A disease of tomato, showing the symptoms of yellows and stunting, was found in Saga and Hiroshima Prefectures in 1983 and 1984, respectively. Electron microscopy revealed the presence of numerous mycoplasmalike organisms (MLOs) in the phloem tissues of the diseased plants. Of the two leafhoppers tested, Macrosteles orientalis Virbaste and Scleroracus fiavopictus Ishihara, only M. orientalis transmitted the disease. Tomato yellows MLO described in this work had a wide host range similar to that of onion yellows MLO.
A bacterial disease of tea plant was observed in Shizuoka Prefecture in July, 1983. The symptoms were characterized by leaf spots with irregular shape and apparent necrosis of the spongy parenchyma tissue. Two distinct pseudomonads were isolated from these lesions. On the basis of bacteriological and pathological tests, they were identified as Pseudomonas syringae pv. theae and P. avenae, respectively. P. syringae pv. theae was isolated with high frequency, and produced the typical shoot blight symptoms or the characteristic leaf spot symptoms depending upon the temperature and humidity in inoculation tests and the variety of tea plants. P. avenae was isolated with lower frequency, and produced leaf spot symptoms different from those observed in the field in color and shape. From these results, the present disease was determined as one of the symptoms of bacterial shoot blight caused by P. syringae pv. theae. The role of P. avenae in this hacteriosis remained to be clarified.
Rice panicles spontaneously infected with Pyricularia oryzae Cav. were stained with calcofluor white to impart fluorescence to fungal structures. The procedure facilitated observation of conidiophores and conidia formed on infected sites such as neck, rachis, panicle branch, pedicel and husk, and of invading hyphae in the cells of neck, rachis and panicle branch. It is also possible to observe conidia attached to the epidermis of neck, rachis, panicle branch, pedicel and husk.
Indirect fluorescent-antibody technique was applied for diagnosis of the clubroot of Brassicaceae caused by Plasmodiophora brassicae Woron. IgG (γ-globulin; 0.91 mg/ml) was purified from antiserum against resting spores of P. brassicae prepared from a rabbit. Infested soil and root were stained by fluorescent-antibody technique with the IgG and FITC conjugated antirabbit IgG-sheep IgG. (Cappel Lab.) Resting spores were effectively detected, and also clearly differentiated from small particles of soil and tissues of plant in the reflected light fluorescence microscope (Olympus BHS-RF-A, B-excitation). This method is considered to be suitable for the detection of P. brassicae.
Watering of 200ml 0.025-1% benomyl (50% WP) suspension per plant to the basement soil of potted Samsun tobacco plants caused very considerable reduction of the severity of TMV-L (a tomato strain of TMV) symptoms. ELISA absorbance showed that in two weeks after inoculation TMV-L concentration of upper leaves of tobacco plants treated with 200ml 0.1% benomyl suspension was a quarter of that of control plants. In one month after inoculation, however, there was no difference between those concentrations. Watering of 200ml 0.1-0.5% benomyl solution per plant to Xanthi-nc tobacco plants caused a slight reduction of the severity of PVY-T (a necrotic strain of PVY) symptoms. Combined application of benomyl and 2, 4-dioxohexa-hydro-1, 3.5-triazine (2% granules) showed no obvious effects of combination against the symptoms by TMV-L or PVY-T.