Rice stripe disease is one of the viral diseases caused by Rice stripe virus (RSV), and can be controlled effectively by using resistant cultivars. The resistance gene introduced into those rice cultivars is Stvb-i derived from an indica rice cultivar "Modan". In order to understand the mechanism of the stripe resistance, infection of RSV and disease symptoms were examined in detail in rice resistant cultivars harboring the Stvb-i gene, “St. No. 1” and “Tsukinohikari”. Several tens of percent of resistant rice plants were infected with RSV, but not all the infected rice plants showed disease symptoms. The concentration of RSV was low and the viral spread to the upper leaves was suppressed in initial stage of RSV infection as compared to the susceptible rice. Taken together with information on RSV infection in the susceptible rice reported by other researchers, the results in this study suggested a quantitative effect of Stvb-i gene to viral infection and propagation in and around the apical meristem in the initial stage of RSV infection.
In November 2007, fruits of okra (Abelmoschus esculentus) cultivated in a nursery were found rotted in Mie prefecture. Petals had not fallen and remained on the fruits. The causal agent of the fruit rot with a pale brown color was identified to Botrytis cinerea and that with a white color as Sclerotinia sclerotiorum. On the other hand, leaf rot of okra was found in a nursery in Hokkaido in July 2008. Rotted petals remained on the leaves after falling from fruits. The causal agent was also identified as B. cinerea. This is the first report of okra diseases during cultivation caused by B. cinerea and S. sclerotiorum in Japan.
Rhizopus rot of mango, atemoya and white sapote fruits occurred on Chichijima in Ogasawara (Bonin) Islands in 2012 and 2013. Fungi isolated from the disease plants were identified as Rhizopus stolonifer var. stolonifer. Inoculation tests confirmed that this fungus was the causal agent of the diseases. This is the first report of these diseases in Japan.
Passiflora root-rot of Passiflora edulis Sims. occurred on Hachijo Island of Tokyo Metropolis in 2012. Two species of Globisporangium (Pythium) isolated from the diseased plants were identified as G. splendens and G. irregurale based on morphological characteristics as well as molecular analyses of the rDNA-ITS region. Inoculation tests showed that these fungi were the causal agents of the disease. This is the first report of the disease in Japan.
Southern blight of fish mint Houttuynia cordata, geranium herb Geranium thunbergii and American mandrake Podophyllum peltatum occurred in Tokyo Metropolis and Saitama Prefecture in 2012. The causal fungus isolated from the diseased plants was identified as Sclerotium rolfsii Sacc. based on morphological characteristics as well as molecular analyses of the rDNA-ITS region. Inoculation tests confirmed that the fungus was a causal agent of these diseases. This is the first report of the disease in Japan.
Penicillium leaf spot of mouse thorn (Ruscus hypoglossum L.) and anthracnose of fairy bells (Disporum pullum) occurred on Hachijo Island of Tokyo Metropolis in 2011 and 2012, respectively. The causal fungi isolated from the diseased plants were identified as Penicillium copticola Houbraken, Frisvad & Samso on mouse thorn and Colletotrichum kahawae J. M. Waller & Bridge (C. gloeosporioides species complex) on fairy bells. Inoculation tests showed that each of the two fungi was the causal agent of the disease, respectively. This is the first report of the diseases in Japan.
Southern blight of mukdenia (Mukdenia rossii) and lily of the valley (Convallaria majalis var. majalis) occurred in Tokyo Metropolis and Saitama Prefecture in summer 2013. The causal fungus isolated from the diseased plants was identified as Sclerotium rolfsii Sacc. based on morphological characteristics as well as molecular analyses of the rDNA-ITS region. Inoculation tests confirmed that the fungus was a causal agent of the diseases. This is the first report of the diseases in Japan.
In 2012, pineapple lily (Eucomis autumnalis), prairie poppy mallow (Callirhoe involucrata), creeping phlox (Phlox stolonifera) and white cup (Nierembergia rivularis) were blighted in flower beds in Saitama Pref., and similar symptoms occurred in melampodium (Melampodium paludosum) in flower beds in Tokyo Metro. The pathogens isolated from each diseased plant were identified as Sclerotium rolfsii by morphological observations. In addition, the homology of the rDNA-ITS region is high to that of S. rolfsii. This is the first report of the diseases in Japan.
Southern blight of Centaurea montana, Chrysanthemum makinoi, Verbena × hybrida, Rehmannia elata, Thymus serpyllum, Lychnis coronaria, Phlox paniculata and Geranium sanguineum occurred at several flowerbeds in Saitama Pref. in 2013. The causal fungus isolated from each diseased plant was identified as Sclerotium rolfsii Sacc. by morphological observations as well as molecular analyses of the rDNA-ITS region. Inoculation tests showed that the fungus was the causal agent of the disease. This is the first report of this disease on these plants in Japan.
We investigated susceptibility to two diamide and ten other insecticides in four local populations of the diamondback moth, Plutella xylostella collected from cabbage (Brassica oleracea var. capitata) fields in Asahi City, a rape flower (Brassica rapa var. nippo-oleifera) field and a daikon (Raphanus sativus var. longipinnatus) field in Minamibousou City from October to December 2013 in Chiba Prefecture. For the larvae of two Asahi populations, fed with cabbage leaf disks treated with flubendiamide or chlorantraniliprole, the corrected mortalities at 72 hours after treatment were zero and the leaf areas damaged by the larvae were not significantly different from that of the control, showing a reduced susceptibility to these diamide insecticides. On the other hand, these diamide insecticides were highly effective against two Minamibousou populations. Spinetoram, emamectin benzoate, indoxacarb, tolfenpyrad, Bt and cartap hydrochloride were highly effective against all four populations.
We investigated the influence of sugar foods presented in a bottle-type feeding device on female longevity and life-time fecundity of Cotesia vestalis, a larval parasitoid of the diamondback moth Plutella xylostella. Solutions of honey and sugar mixture (sucrose, glucose and fructose) prolonged female longevity significantly more than water, irrespective of the mating status and oviposition experience. These sugar foods also significantly enhanced life-time fecundity of mated parasitoids more than water. We also investigated the continuity of these sugar foods in bottle-type feeding devices installed in a greenhouse for different periods (30 and 120 days). Even 120 days after the installation of these feeding devices, honey and sugar mixtures in feeding devices could respectively enhance female longevity in laboratory experiments. These results indicated that those sugar foods provided by bottle-type feeding devices are useful for maintaining the parasitoids for at least several months in a greenhouse where potential sugar sources (e.g. flowers) are limited.
The effects of several insecticides on the emergence of the parasitoid, Encarsia smithi (Silvestri) parasitizing the tea spiny whitefly Aleurocanthus camelliae Kanmiya & Kasai were evaluated by both laboratory and field experiments. Tea leaves with the pupae of A. camelliae parasitized by E. smithi were collected from a tea field and these leaves were dipped in 13 insecticides diluted with water to ordinary use concentration, and the emergence rate of the parasitoid was checked one month after the treatments in the laboratory experiment. In the field experiment, the emergence rate of the parasitoids was checked 70 days after the application of 13 insecticides in a tea field. The results of these experiments showed that machine oils (two dilutions), methidathion, profenofos and tolfenpyrad were seriously harmful; clothianidin, spinetoram, fenpyroximate·bupurofezin mixer, and methomyl were slightly harmful; and spiromesifen, chlorfenapyr, pyrifluquinazon and diafenthiuron were harmless on the emergence of E. smithi.
Bactericidal or bacteriostatic effect of chlorine dioxide (ClO2) on the plant pathogenic bacteria occurring in hydroponics was examined. In distilled water, 0.1 ppm ClO2 showed an effect on Pseudomonas cichorii (bacterial rot of lettuce), Pectobacterium carotovorum subsp. carotovorum (bacterial soft rot of lettuce), Pec. c. ssp. odoriferum (causing similar symptoms on lettuce as are caused by ssp. carotovorum), and on Ralstonia solanacearum (bacterial wilt of tomato) in a minute. In hydroponic culture fluid, 0.5 or 1.0 ppm ClO2 showed an effect on them in a minute. Thus, ClO2 is a potential control agent or a disinfectant for the diseases occurring in hydroponics.
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