Accumulation of antifungal compounds in tea leaf tissue infected with Bipolaris carbonum

Varietal resistance of tea towards Bipolaris carbonum was tested following detached leaf inoculation technique. Among the fourteen varieties tested, three were found to be highly susceptible, while other three were resistant. Leaf exudates and diffusates collected from the resistant varieties were more fungitoxic than those from the susceptible ones. Two antifungal compounds isolated from healthy and B. carbonum-infected tea leaves exhibited clear inhibition zones at RF 0.8 and 0.65, respectively, in a chromatographic bioassay. On the basis of their color reaction on TLC and UV-spectra these were identified to be catechin and pyrocatechol. Resistant and susceptible varieties accumulated 439-510 and 187-212 micrograms/g fresh mass tissue of pyrocatechol, respectively, 2 d after inoculation with B. carbonum, while a low concentration (45-58 micrograms/g) of this compound was detected in healthy leaf tissue.