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Oda S.,Tohoku University | Kaneko F.,Tohoku University | Yano K.,Meiji University | Fujioka T.,Tohoku University | And 13 more authors.
Genes and Genetic Systems | Year: 2010

Cool temperature conditions are known to lead to pollen sterility in rice. Pollen sterility is an agriculturally important phenomenon because it imparts a large influence directly on rice yield. However, cool temperature stress tolerance varies among rice cultivars and avoidance of cool temperature stress is difficult by prac- tical method of agriculture. In this study using two rice cultivars, Hitomebore (high tolerance) and Sasanishiki (low tolerance), we analyzed morphological fea- tures and gene expression profiles, under cool temperature stress, in anther devel- opment of rice. Hitomebore was given cool temperature stress (19°C) at flowering stage, and showed 87.3% seed fertility. Meanwhile, the seed fertility decreased to 41.7% in the case of Sasanishiki. A transverse section of Hitomebore anther revealed that the degradation of the tapetum started at the uninucleate microspore stage, and the tapetum had completely vanished at mature stage. The tapetum provides nutrients for pollen development, and its degradation occurs at a late stage in pollen development. In contrast, degradation of the tapetum did not occur at the uninucleate microspore stage in Sasanishiki, and the tapetum was clearly intact at mature stage, suggesting that tapetum degradation is critical for accurate pollen development and cool temperature tolerance correlated with the degree of tapetum degeneration. In gene expression analysis of anther, 356 genes that showed different expression levels between two cultivars at cool temperatures were found. These genes will lead to understanding the mechanism of cool temperature stress response in rice pollen development and the identification of genes involved in accurate tapetum degradation.

Kashin J.,Miyagi Prefectural Furukawa Agricultural Experiment Station
Japanese Journal of Applied Entomology and Zoology | Year: 2011

To clarify the seasonal change in the dispersal ability of the two-striped leaf beetle, Medythia nigrobilineata, the occurrence and ovarian development of adult insects were investigated in soybean fields in Miyagi Prefecture, Japan. Soybean seedling traps were installed from April to May before the germination of soybean seeds sown in the fields. Overwintered adults were observed in the traps from late April to early May, about one month before the normal germination of soybean. Two methods were used to collect insects: tapping on soybean plants and the use of sticky traps set in the soybean fields. The number of adults of the 1st generation captured using sticky traps was smaller than for overwintered and 2nd generations. Among the overwintered generation, female adults collected on the soybean seedlings had developed ovaries and mature eggs, whereas the adults captured using sticky traps had poorly developed ovaries. Female adults of the 1st generation collected both by tapping on soybean plants and by using sticky traps had developed ovaries. The ovaries of the female adults of the 2nd generation were immature, showing no difference between the collection methods used. The sex ratio of the adults captured using sticky traps showed no significant difference from that of adults collected by tapping on soybean plants. These results suggest that immature adults have high flight activity, and that overwintered and 2nd generation adults are involved in the flight dispersal of the species.

Yoshida S.,Japan National Institute for Agro - Environmental Sciences | Ohba A.,Miyagi Prefectural Furukawa Agricultural Experiment Station | Liang Y.-M.,Beijing Forestry University | Koitabashi M.,Japan National Institute for Agro - Environmental Sciences | Tsushima S.,Japan National Institute for Agro - Environmental Sciences
Microbial Ecology | Year: 2012

The specificity of culturable bacteria on healthy and Fusarium head blight (FHB)-infected spikelets of wheat heads was investigated to find a candidate of biocontrol agents against FHB. The bacterial genus Pseudomonas was commonly isolated from the tissues, and phylogenetic analysis using 16S ribosomal RNA gene sequences of isolates of the genera revealed that particular phylogenetic groups in the genus specifically inhabited either healthy or infected spikelet tissues. The specificity of each group was suggested to be due to differences in the ability to form biofilms and colonize spikelet tissues; isolates originated from healthy spikelets formed biofilms on polyvinyl chloride microplate wells and highly colonized the spikelet tissues. Other bacterial groups obtained from FHB-infected spikelets less formed biofilms and attached with low densities on the spikelet tissues. Their colonization on the tissues, however, was promoted when co-inoculated with the causal pathogenic fungus, Fusarium graminearum, and several isolates were observed to smash the mycelia in vivo. Moreover, based on results of in vitro mycelial growth inhibition activity, the diseased tissue-originated isolates were verified to have a negative effect on the fungal growth. These results suggest that Pseudomonas isolates obtained from infected spikelet tissues were highly associated with the FHB pathogen and have potential as candidates for biological control against FHB. © 2012 Springer Science+Business Media, LLC.

Kashin J.,Miyagi Prefectural Furukawa Agricultural Experiment Station | Watanabe T.,Japan National Agriculture and Food Research Organization
Applied Entomology and Zoology | Year: 2012

Appropriate droplet size and the preferred sex and age of insects for insecticides used in topical application were investigated to standardize the method of testing the susceptibility of Stenotus rubrovittatus (Matsumura). The overflow of acetone droplets applied on the notum of the thorax of S. rubrovittatus adults occurred when the droplet size exceeded 0. 20 μl per insect, and the overflow occurred more frequently in males than in females. No effect of acetone solution on mortality was observed at less than 0. 20 μl droplet size per insect within 72 h after treatment. The LD50 values and relative potencies of fenitrothion 24 and 48 h after treatment were almost the same in each sex. The fenitrothion susceptibility of males was twice higher than that of females. The fenitrothion susceptibility increased with age after emergence. However, there were small differences in LD50 values and relative potencies between 4-7 and 8-11 days after emergence because the females 4-11 days after emergence had a small difference in body weight. These results led us to conclude that the recommended size of acetone droplets per insect is less than 0.20 μl and that it is suitable to use S. rubrovittatus females 4-11 days after emergence for topical application. © 2012 The Japanese Society of Applied Entomology and Zoology.

Kashin J.,Miyagi Prefectural Furukawa Agricultural Experiment Station
Japanese Journal of Applied Entomology and Zoology | Year: 2014

Scirpus juncoides is a noxious weed species in rice fields that intensifies damage to rice grains caused by the sorghum plant bug Stenotus rubrovittatus, by serving as the oviposition site. In this study, we examined whether herbicide application for the elimination of S. juncoides has a controlling effect on the bug. In the non-bentazon-applied fields, the bug's invasion into the rice fields prior to the heading period of rice and the nymphal emergence were observed. When bentazon was applied 41 days or 62 days after transplanting in S. juncoides-infested rice fields, the bug's invasion into the fields occurred only after the heading period of rice, and the nymphal emergence of the bugs was not observed. When bentazon was applied 77 days after transplanting, the bug's occurrence resembled that in the non-bentazon-applied fields. These results indicated that the bug's propagation could not be avoided, when the herbicide application timing is later than the occurrence of the first-generation adults. The effects of the timing on damage to rice grains were unclear. Therefore, judging from differences in the bug's occurrence between the rice fields studied, it seems reasonable to conclude that the elimination of S. juncoides with herbicides before the occurrence of the first-generation adults is effective for the control of the bug.

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