Resistance Of Tea Plants Research Articles

Fulvic acid enhances drought resistance in tea plants by regulating the starch and sucrose metabolism and certain secondary metabolism

The aim of this work was to gain insight into the molecular mechanisms underlying the effect of fulvic acid on drought-exposed tea plants. We performed proteomic analysis of fulvic acid-treated tea leaves from the target plants using tandem mass tag quantitative labeling technology and compared the results with those of a previous transcriptomic analysis. We identified 48 and 611 differentially abundant proteins in the leaves of tea plants treated with fulvic acid compared with the control under mild and severe drought, respectively. Comparative analysis showed that, under severe drought, 55 genes had similar expression patterns at the transcriptome and proteome levels, such as PAL, GBE, GBSS and bAS. Bioinformatic analysis revealed that those genes were mainly related to the starch and sucrose metabolism, phenylpropanoid biosynthesis and triterpenoid biosynthesis. SignificanceThis study broadens the understanding of the molecular mechanisms underlying the improved drought resistance seen in tea plants in the presence of fulvic acid and provides a basis for further research on the genomics of drought tolerance in these plants. In addition, these findings could be used to develop new guidance strategies for improved drought management systems in tea plantation.

Transformation of Salicylic Acid and Its Distribution in Tea Plants (Camellia sinensis) at the Tissue and Subcellular Levels.

Salicylic acid (SA) is a well-known immune-related hormone that has been well studied in model plants. However, less attention has been paid to the presence of SA and its derivatives in economic plants, such as tea plants (Camellia sinensis). This study showed that tea plants were rich in SA and responded differently to different pathogens. Feeding experiments in tea tissues further confirmed the transformation of SA into salicylic acid 2-O-β-glucoside (SAG) and methyl salicylate. Nonaqueous fractionation techniques confirmed that SA and SAG were mostly distributed in the cytosol of tea leaves, consistent with distributions in other plant species. Furthermore, the stem epidermis contained more SA than the stem core both in C. sinensis cv. “Jinxuan” (small-leaf species) and “Yinghong No. 9” (large-leaf species). Compared with cv. “Yinghong No. 9”, cv. “Jinxuan” contained more SAG in the stem epidermis, which might explain its lower incidence rate of wilt disease. This information will improve understanding of SA occurrence in tea plants and provide a basis for investigating the relationship between SA and disease resistance in tea plants.

Indole primes defence signalling and increases herbivore resistance in tea plants.

Upon herbivore attack, plants emit herbivore-induced plant volatiles (HIPVs). HIPVs can prime defences and resistance of intact plants. However, how HIPVs are decoded and translated into functional defence responses is not well understood, especially in long-lived woody plants. Here, we investigated the impact of the aromatic HIPV indole on defence-related early signalling, phytohormone accumulation, secondary metabolite biosynthesis and herbivore resistance in tea plants. We find that tea plants infested with tea geometrid caterpillars release indole at concentrations >450 ng*hr-1 . Exposure to corresponding doses of synthetic indole primes the expression of early defence genes involved in calcium (Ca2+ ) signalling, MPK signalling and jasmonate biosynthesis. Indole exposure also primes the production of jasmonates and defence-related secondary metabolites. These changes are associated with higher herbivore resistance of indole-exposed tea plants. Chemical inhibition of Ca2+ and jasmonate signalling provides evidence that both are required for indole-mediated defence priming and herbivore resistance. Our systematic assessment of the impact of indole on defence signalling and deployment shows that indole acts by boosting Ca2+ signalling, resulting in enhanced jasmonate-dependent defence and resistance in a woody plant. Our work extends the molecular basis of HIPV-induced defence priming from annual plants to an economically important tree species.

Identification and characterization of two sesquiterpene synthase genes involved in volatile-mediated defense in tea plant (Camellia sinensis)

Terpenes and their derivatives are vital components of tea aroma. Their constitution and quantity are highly important criteria for the sensory evaluation of teas. Biologically, terpenes are involved in chemical resistance of tea plant against biotic and/or abiotic stresses. The goal of this study is to identify volatile terpenes of tea plants implicated in defense against herbivores and to identify terpene synthase (TPS) genes for their biosynthesis. Upon herbivory by tea geometrid (Ectropis obliqua Prout), tea plants were found to emit two sesquiterpenes, (E, E)-α-farnesene and (E)-nerolidol, which were undetectable in intact tea plants. The induced emission of (E, E)-α-farnesene and (E)-nerolidol suggests that they function in either direct or indirect defense of tea plants against the tea geometrid. Candidate TPS genes were identified from the transcriptomes of tea plants infested by tea geometrids. Two dedicated sesquiterpene synthases, CsAFR and CsNES2, were identified. CsAFR belongs to the TPS-b clade and can catalyze the formation of (E, E)-α-farnesene from (E, E)-FPP. CsNES2 belongs to the TPS-g clade and can synthesize (E)-nerolidol using (E, E)-FPP. The two genes were also both dramatically upregulated by herbivore damage. In summary, we showed that two novel sesquiterpene synthase genes CsAFR and CsNSE2 are inducible by herbivory and responsible for the elevated emission of herbivore-induced (E, E)-α-farnesene and (E)-nerolidol, which are implicated in tea plant defense against herbivores.

Integrated transcriptomic and metabolomic analyses reveal the effects of callose deposition and multihormone signal transduction pathways on the tea plant-Colletotrichum camelliae interaction

Colletotrichum infects diverse hosts, including tea plants, and can lead to crop failure. Numerous studies have reported that biological processes are involved in the resistance of tea plants to Colletotrichum spp. However, the molecular and biochemical responses in the host during this interaction are unclear. Cuttings of the tea cultivar Longjing 43 (LJ43) were inoculated with a conidial suspension of Colletotrichum camelliae, and water-sprayed cuttings were used as controls. In total, 10,592 differentially expressed genes (DEGs) were identified from the transcriptomic data of the tea plants and were significantly enriched in callose deposition and the biosynthesis of various phytohormones. Subsequently, 3,555 mass spectra peaks were obtained by LC–MS detection in the negative ion mode, and 27, 18 and 81 differentially expressed metabolites (DEMs) were identified in the tea leaves at 12 hpi, 24 hpi and 72 hpi, respectively. The metabolomic analysis also revealed that the levels of the precursors and intermediate products of jasmonic acid (JA) and indole-3-acetate (IAA) biosynthesis were significantly increased during the interaction, especially when the symptoms became apparent. In conclusion, we suggest that callose deposition and various phytohormone signaling systems play important roles in the tea plant-C. camelliae interaction.

Effects of nitric oxide on the GABA, polyamines, and proline in tea (Camellia sinensis) roots under cold stress

Tea plant often suffers from low temperature induced damage during its growth. How to improve the cold resistance of tea plant is an urgent problem to be solved. Nitric oxide (NO), γ-aminobutyric acid (GABA) and proline have been proved that can improve the cold resistance of tea plants, and signal transfer and biosynthesis link between them may enhance their function. NO is an important gas signal material in plant growth, but our understanding of the effects of NO on the GABA shunt, proline and NO biosynthesis are limited. In this study, the tea roots were treated with a NO donor (SNAP), NO scavenger (PTIO), and NO synthase inhibitor (L-NNA). SNAP could improve activities of arginine decarboxylase, ornithine decarboxylase, glutamate decarboxylase, GABA transaminase and Δ1-pyrroline-5-carboxylate synthetase and the expression level of related genes during the treatments. The contents of putrescine and spermidine under SNAP treatment were 45.3% and 37.3% higher compared to control at 24 h, and the spermine content under PTIO treatment were 57.6% lower compare to control at 12 h. Accumulation of proline of SNAP and L-NNA treatments was 52.2% and 43.2% higher than control at 48 h, indicating other pathway of NO biosynthesis in tea roots. In addition, the NO accelerated the consumption of GABA during cold storage. These facts indicate that NO enhanced the cold tolerance of tea, which might regulate the metabolism of the GABA shunt and of proline, associated with NO biosynthesis.

Proanthocyanidin-Aluminum Complexes Improve Aluminum Resistance and Detoxification of Camellia sinensis.

Aluminum (Al) influences crop yield in acidic soil. The tea plant (Camellia sinensis) has high Al tolerance with abundant monomeric catechins in its leaves, especially epigallocatechin gallate (EGCG), and polymeric proanthocyanidins in its roots (rPA). The role of these polyphenols in the Al resistance of tea plants is unclear. In this study, we observed that these polyphenols could form complexes with Al in vitro, and complexation capacity was positively influenced by high solution pH (pH 5.8), polyphenol type (rPA and EGCG), and high Al concentration. In the 27Al nuclear magnetic resonance (NMR) experiment, rPA-Al and EGCG-Al complex signals could be detected both in vitro and in vivo. The rPA-Al and EGCG-Al complexes were detected in roots and old leaves, respectively, of both greenhouse seedlings and tea garden plants. Furthermore, in seedlings, Al accumulated in roots and old leaves and mostly existed in the apoplast in binding form. These results indicate that the formation of complexes with tea polyphenols in vivo plays a vital role in Al resistance in the tea plant.

JA-Ile-macrolactone 5b Induces Tea Plant (Camellia sinensis) Resistance to Both Herbivore Ectropis obliqua and Pathogen Colletotrichum camelliae.

Jasmonates (JAs), the group of lipid-derived hormones, were found to control the defense responses in a myriad of plants. Meaningfully, the macrolactones of 12-hydroxy jasmonate isoleucine (12OH-JA-Ile) were reported to induce the defensive response of wild tobacco. However, little to nothing has been known about the elicitation effect of JA-Ile-macrolactones on woody plants to harmful organisms, let alone its underlying mechanisms. Here, we first optimized the synthetic routine using mild toxic reagent isobutyl chloroformate instead of ethyl chloroformate for conjugation, and we used acetonitrile (MeCN) instead of ethyl alcohol for the better dissolution of p-toluenesulfonic acid (p-TsOH) to gain JA-Ile-macrolactones. JA-Ile-macrolactone 5b-treated tea plants significantly inhibited the larvae weight gain of Ectropis obliqua larvae and the lesions caused by Colletotrichum camelliae. Furthermore, the expression level of CsOPR3 was significantly upregulated in 5b-treated leaves. Meanwhile, 5b reduced the accumulation of eriodictyol 7-O-glucuronide (EDG) in tea plants, which was confirmed to promote the growth rate of E. obliqua larvae by artificial diet assay. In conclusion, our study proved that the exogenous application of 5b could induce the tea plant resistance both to herbivore E. obliqua and pathogen C. camelliae, and EDG was identified as one of the secondary metabolites that could influence the growth rate of E. obliqua, but it did not directly influence the infection of C. camelliae in vitro. Further research should be carried out to clarify the mechanism through which 5b induces tea plant resistance to C. camelliae.

Alteration of local and systemic amino acids metabolism for the inducible defense in tea plant (Camellia sinensis) in response to leaf herbivory by Ectropis oblique

Leaf herbivory on tea plants (Camellia sinensis) by tea geometrids (Ectropis oblique) can cause severe yield loss and quality damage for tea. In previous work, we discovered that leaf herbivory triggered systemic carbon depletion in undamaged roots to enhance resource investment for local defense induced in damaged leaves. Here, we investigated the dynamics of amino acids in the local and systemic responses and the roles of nitrogen resource reallocation for the inducible defense in tea plants in response to leaf herbivory. The comparative analysis of the dynamics of flavonoids, caffeine, theanine and basic amino acids at metabolic and transcriptome levels revealed that leaf herbivory triggered the differential reconfiguration of these amino acid-derived defensive metabolites and nitrogenous primary metabolism between the local and systemic responses. The tight association of the metabolism and reallocation of amino acids with the activation of defensive secondary metabolism indicated that the systemic nitrogen reallocation played a potentially important role for the resource investment in tea plant resistance against leaf herbivory. This study provided an extended understanding of the role of systemic nitrogen reallocation for the interaction of tea plants and geometrids and the root-mediated resource-based resistance strategy employed by tea plants in response to leaf herbivory.

The Jasmonic Acid Pathway Positively Regulates the Polyphenol Oxidase-Based Defense against Tea Geometrid Caterpillars in the Tea Plant (Camellia sinensis).

Polyphenol oxidases (PPOs) as inducible defense proteins, contribute to tea (Camellia sinensis) resistance against tea geometrid larvae (Ectropis grisescens), and this resistance has been associated with the jasmonic acid (JA) signaling by testing geometrid performance in our previous work. However, the regulation of PPO-based defense by JA and other hormone signaling underlying these defense responses is poorly understood. Here, we investigated the role of phytohormones in regulating the PPO response to tea geometrids. We profiled levels of defense hormones, PPO activity and CsPPO genes in leaves infested with tea geometrids. Then, hormone levels were manipulated by exogenous application of methyl jasmonate (MeJA), gibberellin acid (GA3), abscisic acid (ABA), JA biosynthesis inhibitors (sodium diethyldithiocarbamate trihydrate, DIECA and salicylhydroxamic acid, SHAM) and GA inhibitor (uniconazole, UNI). Upon geometrid attack, JA levels significantly increased, whereas GA levels notably decreased and ABA level was slightly decreased. And the PPO activity significantly increased in line with the transcript levels of CsPPO2 and CsPPO4 but not CsPPO1. There were an obvious antagonistic cross-talk between JA and GA signals and an association among JA signals, PPO response and herbivore resistance in tea plants. Pretreatment with MeJA increased PPO activity by activating the transcripts of CsPPO2 and CsPPO4, whereas application of JA inhibitor DIECA suppressed PPO activity. GA3 strongly enhanced PPO activity, but ABA did not alter PPO activity. These findings strongly suggest that JA is a central player in PPO-mediated tea resistance against tea geometrids in a manner that prioritizes defense over growth.

Defensive Responses of Tea Plants (Camellia sinensis) Against Tea Green Leafhopper Attack: A Multi-Omics Study.

Tea green leafhopper [Empoasca (Matsumurasca) onukii Matsuda] is one of the most devastating pests of tea plants (Camellia sinensis), greatly impacting tea yield and quality. A thorough understanding of the interactions between the tea green leafhopper and the tea plant would facilitate a better pest management. To gain more insights into the molecular and biochemical mechanisms behind their interactions, a combined analysis of the global transcriptome and metabolome reconfiguration of the tea plant challenged with tea green leafhoppers was performed for the first time, complemented with phytohormone analysis. Non-targeted metabolomics analysis by ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-QTOF MS), together with quantifications by ultra-performance liquid chromatography triple quadrupole mass spectrometry (UPLC-QqQ MS), revealed a marked accumulation of various flavonoid compounds and glycosidically bound volatiles but a great reduction in the level of amino acids and glutathione upon leaf herbivory. RNA-Seq data analysis showed a clear modulation of processes related to plant defense. Genes pertaining to the biosynthesis of phenylpropanoids and flavonoids, plant-pathogen interactions, and the biosynthesis of cuticle wax were significantly up-regulated. In particular, the transcript level for a CER1 homolog involved in cuticular wax alkane formation was most drastically elevated and an increase in C29 alkane levels in tea leaf waxes was observed. The tea green leafhopper attack triggered a significant increase in salicylic acid (SA) and a minor increase in jasmonic acid (JA) in infested tea leaves. Moreover, transcription factors (TFs) constitute a large portion of differentially expressed genes, with several TFs families likely involved in SA and JA signaling being significantly induced by tea green leafhopper feeding. This study presents a valuable resource for uncovering insect-induced genes and metabolites, which can potentially be used to enhance insect resistance in tea plants.

Genome-wide investigation of superoxide dismutase (SOD) gene family and their regulatory miRNAs reveal the involvement in abiotic stress and hormone response in tea plant (Camellia sinensis).

Superoxide dismutases (SODs), as a family of metalloenzymes related to the removal of reactive oxygen species (ROS), have not previously been investigated at genome-wide level in tea plant. In this study, 10 CsSOD genes were identified in tea plant genome, including 7 Cu/Zn-SODs (CSDs), 2 Fe-SODs (FSDs) and one Mn-SOD (MSD), and phylogenetically classified in three subgroups, respectively. Physico-chemical characteristic, conserved motifs and potential protein interaction analyses about CsSOD proteins were carried out. Exon-intron structures and codon usage bias about CsSOD genes were also examined. Exon-intron structures analysis revealed that different CsSOD genes contained various number of introns. On the basis of the prediction of regulatory miRNAs of CsSODs, a modification 5’ RNA ligase-mediated (RLM)-RACE was performed and validated that csn-miR398a-3p-1 directly cleaves CsCSD4. By prediction of cis-acting elements, the expression patterns of 10 CsSOD genes and their regulatory miRNAs were detected under cold, drought, exogenous methyl jasmonate (MeJA) and gibberellin (GA3) treatments. The results showed that most of CsSODs except for CsFSD2 were induced under cold stress and CsCSDs may play primary roles under drought stress; exogenous GA3 and MeJA could also stimulated/inhibited distinct CsSODs at different stages. In addition, we found that csn-miR398a-3p-1 negatively regulated the expression of CsCSD4 may be a crucial regulatory mechanism under cold stress. This study provides a certain basis for the studies about stress resistance in tea plants, even provide insight into comprehending the classification, evolution, diverse functions and influencing factors of expression patterns for CsSOD genes.

Exogenous Brassinosteroid Enhances Plant Defense Against Colletotrichum gloeosporioides by Activating Phenylpropanoid Pathway in Camellia sinensis L.

The phytohormones brassinosteroids (BRs) regulate multiple aspects of plant growth, development, and responses to stress. However, the role of BRs in the defense response of tea (Camellia sinensis L.), one of the most important beverage crops, remains largely unknown. Previously, we reported that BRs improve tea quality both under normal and unfavorable temperature conditions. Here, we showed that 24-epibrassinolide (EBR, a bioactive BR) enhanced defense against Colletotrichum gloeosporioides in tea plants, which was associated with EBR-induced reduction in H2O2 accumulation in tea leaves. C. gloeosporioides-caused necrotic lesions and its actin gene expression increased over the postinoculation period, but exogenous EBR remarkably suppressed C. gloeosporioides spread. Time-course analysis of a key enzyme, phenylalanine ammonia-lyase (PAL), involved in phenylpropanoid biosynthesis, revealed that PAL activity gradually increased from 6 to 24 h postinoculation with C. gloeosporioides following an initial decline. Meanwhile, exogenous EBR sharply increased PAL activity of inoculated leaves compared with that of only C. gloeosporioides inoculation. Expression analysis of genes involved in phenylpropanoid pathway showed that both exogenous EBR and C. gloeosporioides inoculation increased transcript levels of CsPAL, CsC4H, and Cs4CL; however, combined treatment with EBR and C. gloeosporioides resulted in a greater increase. Furthermore, CsPR1 and CsLOX1 expression analyses revealed that EBR potentially activates systemic induced tolerance, but not the lipoxygenase pathway to enhance tea plant resistance to C. gloeosporioides. These findings indicate a positive role of BR in strengthening disease resistance and thus may have potential implications in the control of C. gloeosporioides-caused disease in tea plants.

Genomic and transcriptomic analyses of HD-Zip family transcription factors and their responses to abiotic stress in tea plant (Camellia sinensis)

Tea plant (Camellia sinensis (L.) O. Kuntze) is a perennial evergreen woody plant, and its leaves contain various beneficial ingredients and have healthy efficacy. HD-Zip (homeodomain-leucine zipper) transcription factors (TFs) are widely distributed in plants and play an important role in plant growth and environmental response. To date, knowledge on HD-Zip gene family in tea plant is still limited. In this study, 33 HD-Zip TFs were selected based on the genomic and transcriptomic databases of tea plant. The conserved domains and common motifs of these TFs were predicted and analyzed. These 33 Cshdz TFs were divided into four groups (HD-Zip I, HD-Zip II, HD-Zip III, and HD-Zip IV). The interaction network of the HD-Zip proteins of tea plant was established based on the data of Arabidopsis. In addition, the expression levels of these Cshdz genes in tea plant cv. ‘Longjing43’ were detected and analyzed under five abiotic stress treatments. Results showed that the different expression profiles of Cshdz genes were associated with different abiotic stress treatments. Our findings suggested a potential relationship between the resistance of tea plant and its Cshdz genes.

Benzothiadiazole and B-Aminobutyricacid Induce Resistance to Ectropis Obliqua in Tea Plants (Camellia Sinensis (L.) O. Kuntz).

In order to investigate the effect of benzothiadiazole (BTH) and β-aminobutyric acid (BABA) on the resistance of tea plants (Camellia sinensis) to tea geometrid (Ectropis obliqua), three levels each of benzothiadiazole (BTH) and β-aminobutyric acid (BABA) were sprayed on 10-year-old tea plants. Generally PPO and PAL activities increased with low concentrations of BTH and BABA treatments. Quantitative RT-PCR revealed a 1.43 and 2.72-fold increase in PPO gene expression, and 3.26 and 3.99-fold increase in PAL gene expression with 75 mg/L BTH and 400 mg/L BABA respectively. Analysis of hydrolysis of synthetic substrates also revealed that chymotrypsin-like enzyme activity present in larval midgut extracts was not significantly inhibited by BTH and BABA. However, proteinase activity was found to be inversely proportional to the age of tea geometrid. Larvae pupation rate decreased by 8.10, 10.81 and 21.62% when tea geometrid were fed with leaves treated with 25, 50 and 75 mg/L BTH solutions, while 100, 200 and 400 mg/L BABA solutions decreased same by 8.10, 16.21 and 13.51% respectively. Also, larvae development period delayed to 23.33 and 26.33 days with 75 mg/L BTH and 400 mg/L BABA treatments respectively. The results in this study; therefore, suggest that benzothiadiazole (BTH) and β-aminobutyric acid (BABA) play a role in inducing resistance in tea plants to tea geometrid, with the optimal effect achieved at BTH-3 (75 mg/L) and BABA-3 (400 mg/L), respectively.

Transcriptional analysis and histochemistry reveal that hypersensitive cell death and H2O2 have crucial roles in the resistance of tea plant (Camellia sinensis (L.) O. Kuntze) to anthracnose

Anthracnose causes severe losses of tea production in China. Although genes and biological processes involved in anthracnose resistance have been reported in other plants, the molecular response to anthracnose in tea plant is unknown. We used the susceptible tea cultivar Longjing 43 and the resistant cultivar Zhongcha 108 as materials and compared transcriptome changes in the leaves of both cultivars following Colletotrichum fructicola inoculation. In all, 9015 and 8624 genes were differentially expressed between the resistant and susceptible cultivars and their controls (0 h), respectively. In both cultivars, the differentially expressed genes (DEGs) were enriched in 215 pathways, including responses to sugar metabolism, phytohormones, reactive oxygen species (ROS), biotic stimuli and signalling, transmembrane transporter activity, protease activity and signalling receptor activity, but DEG expression levels were higher in Zhongcha 108 than in Longjing 43. Moreover, functional enrichment analysis of the DEGs showed that hydrogen peroxide (H2O2) metabolism, cell death, secondary metabolism, and carbohydrate metabolism are involved in the defence of Zhongcha 108, and 88 key genes were identified. Protein–protein interaction (PPI) network demonstrated that putative mitogen-activated protein kinase (MAPK) cascades are activated by resistance (R) genes and mediate downstream defence responses. Histochemical analysis subsequently validated the strong hypersensitive response (HR) and H2O2 accumulation that occurred around the hyphal infection sites in Zhongcha 108. Overall, our results indicate that the HR and H2O2 are critical mechanisms in tea plant defence against anthracnose and may be activated by R genes via MAPK cascades.

Transcriptomic analysis reveals the molecular mechanisms of Camellia sinensis in response to salt stress

Tea plant [Camellia sinensis (L.) O. Kuntze] constitutes one of the most important economic crops in many countries. However, in many areas, tea plants are subjected to high salinity, which severely affects the growth and development of these plants. To understand the potential molecular mechanisms of tea plants in response to salt stress, we used RNA-Seq technology to compare the transcriptomes from tea plants treated with and without NaCl and analyzed the differentially expressed genes (DEGs). In total, 470,738 transcripts and 150,257 unigenes were obtained that had average lengths of 1422.09 and 680.40 nt, respectively, and 28,831 of these sequences were annotated in public databases. In addition, 1769 DEGs were identified, including 947 up-regulated and 822 down-regulated ones. Many of these DEGs were involved in Ca2+ signal transduction, the abscisic acid (ABA) pathway, and mitogen-activated protein kinase (MAPK) cascades. Many DEGs were also transcription factors and key functional proteins involved in salt resistance in tea plants; these genes constitute a regulatory network in response to salt stress. qRT-PCR analyses of nine unigenes were performed to confirm the validity of the data, and the results were highly consistent with the RNA-Seq results. Taken together, these findings reveal the underlying molecular mechanism of tea plants in response to salt stress and could provide many candidate genes for additional studies, especially those involving the genetic engineering and breeding of tea plants that are highly resistant to salt stress.

Analysis of tea plant resistance to tea green leafhopper, Empoasca onukii, by detecting stylet‐probing behavior with DC electropenetrography

AbstractThe tea green leafhopper, Empoasca onukiiMatsuda (Hemiptera: Cicadellidae: Typhlocybinae), is a serious pest of tea plants in East Asia. Previous work has shown that two tea germplasms, Cd19 and Cd289, sustain less hopperburn damage by E. onukii than does Camellia sinensis (L.) O. Kuntze cv. ‘Yabukita’ (Theaceae), and E. onukii excretes less honeydew on these germplasms than on the susceptible Yabukita. This study investigated the feeding behavior of E. onukii with a direct current electropenetrograph (DC EPG) to compare feeding behaviors, including ingestion, on resistant tea germplasms and Yabukita. Feeding behaviors on the resistant germplasms were significantly restricted, with few bouts of active ingestion of short duration and long periods of non‐probing, whereas E. onukii engaged in active ingestion of long duration many times on the susceptible cv. Yabukita. The tea germplasms, Cd19 and Cd289, therefore showed strong resistance to E. onukii. Furthermore, the shape of puncture holes left after probing was compared between the susceptible Yabukita and the resistant germplasms. The puncture holes on Cd19 and Cd289 were indistinct in shape and closed compared with those on Yabukita.

Phenylalanine ammonia‐lyase gene induction with benzothiadiazole elevates defence against Lasiodiplodia theobromae in tea in India

AbstractTea is widely used as an aromatic beverage cultivated in more than 35 countries from different continents. The global production of tea during the year 2015–2016 was 5,303 million kg where India stands 2nd contributing 23% of the world production. Diplodia disease is one of the most common diseases of tea in sub‐Himalayan West Bengal, India. Phenylpropanoids act as a precursor of several secondary metabolites that are synthesized at the time of biotic and abiotic stress conditions. During the induction of systemic acquired resistance, salicylic acid production is regulated by phenylalanine ammonia‐lyase (PAL) gene expression. In this communication, twelve‐month‐old tea seedlings (TV‐26) were treated with benzothiadiazole (BTH) and inoculated with Lasiodiplodia theobromae. Transcript accumulation in different treatments, that is treated‐uninoculated, untreated‐inoculated and treated‐inoculated were measured in comparison with untreated‐uninoculated control to study the effect of BTH in defence induction. From the results, it was evident that BTH‐treated and L. theobromae‐inoculated plants showed higher transcript accumulation (3.81 μg/μl) and reduced disease index (3.8 ± 0.02) in comparison with untreated control where transcript accumulation was 3.26 μg/μl and disease index reduced to 14.6 ± 0.05. After sequencing, nucleotide and deduced protein sequences were compared, and 3D structure was established where three lyase superfamily (cl26059) motifs were found. The increase in PAL activity was also observed in treated‐inoculated plants (from 2.5 to 4.4 μmol min−1 g−1) in comparison with healthy control (from 2.5 to 2.7 μmol min−1 g−1) after 4th day of treatment. Nonetheless, BTH might be one of the significant inducers of PAL which can be used to induce of disease resistance in tea plants in India.

Induction of resistance in tea plants against Sclerotium rolfsii by application of amendments and associated changes in level of phenolic content

Application of neem cake,oil cake and organic amendments including cow- dung, rabbit manure and chicken manure on four varieties of tea Camellia sinensis (L.) O. Kuntze were evaluated for induction of resistance against Sclerotium rolfsii Sacc. The emphasis was on the involvement of phenolics. It was observed that total phenol levels (total phenol and ortho-dihydroxy phenols) increased in treated inoculated tea root varieties with S. rolfsii than treated uninoculated tea root varieties. Oil cake and rabbit manure induced a rapid and distinct accumulation of phenolics in contrast to neem cake, cow dung and chicken manure.