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Takinami Y.,University of Tokyo | Maejima K.,University of Tokyo | Takahashi A.,Gunma Agricultural Technology Center | Keima T.,University of Tokyo | And 5 more authors.
Journal of General Plant Pathology | Year: 2013

Phytoplasma-induced floral malformations such as virescence, phyllody, and proliferation were observed on hydrangeas in Gunma Prefecture, Japan. Phylogenetic analyses based on 16S rRNA, secY, groEL, and amp gene sequences indicated that the affected hydrangea plants were associated with phytoplasmas belonging to 'Candidatus Phytoplasma asteris', but not to 'Ca. P. japonicum', which occurs in hydrangeas showing phyllody in Japan. This is the first molecular evidence of an association of 'Ca. P. asteris' with hydrangea plants in Japan. © 2013 The Phytopathological Society of Japan and Springer Japan.

Kato Y.,University of Tokyo | Osawa M.,Gunma Agricultural Technology Center
European Journal of Agronomy | Year: 2013

Wheat often overproduces kernels when grown in favorable environments, resulting in low kernel weight with high kernel screenings. This indicates that photoassimilation after heading would not be sufficient to support the growth of a large number of kernels. The objective of this study was to examine the effects of crop thinning at heading (experiment 1) and double-row planting (compared with equidistant row spacing; experiment 2) on kernel weight and yield of Japanese wheat cultivars under different levels of soil fertility. In experiment 1, elimination of aboveground competition for radiation by thinning increased yield by up to 32%, mainly due to increased kernel weight. In experiment 2, double-row planting increased kernel weight significantly (by 4-10%) without yield loss by moderately suppressing maximum stem number (by 7-14%) and spike and kernel number (by up to 14%) under high fertility. In both experiments, the effect of crop thinning or row configuration on wheat yield and kernel weight was negligible under low fertility because of little competition for radiation. The results suggested that control of vegetative growth and kernel production would help avoid the shortage of assimilates for kernel growth in fertile environments. For further increasing wheat yield under favorable conditions in Japan, the appropriate crop management options (e.g., planting geometry) should be combined with the suitable varieties having a more communal ideotype (sparse tillering with upright posture) than a competitive phenotype (profuse tillering with lax posture) to enhance photoassimilation after heading. © 2013 Elsevier B.V.

Kato N.,Japan National Agriculture and Food Research Organization | Kihou N.,Japan National Institute for Agro - Environmental Sciences | Fujimura S.,Fukushima Agricultural Technology Center | Ikeba M.,Agricultural Research Institute | And 4 more authors.
Soil Science and Plant Nutrition | Year: 2015

Huge amounts of radionuclides, particularly radiocesium, were discharged from the Fukushima Daiichi Nuclear Power Plant (FDNPP), and widespread of contamination of the land, including paddy fields, was observed. Because rice is a staple food in Japan, contamination of paddy fields is a serious problem, and practical countermeasures to reduce radiocesium contamination of rice are urgently required. Potassium (K) fertilization was previously shown to be an effective countermeasure in fields contaminated by the Chernobyl accident, but researchers did not study the effects on rice (Oryza sativa L.). In the present study, we performed urgent field experiments to test the use of K fertilization, as well as other soil amendments, to reduce radiocesium contamination of rice. We found that K fertilization was an effective and practical countermeasure to reduce radiocesium uptake by rice from several soil types in Japanese paddy rice culture. Other treatments, including the application of expanded vermiculite or manure, were effective, and the effect appears to be explained by their K content. Based on these results, the recommended level of exchangeable soil potassium to lower the radiocesium content of rice to acceptable levels is about 200 mg K kg–1 soil before the usual fertilization. This K fertilizer application criterion was applied in a wide, low-contaminated area from the 2012 cropping season, and satisfactory results have been obtained generally. © 2014 Japanese Society of Soil Science and Plant Nutrition

Ikeda K.,science | Ikeda K.,Gunma Agricultural Technology Center
Journal of General Plant Pathology | Year: 2010

Pepper (Piper nigrum L.) root rot caused by Fusarium solani f. sp. piperis (FSP; teleomorph: Nectria haematococca f. sp. piperis) includes two symptom types called root rot (RR) type and stem rot (SR) type. In this study, the temporal and spatial associations between perithecial formation of FSP and development of SR were investigated in naturally infested fields to verify the hypothesis that ascospores from the perithecia are the major inoculum source of the SR type on vines in the field. In surveys of all vines in two neighboring pepper fields every month from December 2005 to November 2006, I mapped the locations of all vines with perithecia and all vines the SR type. The frequency of vines with perithecia increased during April and May, the late rainy season. In June, the early dry season, the number of vines with SR type greatly increased. The vertical range of perithecial formation on the vines extended to 200 cm in height, but was restricted to 30 cm in the dry season in both fields. The join-count statistics showed a significant spatial association between vines with perithecia and vines with SR type in one field (P = 0.042), while no significant spatial association was recognized in another field. The results suggested that ascospores from perithecia of FSP on pepper vines are likely to be one of the main inoculum sources of the SR type of the disease on adjacent vines, but they may not be the exclusive source. © 2010 The Phytopathological Society of Japan and Springer.

Banno S.,Toyo University | Ikeda K.,Gunma Agricultural Technology Center | Saito H.,Toyo University | Sakai H.,Gunma Agricultural Technology Center | And 4 more authors.
Journal of General Plant Pathology | Year: 2015

Verticillium longisporum is an allodiploid hybrid fungus that consists of at least three groups, A1/D1, A1/D2, and A1/D3. PCR-based analysis of 18S rDNA, 5.8S rDNA-ITS region, mtSSU-rDNA, cytochrome b gene, and mating type gene, as well as RAPD analysis, revealed that Verticillium wilt of cabbage in Gunma Prefecture in Japan is caused by two groups of V. longisporum—A1/D1 and A1/D3—and by V. dahliae. A1/D1 and A1/D3 lineage strains were equally distributed in cabbage fields, whereas V. dahliae strains were most frequently isolated. The proportion of the three types of Verticillium had not changed in 1998 and 2008. Although both V. longisporum strains produced longer conidia than the V. dahliae strains, the A1/D3-type strains produced larger conidia than A1/D1-type strains. In addition, the A1/D3-type strains formed microsclerotia that were distinguishable from those of A1/D1-type of V. longisporum and V. dahliae. The pathogenicity of the A1/D3-type strains on cabbage was similar to that of the A1/D1-type strains. These results will contribute to understanding of genotypic diversity, distribution, and pathogenicity of Verticillium species pathogenic on cabbage. © 2014, The Phytopathological Society of Japan and Springer Japan.

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