Preformed and Induced Chemical Resistance of Tea Leaf Against Exobasidium vexans Infection

Abstract

Levels of (-)-epicatechin in tea cultivars (Camellia sinensis) resistant to blister blight leaf disease (Exobasidium vexans Massee) were significantly higher than those in susceptible cultivars, while the reverse was true for (-)-epigallocatechin gallate suggesting that epicatechin was involved in the resistance mechanism. The content of the methylxanthines, caffeine and theobromine in the leaf increased significantly in the initial translucent stage of the disease, probably as a defense response to fungal attack. Epicatechin and epigallocatechin levels were significantly less than in healthy tissues at this stage, but increases in the corresponding gallate esters suggested that they were being converted into esters. Although epicatechin and epigallocatechin levels decreased from translucent to mature blister stages, the decrease was not significant. The decrease in levels of epicatechin, epigallocatechin and their esters on infection and the formation of cyanidin and delphinidin on oxidative depolymerization of the blisters suggest that proanthocyanidins may play a role in the defense mechanism. The very high resistance of a purple-green leafed cultivar is attributed to the additional catechin source provided by the high levels of anthocyanins present. Cyanidin and delphindin were identified as two anthocyanidins in the red tea cultivar TRI 2043.Infection of leaves of tea (cultivar TRI 2025), which was susceptible to blister blight resulted in a shift of the proanthocyanidin stereochemistry away from 2,3-trans (e.g. catechin and gallocatechin) and towards 2,3-cis (e.g. epicatechin and epigallocatechin). Infection also resulted in increased gallic acid esterification of the initiating subunits of proanthocyanidins. This was shown by both mass spectroscopy and phloroglucinolysis. Proanthocyanidins isolated from healthy tissue had a predominantly 2,3-trans stereochemistry which accounted for 53% and 61% of the total initiating and extension units of proanthocyanidin, respectively. Conversely in infected tissue, proanthocyanidin subunits with a 2,3-trans stereochemistry accounted for 26% and 40% of the total initiating and extension units, respectively. Infection had little impact on the hydroxylation state of the B-rings of proanthocyanidins. The products of acid hydrolysis under oxidative conditions had a slight excess of di-hydroxylated B-rings with cyanidin accounting for 58.3 ± 0.05% and 60.4 ± 0.2% of the total anthocyanidin recovered following hydrolysis of proanthocyanidin isolated from infected and healthy leaves, respectively. Similar results were obtained by phloroglucinolysis. Thus it is possible that increased resistance of some tea cultivars to may be a result of higher levels of epicatechin or changed proanthocyanidin composition. The occurrence of flavan-3,4-

Regulation of defence responses in avocado roots infected with Phytophthora cinnamomi (Rands)

“…These authors concluded that cultivar resistance is related to the amount of epicathechin in the avocado peel, and noted that fruit became susceptible to C. gloeosporioides during fruit ripening, when epicatechin levels decreased. In the same way, levels of (−)-epicatechin in tea cultivars resistant to blister blight leaf disease were significantly higher than those in susceptible cultivars (Punyasiri et al 2005), suggesting that epicatechin was involved in the resistance mechanism.…”

Nitrogen fertilizer and gender effects on the secondary metabolism of yaupon, a caffeine-containing North American holly

“…For example, given that many plant secondary metabolites are putative defenses against pathogens and herbivores, predictions about allocation patterns for their production should reflect the selective pressures to which they are a response (Berenbaum 1995). Induction of caffeine and/or theobromine synthesis upon attack by fungal pathogens in tea (Camellia sinensis; Kumar et al 1995;Punyasiri et al 2005) and cacao (Theobroma cacao; Aneja and Gianfagna 2001), for example, provides evidence that selective agents may shape the production patterns of these alkaloids. Although plant nutrient concentrations have long been correlated with herbivore preferences (e.g., Mattson 1980), the effect of nitrogen availability on chemical responses to herbivores and pathogens has not been extensively explored.…”

Functional Characterization of Proanthocyanidin Pathway Enzymes from Tea and Their Application for Metabolic Engineering

“…The levels of (2)-E (for epicatechin) in resistant cultivars are significantly higher than in susceptible ones, whereas the levels of EGCG in resistant cultivars are significantly lower than in susceptible ones. Epicatechin and EGC levels declined significantly in the infested areas of the leaf during blister blight infection, whereas the levels of ECG and EGCG increased at the translucent stage of the infection and declined on maturation of the blister (Punyasiri et al, 2005). Furthermore, infection of tea leaves susceptible to blister blight gave rise to a shift in the PA stereochemistry away from 2,3-trans (53% and 61% of the total starter and extension units of the PAs, respectively) toward 2,3-cis (26% and 40%, respectively; Nimal Punyasiri et al, 2004), and infection also resulted in increased gallic acid esterification of catechin and epicatechin.…”