We cloned duck microsatellite repeat sequences from genomic DNA of an Indonesian native duck to evaluate the genetic relationships among native breeds of duck. A (CA)_n-enriched library was constructed using the method of Takahashi et al. (1996) with modifications. In the library, 8.3% of the clones were CA-positive. The average number of uninterrupted (CA)_n repeats among 22 duck microsatellites was 11.4. Fifteen clones which could be developed as PCR primer pairs to detect (CA)_n repeat length polymorphisms were identified. They should provide a valuable tool for studies related to biodiversity and population structure in duck.

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Ergot pathogens of sorghum occurring in Japan were identified as Claviceps sorghicola and C. africana. C. sorghicola is the original fungus and it differs from the other Claviceps species infecting Sorghum in the color and texture of the sclerotia, morphology of stromata with clavicipitaceous stipes and capitula and the size of ascospores and conidia. It is predominant and widely distributed in Japan. C. africana is a pathogen with worldwide distribution which occurs mainly in the southern part of Japan. Host ranges of these fungi were restricted only to the genus Sorghum, based on the results of inoculation tests. Field tests showed that the method applied to sow the resistant sorghum lines at an earlier time was effective to avoid or control the occurrence of the ergot.

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Eradication programs are being implemented for 2 sweetpotato weevil pests, Cylas formicarius and Euscepes postfasciatus, in the Ryukyu Islands located in the southernmost part of Japan by the application of the sterile insect technique (SIT). As it is essential for the implementation of the programs to assess the dispersal ability of the weevils, recent studies were reviewed. Both the flight and walking ability of C. formicarius was much higher in males than in females when determined in the laboratory. Synthesized sex pheromone of C. formicarius has been used as a strong lure to capture the males in the field. Results of the mark-recapture experiments suggest that a distance of at least 2 km is needed for the range of the buffer zone to separate the SIT target area from others. Since E. postfasciatus is unable to fly, only the walking ability was evaluated in the laboratory, indicating that the females exhibited a fairly higher locomotion activity compared with the males. Since no effective attractant for E. postfasciatus has been identified yet, information on the dispersal activity in the field is limited. Fundamental studies should be conducted to determine the dispersal ability of both weevil pests to implement successfully the eradication programs.

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A current and water quality observation system consisting of drift type buoys equipped with differential GPS (DGPS) was developed. This report presents the outline of the system that was developed and the results of the verification of the field observations. The system was used to perform current observations along the coast of the Ariake Sea to measure the current and quality of water (salinity concentration and turbidity) carried by the current downstream from a tide gate. The results showed that the system enabled to perform current and water quality observations with accuracy for practical use. The system showed the following characteristics: 1) It enabled to determine easily the path line and the velocity of a surface current; 2) The method was effective for analyzing currents where flowing fresh water converges and where dangerous conditions prevail; 3) The buoys could be equipped with a variety of water quality observation devices; and 4) The risk of observations performed during flooding and under other dangerous conditions could be reduced. The system was found to be effective for performing easily high precision observations of currents and water quality over a wide area extending from river mouths to the open sea.

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A mathematical model was developed to simulate soil erosion and sediment transport along rills in a field. For the model, a continuity equation for sediment with a term for the sediment transport capacity of rill flow was used. The Yang sediment transport equation was used to estimate this capacity. First, the equation of the model was solved under various intensities of rainfall events occurring during the observation, and the characteristics of the sediment load distribution along the rill in the field for study were clarified based on the results obtained. Second, net rill erosion at many positions along the rill was calculated using the solutions of the equations. Due to the good agreement between the calculated and observed values, the sediment transport model was found to be valid. Third, the effect of the sediment transport rate on the detachment rate along the rill was analyzed. The results showed that the effect was not appreciable in the case of moderate or higher rainfall intensity throughout the rill, while it became more pronounced when the distance along the rill increased under low intensity rainfall.

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In wet rice fields with heavy clay soil, the decrease of the rate of soil pulverization and excess moisture injury are major constraints on the cultivation of vegetables as alternative crops. Deep tillage which is very important for the consolidation of the paddy field soil structure leads to the decrease of the soil pulverization and small clod rates, resulting in the increase in power requirement. In this study, implements based on a reverse-rotating tiller (up-cut rotary tiller) equipped with tines differing in length, were developed. The use of the implements enabled to perform deep tillage in the ridges and shallow tillage in the inter-ridge spaces. It became possible to cultivate soil and make ridges simultaneously. The working efficiency was 2-3 times higher than that by other methods. Also the trafficability of the implements in the inter-ridge spaces was improved. The developed implements did not require a large amount of power and did not lead to a decrease in the soil pulverization rate. The rooting zone of the ridges expanded and the soil water content inside the ridges decreased. Furthermore, the oxygen concentration in the ridge soil increased and cabbage yield increased.

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The role of gibberellins (GAs) in the control of growth and flowering in stock, Matthiola incana (L.) R. Br., and the possibility of their regulation by manipulation of GA biosynthesis were investigated. In M. incana, GAs were found to be necessary for stem elongation and flowering. GA₄ in the non-13-hydroxylation pathway of GA biosynthesis was the most active component for stem elongation and flowering. It was shown that GA biosynthesis inhibitors of acylcyclohexanedione type could promote stem elongation and flowering. These results indicate that the balance of activities among GA biosynthetic and catabolic enzymes is very important for stem elongation and flowering. Furthermore, development of responsiveness to active GAs for flowering may be one of the essential factors in the flower bud initiation process in M. incana. Based on the above results, we demonstrated that acceleration of the flowering time in summer-sown M. incana could be obtained by prohexadione-calcium (PCa) treatment under plastic-film greenhouse conditions.

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The concentrations of PO₄-P, NH₄-N and certain minerals (Mg, Ca, K, Cu, Zn) in effluents of bio-gas digesters were determined in 6 swine farms in Tan Phu Thanh and Hoa An villages in Can Tho Province, Vietnam, for the evaluation of water pollution from swine husbandry with the incorporation of a bio-gas digester into the farming system. Phosphate, NH₄-N, Mg and Ca occurred at high concentrations in the effluents. However, the phosphorus and nitrogen balance associated with the cycling of the components in the farming system was considered to be satisfactory, because the total volume of effluents was small compared to the area of the ponds and rivers where the effluents were discharged. It was demonstrated that sludge in a bio-gas digester contains high concentrations of P, Mg and Ca, which are considered to be effective fertilizers. Artificial crystallization reactions (MAP and HAP reactions) were examined for the effluents of the bio-gas digester with the pH adjusted by NaOH to confirm the possibility of removing and recovering PO₄-P, Mg and Ca from the effluent. Because of the high density of crystals, the components could be removed and recovered easily by sedimentation.

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In order to improve the water quality and shoreline aesthetics of eutrophic lakes in urban areas, we developed a technique for planting trees in the shallow waters along the shore. Our studies indicated that Taxodium seedlings directly planted in water less than 1 m deep and Salix spp. cuttings planted in perennial water in wetlands, grew well and could become revegetation agents. Floating planters of Taxodium and Salix spp. also grew well. The storage capacity of a 1 m high Salix gilgiana tree was 13.4 mg for N and 1.72 mg for P per day in the growing season. Total absorption of Zn by the tree form of T. distichum 3 months after planting was 9.3 mg/100 gdw (dry weight) and that of Cu was 2.3 mg/100 gdw. Moreover, the floating planters attracted fish and waterfowl.

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About 200 kinds of marine algae grow in the ocean surrounding Japan. Moreover, a large amount of marine algae is cultivated domestically for use as foods and industrial materials. The production of marine algae was 639,210 t, amounting to ￥164,642 million in 1998. The marine algae used as foods consist of about 50 species, and the production was about 172,000 t in 1996. Japanese have eaten marine algae as a source of supply of minerals and vitamins. However, the dietary intake of marine algae is about 1/5 compared with that of fish. Recently, it has been suggested that the increase in the incidence of adult diseases in Japan, such as diabetes, hypertension, hyperlipidemia, etc. was caused by the decrease in the dietary intake of fish, shellfish and marine algae. The nutritional role of marine algae was examined and it was recognized that marine algae contribute to the prevention and treatment of various diseases. We also analyzed the effect of Undaria pinnatifida (Wakame) on the decrease of the concentration of serum and liver triacylglycerol in rats.

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