This study was conducted to establish an efficient selection method for breeding highly palatable rice cultivars with less deterioration in palatability during storage. The palatability of the rice stored at room temperature for one yr (old rice) negatively and significantly correlated with the content of free fatty acids in the polished rice and the hardness/adhesion ratio (H/-H ratio) of the cooked rice. Thus, we examined the correlation coefficients of the content of free fatty acids and the H/-H ratio for the old rice and rice stored in a stability-testing chamber (STC) kept at 40°C and relative humidity of 95% for various periods (10, 20, 30 and 60 d). The highest correlation coefficient was observed between the values in the old rice and those in the rice stored in the STC for 30 d. The palatability of the old rice did not correlate with the content of free fatty acids after a 30-d stored in the STC, but negatively and significantly correlated with the H/-H ratio after a 30 d stored in the STC. These results show that we can efficiently evaluate the palatability deterioration during storage in rice by measuring the H/-H ratio of the cooked rice after the stored in the STC for 30 d. The content of the free fatty acids is an effective indicator of palatability deterioration in the old rice, but that in the rice stored in the STC for 30 d is not.

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Most of the supernodulating soybean lines were agronomically inferior to conventional genotypes. Our previous tests with ‘En6500’, a supernodulating mutant derived from a variety ‘Enrei’, revealed that its low growth and yield were not necessarily due to supernodulation. In our attempts to improve the yield of En6500 through crossing with Enrei, we recently succeeded in selecting a supernodulating line showing vigorous growth. Field experiments with this new supernodulating line ‘En-b0-1-2’ for three years revealed that it yielded much more than En6500. When the overall yield level was low, it even tended to yield more than Enrei. En-b0-1-2 thus showed a remarkably higher productivity than other supernodulating lines reported so far. Its improved yield was largely due to : (a) better seed filling, (b) vigorous vegetative growth during flowering period, and (c) high leaf area index and leaf N content that enabled production of more photosynthates to enhance N fixation and dry matter accumulation during the period of pod and seed development.

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In order to identify the key factors that arrest yield improvement in rice, we observed fifteen divergent cultivars in a field at Kyoto, Japan in 1995 and 2001 under various nitrogen (N) regimes. The contribution that sink size (spikelet number×single fully ripened grain mass), source size (total available carbohydrate), and source components, non-structural carbohydrate (pre-reserved) at full heading (NSC_h) and dry matter production during grain filling (DMP) had to the variation in yield among cultivars was examined. The dry weight of rough brown rice (Y) ranged from 310 to 743 g m^-2 throughout two years and under all N regimes examined. Although Y correlated with both sink and ource sizes, it tended to correlate more closely with source size than with sink size. In many cultivars, source size was smaller than sink size at all conditions examined except for the low nitrogen regime. The contribution of source components to Y was analyzed with the equation : Y=C_n NSC_h+C_d DMP, where C_n and C_d are coefficients of NSC utilization and of DMP utilization for grain filling. Y correlated with DMP more closely than with NSC_h. ΔNSC (NSC_h - NSC_m), where NSC_m is NSC at maturity and “C_n” vaguely correlated with the difference between sink size and DMP, showing that NSC is used to ompensate for the shortage of DMP to fill grains. At the same time, there were cultivar differences in NSC_h and “C_n”. The highest yielding cultivar Takanari always had the greatest DMP, relatively high NSC_h and stably high values of “C_n”. In conclusion, yield variation among rice cultivars correlated with source size more closely than with sink size, and DMP rather than NSC_h primarily contributed to Y. While NSC_h tended to be utilized complementarily to DMP, the contribution of NSC_h seemed to depend on the ability of rice cultivars to utilize NSC.

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Screening of crop varieties tolerant to a low oxygen environment caused by heavy rain has become an important work in monsoon Asia countries in recent years. We examined the growth of sesame (Sesamum indicum L.) germinated for 5 d in air with 0.05 O₂ m³ m^-3 (low oxygen concentration, LO), in comparison with those germinated in air containing 0.20 O₂ m³ m^-3 (ambient oxygen concentration, AO). The growth of sesame was not suppressed but rather accelerated by LO. Immediately after the exposure to LO, seedlings had a 2 fold larger number of secondary roots, and more than 13.0% and 7.4% heavier in leaves and roots, respectively, over those under AO. After the oxygen treatments were over, the seedlings were immediately transferred to normal conditions to grow. One month later, the seedlings exposed to LO accelerated about two-fold dry matter (DM) over those under AO. In spite of lower content of chlorophyll, the leaf area ratio (LAR) and the net assimilation rate (NAR) of the plants exposed to LO were higher than those under AO. Compared to plants under AO, the ultimate leaf size of the cotyledon, the 1st leaf and the 2nd leaf of plants exposed to LO were 20.0, 22.9, and 27.0% greater, respectively. In comparison with pea (Pisum sativum L.), sesame respired in a different way. The total biomass yield and grain yield of plants exposed to LO were higher by 8.3% and 11.6% respectively than those under AO. These observations revealed that the hypoxic stress induced some different metabolic processes in the earlier growth stage of the plant and obviously had an advantageous effect on the subsequent growth of the plant.

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The cytological and biochemical effects of APM on the mitotic cells of root meristems of Triticum durum were studied by exposure to concentrations of 2 μM to 10 μM for 16 h. The results showed that multipolar spindle cells, chromosome-condensation, bridge-fragments and micronuclei were induced in the cells of rootmeristems by treatment with 4 μM APM. Five protein species which have a molecular weight and pI of 40 KD/pI 5.5, 40 KD/pI 5.6, 48 KD/pI 7.0, 88 KD/pI 6.4, 120 KD/pI 6.6 were lost and 12 new protein species which have a molecular weight and pI of 16 KD/pI 6.2, 18 KD/pI 6.7, 19 KD/pI 7.0, 20 KD/pI 6.5, 22 KD/pI 7.0, 23 KD/pI 6.7, 24 KD/pI 4.7, 24 KD/pI 5.8, 26 KD/pI 5.8, 88 KD/pI 6.6, 86 KD/pI 6.7, 95 KD/pI 6.5 were induced by 10 μM APM in the root meristems.

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A field experiment was conducted at the experimental farm of Khon Kaen University in 2001. The objectives of this study were to investigate growth, yield and yield components of corn, peanut, soybean and mungbean under intercropping and single cropping, as well as to assess the land use efficiency. Yield and yield components of corn was unaffected by intercropping system. In legume crops; peanut, soybean and mungbean, intercropping systems reduced the leaf area and top dry weight per plant as compared with single cropping. Grain yield of peanut, soybean and mungbean was reduced by 28%, 39% and 51%, respectively, as compared with single cropping. The pod number per plant was the most affected by intercropping among the yield components. However, corn-legume intercropping increased land use efficiency by 48% to 66% depending on legume species. Corn-peanut intercropping gave the highest land use efficiency. The effects of light penetration and nutrient competition are discussed.

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Mini-watersheds called Nong in Thai are geographical components of rainfed lowland rice culture in Northeast Thailand, and constitute distinct units in understanding environmental constraints for low and unstable rainfed rice production there. The toposequential variation of soil fertility and its relation to rice productivity within mini-watersheds, was examined by phytometry of sampled soils and field measurements of rice growth and yield. The phytometry experiment with irrigated potted rice using soils sampled from various rice fields within each mini-watershed, revealed that soil fertility as evaluated by rice dry matter production showed a 5 times difference among the fields at most. The difference in the soil fertility was ascribed primarily to that in nitrogen (N) supply capacity, which itself had a strong correlation with soil organic carbon (SOC) content. Accordingly, the biomass production of pot-grown rice was proportional to SOC content, which suggested the usefulness of SOC as an index for soil fertility evaluation. The effect of clay on the soil fertility was much less than that of SOC. The actual rice yield in each field also showed quite large field-to-field variation, most of which was explained by the SOC content, rice growth duration and fertilizer application rate even though water availability also affected the yield. The yield positively correlated with growth duration and hence with earlier transplanting. Both SOC and clay contents of fields showed steep gradients with ascending field elevation within mini-watersheds, resulting in a marked toposequential distribution of rice yield. The toposequential distributions of SOC and clay contents imply that rice culture after deforestation accelerated soil erosion from upper to lower fields. The large toposequential gradient in soil fertility requires different resource and crop management for each toposequential position, in order to improve rice productivity of the mini-watershed as a whole.

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