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ABSTRACTSTea ( Camellia sinensis L.) is a high valued beverage worldwide since ancient times; more than three billion cups of tea are consumed each day. Leaf extracts of the plant are used for food preservation, cosmetics, and medicinal purposes. Nevertheless, tea contaminated with mycotoxins poses a serious health threat to humans. Mycotoxin production by tea fungi is induced by a variety of factors, including poor processing methods and environmental factors such as high temperature and humidity. This review summarizes the studies published to date on mycotoxin prevalence, toxicity, the effects of climate change on mycotoxin production, and the methods used to detect and decontaminate tea mycotoxins. While many investigations in this domain have been carried out on the prevalence of aflatoxins and ochratoxins in black, green, pu-erh, and herbal teas, much less information is available on zearalenone, fumonisins, and Alternaria toxins. Mycotoxins in teas were detected using several methods; the most commonly used being the High-Performance Liquid Chromatography (HPLC) with fluorescence detection, followed by HPLC with tandem mass spectrometry, gas chromatography and enzyme-linked immunosorbent assay. Further, mycotoxins decontamination methods for teas included physical, chemical, and biological methods, with physical methods being most prevalent. Finally, research gaps and future directions have also been discussed.

Gray blight, a fungal disease caused by Pestalotiopsis-like species, is a widespread disease affecting tea crop (Camellia sinensis (L.) Kuntze) in many tea-growing countries, including India, resulting in huge losses in tea production. In India, several studies have been conducted to understand the fungal diseases of tea crop, but gray blight has not been well described in major tea growing areas such as in North Bengal, based on its geographic distribution, molecular analysis, or pathogenicity, and even fungicide resistance. The objective of this study was to identify and characterize the causative agents of gray blight disease in symptomatic leaf sample of tea crop collected from 27 tea gardens located in North Bengal, India and to evaluate some common fungicides against them in order to understand the resistance mechanism. In this study, we characterized Pestalotiopsis-like species based on the phylogenies of DNA sequences (internal transcribed spacers) and assessment of conidial characteristics. The study revealed that out of 27 isolates of gray blight pathogens, 17 belonged to the genus Pseudopestalotiopsis (Ps.), six isolates were Neopestalotiopsis, and four were Pestalotiopsis. Two novel species, Ps. thailandica and N. natalensis were introduced through this study. The most frequently isolated genus from C. chinensis was Pseudopestalotiopsis. Pathogenicity tests showed that the isolates displayed significantly different virulence when inoculated onto wounded tea leaves and the mycelial growth rate was positively correlated with pathogenicity (P < 0.01). Based on the 13 ISSR (Inter Simple Sequence Repeat) markers used and principal coordinate analysis, it was found that isolates were very diverse. Out of 27 isolates, IND0P2, DLG0P10, and BHAT0P11 isolates were insensitive against both MBC + M3 (Carbendazim + Mancozeb) and DMI (Hexaconazole) fungicides, while isolates SANY0P18, PAHG0P19, RANG0P24, and SING0P25 were insensitive only against MBC + M3 fungicide. Further, these insensitive isolates were grouped into separate clusters by ISSR, indicating their distinctiveness. However, all the evaluated isolates were susceptible to M1 (copper oxychloride) and another DMI (propiconazole) fungicides. Therefore, to manage gray blight, fungicide resistance management strategies as recommended by Fungicide Resistance Action Committee should be implemented., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Gray blight caused by Pestalotiopsis-like species is a major disease of tea crop worldwide including India, causes significant losses in tea production. Management of disease using fungal biocontrol agents is considered an alternative eco-friendly approach to synthetic fungicides. The present study explores the efficacy of Trichoderma reesei in the gray blight management in tea crop and activation of defense related enzymes against gray blight pathogen by developing a tri-trophic interaction system. Out of 16 isolates of Trichoderma species screened in laboratory against Pseudopestalotiopsis theae, a gray blight pathogen, isolate TRPATH01 had highest antagonistic activity (81.2%) against Ps. theae and was found to produce inhibitory volatile and non-volatile metabolites. Based on ITS and TEF-1 alpha sequencing, the isolate TRPATH01 was recognised as T. reesei. The methanolic extract of T. reesei was also found effective against Ps. theae at 200 μg/mL also confirmed presence of highest volatile compounds. The isolate also produced hydrolytic enzymes such as chitinase, cellulase, protease, and lipase. Under nursery conditions, 2% and 5% concentrations with 2 × 10 6 conidia/ml of T. reesei were able to reduce 67.5% to 75.0% of disease severity over pathogen inoculated controls. Moreover, compared with positive and negative controls, T. reesei -treated tea plants showed increased shoot height, stem diameter, shoot and root fresh weight at 45 days after inoculation. Principal component analysis capturing 97.1% phenotypic variations, which revealed that the tea plants co-inoculated with Ps. theae and T. reesei exhibited significantly upregulated accumulation of defensive enzymes viz., polyphenol oxidase, peroxidase, phenylalanine ammonia lyase, phenolics, β-1, 3-glucanase, and chitinase when compared to both controls. Hence, T. reesei could provide an eco-friendly and viable mitigation option for gray blight in tea gardens by inducing defense-related enzymes., Competing Interests: Declaration of Competing Interest Authors declare no conflict of interest., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Fusarium dieback is a prevalent disease of tea (Camellia sinensis (L.) Kuntze) in India and China. The pathogen affects plucking shoots and causes complete crop loss under favourable conditions. Although, other fungal diseases that infect tea were widely explored for pathogen identification and characterization, little is known about Fusarium dieback in major tea growing regions of India. Therefore, in this study 24 isolates of Fusarium species causing dieback on tea in 24 tea gardens of Assam and North Bengal were isolated and characterized through micro-morphological and molecular analysis using multi-locus DNA sequences to determine whether multiple species of Fusarium are responsible for dieback disease. Molecular analysis revealed the association of four species of Fusarium , namely F. concentricum, F. solani, F. fujikuroi, and F. oxysporum. The most dominant species was F. concentricum (62.5%), whereas the occurrence frequencies of F. solani, F. fujikuroi, and F. oxysporum were 20.8%, 12.5%, and 0.04%, respectively. All Fusarium isolates were pathogenic to tea leaves when individually and co-inoculated, with F. concentricum HPE0F10 and NHT0F17 exhibiting 19.3 mm lesion length being the most virulent isolates. The growth rate of the pathogen was positively correlated with lesion lengths (P < 0.001). Co-infection of two or multiple Fusarium species enhanced the disease severity and quicker disease development compared to single inoculation. All the isolates showed diverse genetic backgrounds based on Inter Simple Sequence Repeat (ISSR) primers and principal coordinate analysis. In fungicide screening test, all isolates except HPE0F10, NDS0F18, and SNY0F22 were insensitive to M1 fungicide (copper oxychloride). Isolates GNP0F8 and LKW0F16 were insensitive to MBC + M3 (Carbendazim + Mancozeb), whereas HPE0F10, NLG0F11, IND0F13, and NLW0F19 were insensitive to DMI (respective each two to Hexaconazole and Valextra) fungicides. Notably, all the isolates were susceptible to propiconazole. Further, ISSR segregated isolates insensitive to MBC + M3 and M1 fungicides into two separate clusters, representing their distinctiveness. The fungicide screening results indicate that fungicide resistance can be managed by rotating different modes of action of fungicides against multiple Fusarium species causing tea dieback. • Fusarium concentricum, F. fujikuroi, F. oxysporum, and F. solani were identified as causal agents of tea dieback. • The identification was confirmed by multi-locus phylogenetic analysis. • Fusarium isolates showed variable pathogenicity through individual and co-inoculation tests. • ISSR primers revealed diverse genetic backgrounds among 24 Fusarium isolates. • Propiconazole was effective against all Fusarium isolates tested. [ABSTRACT FROM AUTHOR]