The development of tea blister caused by Exobasidium vexans in tea (Camellia sinensis) correlates with the reduced accumulation of some antimicrobial metabolites and the defence signals salicylic and jasmonic acids

Abstract

Blister blight (causal agent, Exobasidium vexans) is an economically devastating disease of tea (Camellia sinensis). To determine what metabolite changes occur with tea blister that could be linked to disease progression, metabolomic approaches were used on E. vexans infected tea from a Darjeeling (India) plantation. Samples were classified according to disease phenotypes, i.e. either healthy or at one of three stages of disease progression. Initial metabolite fingerprinting using Fourier transform infrared (FTIR) spectroscopy indicated that metabolite changes could be related to disease stage. Electrospray ionization mass spectrometry (ESI‐MS) highlighted caffeine and flavonoid metabolism changes as disease progressed. High‐performance liquid chromatography (HPLC) with online photodiode array detection and electrospray ionization‐tandem mass spectrometry (HPLC‐PDA‐ESI/MSn) was used to characterize the caffeine, flavan‐3‐ol, flavone and flavonol profiles. There were increases in quercetin and kaempferol glucosides, kaempferol triglycosides and some catechin‐class antioxidants, but also substantial reductions in apigenin and myricetin glycosides and, particularly, caffeine as disease progressed. The content of important defence hormones, salicylic acid and jasmonic acid, was also reduced in blister blight diseased samples. Thus, E. vexans infections perturb defence signalling and reduce many potentially antimicrobial compounds, such as caffeine, to aid disease progression.

Climate-Fungal Pathogen Modeling Predicts Loss of Up to One-Third of Tea Growing Areas

“…This fungus is known to remain dormant during periods of unfavorable conditions, only becoming pathogenic under optimal climatic conditions. If not controlled by fungicides, tea losses due to this pathogen may range from 25 to 43% ( Mur et al., 2015 ). Suitable modeled areas for E. vexans on tea are in Australia, South America, Africa, and Asia.…”

Recent Advances in the Specialized Metabolites Mediating Resistance to Insect Pests and Pathogens in Tea Plants (Camellia sinensis)

“…Additionally, flavonoids have been found to be elicited by pathogen infections. For example, E. vexans infection elevated the accumulation of quercetin and kaempferol glucosides and kaempferol triglycosides but substantially reduced the accumulation of apigenin and myricetin glycosides [ 76 ]. In summary, flavonoids responded specifically to different insects and pathogens; nevertheless, targeted metabolites and the underlying precise mechanisms of defense against insects and pathogens need in-depth investigations, according to the current studies.…”

“…Furthermore, E. vexans infection induced the accumulation of C, EC, EGC, and EGCG. These results suggested that herbivory and pathogen attacks elicited the differences in catechin metabolism [ 76 ]. Among seven catechins, both C and EGCG were effectively triggered upon attack by E. grisescens , E. obliqua , E. onukii , C. fructicola , and E. vexans , which suggested that C and EGCG could respond conservatively to different herbivores and pathogens, while other components responded differently.…”

“…An E. obliqua attack activated the caffeine biosynthesis and increased its accumulation, while an E. onukii infestation did not change the levels of caffeine. A C. fructicola infection induced caffeine accumulation, and caffeine strongly inhibited mycelial growth by affecting the mycelial cell walls and plasma membranes in vitro; however, an E. vexans infection reduced caffeine levels [ 20 , 41 , 73 , 76 ] ( Table 3 ). These studies suggest that caffeine responds differently to different insects and pathogens.…”

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

“…According to habitat suitability modelling studies, it has a suitability of 10.20% ( C. sinensis ) and 11.90% ( C. assamica ), and areas with increased future risk include southeast Asian countries (Tibpromma et al, 2021). Research suggests that owing to E. vexans infection, the content of important defence hormones, salicylic acid and jasmonic acid in tea plants is downgraded, thus, disturbing the defence signalling and many potentially antimicrobial compounds to aid disease progression (Mur et al, 2015). Colletotrichum acutatum is yet another significant tea anthracnose pathogen.…”