Harvested fruit of mandarin orange developed rot caused by green mold (Penicillium digitatum), in plastic greenhouses, orchards, and packing houses in August to September 1993 in Saga Prefecture. When the disease was found, many benzimidazole-resistant strains were present among strains of P. digitatum isolated from packing houses at different locations in Saga Prefecture. Benzimidazole-resistant strains were also frequently detected among strains of P. digitatum that were collected from fruit of very early ripening Satsuma in plastic greenhouses and from orchards before any benzimidazoles were sprayed. Thus, benzimidazole sprays would not have prevented fruit rot in those orchards, strongly suggesting that the benzimidazole-resistant strains were widely prevalent at harvest, resulting in that rot was found on the harvested fruit in the packing house and market an epidemic of rot on harvested fruit. This finding differs from the previous view that the populations of resistant strains are extremely low before harvest.
Viroplasms (Vps) are considered the assembly sites of virus particles associated with virus multiplication in host cells. The intracellular Vps of 37 viruses containing classified and unclassified plant viruses were observed with electron microscopy and compared. Vps were generally amorphous or spherical, electron-dense or -lucent, granular/fibrillar/striated structures. These profiles differed among viruses or virus groups. In Caulimoviridae, viruses of Caulimovirus (4 viruses), Petuvirus (PVCV) and Soymovirus (SbCMV) induced similar Vps in the cytoplasm, but their profiles differed. Phytoreovirus (RDV) and Fijivirus (RBSDV) in Reoviridae induced different cytoplasmic Vps. Viruses of Alphacryptovirus (RYEV) in Partitiviridae and Waikavirus (RTSV=RWV) in Sequiviridae were localized in the phloem cells, and induced cytoplasmic Vps. RTSV also induced specific vesicles containing nucleic acid-like strands associated with the Vps, suggesting a relationship with genome replication of the virus. Tospovirus (TSWV, MYSV) of Bunyaviridae induced cytoplasmic Vps, and seemed to occur where the ER membrane was budding around the Vps. Very few particles of MYSV were found. In Rhabdoviridae, Nucleorhabovirus (8 viruses) induced nuclear Vps and seemed to bud at the nuclear inner membrane, whereas Cytorhabovirus (6 viruses) induced cytoplasmic Vps, and seemed to bud at the ER membrane. In unclassified viruses, small, non-enveloped bacilliform viruses were grouped into the nuclear and cytoplasmic types based on multiplication profiles. Virus particles seemed to mature at the nuclear inner membrane in the nuclear types (5 viruses), and at the ER membrane in the cytoplasmic types (5 viruses). Rod-shaped BuMoV from Japan induced electron dense-cytoplasmic Vps in many cells.
The effects of hydroxyl radicals (OH radicals) generated in a solution of hydrogen peroxide, oxalic acid and iron (III) under natural sunlight (“photo-Fenton reaction”) was tested against strawberry powdery mildew [Sphaerotheca aphanis (Wallroth) Braun var. aphanis]. Applications of the OH-radical-generating solution to whole plants before inoculation with a conidial suspension protected plants against the disease. The solution also had a suppressive effect for plants already diseased. Conidial germination was suppressed within 20 min of exposure of the solution in sunlight. These results suggested that OH radicals generated by the photo-Fenton reaction ultimately protected against new disease and suppressed further disease development.
Isolates of Colletotrichum gloeosporioides (Glomerella cingulata), obtained from strawberry leaves with anthracnose in Saga Prefecture in 2003, were bioassayed for sensitivity to strobilurin fungicides (azoxystrobin and kresoxim-methyl). The two isolates had little sensitivity to these fungicides, and they were regarded as resistant. Sequence analysis showed that the deduced amino acid at codon 143 of the mitochondrial cytochrome b gene was altered from glycine (GGT) to alanine (GCT). Polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) using the restriction enzyme ItaI could be employed in practice for rapid testing of resistance to strobilurin fungicides.
A new leaf spot disease of sugarcane (Saccharum officinarum L.) was found in Tokunoshima, Kagoshima Prefecture, Japan in June 2005. Reddish-brown and spindle-shaped lesions formed on the leaves of mericlone seedlings grown in the glasshouse. The causal fungus was exclusively isolated from the lesions, and typical symptoms were reproduced after inoculation with the isolate. The causal fungus was identified morphologically and phylogenetically as Curvularia lunata (Wakker) Boedijn. Hyphae grew at 10-38°C with optimum growth at 30°C. The name leaf spot of sugarcane, in Japanese “Hanten-byo”, is proposed for the disease.