Effects of temperature and defoliation (mechanical wounding of leaves) on flower bud induction after treatment with various chemicals in pineapple plants were investigated. Pineapple plants showed high percentage of flower bud induction at relatively low temperatures (20°C) for 3 hours from 7 to 10 hours after ethephon treatment even after transfer to high temperature conditions (32°C) . Flower bud induction was impeded by high temperature (32°C) for more than 10 hours and by defoliation within 10 hours after ethephon treatment. Defoliation of the leaves in the upper part of the plant impeded flower bud induction with ethephon treatment. Effects of fall of the leaves in the middle part of the plants on flower bud induction were more impediment than those of the fall of the leaves of lower part of the plants. Treatment with NAA induced flower bud induction. The strong effect of ethephon and NAA on flower bud induction in pineapple plants required two conditions as follows: the presence of healthy green leaves and a relatively low temperature (20°C) for 3 hours. It was considered that impediment of flower bud induction was directly affected by defoliation and indirectly by high temperature. It was found that the effect of chemical inducers on flower bud induction varied with the changes in the environmental conditions such as mechanical wounding of leaves due to heavy rain and wind by typhoon, and changes in the temperature.

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Four Oryza glaberrima lines were characterized with respect to the mechanism of physiological tolerance and morphological avoidance of submerged conditions compared to two O. sativa varieties. The two O. glaberrima lines (TOG 5810 and TOG 6283) were deep water ecotypes, and the other two (CG 14 and CG 20) were upland ecotypes. Under overhead flooding conditions, all the O. glaberrima lines showed a higher photosynthetic O₂ evolution rate and chlorophyll content than Normn 30, an O. sativa subspecies of japonica type, while IR36, an O. sativa subspecies of indica type, showed a photosynthetic rate and chlorophyll content almost as high as those of the O. glaberrima lines. Moreover, the O. glaberrima lines displayed higher elongation rates than the O. sativa varieties under submerged conditions. These findings indicated that O. glaberrima exhibited mechanisms of tolerance and avoidance of submergence, suggesting that O. glaberrima could be a genetic source for the breeding of deep water varieties. No clear difference was observed in the level of tolerance and avoidance of submergence between deep water and upland ecotypes of O. glaberrima.

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Several water yam strains have been introduced from areas at an elevation of 600m to areas at an elevation 1800m in Nepal. These strains were grown in Kagoshima, and their growth and enlargement of the tubers were investigated to evaluate their performance and earliness. All the tested strains were found to belong to early-maturing types. Furthermore, extremely early-maturing strains were detected in this group. In this type, the tubers began to enlarge and mature earlier than extremely early-maturing strains originating from Kagoshima, Japan. These strains were distributed in high-altitude areas, where the growth period is limited because of lower temperature. The difference in the maturity and, growth period appeared to be related to the altitude where the temperature is lower in the tropical and sub-tropical regions. Based on these results, the following conclusion was drawn; Late-maturing strains are characterized by long growth period and high yield, hence these strains are distributed in the lowlands of tropical regions. In contrast, early maturing strains exhibit a relatively short growth period and are consequently, distributed in high-altitude areas in the tropical and sub-tropical regions. It may thus be possible to cultivate extremely early-maturing strains with low sensitivity to day length in temperate regions. The growth pattern of the tubers in the extremely early-maturing strains of water yam was similar to that in the Naga-imo and Icyo-imo groups of Chinese yams (D.opposita) . These findings suggest that further experimental data should be collected to determine whether decreased day length is the main factor that triggers the enlargement of the tubers in the extremely early-maturing strains of water yams.

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We developed rice varieties during a collaborative rice breeding research project using a wide diversity of genetic resources from Yunnan, China, and Japan. In 1999, the new varieties developed during the project covered more than 200, 000 ha in Yunnan. To develop higher yielding and widely adaptable varieties, we analyzed statistically the genotype-environment (GE) interaction using multilocation yield test data in Yunnan. Uniform rice nursery data from 12 locations and two years were used as a basis for examining variety adaptability in Yunnan. Variance components for varieties × locations and varieties × locations × years indicated that the interaction of varieties with environments was very important in determining relative yields. Progress in the development of high-yielding and adaptable varieties was apparent in the comparison of Hexi 34 and Hexi 35 with a standard variety, Yunjing 9, and other improved Yunnan varieties. Some statistical methods were used to group the varieties based on the analysis of the GE interaction. The sum of squares (SS) of GE interaction was partitioned by linear regression into joint, genotypic, and environmental regression, stability variance analysis, and by additive main effects and the multiplicative interaction (AIVIMI) model into three significant principal component axes. The AMMI model was most effective in partitioning the interaction SS among the three methods. The AMMI analysis suggested the presence of certain close relationships between yield stability and some agronomic characteristics of rice varieties, such as early maturing habit, panicle density, and seed fertility.

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Since the late 1980's, soybean yields in Paraguay had steadily increased with the expansion of no-tillage fields. The average yield has been maintained at about 3t/ha for nearly 10 years. However, the increase of yield has shown a limitation and recently the yield has even tended to decrease. Although the causes of this phenomenon have not been elucidated yet, it is considered that long-term no-tillage practice adversely affects the soil conditions, resulting in an inhibition of soybean root development. The characteristics of the soybean root distribution in 11 fields depending on the differences in the duration of application of the no-tillage practice, differences in the crops preceding the cultivation of soybean and soil types were examined. In the majority of the no-tillage fields, more than 50% of the soybean tap roots did not elongate vertically in the deep soil profile, and lateral roots in surface soil grew vigorously near the soil surface, which resulted in a concentrated root distribution only in the uppermost soil layers. On the other hand, soybean tap roots in the year immediately after reclamation and in plowed fields showed a relatively deeper penetration with improved vertical root distribution. The occurrence of soybean plants whose tap roots did not penetrate into deep soil layers increased with the soil hardness and phosphorus accumulation in the uppermost layers. These results suggest that in the no-tillage fields the adverse soil conditions associated with the increase of soil hardness and phosphorus accumulation in the uppermost soil layers inhibited soybean root development in the deeper soil layers, and resulted in the recent decrease of soybean yields in Yguazu.

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Morphological differences in the floral organ and fruit were analyzed among white sapote cultivars which had been experimentally introduced into Japan to select suitable cultivars for pollination or commercial fruit production.
Floral morphology of forty-one 3-4 year-old cultivars of white sapote trees grown in a plastic house was examined using a dissecting and light microscope. All the flowers examined were structurally hermaphrodite and showed five petals and five stamens. The ovary lay on a round receptacle without a peduncle. Some cultivars had large yellow anthers containing many pollen grains while some cultivars had pale yellow small anthers without pollen.
Observation of the floral morphology of forty 7-8 year-old cultivars of white sapote grown in open fields using a dissecting microscope, showed that these cultivars could be divided into three groups; cultivars with large ovaries (and stigmas) and lacking pollen (Type I; twenty-four cultivars such as ‘Florida’, ‘McDill’), cultivars with small ovaries (and stigmas) and producing pollen in large anthers (Type II; fifteen cultivars such as ‘Suebells’, ‘Vernon’), and only one cultivar with a large ovary (and stigma) producting pollen in large anthers (Type III; ‘Maltby’) . Type III cultivar exhibited a floral morphology that had not been reported hitherto. No seasonal changes in the floral morphology were observed in any of the cultivars.
In Type I cultivars which produced more than 200g fruits, the seed weight and the number of fertile seeds were larger. These findings indicate that Type I cultivars are suitable for large fruit production and Type II or Type III cultivars could be used as pollinators.

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We tried to confirm the availability of salt wort (Salicornia herbacea L.) as a feedstuff in ruminants.
Salt wort seeds were sown in 28 plastic cases (85 × 55 × 20cm) containing sandy soil on May 8, 1997 and irrigated with 3.4 l of standard solution once every 2 weeks from May 8 to June 22. Standard solution containing 0.3% NaCI concentration was used for irrigation once a week from June 23 to August 13. After all the plant shoots were harvested on August 20 and washed with tap water, the shoots were dried for 5 days at 80°C, and then cut into fragments of about 10 cm long to prepare a mixed diet.
Three goats were used for the digestion trials divided into two consecutive experimental periods, during which the control (alfalfa hay-cubes only) period extended from October 20 to 29, and the treatment period (alfalfa hay-cubes / salt wort : 8/2 : w/w) from October 29 to November 7. Goats were given the diet at a rate of 2.5% D.M. of body weight per day. In the last 3 days of each period, all the excrements were collected and the digestibility of the diets was determined by the total collection method.
Goats could eat the mixed diet of alfalfa and salt wort without harmful effects on their health apparently. Apparent digestibility of crude fiber in the mixture was higher than alfalfa hay-cubes. However, the TDN value in both diets was almost the same, because of the lower digestibility of crude fat and crude protein in the mixture.

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The objective of this study was to identify the factors related to rice yield differences among the main rice-producing districts in Narathiwat Province, southern Thailand. In Narathiwat Province, about 70% of total rice is produced in three districts; Tak-bai, Bacho and Yi-ngo. Yield survey showed that Yi-ngo district recorded the highest average yield throughout three consecutive years (3.5 t⋅ha^-1), followed by the mountain area of the Bacho district (2.7 t⋅ ha^-1), alluvial area of the Bacho district (2.6 t⋅ha^-1), and Tak-bai district (2.2t⋅ ha^-1) . The yield differences among the districts were not significantly associated with the planting density or fertilizer application level, but were mainly due to the difference in rice varieties. When Colijor and Litmus, the main cultivars in Yi-ngo, were grown in Takbai, they produced a higher grain yield than the traditional varieties cultivated in Tak-bai. These findings suggested that if the highyielding varieties could be introduced to other districts in Narathiwat Province, the average yield in the districts would increase. The soil properties were another determinant of the yield differences among the districts. Though the yield differences were not associated with the soil nitrogen content and soil organic matter content, they were closely correlated with the soil texture. The soil in Yi-ngo contained more sand, compared with the soil in Tak-bai, which was considered to be conducive to a high drainage efficiency.

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To elucidate the physiological mechanism of inhibition of photosynthesis by salt stress in soybean (Glycine max (L.) Merr.), the photosynthetic activity, Na⁺ accumulation and ABA content of two soybean cultivars, Lee (salt-tolerant) and Enrei (salt-sensitive), were investigated. After 4 weeks of exposure to various NaCl concentrations, photosynthesis and growth in Enrei were more strongly inhibited by salt stress (50 mM NaCl) than in Lee. The evolution of oxygen was inhibited by salt stress only in Enrei. Therefore, the reduction of photosynthesis in Enrei can be partly explained by the increase in the involvement of non-stomatal components. Since the Na⁺ concentration in Enrei leaves was increased remarkably under 50 mM NaCI treatment, it was assumed that a high Na⁺ content might contribute to non-stomatal components. Lee may also be endowed with some mechanism (s) of prevention of Na⁺ accumulation in shoots, since Lee accumulated more Na⁺ in roots than Enrei. These results suggested that the difference in salt tolerance between these two soybean cultivars was due to the inhibition of photosynthesis by non-stomatal components caused by Na⁺ accumulation in shoots. On the other hand, the leaf ABA content in Lee increased significantly under salt stress, while that in Enrei showed only a slight increase. It is thus possible that ABA enhances salt tolerance in soybean.

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An investigation on the agricultural condition and international cooperative activities in West Africa was carried out by a survey team organized and dispatched by the Nippon Foundation from Aug. 26 to Sep. 9, 1998. Observation of agricultural crops was also carried out at three markets in Cote d'Ivoire to obtain information about the agricultural and food supply situation for the development of technical cooperation and to promote the study of agriculture. Among these agricultural crops, 49 species were identified, including 15 fruit vegetables, 10 fruits, 7 leaf and stem vegetables, 5 root vegetables, 5 tubers, 5 cereals and pulses and 4 crops for seasoning and oil. The identified crops belonged to 26 families; 7 species belonged to Solanaceae, 6 species to Leguminosae and Cucurbitaceae, respectively, 4 species to Gramineae, and 3 species to Liliaceae. Each species exhibited wide variations, especially fruit vegetables. On the other hand, some young children in rural areas suffer from malnutrition because of the ignorance of their parents about basic dietetics. The presence of various agricultural crops observed in three markets in this study will be essential to solve nutritional problems.

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