Comparison of the growth of age-1 Pacific saury <Emphasis Type="Italic">Cololabis saira</Emphasis> in the Western and the Central North Pacific

The growth of age-1 Pacific saury Cololabis saira was compared based on an analysis of the body-length frequency distributions, radius of the annual ring (otolith hyaline zones; ROH), and growth patterns in otolith increments. Fish were sampled at various locations between off the Japanese coast (144°E) and in the Central Pacific (160°W) in June and July 2006, and the measurements were compared among the stations ranging over six longitudinal areas, each with a longitudinal area of 10°. The mode of body-length frequency distributions of age-1 fish was larger in fish sampled west of 160°E (size class modes of 32.0–32.5 and 31.5–32.0 cm, respectively, in each 10° longitude area) than in those sampled east of 170°E (28.5–29.0 or 29.0–29.5 cm in 3 areas). The ROH was also larger in the former group (west of 160°E) than in the latter group (east of 170°E), but hatch periods of these two groups and age in days when the hyaline zones form in August or September did not differ based on the analysis of otolith growth increments. The growth difference occurred in the period between when the fish started their northward migration and when the hyaline zone was formed. These results indicate that the habitats of the two groups were separate until at least June or July of their second year of life.     

Zn Uptake and Translocation in Rice Plants

Zinc (Zn) is an essential micronutrient with numerous cellular functions in plants, and its deficiency represents one of the most serious problems in human nutrition worldwide. Zn deficiency causes a decrease in plant growth and yield. On the other hand, Zn could be toxic if excess amounts are accumulated. Therefore, the uptake and transport of Zn must be strictly regulated. In this review, the dominant fluxes of Zn in soil?Croot?Cshoot translocation in rice plants (Oryza sativa) are described, including Zn uptake from soils in the form of Zn²⁺ and Zn-DMA at the root surface, and Zn translocation to shoots. Knowledge of these fluxes could be helpful to formulate genetic and physiologic strategies to address the widespread problem of Zn-limited crop growth.     

Spatial distribution of spawning redds and larvae of Rhinogobius flumineus in relation to hydrogeomorphological characteristics in Kamo River,Japan

Paddy and Water Environment - A freshwater goby, Rhinogobius flumineus, is one of the dominant species in the Kamo River and the Takano River, Kyoto City, Japan. We investigated the spatial...     

Alleviative effects of mixed-cropping with rice on the growth inhibition of pearl millet caused by flooding at reproductive stage

Flooding has globally become common, and thus cultivation techniques to adapt to the stress are required. We have developed a technique called “close mixed-planting” using flood-adapted rice (Oryza sativa L.) and upland crops with tangled root systems, showing that this technique can mitigate the damage caused to upland crops by flooding. However, the plant response during the reproductive stage has not yet been examined. In this study, we estimated the alleviative effects of close mixed-planting on the growth inhibition and physiological damage to pearl millet (Pennisetum glaucum) caused by flooding at the reproductive stage in northern Namibia. Pearl millet and NERICA4 (Oryza spp., interspecies of O. sativa and O. glaberrima) were used. Four-week-old single- and mixed-crop pearl millets were transplanted and grown for 22 days, and then flooding treatment was administered for 28 days. The growth and physiological parameters of single pearl millet were significantly decreased by flooding stress, and the parameters did not recover during a 14-day recovery period compared with those of unflooded single and mix-cropped pearl millet. On the other hand, the damage to mix-cropped pearl millet by flooding was suppressed. Thus, the mixed-cropping mitigated the anoxic stress of pearl millet caused by flooding at the reproductive stage and contributed to the improved growth after the recovery period. This result suggested that the close mixed-planting with rice can contribute to the mitigation of flooding damage not only at the vegetative stage but also at the reproductive stage of pearl millet in the semi-arid African country, Namibia.     

Development of a new selection method and quality improvement of sugary-1 rice mutants

Brown rice of sugary-1 mutants has a wrinkled character because of the presence of phytoglycogen instead of starch in the inner part of the endosperm. Because the wrinkled phenotype was used as a sole selection marker for progeny of the sugary-1 strain, identification of mutant seeds with improved appearance is very difficult. We found that sugary-1 varieties contained not only phytoglycogen but also free glucose in the endosperm, and these were positively correlated. In the segregated F₂ seeds that resulted from crossing Hokurikutou237 (sugary-1) and Koshihikari strains, glucose and phytoglycogen were also significantly correlated. Thus, we identified new sugary types with improved appearance from these progeny using glucose measurements. The F₄ seeds of the improved strain had moderate phytoglycogen contents and seed germination characteristics. Native-PAGE showed that pullulanase activity in the improved strain increased in developing seeds compared with Hokurikutou237, although isoamylase activity was extremely low and similar to that in sugary-1 types. The new selection method in this study efficiently aids the development of improved sugary rice types that lack the wrinkled phenotype.     

Development of cleaved amplified polymorphic sequence (CAPS)-based markers for identification of sweetpotato cultivars

To develop a simple and reliable method to identify sweetpotato cultivars, we designed cleaved amplified polymorphic sequence (CAPS)-based markers and used them to perform genotyping of Japanese sweetpotato cultivars. In order to screen the CAPS-based markers, 13 primer pairs were designed from the exon sequences of 11 sweetpotato genes to amplify fragments containing an intron. By digesting the amplified products with 8 restriction enzymes having different recognition sites, a total of 27 polymorphic marker fragments were obtained. Genotyping of 60 Japanese sweetpotato cultivars using these markers suggested that the markers can effectively distinguish sweetpotato cultivars. Among the genes used for primer design, the gene encoding the dihydroflavonol 4-reductase (DFR) showed the largest degree of polymorphism. To our knowledge, this is the first report on the development of CAPS-based markers in sweetpotato.     

Changes in size of soil seed bank in Robinia pseudoacacia L. (Leguminosae), an exotic tall tree species in Japan: Impacts of stand growth and apicultural utilization

This study examined the factors that influence the size of a soil seed bank in Robinia pseudoacacia stands. We proposed two hypotheses: the amount of buried seeds of R. pseudoacacia is proportional to stand biomass rather than stand age, and apicultural utilization influences the size of the soil seed bank. R. pseudoacacia generally produces seeds with various degrees of physical dormancy. In addition, this tree is short-lived, and fecundity declines after 30–40 years in relation to tree vigor. However, R. pseudoacacia is intensively used in apiculture as an important honey source, and supply of honeybees by beekeepers could influence seed crops. We investigated 25 plantations in Hokkaido (Central, Hidaka, and Oshima) and in Nagano, Japan, where many naturally regenerated R. pseudoacacia stands occur. We found great variation in the size of the soil seed bank among stands, ranging from 13,757 to 6.4 seeds m⁻² per plot. A generalized linear mixed model revealed that both basal area (BA_Rp) and apicultural utilization best explained the size of the soil seed bank. Both the positive effect of BA_Rp and small contribution of stand age to the model implied that the soil seed bank is transitory, and will not persist for very long time. The large contribution of apicultural utilization to the size of the soil seed bank implied pollinator limitation under natural conditions. R. pseudoacacia often has large flower crops, and native pollinators can not keep up with the demand for pollination. Thus, the supply of honeybees by beekeepers should improve the pollination success of R. pseudoacacia. From these results, we conclude that we must consider stand history with respect to apicultural utilization if the land is harvested or a stand declines.     

In vivo immunomodulatory effects of dietary purple sweet potato after immunization in chicken

This study was intended to determine the modulatory effects of dietary supplementation of purple sweet potato ( Ipomoea batats Poir., PSP) on the immune response of chickens. PSP was included in a basal starter diet by 1% (PSP^L) or 3% (PSP^H) and continually fed. Newcastle disease (NDV) vaccine, Brucella abortus (BA) and sheep red blood cells (SRBC) were used for chicken immunization. Antibody titers against these antigens were used to estimate humoral immunity. Concanavalin A (Con A)-induced proliferations of splenocytes, thymocytes and peripheral blood lymphocytes (PBL), ratios of CD4- and CD8-single positive and CD4-CD8-double negative (DN) cells in splenocytes, were both used to indicate cellular immunity. Relative weights of spleen, thymus and bursa and white blood cell (WBC) counts were studied. PSP^H increased anti-NDV ( P  < 0.05), anti-BA ( P  < 0.01) and anti-SRBC titers ( P  < 0.05) in response to secondary immunization, whereas PSP^L increased titers of anti-BA ( P  < 0.05) and anti-SRBC ( P  < 0.01). Proliferations of splenocytes and thymocytes were augmented with PSP^L ( P  < 0.05). PSP^H-treated chickens had lower ( P  < 0.05) ratios of CD4-sigle positive lymphocytes. Proliferation of PBL, weights of lymphoid organs and WBC counts were not affected. These results suggest that dietary PSP supplementation could enhance the immune response after immunization in chickens.     

Chlamydial species among wild birds and livestock in the foothills of Mt. Afadjato,Ghana

The members of family Chlamydiaceae have a broad host range and cause many kinds of diseases in humans and animals. Several cases of Chlamydiaceae being detected in atypical hosts have been reported recently. Consequently, cross-species monitoring of Chlamydia in wildlife and livestock is pertinent for public health, animal hygiene and wildlife conservation. In this study, we conducted molecular surveillance of Chlamydia in wild birds and livestock around a small village in the foothills of Mt. Afadjato, Ghana where direct contact between wildlife and livestock occurs. Among 29 captured wild birds and 63 livestock, 5 sheep, 30 goats and 28 chickens, the positive ratios of Chlamydia were 24.1%, 40.0%, 43.3% and 26.9%, respectively. Chlamydia pecorum was detected in wild birds, goats, sheep and chickens. On the basis of the variable domain 2 region of ompA, several samples from different hosts showed identical sequences and were phylogenetically located to the same clusters. In addition, using ompA, C. psittaci, C. abortus and C. gallinacea were also detected in this small habitat. Further genetic and pathogenic analyses of the chlamydial distribution in this area, which represents the interface of wild and domestic animal interactions, may improve our knowledge of their transmission among different hosts.