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Blister blight infection with Exobasidium vexans is one of the most destructive foliar diseases that seriously affect the quality and yield of tea. This research investigated the metabolite changes of healthy and infected leaves on tea cultivar 'Fuding Dabaicha' and further explored the potential antimicrobial substances against E. vexans infection. In total, 1,166 compounds were identified during the entire course of an infection, among which 73 different common compounds were significantly accumulated involved in the important antimicrobial substances of flavonoids and phenolic acids, including kaempferol (3,5,7,4'-tetrahydroxyflavone), kaempferol-3-0-sophoroside-7-0-glucoside, phloretin, 2,4,6-trihydroxybenzoic acid, galloylprocyanidin B4, and procyanidin Cl 3'-O-gallate, which indicated that these metabolites might positively dominate resistance to E. vexans. Furthermore, relevant biological pathways, such as the flavone and flavonol biosynthesis, flavonoid biosynthesis, and phenylpropane pathways, were more closely related to resistance to E. vexans. Additionally, total flavonoids, phenolics, alkaloids, and terpenoids contributing to antimicrobial and antioxidant capacity were significantly altered during four different infection periods, especially the Leaf_S2 stage (the second stage of infection), in which the most concentration accumulated. The leaves affected by E. vexans infection at the second stage had the relatively highest antioxidant activity. Accordingly, this study provides a theoretical support for and comprehensive insights into the effects on the metabolite changes, tea quality components, and antioxidant activity of blister blight caused by E. vexans. [ABSTRACT FROM AUTHOR]

This work embodies the development of a real time loop mediated isothermal amplification (RealAmp) assay for the rapid detection of the cryptic tea phytopathogen, Exobasidium vexans, the causal organism of blister blight disease. Due to the widespread popularity of tea as a beverage and the associated agro-economy, the rapid detection and management of the fast-spreading blister blight disease have been a longstanding necessity. Loop-mediated isothermal amplification (LAMP) primers were designed targeting the E. vexans ITS rDNA region and the reaction temperature was optimized at 62 °C with a 60 min reaction time. Amplification of the E. vexans isolates in the initial LAMP reactions was confirmed by both agarose gel electrophoresis and SYBR Green I dye based colour change visualization. The specificity of the LAMP primers for E. vexans was validated by negative testing of seven different phytopathogenic test fungi using LAMP and RealAmp assay. The positive findings in RealAmp assay for E. vexans strain were corroborated via detecting fluorescence signals in real-time. Further, the LAMP assays performed with gDNA isolated from infected tea leaves revealed positive amplification for the presence of E. vexans. The results demonstrate that this rapid and precise RealAmp assay has the potential to be applied for field-based detection of E. vexans in real-time. [ABSTRACT FROM AUTHOR]

Citral (Eo) exhibits excellent fungicidal activities. However, it is difficult to maintain long-term fungicidal activity due to its strong volatility. Herein, a controlled-release strategy by using biomass-derived porous carbon (BC) was developed to overcome the drawback of Eo. New composite materials were prepared by loading Eo on tea stem porous carbon (BC@Eo), and their controlled-release fungicidal activity against Exobasidium vexans was assessed. BC with a large specific surface area of 1001.6 m²/g and mesoporous structure was fabricated through carbonization temperature of 700°C. The BC@Eo materials were characterized using Fourier-transform infrared spectroscopy and X-ray powder diffraction. The results suggested that chemical and physical interactions occurred in BC@Eo. The Eo release profile suggested a biphasic pattern with an initial fast release on days 1-14 and a subsequent controlled phase on days 14-30. The in vitro cumulative release percentage of Eo from BC@Eo was 51% during one month, and this result was significantly lower than that from free Eo (cumulative release percentage of Eo of 82% in one week). The antifungal activities of Eo and BC@Eo against E. vexans were determined using the inhibition zone method. The results indicated that Eo and BC@Eo formed large inhibition zones of 19.66 ± 0.79 and 21.92 ± 0.77 mm, respectively. The influence on the hyphal structure of E. vexans was observed by scanning electron microscopy on day 30. The hyphal structure of E. vexans treated with BC@Eo was more shrunken than that treated with Eo at 30 days, suggesting that BC@Eo prolongs the fungicidal activity against E. vexans. This study demonstrated that the encapsulation of Eo in BC for developing the BC@Eo materials could be a promising strategy to inhibit volatility and maintain the fungicidal activity of Eo and provide a potential alternative for the reuse of abundant tea biomass waste resources. [ABSTRACT FROM AUTHOR]

Indonesia is one of the ten largest tea-producing countries in the world, with a plantation area of 104,420 hectares and a production of 139,285 thousand tons in 2018. Blister blight can cause massive crop losses across tea-growing regions of Asia, particularly in India, Sri Lanka, Indonesia, and Japan. The infection causes a 40% yield loss. The study aimed to determine the genetic diversity in Exobasidium vexans that cause blister blight based on polymerase chain reaction-random amplified polymorphic DNA (PCR-RAPD). Sampling was conducted at Pagilaran, a tea plantation located in Central Java, Indonesia, with sampling based on altitude, Andongsili (>1,000 meters above sea level [masl]), Kayulandak (±1,000 masl), and Pagilaran (<1,000 masl) with clones TRI 2024, TRI 2025, Gambung 3, Gambung 7, Gambung 9, and Pagilaran 15. This study used the PCR method using internal transcribed spacers (ITS) 1F and ITS 4 primers. Four primers used in PCR-RAPD were OPA-02, OPA-03, OPA-05, and OPB-17. The characteristics of E. vexans observed were ellipse-shaped basidiospore, hyaline, unicellular with one septate, formed at the tip of the sterigma with hyaline and elliptical shapes, with a range size of 7--15.5 µm x 2.3-4.5 µm. PCR-RAPD method was able to show the diversity of E. vexans samples between clones, in which three clusters were formed at a coefficient of 0.63. Cluster I consisted of TRI 2024 Andongsili and PGL 15 Pagilaran; Cluster II consisted of TRI 2025 Andongsili and Gambung 3 Andongsili; Cluster III consisted of Gambung 7 Andongsili, Gambung 7 Kayulandak, and Gambung 9 Andongsili. [ABSTRACT FROM AUTHOR]

Exobasidium vexans, causing tea blister blight, is an obligate parasitic fungus and one of the most detrimental pathogens in most tea plantations in Asia. Information about genetic diversity of E. vexans is necessarily needed to develop disease management based on pathogen evolution. This study aimed to understand the genetic diversity of E. vexans from three different locations in Wonosobo, Central Java, and Indonesia. Isolates used in this study were collected from blister light symptomized leaves, in three different locations. Isolates were identified using morphological indicators and DNA sequencing, and then genetic diversity was analysed using RAPD markers. Basidiospore size and shape were not different among isolates. Molecular identification based on ITS genes confirmed that ten isolates causing tea blister blight taken from the three locations were E. vexans. Clustering analysis indicates recombination occurred which triggered the high genetic diversity among samples. The polyculture system may have caused high genetic diversity. [ABSTRACT FROM AUTHOR]

The objective of the present study was to synthesize Cu doped ZnS nanocore crosslinked with lignocellulose (represented as Cu:ZnS-lignocellulose nanocomposite) for antifungal action against the devastating tea blister blight pathogen Exobasidium vexans. The characteristic features of the nanocomposite were analyzed via different physicochemical techniques like FTIR, XRD, XPS, SEM, SEM–EDX, Elemental mapping, PCS, and UV-PL studies. The FTIR and XPS investigations revealed the crosslinking between lignocellulose and the Cu:ZnS. The presence of lignocellulose was seen to attribute a potent antifungal efficacy, also enhancing the stability of the resulting nanocomposite in aqueous suspensions. The antifungal efficacy confirmed through disk diffusion and broth dilution assays have a maximum zone of inhibition of 1.75 cm2 and a MIC50 of 0.05 mg/ml against E. vexans. Additionally, the antisporulant activity was evident as the basidiospores failed to germinate in presence of the Cu:ZnS-lignocellulose nanocomposites. This shows potential for stemming the rapid infectivity of E. vexans by achieving disease inhibition at the early stage. Finally, the comparison with two commonly used commercial fungicides (copper oxychloride and fluconazole) demonstrated > tenfold higher antifungal activity for Cu:ZnS-lignocellulose nanocomposites. [ABSTRACT FROM AUTHOR]

Tea is one of the most consumed beverages and is produced from the tender leaves of the tea plant. Various biotic and abiotic factors are directly related to tea productivity. Among the biotic factors the most destructive one is the blister blight disease of tea caused by an obligate parasitic fungus Exobasidium vexans Massee. The pathogen attacks the tender leaves of the tea plant which directly interferes with the economic growth of the tea growing countries as tea has tremendous export value. Numerous studies have identified the symptoms, epidemiology of the pathogen and its control strategies. Application of protectant and eradicant fungicides have shown promising results for controlling blister blight but overuse of chemical pesticides causes phytotoxicity, residual effects, thus use of microbial biocontrol agents are gaining more impetus. Different integrated disease management strategies along with modern emerging management approaches like elicitor mediated defense responses, development of transgenic tea plant, transcriptome study that induce many R-genes which ultimately provide innate immunity in tea plants. This review presents up-to-date information on blister blight disease which would help the future researchers to understand the host-pathogen interaction and the effective control measures to be adopt in a better way.

Tea ( Camellia sinensis [L.] O. Kuntze) is cultivated as a beverage crop. Despite being a hardy perennial, the tea plant is susceptible to various biotic stresses. Among them, the foliar disease blister blight (BB) is considered the most serious threat to the tea industry, particularly in Asia. BB caused by Exobasidium vexans (Basidiomycetes) was first reported from Northern India in 1868 and gradually established in other tea-growing countries. The fungus E. vexans attacks young harvestable shoots and causes 20 to 50% crop loss. Over the past 150 years, scientific research has delved into various aspects of BB disease, including pathogen biology, disease cycle, epidemiology, disease forecasting, crop loss assessment, and disease management strategies. In a recent shift in research focus, scientists have begun to investigate the resistance mechanisms of tea plants against BB and apply this knowledge to commercial tea cultivation. Although progress has been significant in understanding the fundamental aspects of BB resistance, the detailed molecular mechanisms driving this resistance remain under investigation. This paper focuses on the current understanding of defense mechanisms employed by tea plants against E. vexans and, conversely, how E. vexans overcomes these defenses. Furthermore, we discuss the application of plant resistance strategies in commercial tea cultivation. Lastly, we identify existing research gaps and propose future research directions in the field., Competing Interests: The author(s) declare no conflict of interest.

Blister blight caused by Exobasidium vexans is one of the important diseases in the tea crop. This disease could decrease the production of tea between 20−90%, so that it required a proper and eco-friendly strategy for managing the development of plant disease epidemics. This study was aimed to determine the daily dispersal time of basidiospores of E. vexans, and to study the effect of dew, rain water, and sterile water to the germination of basidiospores of E. vexans. The method used was trapping basidiospores using a spore trap Kiyosawa type on which the object glasses were successively placed for 4 hours at 6:00 a.m., 10:00 a.m., 2:00 p.m., 6:00 p.m., 10.00 p.m., and 2.00 a.m.. The germination of basidiospores was observed with three treatments; i.e. sterile water, rain water and dew. The results revealed that the dispersal of basidiospores of E. vexans mostly occured between 2:00 to 6:00 a.m. Basidiospores of E. vexans could germinate in all kinds of water, but they germinated very well in dew and rain water. Intisari Penyakit cacar daun teh yang disebabkan oleh Exobasidium vexans merupakan salah satu penyakit penting pada tanaman teh. Penyakit ini dapat menurunkan produksi teh antara 20−90%, sehingga perlu ada strategi yang tepat dan dapat diterima lingkungan untuk mengelola perkembangan epideminya. Penelitian ini bertujuan untuk mengetahui waktu pemencaran harian basidiospora E. vexans, dan mengetahui pengaruh embun, air hujan, dan air steril terhadap perkecambahan basidiospora E. vexans. Metode yang digunakan adalah penangkapan basidiospora menggunakan alat spore trap tipe kiyosawa yang dipasang gelas benda pada setiap 4 jam sekali, yaitu pada pukul 06.00, 10.00, 14.00, 18.00, 22.00, dan 02.00. Metode yang dipakai dalam mengamati perkecambahan basidiospora menggunakan tiga perlakuan; embun, air hujan, dan air steril. Hasil penelitian menunjukkan bahwa pemencaran basidiospora E. vexans paling banyak terjadi antara pukul 02.00−06.00. Basidiospora E. vexans dapat berkecambah pada embun, air hujan, dan air steril namun perkecambahan paling baik terjadi pada embun dan air hujan.

Tea is one of the most consumed beverages and is produced from the tender leaves of the tea plant. Various biotic and abiotic factors are directly related to tea productivity. Among the biotic factors the most destructive one is the blister blight disease of tea caused by an obligate parasitic fungus Exobasidium vexans Massee. The pathogen attacks the tender leaves of the tea plant which directly interferes with the economic growth of the tea growing countries as tea has tremendous export value. Numerous studies have identified the symptoms, epidemiology of the pathogen and its control strategies. Application of protectant and eradicant fungicides have shown promising results for controlling blister blight but overuse of chemical pesticides causes phytotoxicity, residual effects, thus use of microbial biocontrol agents are gaining more impetus. Different integrated disease management strategies along with modern emerging management approaches like elicitor mediated defense responses, development of transgenic tea plant, transcriptome study that induce many R-genes which ultimately provide innate immunity in tea plants. This review presents up-to-date information on blister blight disease which would help the future researchers to understand the host-pathogen interaction and the effective control measures to be adopt in a better way. [ABSTRACT FROM AUTHOR]

The blister blight disease caused by the fungus, Exobasidium vexans has serious implications on the quality of tea production. The disease however, has been poorly studied and hence there is very limited information on the pathogen and as such the pathogenesis of blister blight infection. One of the major roadblocks in understanding E. vexans is the obligate and biotrophic nature of the fungus which limits the establishment and maintenance of in vitro cultures. To address this issue, a Central Composite Design based Response Surface Methodology (RSM) was adopted to study the modification of three fungal culture media viz. czapek dox, potato dextrose, and v8 juice, and the effect of altered media composition on growth conditions and media compositions were assessed. The response parameter for the RSM experiments was the mycelial biomass produced under different culture conditions. The uni and bi-parametric interactions among the experimental variables provided the basis for the statistically optimized conditions for maximal fungal growth. The study thus presents the recommended modifications of existing media that can lead to the successful establishment and maintenance of E. vexans in vitro cultures. [ABSTRACT FROM AUTHOR]

Blister blight is the most prevalent leaf disease of tea, an economical perennial crop. The disease is caused by a biotrophic fungus, Exobasidium vexans. The objective was set to study whether the combine over-expression of Solanum tuberosum class I chitinase gene and Vigna radiata defensin genes in transgenic tea would give more disease resistance compared to transgene over-expressed singly. Taking two constructs containing S. tuberosum class I chitinase (AF153195) and mung bean defensin (AY437639) gene respectively, three Agrobacterium-mediated transformation events were conducted with two individual constructs and combination of both the constructs. This is a first report about the preparation of transgenic tea by co-transformation for blister resistance. Transformation was successful in all three events. Comparative analysis showed a very interesting result. Minimum overall transformation efficiency was noticed in transformation of tea with pCAMBIA 1301-Chi (2.20%) followed by pBI121-Def (2.39%) and co-transformation with pCAMBIA 1301-Chi and pBI121-Def (3.41%). The fungal bioassay with E. vexans for the transformation event with pCAMBIA 1301-Chi gave the best disease resistance having minimum diameter (7.05 mm) of hypersensitivity zone followed by 15.05 mm in pBI121-Def and 18.14 mm in combination of pCAMBIA 1301-Chi and pBI121-Def. [ABSTRACT FROM AUTHOR]

• Transcriptomics provides insights into response mechanism of tea against blister blight disease. • Transcriptome analysis revealed that the majority of disease-resistant genes were activated in response to pathogen invasion. • SA acted as a crucial role in defense activation of tea immunity against E. vexans infection. • JA- and BR-, ETH-, AUX-signaling might synergistically activate the expression of some defense-related genes after E. vexans infection. Blister blight caused by obligate biotrophic pathogen Exobasidium vexans is a prevalent foliar disease in tea plants that results in significant losses in both yield and quality. To further understand the response mechanism of tea plants against E. vexans infection, transcriptomics and targeted hormone metabonomics were performed to investigate the gene expression and phytohormone signaling networks. Transcriptome analysis revealed that the most of differentially expressed genes (DEGs) were highly enriched in the pathways of "photosynthesis-antenna proteins", "plant hormone signal transduction", "plant-pathogen interaction", "MAPK signaling pathway-plant", and "phenylpropanoid biosynthesis". The majority of disease resistance (R) genes (e.g., CDPK, PIK1, and PRS4) were activated in response to pathogen invasion in the fungal PAMP related pathway. The activation of infection-induced genes corresponds to transcription factors such as WRKY, MYB, bHLH and AP2/ERF. SA acted as a crucial role in defense activation of tea immunity against E. vexans infection, which substances (SA and SAG) were positively correlated with the expression levels of disease-resistant genes (NPR1, TGA, and PR1) in the SA signaling pathway. The biosynthesis of defense-associated hormone metabolites such as JA, ETH, and BRs might be involved in associated with the defense response of tea plants to E. vexans infection. The correlation analysis of DEGs and hormone metabolites exhibited that JA and JA-ILE were positively regulated by the DEGs (e.g., BSK, ERF1/2, ETR, SAUR, and DELLA), suggesting JA- and BR-, ETH-, AUX-signaling might synergistically activate the expression of some defense-related genes. This finding was further validated through quantitative real-time PCR, which displayed the involvement of defense-related gene expressions in the response of tea plant to the infection caused by E. vexans. Collectively, this study provides comprehensive insights into the response mechanism of tea defense against blister blight disease to act as a valuable resource for understanding plant immunity against diverse pathogen infection and other biotic stresses in tea plants. [ABSTRACT FROM AUTHOR]

Blister blight infection with Exobasidium vexans is one of the most destructive foliar diseases that seriously affect the quality and yield of tea. This research investigated the metabolite changes of healthy and infected leaves on tea cultivar 'Fuding Dabaicha' and further explored the potential antimicrobial substances against E. vexans infection. In total, 1,166 compounds were identified during the entire course of an infection, among which 73 different common compounds were significantly accumulated involved in the important antimicrobial substances of flavonoids and phenolic acids, including kaempferol (3,5,7,4'-tetrahydroxyflavone), kaempferol-3- O -sophoroside-7- O -glucoside, phloretin, 2,4,6-trihydroxybenzoic acid, galloylprocyanidin B4, and procyanidin C1 3'- O -gallate, which indicated that these metabolites might positively dominate resistance to E. vexans . Furthermore, relevant biological pathways, such as the flavone and flavonol biosynthesis, flavonoid biosynthesis, and phenylpropane pathways, were more closely related to resistance to E. vexans. Additionally, total flavonoids, phenolics, alkaloids, and terpenoids contributing to antimicrobial and antioxidant capacity were significantly altered during four different infection periods, especially the Leaf&#95;S2 stage (the second stage of infection), in which the most concentration accumulated. The leaves affected by E. vexans infection at the second stage had the relatively highest antioxidant activity. Accordingly, this study provides a theoretical support for and comprehensive insights into the effects on the metabolite changes, tea quality components, and antioxidant activity of blister blight caused by E. vexans ., Competing Interests: The author(s) declare no conflict of interest.

Tea (Camellia sinensis [L.] O. Kuntze) plant, one of the most important plantation crops in the world, is infected by a fungus called Exobasidium vexans leading to dreaded blister blight disease. The disease may result in crop losses up to 35% which directly affect the tea industry. Solanum tuberosum endo-1,3-beta-D-glucanase was cloned into tea genome via Agrobacteriummediated transformation. The transformation event initially gave 32 kanamycin-resistant plantlets, out of which PCR analysis confirmed only 10 plantlets about the integration of transgene in the plant genome. Real-time PCR study detected transgene expression in six transgenic plantlets. Upregulation of endogenous C. sinensis pathogenesis-related (PR) genes like PR3 (chitinase I) gene and PR5 (thaumatin-like protein) gene also occurred in transgenic plantlets. Detached leaf infection assay showed resistance to E. vexans in greenhouse-acclimated transgenic plantlets. An inhibitory activity against E. vexans was noticed on the detached leaves of transgenic plantlets compared to control. Transgenic plantlets showed resistance to inoculated fungal pathogen by the formation of hypersensitivity reaction area unlike the formation of fungal lesion on control plantlet. Thus, it can be inferred that constitutive expression of the potato endo-1,3-beta-D-glucanase gene can be a strategy to produce blister blight-resistant tea. [ABSTRACT FROM AUTHOR]

The effect of three aqueous solution of biotin, thiamine and calcium pantothenate, on the growth of Exobasidiumvexans was examined in vitro. The germination process of basidiospores of E. vexans differed from those of the otherExobasidium species. Basidiospore germination commenced after 19.5 hr incubation and chlamydospore-like bodies wereformed after 96 hr of incubation. Addition of biotin, calcium pantothenate, and thiamine to Difco PDA and Czapek’s mediumdid not affect the proportion of germinating basidiospores. The length of germ tubes was enhanced only by addition ofthiamine in the media. Larger size germ tubes (thick germ tubes) were occasionally observed among the ordinary hyphae.Most germlings of basidiospores developed chlamydospore-like bodies or autolysed on the media. Thick germ tubesfrequently appeared on the calcium pantothenate amended media and developed into a colony when these hyphae weretransferred to new calcium pantothenate amended media. However, further transfer of colonies did not successfully bring anew colony to grow on the calcium pantothenate amended media. Vitamin B5, calcium pantothenate, was only partially effective in generating the thick germ tubes and to induce the initial colony formation, whereas amendment of biotin and thiamineto the media did not induce visible colony growth.

Tea is the second most consumed beverage in the world. A crop loss of up to 43 % has been reported due to blister blight disease of tea caused by a fungus, Exobasidium vexans. Thus, it directly affects the tea industry qualitatively and quantitatively. Solanum tuberosum class I chitinase gene (AF153195) is a plant pathogenesis-related gene. It was introduced into tea genome via Agrobacterium-mediated transformation with hygromycin phosphotransferase ( hpt) gene conferring hygromycin resistance as plant selectable marker. A total of 41 hygromycin resistant plantlets were obtained, and PCR analysis established 12 plantlets confirming about the stable integration of transgene in the plant genome. Real-time PCR detected transgene expression in four transgenic plantlets (T28, C57, C9, and T31). Resistance to biotrophic fungal pathogen, E. vexans, was tested by detached leaf infection assay of greenhouse acclimated plantlets. An inhibitory activity against the fungal pathogen was evident from the detached leaves from the transformants compared with the control. Fungal lesion formed on control plantlet whereas the transgenic plantlets showed resistance to inoculated fungal pathogen by the formation of hypersensitivity reaction area. This result suggests that constitutive expression of the potato class I chitinase gene can be exploited to improve resistance to fungal pathogen, E. vexans, in economical perennial plantation crop like tea. [ABSTRACT FROM AUTHOR]

Elicitor-induced natural defense machinery of plants could be proposed as an alternative, non-conventional, and ecologically-friendly approach for plant protection. In this work, the abiotic elicitor, calcium chloride (CaCl), was used for inducing resistance in tea plants against blister blight disease caused by Exobasidium vexans. Foliar application of elicitor resulted in around 80 % disease inhibition over the control set, during the peak time of blister blight incidence at the experimental garden of Darjeeling Tea Research and Development Centre. A significant increase in the activities of defense enzymes like phenylalanine ammonia lyase (PAL), peroxidase, polyphenol oxidase, and β-1,3-glucanase along with higher accumulation of total phenolics was observed. Treated plants also had elevated transcript levels of thaumatin, catalase, PAL, cinnamate 4-hydroxylase, and flavonoid 3′-hydroxylase genes compared to control plants. Further, the treatment-induced nitric oxide (NO) production was confirmed by real-time visualization of the NO burst using a fluorescent probe and spectrophotometric analysis. The result suggested that CaCl induced an array of plant defense responses making this compound a potential phytosanitary product with a challenging issue and a rather attractive option for sustainable organic tea cultivation practice. [ABSTRACT FROM AUTHOR]

This work embodies the development of a real time loop mediated isothermal amplification (RealAmp) assay for the rapid detection of the cryptic tea phytopathogen, Exobasidium vexans, the causal organism of blister blight disease. Due to the widespread popularity of tea as a beverage and the associated agro-economy, the rapid detection and management of the fast-spreading blister blight disease have been a longstanding necessity. Loop-mediated isothermal amplification (LAMP) primers were designed targeting the E. vexans ITS rDNA region and the reaction temperature was optimized at 62 °C with a 60 min reaction time. Amplification of the E. vexans isolates in the initial LAMP reactions was confirmed by both agarose gel electrophoresis and SYBR Green I dye based colour change visualization. The specificity of the LAMP primers for E. vexans was validated by negative testing of seven different phytopathogenic test fungi using LAMP and RealAmp assay. The positive findings in RealAmp assay for E. vexans strain were corroborated via detecting fluorescence signals in real-time. Further, the LAMP assays performed with gDNA isolated from infected tea leaves revealed positive amplification for the presence of E. vexans. The results demonstrate that this rapid and precise RealAmp assay has the potential to be applied for field-based detection of E. vexans in real-time., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Aims The present study was aimed to evaluate the integration of Ochrobactrum anthropi BMO-111 and chemical fungicides (copper oxychloride and hexaconazole) against blister blight disease of tea. Methods and Results Application of the liquid culture of O. anthropi BMO-111 (36-h-old culture broth) was found to be effective in combined sprays with individual chemical fungicides (copper oxychloride and hexaconazole). Spray application of O. anthropi BMO-111 to tea bushes improved the biochemical parameters such as the levels of chlorophyll, polyphenols, and catechins in the harvestable tea shoots. Moreover, in the microplot and large scale trials, the integrated treatment of every two O. anthropi BMO-111 sprays followed by a single fungicides spray was found to be more efficient than the stand alone O. anthropi BMO-111 or chemicals sprays. Further, pathogenicity study employing Swiss albino mice showed no mortality in the test animals when challenged with O. anthropi BMO-111 through oral, intravenous and intranasal routes. Conclusions The field trials clearly established that O. anthropi BMO-111 has capability to reduce incidence in integrated management of blister blight disease of tea and safe to use in the field. Significance and Impact of the Study The results indicate that O. anthropi BMO-111 can be used as an agricultural input in the integrated crop protection systems. [ABSTRACT FROM AUTHOR]

Aims The present study was carried out to screen the phylloplane bacteria from tea for antagonism against grey blight caused by Pestalotiopsis theae and blister bight caused by Exobasidium vexans and to further evaluate the efficient isolates for disease control potential under field condition. Methods and Results A total of 316 morphologically different phylloplane bacteria were isolated. Among the antagonists, the isolates designated as BMO-075, BMO-111 and BMO-147 exhibited maximum inhibitory activity against both the pathogens under in vitro conditions and hence were selected for further evaluation under microplot field trial. Foliar application of 36-h-old culture of BMO-111 (1 × 108 colony-forming units ml−1) significantly reduced the blister blight disease incidence than the other isolates. The culture of BMO-111 as well as its culture filtrate effectively inhibited the mycelial growth of various fungal plant pathogens. The isolate BMO-111 was identified as Ochrobactrum anthropi based on the morphological and 16 S r DNA sequence analyses. Conclusions It could be concluded that the biocontrol agent O. anthropi BMO-111 was effective against blister blight disease of tea. Significance and Impact of the Study Further study is required to demonstrate the mechanism of its action and formulation for the biocontrol potential against blister blight disease of tea. [ABSTRACT FROM AUTHOR]

The effect of three aqueous solution of biotin, thiamine and calcium pantothenate, on the growth of Exobasidium vexans was examined in vitro. The germination process of basidiospores of E. vexans differed from those of the other Exobasidium species. Basidiospore germination commenced after 19.5 hr incubation and chlamydospore-like bodies were formed after 96 hr of incubation. Addition of biotin, calcium pantothenate, and thiamine to Difco PDA and Czapek's medium did not affect the proportion of germinating basidiospores. The length of germ tubes was enhanced only by addition of thiamine in the media. Larger size germ tubes (thick germ tubes) were occasionally observed among the ordinary hyphae. Most germlings of basidiospores developed chlamydospore-like bodies or autolysed on the media. Thick germ tubes frequently appeared on the calcium pantothenate amended media and developed into a colony when these hyphae were transferred to new calcium pantothenate amended media. However, further transfer of colonies did not successfully bring a new colony to grow on the calcium pantothenate amended media. Vitamin B5, calcium pantothenate, was only partially effective in generating the thick germ tubes and to induce the initial colony formation, whereas amendment of biotin and thiamine to the media did not induce visible colony growth. [ABSTRACT FROM AUTHOR]

Aims: Pathogenicity of Exobasidium vexans, causal agent of blister blight of tea, was studied in 30 commercially cultivated tea varieties by analysing the antigenic patterns of host and pathogen using immunological techniques. Methods and Results: Whole plant inoculation of tea varieties with E. vexans showed that T-78 and T-17/1/54 were most susceptible and most resistant respectively. Antigen preparations from tea varieties, pathogen, nonpathogen ( Fusarium oxysporum) and of nonhosts ( Glycine max, Leucaena leucocephala and Oryza sativa) were compared by indirect enzyme-linked immunosorbent assay and dot-immunobinding assay using polyclonal antibodies raised against the pathogen, nonpathogen, susceptible and resistant tea varieties. Cross-reactive antigens (CRA) were found among susceptible varieties and E. vexans isolates but not in resistant varieties, nonhosts or nonpathogen. Indirect staining of antibodies using fluorescein isothiocyanate indicated CRA were concentrated mainly around epidermal and mesophyll cells in compatible host (T-78). This was substantiated by ultrastructural studies using gold-labelled antibodies through transmission electron microscopy which showed specific localization in the chloroplasts and host cytoplasm. Conclusion: Pathogenicity of E. vexans to different tea varieties is therefore related to the level of antigenic similarity between host and pathogen. Significance and Impact of the Study: Immunological methods proved to be valuable in screening commercially cultivated tea varieties against E. vexans. [ABSTRACT FROM AUTHOR]

Aims: To assess the effects of solar UV-B radiation on phyllosphere bacteria of tea leaves in relation to blister blight disease in the field. Methods and Results: The effects of UV-B radiation on the phyllosphere microbiology of tea ( Camellia sinensis) were studied in contrasting wet and dry seasons at a tropical site. Wavelength-selective filters were used to separate the effects of UV-B from those of other factors. Bacterial populations were quantified in relation to the incidence of blister blight disease. Attenuation of UV-B increased the survival of Xanthomonas sp. when populations were not water limited, and increased the incidence of blister blight, but had no effect on Corynebacterium aquaticum. Conclusions: The effects of solar UV-B on phyllosphere bacteria were substantial but depended on both species and interactions with other environmental variables. Xanthomonas sp. was more sensitive to UV-B than C. aquaticum, but this did not result in differences in population density under high radiation conditions (dry season), but only in the wet season when other factors were not limiting. Significance and Impact of the Study: The role of UV-B on leaf surface microbiology in the tropics is marked but depends on other conditions, and the contrasting UV-B responses of different organisms can be masked by other limiting factors. [ABSTRACT FROM AUTHOR]

Abstract: Plant growth-promoting rhizobacteria (PGPR) bioformulations (Pseudomonas and Bacillus) were tested for their efficacy against blister blight (Exobasidium vexans) disease in tea (Camellia sinensis) under field conditions for two seasons. Among the bioformulations tested, foliar application of Pseudomonas fluorescens Pf1 at 7-d intervals consistently reduced the disease incidence of blister blight for two seasons, almost comparable with that of chemical fungicide. In addition to disease control, it also increased tea yield significantly compared to the untreated control. Induction of defense enzymes such as peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, chitinase, β-1,3-glucanase and phenolics were studied. The enzyme accumulation was greater in P. fluorescens Pf1-treated plants compared to control. The study revealed the probable influence of plant growth promotion and induced systemic resistance (ISR) in enhancing the disease resistance in tea plants against blister disease by PGPR bioformulations. [Copyright &y& Elsevier]

Blister blight, caused by Exobasidium vexans Massee, is a serious tea disease and leads to massive damage to tea yield and quality. WRKY transcription factors play an important role in the regulation of biotic stresses. However, the biological and molecular functions of these transcription factors during blister blight in tea plants are not known. The present study isolated a disease resistance gene, CsWRKY14 , from leaves of Camellia sinensis and analysed this gene using bioinformatics. The results demonstrated that CsWRKY14 comprised multiple cis -acting elements and involved in salicylic acid (SA) signal transduction pathway. Moreover, the CsWRKY14 protein belongs to the IIe subgroup of the WRKY family located in the nucleus. The expression of CsWRKY14 was more upregulated in the resistant cultivar 'Zhongcha 108' (ZC) compared to the susceptible cultivar 'Longjing changye' (LJ). Consistently, the endogenous levels of SA and the expression of SA signaling pathway-related genes (NPR1 , PR1 , PR2 , and PR4) were higher in ZC than in LJ, which suggests that CsWRKY14 contributes to the increase of SA concentration and activates the expression level of SA-induced pathogen-associated genes. Histochemical analysis and enzymatic activity assay revealed that the resistant cultivar ZC exhibited less H 2 O 2 accumulation and higher activities of antioxidant enzymes. CsWRKY14 -silenced plants were more sensitive to E. vexans than wild plants and exhibited a decrease in the expression of SA pathway-related genes and the antioxidant enzyme activities. Our results suggest CsWRKY14 can be used as an effective genetic resource for tea breeding against blister blight. [Display omitted] • CsWRKY14 as a positive regulator in tea blister blight resistance. • CsWRKY14 was a Group IIe WRKY member and localized in nuclei. • CsWRKY14 participates in the accumulation of SA. • CsWRKY14 regulates defense-associated genes expression. • Involvement of antioxidant system in CsWRKY14-mediated Exobasidium vexans defense. [ABSTRACT FROM AUTHOR]