Inhibitory Effect of Tea Saponin on Major Apple-Disease-Inducing Fungi

Abstract

Plant secondary metabolites are well-known for their biological functions in defending against pathogenic microorganisms. Tea saponin (TS), one type of secondary metabolite of tea plant (Camellia sinensis), has been shown to be valuable botanical pesticide. However, its anti-fungal activity has not been determined in controlling fungi Valsa mali, Botryosphaeria dothidea, and Alternaria alternata, which induce major diseases in apple (Malus domestica). In this study, we first determined that TS has higher inhibitory activity against the three types of fungi compared with catechins. We further utilized in vitro and in vivo assays to confirm that TS showed high anti-fungal activity against the three types of fungi, especially for V. mali and B. dothidea. In the in vivo assay, application of 0.5% TS solution was able to efficiently restrain the fungal-induced necrosis area in detached apple leaves. Moreover, the greenhouse infection assay also confirmed that TS treatment significantly inhibited V. mali infection in leaves of apple seedlings. In addition, TS treatment activated plant immune responses by decreasing accumulation of reactive oxygen species and promoting the activity of pathogenesis-related proteins, including chitinase and β-1,3-glucanase. This indicated that TS might serve as a plant defense inducer to activate innate immunity to fight against fungal pathogen invasion. Therefore, our data indicated that TS might restrain fungal infection from two aspects, by directly inhibiting the growth of fungi and by activating plant innate defense responses as a plant defense inducer.

Identification of Hsp20 gene family in Malus domestica and functional characterization of Hsp20 class I gene MdHsp18.2b

“…Following B. dothidea infection, the apple calli were collected for measurement of hydrogen peroxide (H 2 O 2 ) levels, superoxide anion (O 2 − ) production rates, chitinase activity and β‐1,3‐glucanase activity, as previously described (Li et al, 2023; Zhang et al, 2020). The determinations were done using specific detection kits (Keming), i.e.…”