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Nabeshima T.,Kyoto University | Hosokawa M.,Kyoto University | Yano S.,Seikoen Co | Ohishi K.,Aichi ken Agricultural Research Center | Doi M.,Kyoto University
Journal of Horticultural Science and Biotechnology

A total of 199 chrysanthemum (Chrysanthemum × morifolium Ramat.) cultivars were used in screening for resistance to chrysanthemum stunt viroid (CSVd). Plants were inoculated with CSVd by attaching leaf primordia-free, shoot apical meristems to CSVd-infected root tips of a CSVd-sensitive cultivar. CSVd titres in the first and third youngest expanded leaves were analysed after 2 months in culture, and a systematic classification into four groups was conducted. Long-term cultivation records provided by a breeding nursery confirmed our findings of those screened cultivars classified in vitro as "non-detected-type" (i.e., those expected to have a high level of resistance). In addition, of the 15 candidate cultivars selected as "non-detected-type", four cultivars were shown to have a high level of CSVd-resistance by ex vitro grafting experiments. From the results of our in vitro and ex vitro experiments, the advantages of our newly-developed in vitro-screening system are discussed. Source

Johkan M.,Osaka Prefecture University | Johkan M.,Japan Central Research Institute of Electric Power Industry | Chiba T.,Osaka Prefecture University | Mitsukuri K.,Osaka Prefecture University | And 7 more authors.
Journal of the American Society for Horticultural Science

There is concern that high temperatures resulting from global warming could reduce fruit set of tomato (Solanum lycopersicum). However, fruit set of parthenocarpic tomato genotypes, which often bears seedless fruit, is not reduced when grown under a high temperature. The cause of seedless fruit development was studied with the aim of increasing the seed number in parthenocarpic tomato. Ovule number at anthesis in parthenocarpic and non-parthenocarpic fruit did not differ, but the proportion of undeveloped ovules increased with time after anthesis in parthenocarpic tomato, whereas most ovules in non-parthenocarpic tomato developed normally. Pollen grains germinated on the stigma and extruded pollen tubes in parthenocarpic and non-parthenocarpic tomatoes, but in parthenocarpic tomato, pollen tube elongation was markedly inhibited in the style base. Elongation of pollen tubes on agar containing indoleacetic acid (IAA) was depressed in parthenocarpic and non-parthenocarpic tomato plants. p-Chlorophenoxyisobutyric acid (PCIB), which inhibits auxin action, did not affect the fruit set and fresh weight in either type of tomato, although seed number per fruit in parthenocarpic tomato was significantly increased from 13 ± 2 to 74 ± 6 seeds by PCIB treatment. These results indicated that a high IAA concentration in the ovary of parthenocarpic tomato inhibited pollen tube elongation, and that poor fertilization resulted in failure of ovule development. Moreover, floral organs in parthenocarpic tomato were normally developed as in non-parthenocarpic tomato, and seed development could be induced in parthenocarpic tomato by PCIB treatment. Source

Watanabe T.,Nagoya University | Wang G.,Nagoya University | Wang G.,Chinese Academy of Sciences | Taki K.,Aichi ken Agricultural Research Center | And 3 more authors.
Soil Science and Plant Nutrition

Vertical changes in bacterial and archaeal communities (mainly methanogen) with soil depth in three Japanese paddy fields (Tatsuta, Nagakute and Ichinomiya, Aichi prefecture) were investigated by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative PCR. All fields were located in an alluvial area and the soil texture differed among the layers. The Nagakute and Ichinomiya paddy fields were well-drained paddy fields (Gray Upland soil and Gray Lowland soil, respectively), whereas the Tatsuta paddy field was a wet paddy field (Gley soil). The amount of extracted DNA drastically decreased below a depth of 20 cm and remained at a low level in the deeper layers in all fields. Numbers of mcrA genes, encoding the methyl-coenzyme M reductase α subunit of methanogenic archaea, drastically decreased with depth in the Nagakute and Ichinomiya paddy fields; high numbers of mcrA genes were retained through the layers in the Tatsuta paddy field. Cluster analysis of the DGGE band patterns of the bacterial and archaeal communities showed that their patterns in each field were initially divided into two groups, upper and lower layers, except for the bacterial community in the Tatsuta paddy field. These differences in the communities roughly corresponded to the distribution of the rice roots. Sequencing analysis of representative DGGE bands of the archaeal communities showed that diverse methanogens belonging to members of Methanomicrobiales, Methanosarcina spp., Methanosaeta spp., Methanocellales and Methanobacteriaceae inhabited the plowed soil layer, whereas uncultured members in the cluster ZC-I group of Methanosarcinales were more predominant beneath the plowed soil layer. Archaeal members other than methanogens inhabited the deeper layers of the Nagakute and Ichinomiya paddy fields. These results showed that the populations and compositions of bacterial and archaeal communities in paddy fields distinctly varied with soil depth, and indicated that the distribution of rice roots and the groundwater level might affect the populations and compositions in the subsoil. © 2010 Japanese Society of Soil Science and Plant Nutrition. Source

Takahashi R.,Nagoya University | Bowatte S.,Agresearch Ltd. | Taki K.,Aichi ken Agricultural Research Center | Ohashi Y.,Aichi ken Agricultural Research Center | And 2 more authors.
Soil Science and Plant Nutrition

Phages cause significant mortality of bacteria in aquatic environments and thus play an important role in biogeochemical nutrient cycles through biomass turnover. This study evaluated the frequency of phage infection to bacterial cells and resultant potential for mortality and lysis of bacteria in three soil layers in a Japanese rice field. The frequency of visibly infected bacterial cells (FVIC) was from 8.9% to 12.1% on average in these soil layers. This was significantly greater than the reported FVIC values in aquatic environments, and the estimated fraction of bacterial mortality from phage lysis reached far over 100% in every soil layer. The phage infection to bacterial cells tended to be more frequent for short-rod cells than for long-rod cells. The medians of phage-like particles in a bacterial cell (burst size) ranged from 12.5 to 16 particles cell-1 with the low and high quartiles of 7 and 27, respectively. © 2011 Japanese Society of Soil Science and Plant Nutrition. Source

Takei M.,Aichi Prefectural Government Office | Hamada Y.,Aichi Prefectural Government Office | Nakamura M.,Aichi ken Agricultural Research Center | Ikeda A.,Aichi ken Agricultural Research Center | And 4 more authors.
Plant Production Science

Two-striped leaf beetle (TSLB) larvae are known to damage soybean root nodules but the effect they have on yield has not been quantitatively assessed. This study was aimed to evaluate the impact of TSLB and to establish a technique to control the larvae. We surveyed 106 farmers’ fields in Aichi prefecture for two years to quantify the changes in TSLB adult population, nodule damage by larvae, and nitrogen (N) content of seeds and stems, growth and yields of soybean plants treated with two different pesticides that were applied to furrow at the time of seeding. The results showed that damage caused by TSLB larval feeding of root nodules was observed particularly in soybeans grown in N-poor soil, and that ureide N content was decreased in plants with damage caused by larval feeding of root nodule, and such damage caused reduction of yield consistently in both years. Furthermore, we also showed the effectiveness of applying insecticides to the sowing furrow at the time of seeding. Specifically, the application of disulfoton to the sowing furrow at a rate of 4 g m–2 as a simple method of pest control limited insect occurrences until the beginning of the blooming stage, curbed the feeding damage to root nodules caused by larvae, and increased the yield of soybean by 20%. This method has been adopted widely in Japan because it can be readily implemented using the fertilization application equipment installed on seeding machines and the insecticide is relatively inexpensive. © 2014 by The Crop Science Society of Japan. Source

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