Shoot drooping disease of Acer trifidum HOOK. et ARN. caused by Pseudomonas acernea n. sp

Abstract

Acer trifidum HOOK. et Arn. was introduced from China in 1721, and propagated in our country by grafting on Acer crataegifolium SIEB. et ZUCC., it is familiar to us now. For the last 25 years an epidemic disease of this tree has been noticed in the nursery and avenue, but its cause remained quite unknown. In the last year I had occasion to study it and found that this disease had been caused by a species of bacteria. As a macroscopical symptom, there appear on the leaves irregular spots along the midribs. The spots give at first a water-soaked appearance and, increasing in size, become pale payne's gray or black. Meanwhile affected leaves wither and then, turning black, finally dry up, just like those injured by frost.
Inoculation experiments on the healthy leaves with the organism isolated from the tissue of diseased portions resulted in giving rise to the same symptom, and the same organism could be obtained from the affected tissue. The following species of Acer were proved to be susceptible to this organism; viz., Acer saccharinum L., A. diabolicum BLUME, A. Negundo L., A. aizuense NAKAI, A. palmatum THUNB. var. amabile KOIDZ. subvar. Kagiri KOIDZ., A. capillipes MAXIM., A. insulare MAKINO, A. parviflorum FRANCH. et SAV., A. pictum THUNB. var. typicum GRAF V. SCHW., A. rufinerve SIEB. et ZUCC., A. Sieboldianum MIQ. var. typicum MAXIM., A. Shirasawanum KOIDZ., A. crataegifolium SIEB. et ZUCC. Besides these, Aesculus turbinata BLUME and Koelreuteria paniculata LAXIM. were also infected with the said disease, but the following plants were not attacked by it; viz., Ginkgo biloba L., Juglans Sieboldiana MAXIM., Ulmus parvifolia JACQ., Morus alba L., Euptelea polyandra SIEB. et ZUCC., Cercidiphyllum japonicum SIEB. et ZUCC., Liriodendron Tulipifera L., Liquidambar formosana HANCE, Prunus yedoensis MATSUM., P. Mume SIEB. et ZUCC., P. spinulosa SIEB. et ZUCC., Phaseolus vulgaris L., P. radiatus L. var. aurea PRAIN, Lathyrus odoratus L., Evonymus striata LOES., E. oxyphyllus MIQ., Staphylea bumalda DC., Euscaphis japonica PAX., Sapindus Mukurossi GAERTN., Berchemia racemosa SIEB. et ZUCC., Hovenia dulcis THUNB. var. glabra MAKING, Zizyphus vulgaris LAM. var. inermis BUNGE, Vitis vinifera L., Tilia japonica SIMK., T. Miyabei JACK. and Firmiania platanifolia SCHOTT et ENDL.
The causal organism is rather short rod-shaped Shizomycete with round ends, measuring 0.5-1.2×0.2-0.6μ, usually 0.8×0.4μ, when stained by carbol fuchsin from a 24 hour culture on standard agar, on which it occurs solitarily. It is aërobic and motile by means of one polar flagellum. No spores are formed and no involution forms have been observed even in culture 6 months old. It stains easily with basic anilin dyes and by Gram's stain. It grows on ordinary culture media, viz, , nutrient agar, glucose agar, serum agar, potato agar, steamed potato, nutrient gelatin, bouillon, peptone water, Uschinsky's and Cohn's solutions. On the poured plate of standard agar, the colonies are round, smooth, convex, white, glistening, translucent and entire-margined with amorphous structure. On agar slant, the same filiform streak mentioned above is produced along the inoculated line in 24 hours at 32°C. After 2 days the colour of the streak changes to citron yellow. It liquefies gelatin in cup shape, clears milk slowly without coagulation, produces acid slightly but does not produce gas in fermentation tube from peptone water with saccharose, lactose, maltose, dextrose, laevulose, galactose, mannit and glycerin. It reduces nitrate to nitrite and produces hydrogen sulphide.