Studies on Bacterial Wilt of Strawberry Plants Caused by Pseudomonas solanacearum

2. β-D-Glucogallin, the Antibacterial Substance Detected in the Tissues of Strawberry Plants

Abstract

An antibacterial substance inducing growth inhibition of Pseudomonas solanacearum on agar plates was isolated from strawberry leaves by Sephadex G-25 and Avicel column chromatography. The substance was identified as β-D-glucogallin (β-1-O-galloyl-D-glucose) by paper chromatography, UV absorption spectrum patterns, and acid hydrolysis for determination of the components. The β-D-glucogallin contents of strawberry plants positively correlated with the antibacterial activity in terms of inhibition zone. In assays during the period of one month after inoculation, no detectable change was observed in the content of β-D-glucogallin as well as the antibacterial activity. Extracts taken from younger leaves inhibited the growth of Ps. solanacearum most effectively, those from petioles being next. Extracts from stems and roots showed a lower inhibitory activity compared with the above mentioned. Antibacterial activity of the tissues varied depending on the plant age and growing seasons. The crude extracts from strawberry leaves inhibited not only growth of Ps. solanacearum but also that of some other bacteria such as Ps. meliae, Ps. syringae pv. pisi. Ps. syringae pv. lachrymans, Pseudomonas sp. from Ficus erecta, Ps. andropogonis and Xanthomonas campestris pv. oryzae. No growth inhibition was observed against the other pathovars of X, campestris, erwiniae and corynebacteria. However, production of extracellular polysaccharides was significantly depressed in most of the pathovars of X. campestris.