Epidemics of sheath blight caused by Thanatephorus cucumeris, on no-till and non-paddy rice plants were compared with those on conventionally tilled rice plants in paddy fields treated with compound fertilizers from 1999 to 2001. The no-till rice plants grew more slowly, and produced fewer tillers than did conventional-till rice plants during early growth. Consequently, the length of time for sclerotia of the pathogen to attach to rice plants was delayed on no-till plants. The no-till rice plants had less primary infection by T. cucumeris than did conventional-till plants, and disease development also tended to be suppressed.
Biophoton emissions from suspension-cultured rice cells were elevated after treatment with N-acetylchitohexaose. We examined whether this elicitor-responsive photon emission was correlated with the generation of reactive oxygen species. The strength of elicitor-responsive photon emissions from cells agreed with the amounts of hydrogen peroxide in cell-cultured medium in a time-course study. Superoxide dismutase treatment did not affect the elicitor-responsive photon emissions, whereas catalase treatment suppressed the emission to 62% of the photon emission from cells in the medium without the enzymes. These results suggest that hydrogen peroxide partially contributes elicitor-responsive photon emissions.
In November 1994, a foot rot disease of Aloe spp. was observed in Okinawa, Japan. Lesions on the lower part of the stem were brown to purplish black, gradually caved in. Finally, the plants withered and died. A fungus belonging to the genus Fusarium was isolated from the lesions. Foot rot symptoms, the same as under natural conditions, appeared within 7 days after inoculation with the Fusarium isolate. A similar Fusarium was reisolated from the diseased plants and was identified as F. dimerum based on morphological and cultural characteristics. This is the first record of this fungal species causing a plant disease.
A root rot disease on pansy geranium (Pelargonium tricolor × P. ovale ssp. ovale ‘Splendide’) was found in Shizuoka Prefecture, Japan in June 2003. A fungus was isolated and used to inoculate cuttings to reproduce the root rot symptoms. It was identified as Thielaviopsis basicola. This disease is the first record in Japan and is named black root rot (Kurone-byo) on pansy geranium.
In 2005, a new disease of Chinese chive (Allium tuberosum) with chlorotic spots and whitish necrotic streaks on leaves was found in Tochigi Prefecture. The isolated virus was identified as Iris yellow spot virus (IYSV) by RT-PCR. Chinese chive plants developed the same chlorotic spots followed by necrotic streaks only on inoculated leaves after transmission tests with IYSV-acquired onion thrips (Thrips tabaci). The virus isolated from the necrotic streak is similar to IYSVNL from Dutch iris in the Netherlands. This is the first report on IYSV from Chinese chive, and we propose the name “necrotic streak disease” of Chinese chive.