Discovery of a tree pathogen responsible for decline of lacquer tree plantations

Phytophthora cinnamomic threaten lacquer tree plantations in Japan

Hayato Masuya (a), Masanobu Tabata (b), Yu Ichihara (c), Kouji Kageyama (d)

(a) Department of Forest Microbiology, FFPRI, Tsukuba, Ibaraki, Japan.

(b) Tohoku Research Center, FFPRI, Morioka, Iwate, Japan.

(c) Kansai Research Center, FFPRI, Kyoto, Japan.

(d) Gifu University, Gifu, Japan.

Journal of the Japanese Forest Society, 101(6):318-321, December 2019

With the increase in demand for domestically produced lacquer, efforts to increase the production of Japanese lacquer have gained momentum. Many lacquer tree plantations have been newly established throughout the country. However, only few regions have achieved the desired levels of lacquer harvest; this was attributed to an unknown inhibitory factor that interferes with the growth of lacquer trees. In this study, we investigated a tree pathogen potentially acting as a growth inhibitory factor for lacquer trees in severely declined lacquer tree plantations found across the country. In soil samples from almost all affected lacquer tree plantations in Japan, except for those in Hokkaido and Iwate Prefectures, Phytophthora cinnamomi, a plant-damaging fungus (phytophthora), was detected. This fungus is a well-known tree pathogen worldwide and plays a major role in the decline of forests around the world. When we mixed this fungus with nurturing soil for lacquer saplings, clear signs of decline and withering were observed compared with saplings grown in the control soil containing no fungus. Because this disease had no official name, we proposed that it be identified as a new disease and be called “lacquer root rot disease.

These findings suggest that this tree pathogen is likely to serve as a major inhibitory factor when planting lacquer trees. Urgent measures are required to prevent and control future epidemics.

Photos: Phytophthora cinnamomi detected in a lacquer plantation: a: a zoosporangium (scale bar: 20 µm); b: an oogonium (scale bar: 30 µm); c: clamydospore (scale bar: 200 µm); d: appearance of colonies (left: potato dextrose agar [PDA] medium; right: carrot agar [CA] medium); e: mixing P. cinnamomi with nurturing soil for lacquer saplings resulted in decline and withering (control group, right; mixed group, left; the sapling declined and withered 3 months after mixing the fungus).