Identification and characterization of fungi associated with blister blight lesions of tea (Camellia sinensis L. Kuntze) isolated from Meghalaya, India

Emergence of Lasiodiplodia theobromae induced leaf necrosis in tea (Camellia sinensis [L.] O. Kuntze) from India

The tea plant, Camellia sinensis [L.] O. Kuntze, is a vital global agricultural commodity, yet faces challenges from fungal infections, which affects its production. To reduce the loss in the tea production, the fungal infections must be removed which is managed with fungicides, which are harmful to the environment. Leaf necrosis, which decreases tea quality and quantity, was investigated across Assam, revealing Lasiodiplodia theobromae as the causative agent. Pathogenicity tests, alongside morphological and molecular analyses, confirmed its role in leaf necrosis. Genome and gene analysis of L. theobromae showed multiple genes related to its pathogenicity. The study also assessed the impact of chemical pesticides on this pathogen. Additionally, the findings in this study highlight the significance of re-assessing management approaches in considering the fungal infection in tea.

Effect of blister blight disease caused by Exobasidium on tea quality

Blister blight, as one of the most threatening and damaging disease worldwide, mainly infects young organs and tissues seriously affecting tea growth and quality. In this study, the spread of pathogen on tea leaves were examined by toluidine blue staining, scanning electron microscope and transmission electron microscope analysis. The composition and abundance of fungal community on leaf tissues were firstly analyzed. Sensory evaluation and metabolites analysis indicated that diseased tea leaves had strong sweet taste and soluble sugars contributed significantly to the taste, while metabolites showing bitter and astringent taste (caffeine, catechins) were significantly decreased. According to the biological functions of differential metabolites, sugars including 7 monosaccharides (d-xylose, d-arabinose, d-mannose, d-glucuronic acid, glucose, d-galactose and d-fructose), 2 disaccharide (sucrose and maltose) and 1 trisaccharide (raffinose) were the main differential sugars increased in content (>2 fold change), which was of great significance to sweet taste of diseased tea.

Effects of blister blight disease on endophytic microbial diversity and community structure in tea (Camellia sinensis) leaves

In this study, metagenomic sequencing technology was employed to analyze the ITS1 region sequence of the ITS rDNA gene of endophytic fungi and 16S sequence of endophytic bacteria in tea leaves with varying degrees of infection by tea blister blight disease as well as healthy tea leaves. Subsequently, a comparative analysis was conducted on the endophytic microbial diversity and the community structure in tea leaves. The findings of this investigation reveal a shift in the dominant endophytic fungal genera from Ascomycota to Basidiomycota as the disease progressed. Furthermore, a negative correlation was observed between Exobasidium and Talaromyce, with Talaromyce exhibiting potential as an antagonist against the disease. Meanwhile, our findings reveal that Proteobacteria, Firmicutes, and Actinobacteria were the three most abundant bacteria phyla in tea leaves. As the disease progressed, there was an increase in the relative abundance of Actinobacteria, while Variovorax, Sphingomonas, and Pseudomonas were found to have higher abundance in later stages. The diversity analysis results indicated that the endophytic microbial diversity and the community structure in tea leaves in the diseased group were lower than those in the healthy control group. In general, blister blight disease altered the community structure of endophytic microorganisms in tea leaves, resulting in a few species with high abundance. The study lays a foundation for investigating the pathogenic mechanism of tea blister disease and establishing a theoretical basis for controlling diseases in tea trees.

Molecular and biological investigating of tea plant necrotic ring blotch virus as a worldwide threat

Tea plant necrotic ring blotch virus (TPNRBV) has emerged as a significant threat to tea plantations, primarily in China. Since 2020, similar symptoms have been observed in tea plants in northern Iran, raising concerns about the spread of this viral infection. In this study, we conducted an extensive investigation involving approximately 70 samples collected from both symptomatic and asymptomatic tea plants. Using reverse transcription-polymerase chain reaction with specially designed primers, we successfully amplified DNA fragments from 26 samples, confirming the presence of TPNRBV. Subsequent sequencing of these fragments revealed various segments of the TPNRBV genome. Our phylogenetic analysis revealed that the Iranian TPNRBV isolates formed a distinct sub-cluster alongside Chinese isolates, distinguishing them from Japanese isolates. These finding sheds light on the genetic diversity and relationships of TPNRBV across different regions. Additionally, we explored the potential modes of TPNRBV transmission. Mechanical transmission experiments confirmed the ability of the virus to infect Nicotiana rustica and Chenopodium quinoa seedlings, highlighting the risk of mechanical spread within tea plantations. Moreover, we investigated seed transmission and found evidence of TPNRBV in various parts of tea seeds, suggesting the possibility of seed-borne transmission. Overall, this comprehensive study enhances our understanding of the biological and molecular characteristics of TPNRBV, an emerging threat to global tea production. Our findings provide valuable insights into the virus's transmission dynamics and genetic diversity, which are essential for developing effective management strategies to mitigate its impact on tea cultivation worldwide.

Field Control Effect and Initial Mechanism: A Study of Isobavachalcone against Blister Blight Disease

Blister blight (BB) disease is caused by the obligate biotrophic fungal pathogen Exobasidium vexans Massee and seriously affects the yield and quality of Camellia sinensis. The use of chemical pesticides on tea leaves substantially increases the toxic risks of tea consumption. Botanic fungicide isobavachalcone (IBC) has the potential to control fungal diseases on many crops but has not been used on tea plants. In this study, the field control effects of IBC were evaluated by comparison and in combination with natural elicitor chitosan oligosaccharides (COSs) and the chemical pesticide pyraclostrobin (Py), and the preliminary action mode of IBC was also investigated. The bioassay results for IBC or its combination with COSs showed a remarkable control effect against BB (61.72% and 70.46%). IBC, like COSs, could improve the disease resistance of tea plants by enhancing the activity of tea-plant-related defense enzymes, including polyphenol oxidase (PPO), catalase (CAT), phenylalanine aminolase (PAL), peroxidase (POD), superoxide dismutase (SOD), β-1,3-glucanase (Glu), and chitinase enzymes. The fungal community structure and diversity of the diseased tea leaves were examined using Illumina MiSeq sequencing of the internal transcribed spacer (ITS) region of the ribosomal rDNA genes. It was obvious that IBC could significantly alter the species' richness and the diversity of the fungal community in affected plant sites. This study broadens the application range of IBC and provides an important strategy for the control of BB disease.

Characterization and selection of endophytic actinobacteria for growth and disease management of Tea (Camellia sinensis L.)

Endophytic microbes are vital for nutrient solubilization and uptake, growth, and survival of plants. Here, 88 endophytic actinobacteria (EnA) associated with five tea clones were isolated, assessed for their diversity, plant growth promoting (PGP), and biocontrol traits, and then used as an inoculant for PGP and disease control in host and non-host plants. Polyphasic methods, including phenotypic and genotypic characteristics led to their identification as Streptomyces, Microbacterium, Curtobacterium, Janibacter, Rhodococcus, Nocardia, Gordonia, Nocardiopsis, and Kribbella. Out of 88 isolates, 35 (39.77%) showed antagonistic activity in vitro against major fungal pathogens, viz. Fusarium oxysporum, Rhizoctonia solani, Exobasidium vexans, Poria hypobrunnea, Phellinus lamaensis, and Nigrospora sphaerica. Regarding PGP activities, the percentage of isolates that produced indole acetic acid, siderophore, and ammonia, as well as P-solubilisation and nitrogen fixation, were 67.05, 75, 80.68, 27.27, 57.95, respectively. A total of 51 and 42 isolates showed chitinase and 1-aminocyclopropane-1-carboxylic acid deaminase activity, respectively. Further, two potent Streptomyces strains KA12 and MA34, selected based on the bonitur scale, were screened for biofilm formation ability and tested in vivo under nursery conditions. Confocal laser scanning microscopy and the crystal violet staining technique revealed that these Streptomyces strains can form biofilms, indicating the potential for plant colonization. In the nursery experiment, they significantly enhanced the shoot and root biomass, shoot and root length, and leaf number in host tea plants. Additionally, treatment of tomato seeds by KA12 suppressed the growth of fungal pathogen Fusarium oxysporum, increased seed germination, and improved root architecture, demonstrating its ability to be used as a seed biopriming agent. Our results confirm the potential of tea endophytic actinobacterial strains with multifarious beneficial traits to enhance plant growth and suppress fungal pathogens, which may be used as bioinoculant for sustainable agriculture.

Potentiality of actinobacteria to combat against biotic and abiotic stresses in tea [Camellia sinensis (L) O. Kuntze]

Tea (Camellia sinensis (L) O. Kuntze) is a long-duration monoculture crop prone to several biotic (fungal diseases and insect pest) and abiotic (nutrient deficiency, drought, and salinity) stress that eventually result in extensive annual crop loss. The specific climatic conditions and the perennial nature of the tea crop favor growth limiting abiotic factors, numerous plant pathogenic fungi (PPF), and insect pests. The review focuses on the susceptibility of tea crops to PPF/pests, drought, salinity, and nutrient constraints and the potential role of beneficial actinobacteria in promoting tea crop health. The review also focuses on some of the major PPF associated with tea, such as Exobasidium vexans, Pestalotiopsis theae, Colletotrichum acutatum, and pests (Helopeltis theivora). The phylum actinobacteria own a remarkable place in agriculture due to the biosynthesis of bioactive metabolites that assist plant growth by direct nutrient assimilation, phytohormone production, and by indirect aid in plant defense against PPF and pests. The chemical diversity and bioactive significance of actinobacterial metabolites (antibiotics, siderophore, volatile organic compounds, phytohormones) are valuable in the agro-economy. This review explores the recent history of investigations in the role of actinobacteria and its secondary metabolites as a biocontrol agent and proposes a commercial application in tea cultivation.

Neuroimaging features of angiocentric glioma: A case series and systematic review

BACKGROUND AND PURPOSE

Angiocentric gliomas (AGs) are epileptogenic low-grade gliomas in young patients. We aimed to investigate the MRI findings of AGs and systematically review previous publications and three new cases.

METHODS

We searched PubMed, Elsevier's abstract and citation database, and Embase databases and included 50 patients with pathologically proven AGs with analyzable preoperative MRI including 3 patients from our institution and 47 patients from 38 publications (median age, 13 years [range, 2-83 years]; 35 men). Two board-certified radiologists reviewed all images. The relationships between seizure/epilepsy history and MRI findings were statistically analyzed. Moreover, clinical and imaging differences were evaluated between supratentorial and brainstem AGs.

RESULTS

Intratumoral T1-weighted high-intensity areas, stalk-like signs, and regional brain parenchymal atrophy were observed in 23 out of 50 (46.0%), 10 out of 50 (20.0%), and 14 out of 50 (28.0%) patients, respectively. Intratumoral T1-weighted high-intensity areas were observed significantly more frequently in patients with stalk-like signs (positive, 9/10 vs. negative, 14/40, p = .0031) and regional atrophy (13/14 vs. 10/36, p = .0001). There were significant relationships between the length of seizure/epilepsy history and presence of intratumoral T1-weighted high-intensity area (median 3 years vs. 0.5 years, p = .0021), stalk-like sign (13.5 vs. 1 year, p < .0001), and regional atrophy (14 vs. 0.5 years, p < .0001). Patients with brainstem AGs (n = 7) did not have a seizure/epilepsy history and were significantly younger than those with supratentorial AGs (median, 5 vs. 13 years, p < .0001, respectively).

CONCLUSIONS

Intratumoral T1-weighted high-intensity areas, stalk-like signs, and regional brain atrophy were frequent imaging features in AG. We also found that affected age was different between supratentorial and brainstem AGs.