Development of novel clubroot resistant rapeseed lines (Brassica napus L.) effective against Japanese field isolates by marker assisted selection

Clubroot is an important disease infectible to cruciferous plants and a major threat to rapeseed production in Japan. However, no clubroot resistant rapeseed cultivars have been released. We surveyed pathotype variation of six isolates collected from rapeseed fields and found they were classified as pathotype groups 2 and 4 using Japanese F₁ Chinese cabbage cultivars. We produced the resynthesized clubroot resistant Brassica napus harboring two resistant loci, Crr1 and Crr2, by interspecific crossing and developed resistant rapeseed lines for southern and northern regions by marker-assisted selection and backcrossing. We improved the DNA marker for erucic acid content to remove linkage drag between Crr1 and high erucic acid content and successfully selected lines with clubroot resistance and zero erucic acid for northern regions. A novel line, ‘Tohoku No. 106’, suitable for southern regions showed stable resistance against all six isolates and high performance in infested fields. We conclude that Crr1 and Crr2 are important genes for CR rapeseed breeding and marker-assisted selection is effective in improving clubroot resistance.     

Aurantiochytrium sp. meal can replace fish oil in practical diets for the juvenile Pacific white shrimp

This study evaluated the use of microalgae (Aurantiochytrium sp.) meal as a substitute for fish oil in the diet of juvenile Pacific white shrimp (Litopenaeus vannamei) reared in a clear‐water system. Dietary treatments at five replacement levels (0%, 25%, 50%, 75%, 100%) were performed in triplicate. After 46 days, only a slight difference in shrimp final weight was observed among treatments (0.61 g). An increase in final weight was observed with replacement of up to 50% fish oil for microalgae meal, while the optimal percentage of replacement estimated was 44.7%. Feed conversion rate (FCR) of animals fed a diet of Aurantiochytrium sp.meal to replace up to 50% fish oil decreased, and the optimal percentage of replacement estimated was 49.3%. The fatty acids profile in shrimp muscle tissue demonstrated an increase in docosahexaenoic acid (DHA) from 10.03% to 14.28% with increased replacement of fish oil by microalgae meal in the diet. Therefore, the partial replacement of fish oil by microalgae meal resulted in improved shrimp growth and FCR, and total replacement of dietary fish oil had no negative effects on these parameters. In addition, inclusion of microalgae meal raises the level of DHA in shrimp muscle.     

基于声学摄像仪的溯河洄游幼香鱼计数

至今主要靠目视计数来掌握香鱼(Plecoglossus altivelis)的资源量,这种方法很耗劳动力且精度低.由华盛顿大学研发的声学摄像仪DIDSON(Dual-frequency IDentification SONar)可在浑浊不清的水中摄取接近光学视频画质的图像.其附带软件虽可对体长为几十厘米的大个体鱼计数,但对于体长6 cm以下的小个体鱼,由于其回波信号弱,计数显得非常困难.本文提供了一种基于DIDSON的溯河洄游幼香鱼计数的新方法.首先从声学图像中消除静止的背景,提取出运动目标并除去噪音像素,然后用卡尔曼滤波器对剩下的目标进行跟踪,根据目标移动的特性把目标分为香鱼和垃圾2大类,在除去向下游移动的垃圾之后,可正确地计算向上游移动香鱼的数量.通过现场实测验证了上述声学计数方法的实用性和高效性.     

Insecticidal activity of Sikimi extract and its modulation of the GABAA receptor channel

Sikimi plant (also known as Japanese star anise), Illicium anisatium, is toxic to mammals. Extracts of Sikimi were studied for their insecticidal activity against the larvae of mosquito, Culex quinquefasciatus, and for their mechanism of action on ion channels. Crude methanol extract and its ethyl acetate-soluble fractions were insecticidally active, with EC₅₀ values of 63·0 μg ml^-1 and 43·7 μg ml^-1, respectively. The ethyl acetate-soluble fraction was perfused through the bathing solution and the current induced by a brief (10 ms) application of GABA by pressure ejection through pipette electrode was recorded by the whole-cell patch clamp technique. The extract suppressed GABA-induced currents irreversibly with an EC₅₀ value of 0·42 μg ml^-1. The time constant of current fitted to the single exponential function was shortened by the ethyl acetate-soluble fraction at concentrations ranging from 0·1 μg ml^-1 to 10 μg ml^-1 in a concentration-dependent manner. It was concluded that Sikimi extracts decreased the affinity of GABA for its binding site on the GABA receptor, thereby suppressing GABA-induced currents. © 1998 SCI     

A time-series data analysis to examine effects of subsidies to fishery productions in Japan

A cointegration analysis is conducted to examine the effect of fishery subsidies on fisheries production using data compiled over more than 30 years in Japan. The results illustrate that one fishery production indicator (production value per fishermen) shows a positive relationship with one particular group of government financial transfer (GFT) (that is, government general service expenditures including cost for fishery managements, scientific researches, and other administrative activities). No other tested results between GFTs and fishery indicators showed a real relationship. Although further scrutiny is awaited, this study could provide an empirical basis for an argument that, under an effective fishing management system, fisheries subsidies do not necessarily cause production increases or negative impact on fishing stocks.     

Amorphous clay materials of towada ando soils

Towada Ando soils consisted of five soils—Towada-a (1,000 years old), Towada-b (2,000 years old), Chuseri (4,000 years old), Nanbu (8,600 years old), and Ninokura soils (10,000 years Amorphous clay materials of these soils taken at different localities were studied by the combined use of selective dissolution and differential infrared spectroscopy, X-ray analysis, electron microscopy, etc.

The main clay minerals of Towada-a soils, present-day soils, were montmorillonite-vermic-ulite chloritic intergrades and opaline silica, or these minerals and allophane in the humus horizons, and allophane in the non-humus ones. Towada-b soils overlain by the Towada-a soils showed the clay mineralogical constituents similar to those of Towada-a soils. However, allophane was one of the main clay minerals in all the humus horizons as well as non-humus ones. The main clay minerals of Chuseri soils were allophane and layer silicates consisting chiefly of chloritic intergrades and chlorite in the humus horizons, and allophane in the non-humus ones. Opaline silica was present in minor amounts in the humus horizons of Chuseri soils, but nearly absent in Nanbu and Ninokura soils.

There were remarkable differences in the clay mineralogical composition of Nanbu and Ninokura soils with differences of their environmental conditions. Allophane and imogolite Were dominant in the clay fractions of both humus and non-humus horizons of very shallowly buried Nanbu soil which was subjected to the strong leaching process. Allophane was the main clay mineral of deeply buried Nanbu and Ninokura soils which showed the absence of notable accumulation of bases and silica. On the contrary, halloysite with a small amount of siliceous amorphous material appeared in very deeply buried Nanbu and Ninokura soils where bases and silica were distinctly accumulated. The amounts of halloysite in the clay fractions were larger in the humus horizons than non-humus ones, and in Ninokura soil than Nanbu soil.

Soil age, soil organic matter, and depositional overburden of tephras were observed to be conspicuous among various factors relating to the weathering of amorphous clay materials in Towada Ando soils.     

Sites and processes of nutrient accumulation in the subsoil through water percolation from the plow layer in a submerged paddy soil microcosm

The leaching of nutrients from the plow layer by water percolation and their accumulation in the subsoil observed in a Japanese paddy field (Katoh et al. 2004: Soil Sci. Plant Nutr., 50, 721-729) were determined semi-quantitatively in a soil column experiment. Ca²⁺, Mg²⁺, K⁺, Mn²⁺, Fe²⁺, and phosphate in percolating water from the plow layer soil column were retained in the subsoil columns that were connected to the plow layer soil column. Fe²⁺, K⁺, and phosphate accumulated in the uppermost part of the subsoil. Accumulation of Fe²⁺ in the uppermost part of the subsoil was presmnably due to the cation exchange process with concomitant desorption of Ca²⁺. In contrast, Ca²⁺ and Mg²⁺ in percolating water from the plow layer soil colmnn accumulated once in the subsoil, and translocated downwards slowly with successive water percolation. Considerable amounts of inorganic carbon (IC) and dissolved organic carbon (DOC) in percolating water from the plow layer soil column were also retained in the subsoil columns. IC did not accumulate a gaseous form.     

A mucinous histochemical study on malignancy of aberrant crypt foci (ACF) in rat colon

The relationship between malignancy and number of crypts (crypt multiplicity) comprising aberrant crypt foci (ACF) was investigated, by studying changes in the mucous nature of ACF with 5 crypts or less, ACF with 6-13 crypts, adenomas and invasive adenocarcinomas induced by 1,2-dimethylhydrazine in distal colon of rats. A paradoxical Con A-staining was performed for goblet cell mucins. Of the sulfomucin-dominant ACF with 1-3 crypts, 82.6% had labile class III mucin, similar to the distal colon in the normal rats. However, in most of the goblet cell mucin produced by the ACF with 4-5 crypts with an indicated relation to colorectal carcinoma or the sialomucin (SiM) -dominant ACF with 1-3 crypts, mucin types other than class I were rarely present. The incidence of class I mucin decreased with the increase in crypt multiplicity of ACF or in the degree of histological malignancy, with the lowest incidence of 40% in adenocarcinomas. In contrast, the incidence of class II mucin increased markedly with the increase in crypt multiplicity of ACF or in the degree of histological malignancy, with the highest incidence in adenocarcinomas (95%). The ACF with 6-13 crypts had a mucous profile similar to that of adenomas. These results suggested that malignancy of ACF related to the crypt multiplicity. In the ACF with 1-3 crypts, SiM-dominant ACF had the potential to progress to malignant lesions.