RFLPs of chloroplast and mitochondrial DNA in wild soybean, Glycine soja, growing in China

RFLPs of chloroplast (cp) and mitochondrial (mt) DNA have been used to characterize the cytoplasmic genome of wild soybean, Glycine soja, growing in China. We have found from the RFLPs of that the cytoplasmic genomes of most Chinese wild soybeans have a combination of cpIII with mt-a or a combination of cpII with mt-b accompanied by mtIV or mtV according to our classification. CpII was not observed in combination with mt-a and cpIII was not observed in combination with mt-b. The regional distribution of these two types showed clines with opposite directions. The Yangtze River Valley had the greatest diversity in each of cp and two mt profiles detected in this study and the cytoplasmic genome combining these three profiles showed the highest degree of polymorphism in this region. The Yangtze River Valley may be a center of cytoplasmic diversity of wild soybean and may contain various genetic resources of soybean.     

Beneficial effects on meat quality of yellowtail Seriola quinqueradiata induced by diets containing red pepper

The meat quality of farmed yellowtail Seriola quinqueradiata fed on extruded pellets (EP) containing 0.5% (v/v) red pepper (experimental group) was compared with yellowtail of the same age fed on EP (control group). In 1-year-old yellowtail, the crude lipid content of the dorsal muscle of the experimental group tended to be lower than that of the control group. In contrast, there was no difference in the lipid content of the dorsal muscle between the control group and the experimental group in 2-year-old yellowtail. The muscle texture of the experimental group was significantly firmer than that of the control group, with the effect of red pepper unrelated to fish age and lipid content. Color change of red muscle of the experimental group was significantly lower than that of the control group, and the content of thiobarbituric acid-reactive substances in the red muscle was significantly lower in the experimental group than in the control group. These results are the first to demonstrate that the inclusion of red pepper in the diet is able to reduce the loss of muscle texture firmness and to slow down color change in red muscle of yellowtail.     

Development of an in vitro culture system for producing eel larvae from immature ovarian follicles in Japanese eel <Emphasis Type="Italic">Anguilla japonica</Emphasis>

To standardize conditions during the final maturation and ovulation of ovarian follicles from Japanese eel, we have developed a culture system for the production of fertilizable eggs from post-vitellogenic ovarian follicles in vitro. Post-vitellogenic ovarian follicles were incubated in culture medium supplemented with 17α,20β-dihydroxy-4-pregnen-3-one (DHP) with or without bovine serum albumin (BSA) to assess the effects of protein concentration. Eggs that ovulated during incubation were fertilized, and the remaining follicles were incubated in prostaglandin F_2α (PGF_2α) for a further 3 or 6 h before fertilization. Male eels were injected repeatedly with human chorionic gonadotropin. The quality of eggs obtained under the different culture conditions was evaluated after artificial fertilization in terms of hatching success. Hatching rates tended to decrease with increasing concentrations of BSA in the incubation medium in a dose-dependent manner. The addition of PGF_2α drastically increased the number of eggs that ovulated, but the rate of hatching was greatly decreased compared with eggs obtained earlier by DHP incubation alone. The larvae obtained from artificially fertilized eggs produced in vitro survived for 14 days without feeding. We conclude that in vitro culture systems thus have a great potential for the acquisition of good quality eggs under tightly controlled artificial conditions, culminating in the production of eel larvae.     

Effects of an Enterococcus faecium‐based probiotic on growth performance and health of Pirarucu,Arapaima gigas

Intensive fish farming has resulted in an increased concern for disease outbreaks. Probiotic use is one of the strategies being developed to improve fish health and productivity. Measures of probiotic colonization, growth performance, haematological characteristics and parasite load were used to evaluate the effect of diets supplemented with Enterococcus faecium on growth and health of Arapaima gigas juveniles. A completely randomized design with four treatments (diet with E. faecium at 1 × 10⁶ CFU/g and 1 × 10⁸ CFU/g, control diet and diet with the culture medium MRS) and three replicates was used. Ninety‐six Arapaima juveniles were distributed in 12 cages fed with the specified diet for 68 days. Colonization of the intestinal tract by lactic acid bacteria reduced the total number of heterotrophic bacteria in fish fed with probiotics compared to controls. Fish fed a supplemented diet containing 1 × 10⁸ CFU/g presented higher values of weight gain, survival and fish growth uniformity, and lower values of feed conversion ratio. The prevalence of Trichodina sp. could have affected the survival of fish in the control group. Reduction in parasite load and an increase in haematocrit, the number of erythrocytes, thrombocytes, neutrophils and monocytes were also observed in fish fed the diet containing 1 × 10⁸ CFU/g. Enterococcus faecium presented a probiotic effect in A. gigas juveniles and can be recommended for use at a concentration of 1 × 10⁸ CFU/g to modify the gut microbiota, improve growth performance and haematology and reduce parasitic load.     

Nonrandom distribution of chum salmon stocks in the Bering Sea and the North Pacific Ocean estimated using mitochondrial DNA microarray

More than 1,000 age-identified chum salmon Oncorhynchus keta collected at 23 stations in the Bering Sea and the North Pacific Ocean in June to July 2003 were used to estimate their origin of stocks using a DNA microarray developed for analyzing the mitochondrial (mt)DNA haplotypes. The observed haplotype distribution was nearly the same as that reported previously for fish collected in September 2002 and 2003 in the present surveyed areas. A conditional maximum-likelihood method for estimation of stock compositions indicated that the Japanese stocks mainly distributed in north central Bering Sea, whereas the Russian stocks were mainly in western Bering Sea. The North American stocks were abundant in eastern Bering Sea and around the Aleutian Islands. Such an area-specific stock composition was not significantly different between mature and immature fish. Thus, the combined results of 2 years suggest that the distribution of chum salmon is nonrandom in the surveyed areas in summer and autumn, and that fish of the same origin migrate together to the same area irrespective of age.     

Temperature characteristics in seed germination and growth of <Emphasis Type="Italic">Zostera japonica</Emphasis> Ascherson &; Graebner from Ago Bay,Mie Prefecture,central Japan

The optimal water temperature in seed germination and the upper critical water temperature in seedling growth were determined for Zostera japonica collected from Ago Bay, Japan. The relationship between the seed germination rates and seed storage period (0, 30, and 60 days) at 0°C was also examined. The optimal water temperature in seed germination was in the range 15–20°C regardless of the storage period, in which germination rates were up to 14%. Seedlings, grown from seeds up to 10 cm in total length, were cultured for 1 week at various water temperatures to measure their relative growth rates. The optimal water temperature in early growth was in the range 20–25°C; relative growth rates ranged from 3.8 to 4.2%. Seedlings could survive up to a water temperature of 29°C, but most seedlings withered at 30 or 35°C. The optimal water temperatures for seed germination and seedling growth were related to the seasonal changes of water temperature in the sampling site. Although seedlings were hardly observed in Ago Bay in summer, Z. japonica might extend its distribution as far as where the summer water temperature is lower than 29°C.     

Assessing Silicon Availability in Soils of Rice-Growing Lowlands and Neighboring Uplands in Benin and Nigeria

Silicon(Si) is known as a beneficial nutrient in the cultivation of rice, playing a key role in photosynthesis enhancement, lodging resistance and tolerance to various environmental stress. The present study aimed to examine available Si content in both lowland soils(n = 29) and neighboring upland soils(n = 21) collected from Benin and Nigeria and to evaluate the validity of the assessment results through a pot experiment. Our results revealed that the acetate-buffer method predicted Si concentration in rice straw at the harvest stage(R~2 = 0.68, P < 0.01) better than the anaerobic-incubation method(R2 = 0.31, P > 0.05), and 76% of the uplands and 38% of the lowlands were deficient(< 50 mg/kg) in acetate-buffer soluble Si. These findings suggest that the Si-deficiency soils prevail across the study area, making rice plants starved for Si and prone to environmental stress.     

Fine mapping of the gene for susceptibility to black spot disease in Japanese pear (Pyrus pyrifolia Nakai)

Black spot disease, which is caused by the Japanese pear pathotype of the filamentous fungus Alternaria alternata (Fries) Keissler, is one of the most harmful diseases in Japanese pear cultivation. We mapped a gene for susceptibility to black spot disease in the Japanese pear (Pyrus pyrifolia Nakai) cultivar ‘Kinchaku’ (Aki gene) at the top of linkage group 11, similar to the positions of the susceptibility genes Ani in ‘Osa Nijisseiki’ and Ana in ‘Nansui’. Using synteny-based marker enrichment, we developed novel apple SSR markers in the target region. We constructed a fine map of linkage group 11 of ‘Kinchaku’ and localized the Aki locus within a 1.5-cM genome region between SSR markers Mdo.chr11.28 and Mdo.chr11.34. Marker Mdo.chr11.30 co-segregated with Aki in all 621 F₁ plantlets of a ‘Housui’ × ‘Kinchaku’ cross. The physical size of the Aki region, which includes three markers (Mdo.chr11.28, Mdo.chr11.30, and Mdo.chr11.34), was estimated to be 250 Kb in the ‘Golden Delicious’ apple genome and 107 Kb in the ‘Dangshansuli’ Chinese pear genome. Our results will help to identify the candidate gene for susceptibility to black spot disease in Japanese pear.     

Development of a joint system using a compressed wooden fastener I: evaluation of pull-out and rotation performance for a column—sill joint

Compressed wooden plates and dowels were used to connect members in post-and-beam structures as a substitute for a steel fastener. In order to take advantage of the characteristic properties of compressed wood and to achieve optimum joint performance, two compressed wooden plates were used in each joint to give multiple shear planes for each compressed wooden dowel. Consequently, this type of joint showed very good properties in pull-out and momen-trotation performance, and its engineering design could be further optimized. This joint is expected to be introduced to many kinds of structural systems, including long-span frame structures made of domestic timber found in Japanese residential houses.