The sensitivity of isolates of Glomerella cingulata, the causal fungus of strawberry anthracnose to azoxystrobin, was developed using an agar dilution method. MIC value of azoxystrobin were divided into 0.19-3.12 ppm and >3200 ppm (a.i.) on potato dextrose agar (PDA) containing salicylhydroxamic acid (SHAM, 1000 ppm), an inhibitor of alternative respiration. Strains with MIC >3200 ppm were regarded as resistant: (1) the protective efficacy of azoxystrobin against these strains was extremely low when tested in the bioassy, and (2) the point mutation G143A in mitochondrial cytochrome b gene was confirmed by polymerase chain reaction- restriction fragment-length polymorphism (PCR-RFLP) using the restriction enzyme ItaI. Therefore, the presence or absence of mycelial growth on PDA with 1000 ppm SHAM and 100 ppm (a.i.) azoxystrobin cultured for 4 d at 25°C can be used to determine the azoxystrobin sensitivity of this fungus relatively easier than with the conventional bioassay and PCR-RFLP.
Foot rot of tomato plants (Lycopersicon esculentum Mill.), observed in Tochigi Prefecture in May and June 2004, was characterized by discoloration of main root and wilt. Fungal strains that were isolated from symptomatic tissue, caused the same symptoms on tomato plants after artificial inoculations with the isolates. On the basis of morphological and molecular analyses, together with the pathogenicity tests, the fungus was identified as Fusarium solani f. sp. eumartii. In this report of foot rot disease of tomato caused by F. solani f. sp. eumartii in Japan, we propose the Japanese name “Fusarium kabugusare-byo” of tomato.
To evaluate the effect of a reflective net (Slimwhite®45) and timing of insecticide application on suppressing lisianthus (Eustoma grandiflorum ) necrotic ringspot disease caused by Iris yellow spot virus (IYSV), the incidences of vector thrips (Thrips tabaci ) and necrotic ringspot disease were examined in Karatsu City, Saga Prefecture, Japan in 2007. In a survey plot with reflective net, the total number of captured T. tabaci on a sticky trap outside and inside the greenhouse were lower than those without reflective net. The incidence of necrotic ringspot disease was lower when insecticide (acephate) treatments were timed with the emergence of viruliferous T. tabaci. The disease incidence was drastically reduced when the adjusted insecticide treatments and reflective net were used together.
Gentian tumorous symptoms have been known in Nagano, Iwate and other prefectures since 1985. Previously undescribed virus-like particles were found in gentian (Gentiana spp.) plants collected in Iwate Prefecture that had galls or tumors on stems and roots. In transmission electron micrographs of ultrathin sections of tissue from symptomatic plants, virus-like isometric particles about 60 nm in diameter, which had dense cores about 40 nm in diameter with less dense outer shells, were scattered or aggregated in small masses in the cytoplasm of phloem parenchyma cells and in the sieve tubes of galls or tumors. Virus-like particles were observed in stems, crowns and roots but not in leaves and petals. Similar particles were detected by negative staining using uranyl acetate or phosphotungstic acid (pH 7.0) in homogenates of roots fixed with glutaraldehyde.