Breeding of alfalfa (Medicago sativa L.) for resistance to sclerotinia crown and stem rot (SCR, causal agent: Sclerotinia trifoliorum Eriks.), which is a serious disease in Japan, was initiated in 1983. Increase of resistance to this disease has been examined following repeated selection of surviving plants from artificially inoculated field plots to the 9th generation. The strains selected for SCR resistance showed a higher resistance than Natsuwakaba and Tachiwakaba which were used as breeding materials and control cultivars. The effectiveness of selection based on the survival rate of the progenies increased gradually as generations in which the recurrent selection was performed advanced. Realized heritability was low in the 1st and 2nd generations in which selection was performed but was high in the 3rd to 9th generations. It is considered that the selection effect on the SCR resistance was enhanced in the subsequent generations. The results of these studies may indicate that recurrent selection is effective for the accumulation of resistance genes with minor polygenic effect, especially in the case of breeding work for the improvement of characters, which had been considered almost impossible by short-term selection trials.

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An artificial screening technique based on lethal temperature for 50% kill of plants (LT₅₀) was developed to evaluate the freezing hardiness in ltalian ryegrass (Lolium multiflorum Lam.) breeding programs. This technique was found to be suitable for evaluating the changes in freezing hardiness in natural and artificial environments, and the freezing hardiness of ltalian ryegrass was enhanced through this screening method. To elucidate the mechanisms of freezing hardiness, it was found that the N-terminal amino acid sequence of a protein induced by hardening was similar to the partial amino acid sequence of the abscisic acid (ABA)-inducible protein of alfalfa. ABA thus appeared to be involved in the induction of freezing hardiness in the hardening process. An artificial screening technique based on rooting on the flooded soil surface was also developed to evaluate the wet tolerance. The enhancement of the wet tolerance was achieved through selection using this artificial screening technique. To elucidate the mechanisms of wet tolerance, it was shown that aerenchyma formation in roots under flooding conditions was closely associated with the wet tolerance. lncrease in the number of roots with the development of the aerenchyma thus appeared to enhance the wet tolerance. Analysis of the alcohol dehydrogenase (ADH) isozyme and protein synthesis patterns indicated that anaerobic metabolism was possibly induced in roots under flooding conditions.

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Turpan is an oasis in the arid land of Northwest China. It is generally considered that agriculture would be impossible in arid lands without the oases, which contribute to the improvement of the meteorological conditions. To identify the characteristics of the velocity and direction of the wind in Turpan, and the effect of tree windbreaks on the improvement of the meteorological conditions in this oasis, investigations were carried out from August 27 to September 12, 1997. The prevailing directions of wind with a velocity of more than 5 m/s were W and WSW. The stronger wind in Turpan was attributed to an inflow of cold air mass after the passage of a depression. The effect on the improvement of the meteorological conditions varied considerably depending on the arrangement of the tree windbreaks. In an area of the oasis with strong windbreaks 1 km distant from the desert, where trees were arranged at intervals of more than 10 trees /10 m and the tree height exceeded 10 m, the air temperature decreased by about 5°C and the relative humidity increased by 14% compared with the outside desert. Air temperature and relative humidity were constant in any area of the oasis 1 km apart from the desert. In another oasis area with weak windbreaks, in which trees were arranged at intervals of less than 10 trees /10 m and the tree height was less than 10 m, the effect of the windbreaks on the improvement of the meteorological conditions was negligible.

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Bitter gourd, Momordica charantia, was less palatable to 2 species of armyworms, Spodoptera litura and Pseudaletia separata, than 2 other cucurbitaceous plants. A methanol extract of M. charantia leaves inhibited feeding of the armyworm larvae. The 2 most active fractions obtained by silicagel chromatography were purified by HPLC. Momordicine II, triterpene mono-glucoside, was identified as an antifeedant compound from the most active of these fractions. The second active fraction led to the isolation of a new triterpene di-glucoside. Fresh leaves of M. charantia contained ca. 0.3% of momordicine II. Momordicine II showed a significant antifeedant effect on P. separata at the concentrations of 0.02, 0.1 and 0.5% in artificial diets. Momordicine II caused a significant feeding reduction in S. litura only at the highest concentration (0.5%) tested. The difference in the feeding response of the 2 armyworms to momordicine II may be related to the diversity in their host range. The author also examined whether stress applied to plant exerted an effect on insect′s feeding preference. M. charantia is the host plant for the larvae of the pyralid moth, Diaphania indica but not for those of P. separata. Feeding response to UV-irradiated M. charantia leaves was compared between these 2 insects. D. indica preferred intact leaves, while P. separata preferred UV-irradiated leaves. These differences might be caused by the difference in the contents of antifeedants and feeding stimulants in the intact and UV-irradiated leaves.

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Bionomics of some predators attacking aphids and spider mites of vegetables was investigated in Paraguay. Ladybirds, Eriopis connexa, Coleomegilla maculata, C. quadrifasciata, and Olla v-nigrum, were successfully reared on a drone honeybee powder diet. Total development time was 18.9 days in E. connexa, 21.2 days in C. maculata, 20.0 days in C. quadrifasciata, and 18.9 days in O. v-nigrum at 25°C when they fed on the drone powder diet. Mean adult body weight of each species was 11.7 mg in E. connexa, 18.9 mg in C. maculata, 24.4 mg in C. quadrifasciata, and 16.2 mg in O. v-nigrum. Adult of E. connexa consumed 31.0 Aphis gossypii individuals or 22.1 Lipaphis erysimi individuals per day at 25°C, while C. maculata consumed 34.5 A. gossypii individuals or 6.6 L. erysimi individuals per day. Predatory mites, Phytoseiulus macropilis, P. fragariae, and Amblyseius idaeus were collected in strawberry fields in Caacupé and Itá. The development time was 5.0 days in P. macropilis and 7.0 days in A. idaeus at 25°C. Female of P. macropilis consumed 27.0 eggs of Tetranychus urticae per day and deposited 3.1 eggs, while A. idaeus consumed 18.0 eggs of T. urticae per day and deposited 3.2 eggs at 25°C.

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It is important to accurately evaluate storm runoff loading for preserving the water quality of stagnant water bodies. In this study, we analyzed the effects of hydrological factors on the estimation of storm runoff loading using hourly observed data (rainfall, river flow and water quality) at 2 points located in the center of the Yahagi River basin, and applied simple regression models to estimate the loading. Firstly, we observed close relationships among rainfall, river flow, water quality and loading. Secondly, by evaluating the differences between estimated and observed loading rates during the rainy season, we proposed conditions for upgrading the accuracy of loading estimation. Thirdly, we analyzed the factors that affect storm runoff loading from hydrological aspects, and identified relationships between the cumulative loading residual and factors such as preceding dry weather period. Finally, some conditions for the estimation of storm runoff loading are outlined, which include improving the application of the regression models to estimate the loading.

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Miso (soybean paste), shoyu (soy sauce), sake (rice wine) and katsuo-bushi (dried bonito), which are traditional Japanese fermented foods, have been consumed for a long period of time and are considered to be the safest foods. However, fermented foods may be contaminated with mycotoxins. Fungi used for the fermentation of miso, shoyu, and sake consist of Aspergillus oryzae and A. sojae. Although A. oryzae and A. sojae belong to the A. flavus group, which is known to produce aflatoxins, none of the strains examined actually produced aflatoxins. Aflatoxin contamination of rice, miso, shoyu, sake and katsuo-bushi could not be detected. Aflatoxigenic fungi do not occur in areas with a mean temperature below 16°C. Since the mean temperature in most areas of Japan is lower than 16°C, it appears that food contamination with aflatoxigenic strains does not occur in most parts of Japan. Some koji molds are known to produce kojic acid (KA) and cyclopiazonic acid (CA). Production of KA and CA was examined and the producing strains were eliminated from the commercial fermented foods. The fate of KA and CA in shoyu fermentation was also examined and it became clear that the contents of KA and CA decreased during shoyu fermentation. Contamination of katsuo-bushi with aflatoxins, sterigmatocystin and ochratoxin A could not be detected. As mentioned previously, mycotoxin contamination, which is presently very low, should be completely eliminated in future.

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A deep-sea video monitoring system on a towed sledge (DVMSTS) was developed to estimate the population density of the snow crab Chionoecetes opilio. Population density of the snow crab was investigated using the DVMSTS in a practical survey. The observations were carried out at 7 survey sites ranging from 200 to 340 m in depth on August 20-29, in 1998. These sites were located off both northern and western Oki Islands in the Sea of Japan. The observations were repeated 8 times and video tapes were recorded for 375 min in total. The observed distances were 15,600 m in total, and the towed DVMSTS was able to sweep the sea bottom over an area of 25,900 m². Sweeping area was obtained by multiplying the observed distance by the width of the DVMSTS (1.66 m). A count of 104 crabs was recorded. Crab densities per 1,000 m² for each observation were estimated to be 1, 3, 3, 3.1, 4.0, 5.6, 6.4 and 10 individuals, respectively. Sex of small crabs less than about 9 cm in carapace width could not be defined from the recorded video images. Because the majority of the crabs did not respond to the light, it was assumed that underwater light hardly affected the crab behavior. The method to estimate the population density of the snow crab using the DVMSTS can be effective, especially for a quantitative survey of the stock abundance of the snow crab.

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