced conditions, and mass spectroscopic analysis of differentially expressed protein was identified as plant-defense-activating protein viz., flagellin C (FliC). The flagellin and Flg22 peptides both elicited hypersensitive reaction (HR) in non-host tobacco, activated reactive oxygen species (ROS) scavenging enzymes, and increased pathogenesis-related (PR) gene expression viz., NPR1, PR1, and down-regulation of PR2 (β-1,3-glucanase). Protein docking studies revealed the Flg22 epitope of Xad1, a 22 amino acid peptide region in FliC that recognizes plant receptor FLS2 to initiate downstream defense signaling. Conclusion: The flagellin or the Flg22 peptide from Xad1 was efficient in eliciting an HR in tobacco via salicylic acid (SA)-mediated defense signaling that subsequently triggers systemic immune response epigenetically. The insights from this study can be used for the development of bio-based products (small PAMPs) for plant immunity and health. [ABSTRACT FROM AUTHOR]

Research on a few model plant-pathogen systems has benefitted from years of tool and resource development. This is not the case for the vast majority of economically and nutritionally important plants, creating a crop improvement bottleneck. Cassava bacterial blight (CBB), caused by Xanthomonas axonopodis pv. manihotis (Xam), is an important disease in all regions where cassava (Manihot esculenta Crantz) is grown. Here, we describe the development of cassava that can be used to visualize one of the initial steps of CBB infection in vivo. Using CRISPR-mediated homology-directed repair (HDR), we generated plants containing scarless insertion of GFP at the 3 end of CBB susceptibility (S) gene MeSWEET10a. Activation of MeSWEET10a-GFP by the transcription activator-like (TAL) effector TAL20 was subsequently visualized at transcriptional and translational levels. To our knowledge, this is the first such demonstration of HDR via gene editing in cassava.

Penyakit utama tanaman jeruk yang disebabkan oleh cendawan dan bakteri dapat menghambat pertumbuhan tanaman sehingga berdampak terhadap penurunan produksi tanaman. Pengendalian yang diterapkan selama ini kebanyakan menggunakan pestisida kimia sintetis yang berpotensi memberi dampak negatif pada lingkungan dan kesehatan. Minyak atsiri dari kulit buah jeruk purut (Citrus hystric) mempunyai kandungan senyawa yang berpotensi dalam menghambat pertumbuhan patogen pada tanaman jeruk. Tujuan dari penelitian ini adalah mengetahui aktivitas antifungal dan antibakteri minyak atsiri kulit buah jeruk purut pada lima konsentrasi 0.5%, 1%, 2%, 3%, dan 5% terhadap patogen tanaman jeruk, yaitu Colletotrichum gloeosporioides, Fusarium oxysporum, dan Xanthomonas axonopodis. Hasil penelitian menunjukkan bahwa semua konsentrasi minyak atsiri yang diujikan mempunyai daya hambat kategori rendah terhadap F. oxysporum, dan kategori sedang terhadap C. gloeosporioides. Pengujian terhadap X. axonopodis menunjukkan daya hambat kategori kuat untuk konsentrasi 3% dan 5%. Minyak atsiri kulit buah jeruk purut berpotensi sebagai antifungal dan antibakteri pada tanaman jeruk dan dapat digunakan sebagai teknologi alternatif pengendalian yang ramah lingkungan dan aman.

The antibacterial activity of selected medicinal plants namely Tagetus erecta L. and Pelargonium graveolens extracts was studied against Xanthomonas axonopodis pv. Punicae, the causative agent of bacterial blight of Punica granatum. The plants are selected based on their traditional use as medicinal plants. The water, ethanol and methanol extracts of Taget erecta L. and Pelargonium graveolens were used for antibacterial activity assay by Kirby Bauer disc diffusion method. Among these extracts, only methanol extract of Taget erecta L. has showed substantial antibacterial activity against Xanthomonas axonopodis pv. Punicae and all other extracts showed less antibacterial activity. The phytochemical constituents such as alkaloids, flavonoids, tannins, proteins, resins, proteins, saponins, terpenoids, steroids, and glycosides were found to be present in selected plant extracts as per preliminary phytochemical investigation. The Minimum inhibitory concentration and Minimum bacteriocidal concentration of Tagetus erecta L. methanol extract was found to be 25mg/ml and 50mg/ml respectively. Our study revealed the possible application of Tagetus erecta L. methanol extract in the management of Bacterial blight of Punica granatum. [ABSTRACT FROM AUTHOR]

The citrus canker pathogen Xanthomonas axonopodis has caused severe damage to citrus crops worldwide, resulting in significant economic losses for the citrus industry. To address this, a green synthesis method was used to develop silver nanoparticles with the leaf extract of Phyllanthus niruri (GS-AgNP-LEPN). This method replaces the need for toxic reagents, as the LEPN acts as a reducing and capping agent. To further enhance their effectiveness, the GS-AgNP-LEPN were encapsulated in extracellular vesicles (EVs), nanovesicles with a diameter of approximately 30–1000 nm naturally released from different sources, including plant and mammalian cells, and found in the apoplastic fluid (APF) of leaves. When compared to a regular antibiotic (ampicillin), the delivery of APF-EV-GS-AgNP-LEPN and GS-AgNP-LEPN to X. axonopodis pv. was shown to have more significant antimicrobial activity. Our analysis showed the presence of phyllanthin and nirurinetin in the LEPN and found evidence that both could be responsible for antimicrobial activity against X. axonopodis pv. Ferredoxin-NADP+ reductase (FAD-FNR) and the effector protein XopAI play a crucial role in the survival and virulence of X. axonopodis pv. Our molecular docking studies showed that nirurinetin could bind to FAD-FNR and XopAI with high binding energies (−10.32 kcal/mol and −6.13 kcal/mol, respectively) as compared to phyllanthin (−6.42 kcal/mol and −2.93 kcal/mol, respectively), which was also supported by the western blot experiment. We conclude that (a) the hybrid of APF-EV and GS-NP could be an effective treatment for citrus canker, and (b) it works via the nirurinetin-dependent inhibition of FAD-FNR and XopAI in X. axonopodis pv. [ABSTRACT FROM AUTHOR]

Salah satu penyakit penting yang menyerang tanaman kedelai adalah penyakit pustul daun yang disebabkan oleh bakteri Xanthomonas axonopodis pv. glycines. Penelitian ini bertujuan untuk mengetahui potensi konsorsium mikroba antagonis yang terdiri dari Bacillus subtillis, Pseudomonas fluorescens, serta Trichoderma sebagai agens hayati untuk mengendalikan penyakit pustul daun pada tanaman kedelai yang disebabkan oleh bakteri X. axonopodis pv. glycines. Hasil penelitian menunjukkan bahwa semua perlakuan aplikasi antagonis baik yang berupa konsorsium mikroba antagonis maupun mikroba antagonis tunggal mampu menghambat pertumbuhan bakteri X. axonopodis pv. glycines pada media dalam cawan Petri. Semua perlakuan mikroba antagonis baik tunggal maupun dalam konsorsium juga menekan perkembangan penyakit pustul bakteri pada tanaman kedelai. Kemampuan konsorsium mikroba antagonis dengan konsentrasi 20ml/l, konsorsium mikroba antagonis dengan konsentrasi 30ml/l, mikroba antagonis tunggal B. subtilis, P. fluorescens, dan Trichoderma, setara dengan bakterisida Streptomisin sulfat dalam menekan perkembangan penyakit pustul bakteri pada tanaman kedelai. Perlakuan mikroba antagonis tunggal P. fluorescens dapat meningkatkan tinggi tanaman kedelai.

Lafoensia pacari represents an alternative to control phytopathogens and common bean (Phaseolus vulgaris L.) diseases. This study aimed to investigate the chemical composition of L. pacari phenolics-containing extract obtained from leaves and assess its in vitro and in vivo inhibitory activity against Curtobacterium flaccumfaciens pv. flaccumfaciens, Xanthomonas axonopodis pv. phaseoli, Xanthomonas fuscans subsp. fuscans,Xanthomonas sp., Colletotrichum lindemuthianum, Fusarium oxysporum and Macrophomina phaseolina. The microbial susceptibility screening and the extract’s potential to reduce the anthracnose severity and the common bacterial blight were examined. Eleven phenolic compounds were identified, eight of which were described for the first time in L. pacari leaves: gentisic, caffeic, p-coumaric, protocatechuic and vanillic acids, luteolin, naringenin and quercetin. The L. pacari extract completely inhibited bacterial growth at the concentration of 0.62-1.25 %, as well as the mycelial growth of the C. lindemuthianum (BRM 007626) isolate at the concentration of 5 % (v/v).Under greenhouse conditions, the extract led to the control of the common bacterial blight caused by X. axonopodis pv. phaseoli (BRM 25302) in the Pérola bean cultivar and to a low efficiency in the control of anthracnose caused by C. lindemuthianum (BRM 007447) in the IPA 7419 cultivar.

Bacterial spot, which is the main disease occurring in passion fruit trees, is caused by the bacterium Xanthomonas axonopodis pv. passiflorae, leading to large annual losses in passion fruit crops. This study aims to find extracts and/or bioactive compounds of endophytic fungi of noni (Morinda citrifolia) to treat bacterial spot in passion fruit trees. Nine fungi isolated from a specimen of M. citrifolia from the Brazilian Amazon are studied. The fungus Guignardia mangiferae NF17 shows the best inhibition results and is selected for the isolation of its secondary metabolites by chromatography techniques. The isolated compounds Sydowinol (S1) and Sydowinin A (S2) are identified by nuclear magnetic resonance (NMR). Compounds S1 and S2, as well as the acetonitrile extract from the biomass of G. mangiferae NF17, are tested against four strains of X. axonopodis pv. passiflorae obtained from plants infected by bacterial spot, and which inhibited bacterial growth up to the lowest concentration tested (3.125 µg/mL). This study reports, for the first time, the antibacterial activity against X. axonopodis pv. passiflorae by the compounds Sydowinol and Sydowinin A. Compounds S1 and S2 are reported for the first time for the genus Gignardia. [ABSTRACT FROM AUTHOR]

This study reports genome wide characterization and development of first set of microsatellite markers through in silico analysis of eight sequenced Xanthomonas axonopodis pv. punicae strains available in the public database. SSR survey resulted in identification of ~ 4638 perfect SSRs, with mean marker frequency 901 SSRs/Mb and densitiy of 11,006 bp/Mb aross the eight genomes. Frequency distribution graphs revealed hexa-nucleotide repeats were more prominent fowllowed by tri-, tetra-, di- and penta-nucleotides in the analysed genomes. We desinged 2927 SSR primers that are specific to the strain LMG 859 and ePCR confirmed on seven other Xap genomes. This resulted in identification of 542 informative SSRs that are producing single amplicons, from which 66 primers were successfully validated through wet lab experiments on eight Xap isolates of pomegranate. Furthermore, utility of these SSRs were demostrated by analysing molecular diversity among 22 Xap isolates using 20 Xap_SSR primers. SSRs revealed moderate genetic diversity among Xap isolates (61%) and grouped 11 isolates that are repersenting six different states into one cluster. This proved the earlier evidence of wider spread of ST3 type Xap acoss India using Multi locus Sequence Typing (MLST) technique. In summary, Xap_SSR will serve as powerful genomics tools that would helps in monitoring of population dynamics, taxonomy, epidomology and quarantine aspects in bacterial blight pathogen through development of microsatellite based Multilocus Variable number of Tandem repeat analysis (MLVA) in future. [ABSTRACT FROM AUTHOR]

Biologically synthesized silver nanoparticles are emerging as attractive alternatives to chemical pesticides due to the ease of their synthesis, safety and antimicrobial activities in lower possible concentrations. In the present study, we have synthesized silver nanoparticles (AgNPs) using the aqueous extract of the medicinal plant Euphorbia wallichii and tested them against the plant pathogenic bacterium Xanthomonas axonopodis, the causative agent of citrus canker, via an in vitro experiment. The synthesized silver nanoparticles were characterized by techniques such as UV-Vis spectroscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis and transmission electron microscopy. Moreover, the plant species were investigated for phenolics, flavonoids and antioxidant activity. The antioxidant potential of the extract was determined against a DPPH radical. The extract was also evaluated for phenolic compounds using the HPLC technique. The results confirmed the synthesis of centered cubic, spherical-shaped and crystalline nanoparticles by employing standard characterization techniques. A qualitative and quantitative phytochemical analysis revealed the presence of phenolics (41.52 mg GAE/g), flavonoids (14.2 mg QE/g) and other metabolites of medicinal importance. Different concentrations (1000 µg/mL to 15.62 µg/mL—2 fold dilutions) of AgNPs and plant extract (PE) alone, and both in combination (AgNPs-PE), exhibited a differential inhibition of X. axanopodis in a high throughput antibacterial assay. Overall, AgNPs-PE was superior in terms of displaying significant antibacterial activity, followed by AgNPs alone. An appreciable antioxidant potential was recorded as well. The observed antibacterial and antioxidant potential may be attributed to eight phenolic compounds identified in the extract. The Euphorbia wallichii leaf-extract-induced synthesized AgNPs exhibited strong antibacterial activity against X. axanopodis, which could be exploited as effective alternative preparations against citrus canker in planta in a controlled environment. In addition, as a good source of phenolic compounds, the plant could be further exploited for potent antioxidants. [ABSTRACT FROM AUTHOR]

Common bacterial blight, caused by Xanthomonas axonopodis pv. phaseoli, is an economically important disease of common bean and causes significant yield losses in Ethiopia. A field survey was conducted to understand the spatial distribution, relative importance and association of common bacterial blight epidemics with agro-ecological factors in low and mid-land areas of Southwestern, Ethiopia, during the 2018-19 cropping season. A total 85 bean fields were assessed in four common bean growing districts. High diseases incidence and severity was recorded at Debub Ari (77.6 and 52.7%, respectively) while the lowest was from Male (38.5 and 28.0%, respectively). The associations between disease parameters and agro-ecological factors were analyzed using multiple logistic regression models. Agronomic practices including NPS fertilization, preceding crop, weed management and plant population had highly significant (P

To better understand the behavior of Xanthomonas axonopodis pv. glycines, the causal agent of bacterial pustule of soybean within its host, its global transcriptome within soybean leaves was compared with that in a minimal medium in vitro, using deep sequencing of mRNA. Of 5,062 genes predicted from a draft genome of X. axonopodis pv. glycines, 534 were up-regulated in the plant, while 289 were down-regulated. Genes encoding YapH, a cell-surface adhesin, as well as several others encoding cell-surface proteins, were down-regulated in soybean. Many genes encoding the type III secretion system and effector proteins, cell wall-degrading enzymes and phosphate transporter proteins were strongly expressed at early stages of infection. Several genes encoding RND multidrug efflux pumps were induced in planta and by isoflavonoids in vitro and were required for full virulence of X. axonopodis pv. glycines, as well as resistance to soybean phytoalexins. Genes encoding consumption of malonate, a compound abundant in soybean, were induced in planta and by malonate in vitro. Disruption of the malonate decarboxylase operon blocked growth in minimal media with malonate as the sole carbon source but did not significantly alter growth in soybean, apparently because genes for sucrose and fructose uptake were also induced in planta. Many genes involved in phosphate metabolism and uptake were induced in planta. While disruption of genes encoding high-affinity phosphate transport did not alter growth in media varying in phosphate concentration, the mutants were severely attenuated for growth in soybean. This global transcriptional profiling has provided insight into both the intercellular environment of this soybean pathogen and traits used by X. axonopodis pv. glycines to promote disease.

Copyright of Agricultural Research in the Tropics / Pesquisa Agropecuária Tropical is the property of Pesquisa Agropecuaria Tropical 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 detection of Xanthomonas axonopodis pv vesicatoria (XAV) from chili seeds was carried out to avoid spreading XAV through seed. Detection of XAV in chili seeds through Polymerase Chain Reaction (PCR) using XAVF/XAVR and RST65/RST69 primers sometimes got unclear electrophoresis results. This research was conducted to determine the optimal time and temperature of primer annealing, and primer concentration to detect XAV on chili pepper seeds. Optimization was conducted in three phases, (1) optimization of primer annealing temperature, (2) optimization of annealing time, and (3) determinate primer concentration. The results show that XAVF/XAVR primer is optimal at 60°C for 30 seconds on the primer concentration of 10 pmol, and primer RST65/RST69 is optimal at 58°C for 20 seconds on the primer concentration of 10 pmol. The optimal time, temperature of primer annealing, and primer concentration were validated by three repetitions using positive and negative control. The validation test result shows that optimal time and temperature of primer annealing, and primer concentration consistently produce clear electrophoresis results without smear.

Bacterial spot, which is the main disease occurring in passion fruit trees, is caused by the bacterium Xanthomonas axonopodis pv. passiflorae, leading to large annual losses in passion fruit crops. This study aims to find extracts and/or bioactive compounds of endophytic fungi of noni (Morinda citrifolia) to treat bacterial spot in passion fruit trees. Nine fungi isolated from a specimen of M. citrifolia from the Brazilian Amazon are studied. The fungus Guignardia mangiferae NF17 shows the best inhibition results and is selected for the isolation of its secondary metabolites by chromatography techniques. The isolated compounds Sydowinol (S1) and Sydowinin A (S2) are identified by nuclear magnetic resonance (NMR). Compounds S1 and S2, as well as the acetonitrile extract from the biomass of G. mangiferae NF17, are tested against four strains of X. axonopodis pv. passiflorae obtained from plants infected by bacterial spot, and which inhibited bacterial growth up to the lowest concentration tested (3.125 µg/mL). This study reports, for the first time, the antibacterial activity against X. axonopodis pv. passiflorae by the compounds Sydowinol and Sydowinin A. Compounds S1 and S2 are reported for the first time for the genus Gignardia.

Biologically synthesized silver nanoparticles are emerging as attractive alternatives to chemical pesticides due to the ease of their synthesis, safety and antimicrobial activities in lower possible concentrations. In the present study, we have synthesized silver nanoparticles (AgNPs) using the aqueous extract of the medicinal plant Euphorbia wallichii and tested them against the plant pathogenic bacterium Xanthomonas axonopodis, the causative agent of citrus canker, via an in vitro experiment. The synthesized silver nanoparticles were characterized by techniques such as UV-Vis spectroscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis and transmission electron microscopy. Moreover, the plant species were investigated for phenolics, flavonoids and antioxidant activity. The antioxidant potential of the extract was determined against a DPPH radical. The extract was also evaluated for phenolic compounds using the HPLC technique. The results confirmed the synthesis of centered cubic, spherical-shaped and crystalline nanoparticles by employing standard characterization techniques. A qualitative and quantitative phytochemical analysis revealed the presence of phenolics (41.52 mg GAE/g), flavonoids (14.2 mg QE/g) and other metabolites of medicinal importance. Different concentrations (1000 µg/mL to 15.62 µg/mL—2 fold dilutions) of AgNPs and plant extract (PE) alone, and both in combination (AgNPs-PE), exhibited a differential inhibition of X. axanopodis in a high throughput antibacterial assay. Overall, AgNPs-PE was superior in terms of displaying significant antibacterial activity, followed by AgNPs alone. An appreciable antioxidant potential was recorded as well. The observed antibacterial and antioxidant potential may be attributed to eight phenolic compounds identified in the extract. The Euphorbia wallichii leaf-extract-induced synthesized AgNPs exhibited strong antibacterial activity against X. axanopodis, which could be exploited as effective alternative preparations against citrus canker in planta in a controlled environment. In addition, as a good source of phenolic compounds, the plant could be further exploited for potent antioxidants.

Bacterial leaf blight is a major disease of eucalypt, especially under nursery conditions. Different bacterial species have been associated with the disease in several countries, and despite its importance worldwide, it is not clear to date whether similar disease symptoms are caused by the same or by different etiological agents. In this study, 43 bacterial strains were isolated from blighted eucalypt leaves collected in different geographic areas of Brazil and inoculated onto a susceptible eucalypt clone. Polyphasic taxonomy, including morphological, physiological, biochemical, molecular, and pathogenicity tests showed that only certain strains of Xanthomonas axonopodis caused symptoms of the disease. Strains varied in their aggressiveness, but no correlation with geographic origin was observed. MLSA-based phylogenetic analysis using concatenated dnaK, fyuA, gyrB and rpoD gene sequences allocated the strains in a well-defined clade, corresponding to Rade-marker’s group RG 9.6. Inoculation of nineteen plant species belonging to seven botanical families with representative strain LPF 602 showed it to be pathogenic only on Eucalyptus spp, and Corymbia spp. Based on distinct biochemical and pathogenic characteristics that differentiate the eucalypt strains from other pathovars of the X. axonopodis species, here we propose their allocation into the new pathovar X. axonopodis pv. eucalyptorum pv. nov.

Bacterial blight in pomegranate caused by Xanthomonas axonopodis pv. punicae (Xap) is an increasing threat to pomegranate cultivation in India. To prevent economic losses, it is pivotal to detect the infection in latent stages rather than in symptomatic stages. We have developed an enhanced loop-mediated isothermal amplification (LAMP) technique for the detection of latent Xap infection in pomegranate using six sets of pathovar-specific primers. The DNA-intercalating dye ethidium bromide was standardized for visualizing positive amplification in the LAMP assay. The optimum reaction time was 30 min or more at 65 °C, and assay sensitivity was enhanced down to femtogram (fg) amounts of template DNA (0.153 fg) in the LAMP assay. In artificially inoculated plants, the enhanced LAMP assay detected Xap on the 7th day post inoculation (dpi), while PCR detected Xap only after the 11th dpi. Finally, the specificity of the LAMP assay for Xap was validated against 31 bacterial strains belonging to 22 species. The LAMP assay developed in this study is highly specific, sensitive and robust and can be used as an improved alternative for PCR-based methods for the early detection of Xap infection in pomegranate. Early detection of Xap in pomegranate ensures quality fruits with increased yield by adopting precautionary measures that ensure improved monetary benefit to farmers. [ABSTRACT FROM AUTHOR]

Green synthesis of silver nanoparticles (AgNPs) by utilising plant extract is an emerging class of nanotechnology. It revolutionizes all the field of biological sciences by synthesizing chemical free AgNPs. In the present study, AgNPs were synthesised by utilising Moringa oleifera leaves as the main reducing and stabilising agent and characterised through UV–visible spectroscopy, zeta analyser, X‐ray diffraction spectroscopy (XRD), energy dispersive X‐ray (EDX), and scanning electron microscopy (SEM). The different concentrations of biosynthesised AgNPs (10, 20, 30, and 40 ppm) were exogenously applied on the already infected plants (canker) of Citrus reticulata at different day intervals. The AgNPs at a concentration of 30 ppm was found to be most suitable concentration for creating the resistance against canker disease in Citrus reticulata. The enzymatic activities were also explored and it was found that 30 ppm concentration of biosynthesised AgNPs significantly reduced the biotic stress. Fruit quality and productivity parameters were also assessed and it was found that fruit quality and productivity were significant in response to 30 ppm concentration of biosynthesised AgNPs. The present work highlights the potent role of biosynthesised AgNPs, which can be used as biological control of citrus diseases and ultimately improving the quality and productivity of Citrus. [ABSTRACT FROM AUTHOR]

Citrus bacterial canker (CBC) occurs due to Xanthomonas axonopodis pv. Citri (Xac) is a pathogenic bacteria. It was first reported in Japan, USA and many areas of India in 19th century. Synchronized by the spread of the causative agent the diversity of labelled pathogen continues to spread with new strains appearing in many other regions of the world. However, its diagnosis is quite difficult due to its symptoms similarity with other bacterial strains. This piece of study was designed to identify Xanthomonas axonopodis using polymerase chain reaction (PCR). PCR is more accurate, precise and fast method which is used for detection and quantification of many bacterial species. Two primers Xac01 and Xac02 were used for PCR based CBC detection. These primers were based on rpf gene region which give very specific results in Xac identification and can separate two much similar bacterial strains. There is another Primer pair designed on the pthA gene which act as universal primer and usually used for detection of all varieties of citrus canker bacteria. Leaves sample from different infected Citrus paradisi plants were collected for further analysis. Results confirmed that three samples among five have CBC. It is concluded that using PCR we can detect citrus canker disease more specifically which will help in discovering new eradication methods for its control. [ABSTRACT FROM AUTHOR]

The objective of the present study was to identify citrus canker pathogen (Xanthomonas axonopodis) and disease severity among different citrus cultivars collected from citrus growing area (CRI) of Punjab, Pakistan. Morphological, biochemical and molecular markers characterized the pathogen. Total 95 samples were collected from grapefruit (C. paradis), kumquats (C. japonica) and lemon and limes (C. limon) and subjected to biochemical analysis by API strip. Three different primer sets targeting 16SrDNA and internally transcribed spacer region (ITS) were used to check genetic variability by PCR. The infectious pathogen colonies were found to be small, yellow, mucoid and gram negative by gram staining. The oxidase, urease tests were negative and casesin hydrolysis, citrate utilization, methyl red test, catalase tests were positive for the pathogen via API strips. All the collected samples were positive for the disease by PCR and the disease severity was also measured by percentage mean. The highest disease severity (82%) was observed in grapefruits followed by lemon and limes (70%) while the lowest (30%) was in kumquats. The present results revealed that citrus cultivars have variability towards the susceptibility of citrus canker and phylogenetic analysis revealed that A type citrus canker is prevalent in selected region of Pakistan. [ABSTRACT FROM AUTHOR]

Cassava bacterial blight (CBB) disease caused by Xanthomonas axonopodis pv. manihotis ( Xam ) is a severe disease in cassava worldwide. In addition to causing significant cassava yield loss, CBB disease has not been extensively studied, especially in terms of CBB resistance genes. The present research demonstrated the molecular mechanisms underlining the defense response during Xam infection in two cassava cultivars exhibiting different degrees of disease resistance, Huay Bong60 (HB60) and Hanatee (HN). Based on gene expression analysis, ten of twelve putative defense-related genes including, leucine-rich repeat receptor-like kinases ( LRR-RLKs ), resistance ( R ), WRKY and pathogenesis-related ( PR ) genes, were differentially expressed between these two cassava cultivars during Xam infection. The up-regulation of defense-related genes observed in HB60 may be the mechanism required for the reduction of disease severity in the resistant cultivar. Interestingly, priming with salicylic acid (SA) or methyl jasmonate (MeJA) for 24 h before Xam inoculation could enhance the defense response in both cassava cultivars. The disease severity was decreased 10% in the resistant cultivar (HB60) and was remarkably reduced 21% in the susceptible cultivar (HN) by SA/MeJA priming. Priming with Xam inoculation modulated cassava4.1_013417, cassava4.1_030866 and cassava4.1_020555 (highest similarity to MeWRKY59, MePR1 and AtPDF2.2 , respectively) expression and led to enhanced resistance of the susceptible cultivar in the second infection. The putative cis -regulatory elements were predicted in an upstream region of these three defense-related genes. The different gene expression levels in these genes between the two cultivars were due to the differences in cis -regulatory elements in their promoter regions. Taken together, our study strongly suggested that the induction of defense-related genes correlated with defense resistance against Xam infection, and exogenous application of SA or MeJA could elevate the defense response in both cultivars of cassava. This finding should pave the way for management to reduce yield loss from disease and genetic improvement in cassava. [ABSTRACT FROM AUTHOR]

Common Bacterial Blight (CBB), caused by Xanthomonas axonopodis pv. phaseoli (Xap) and Xanthomonas axonopodis pv. phaseoli var. fuscans (Xapf), is a serious disease that affects common bean production worldwide. In Uganda, it is the most severe and widely occurring bacterial disease, causing significant yield losses in common bean. Although various sources of resistance have been developed around the world, none of the varieties grown in Uganda is known to be resistant. The objective of this study was to identify lines with combined leaf and pod resistance for introgression into locally adapted but susceptible Ugandan genotypes. A total of 132 common bean accessions was evaluated in a screenhouse and under field conditions, in an 11x12 alpha lattice design. Genotypes were inoculated with a local isolate in a screenhouse; while the plants were left to undergo natural infestation in field. Results indicated significant differences (P<0.001) in genotypic reactions against the CBB disease, with a range of disease scores of 2.2 - 7.8 on leaves and 2.6 - 7.1 on pods (1-9 CIAT disease scale), suggesting high genetic variability among the tested germplasm. Relatively low correlation (r = 0.39) was observed between leaf and pod reactions, suggesting differential expression of CBB resistance in these two plant organs. Overall, four genotypes, NE2-14-8, NE17-14-29, NE14-09-78 and VAX3, consistently showed resistance in both screenhouse and field evaluations, leaf and pod inoculations and at all sampling stages. These genotypes were, therefore, identified for transferring CBB resistance into Ugandan susceptible market class bean varieties. [ABSTRACT FROM AUTHOR]

Introduction: Citrus canker, a disease caused by Xanthomonas axonopodis pv. citri ( Xac) bacteria, has been responsible for extensive economic losses in citriculture. In this work, we report the metabolic responses of citrus plants during disease development. This information can be useful for understanding the natural mechanism of plant defense beyond helping design new varieties and/or genetically modified genotypes for tolerance/resistance against citrus canker. Objectives: To understand how primary metabolism is affected in two sweet orange genotypes during citrus canker development. Methods: H NMR spectroscopy together with chemometrics was used to evaluate the metabolic changes caused by Xac infection at various time points (days 4, 12 and 20) in Citrus sinensis L. Osbeck leaves from non-transgenic and transgenic plants expressing the antibacterial peptide sarcotoxin. Results: The results revealed a high level of metabolic similarity between the studied genotypes without Xac infection. However, after Xac infection, the plants responded differently to disease development. The non-transgenic genotype showed altered early precursors of some secondary metabolites (tryptophan, tyrosine and putrescine) in addition to signaling metabolites of biotic stress (putrescine and dimethylamine), and the drastic reduction of gluconeogenesis was the overall metabolic cost for defense. The transgenic genotype suffered late metabolic changes due to the protective stoichiometric role of sarcotoxin. In addition, the oxidative stress response was more balanced in transgenic than in non-transgenic plants. Conclusion: An NMR-based metabolomic approach was useful for understanding plant-pathogen interactions in citrus canker. Our findings provide valuable preliminary insights into different stages of citrus canker development. [ABSTRACT FROM AUTHOR]

Plants protect themselves from diverse potential pathogens by induction of the immune systems such as systemic acquired resistance (SAR). Most bacterial plant pathogens thrive in the intercellular space (apoplast) of plant tissues and cause symptoms. The apoplastic leaf exudate (LE) is believed to contain nutrients to provide food resource for phytopathogenic bacteria to survive and to bring harmful phytocompounds to protect plants against bacterial pathogens. In this study, we employed the pepper-Xanthomonas axonopodis system to assess whether apoplastic fluid from LE in pepper affects the fitness of X. axonopodis during the induction of SAR. The LE was extracted from pepper leaves 7 days after soil drench-application of a chemical trigger, benzothiadiazole (BTH). Elicitation of plant immunity was confirmed by significant up-regulation of four genes, CaPR1, CaPR4, CaPR9, and CaCHI2, by BTH treatment. Bacterial fitness was evaluated by measuring growth rate during cultivation with LE from BTH- or water-treated leaves. LE from BTH-treatment significantly inhibited bacterial growth when compared to that from the water-treated control. The antibacterial activity of LE from BTH-treated samples was not affected by heating at 100°C for 30 min. Although the antibacterial molecules were not precisely identified, the data suggest that small (less than 5 kDa), heat-stable compound(s) that are present in BTH-induced LE directly attenuate bacterial growth during the elicitation of plant immunity.