Influence of climatic factors on eyespot disease of winter wheat was investigated in Hokkaido from 1987 to 1996. Disease severity was associated negatively with the lowest temperature in early May and positively with the number of days with precipitation above 1 mm in early November. The development of eyespot disease was examined for 2 years. Lesions were first observed in late October, and incidence rate increased sharply after late April. We consider that rainfall in early November promoted primary infection, and the low temperature in early May extended the infection period. The control effects of thiophanate-methyl and prochloraz were examined in different growth stages of winter wheat for 3 years. Early May (GS 31) was the most effective, followed by late April (GS30) and mid-May (GS 33). This study suggested that disease severity of eyespot disease can be predicted from climatic factors to determine the necessity of control.
In 2016, malformation and spotted wilt of leaves and fruit malformation were observed on cucumber (Cucumis sativus) in Kanagawa Prefecture. RT-PCR to amplify an RNA dependent RNA polymerase gene region of tospovirus and sequencing of the amplified fragment indicated highest identity with watermelon silver mottle orthotospovirus (WSMoV). The virus was isolated through two rounds of single lesion isolation and identified as WSMoV based on the nucleocapsid gene sequence. Cucumber plants inoculated with the isolated virus developed the same symptoms, and only WSMoV was shown to be present in RNA from symptomatic plants; nine other cucumber viruses were absent. This is the first report describing WSMoV symptoms on cucumber.
Aboveground parts of mizuna plants were sprayed with 100 μg/ml L-methionine solution 3 or 10 days before inoculation. These plants were replanted in soil including Fusarium oxysporum f. sp. conglutinans (FOC). Disease severity scored at 14 days post-inoculation (dpi) was lower on L-methionine-treated plants than on untreated plants. No effect of L-methionine on mycelial growth of FOC was visible microscopically. Quantitative RT-PCR analyses of marker genes for plant defense responses (BrPR1, BrBGL2, BrLOX2, BrVSP2) in root tissues at 2 dpi showed that expression of these genes was higher in treated plants than in control plants.
Satsuma dwarf virus (SDV) causes serious damage to citrus production, reducing fruit quality and yield. In this study of the effect of SDV infection on growth of 2-year-old pot-grown trees of Satsuma mandarin (Citrus unshiu) and citrus hybrids ‘Setoka’, ‘Tamami’, and ‘Harumi’, SDV-infected trees of Satsuma mandarin, ‘Tamami’, and ‘Setoka’ had altered leaf shapes, shorter leaves and tree forms than did virus-free trees, but these traits did not differ significantly between SDV-infected and SDV-free trees of ‘Harumi’.