Induced biochemical responses in tea plant leaves after infection by the tea blister blight pathogen

The activities of enzymes such as phenylalanine ammonia-lyase, polyphenol oxidase and peroxidase, as well as the levels of proteins, proline and phenolic compounds in the leaves, were studied after tea plant leaves were infected by the tea blister blight pathogen. The study showed that in diseased leaves the activity of phenylalanine ammonia-lyase decreased, while the activities of peroxidase and polyphenol oxidase increased. Analysis of peroxidase isoenzymes by polyacrylamide gel electrophoresis using benzidine as substrate showed that healthy tea plant leaves had 4 isoenzymes, whereas diseased leaves had 5 isoenzymes. The proline content in diseased leaves increased markedly, but decreased at the early stage of infection. SDS-PAGE analysis showed that leaves lost a certain amount of protein upon infection. Compared with healthy leaves, the total phenolic compounds in diseased leaves increased markedly. According to the agar cup assay, the phenolic compounds from both healthy and diseased leaves showed antifungal activity. This antifungal activity was higher in healthy leaves. HPLC analysis of catechin compounds extracted from healthy and diseased leaves showed that differences in both quality and quantity existed between the two types of leaves.