Yuji Matsue

Countermeasures for heat damage in rice grain quality under climate change

Abstract Climate change has been an increasingly significant factor behind fluctuations in the yield and quality of rice (Oryza sativa L.), particularly regarding chalky (white-back, basal-white, and milky-white) grain, immature thin grain, and cracked grain. The development and use of heat-tolerant varieties is an effective way to reduce each type of grain damage based on the existence of each varietal difference. Cultivation methods that increase the available assimilate supply per grain, such as deep-flood irrigation, are effective for diminishing the occurrence of milky-white grains under high temperature and low solar radiation conditions. The application of sufficient nitrogen during the reproductive stage is important to reduce the occurrence of most heat damage with the exception of milky-white grain. In regard to developing measures for heat-induced poor palatability of cooked rice, a sensory parameter, the hardness/adhesion ratio may be useful as an indicator of palatability within a relatively wide air–temperature range during ripening. Methods for heat damage to rice can be classified as either avoidance or tolerance measures. The timing of the measures is further divided into preventive and prompt types. The use of heat-tolerant varieties and late transplanting are preventive measures, whereas the application of sufficient nitrogen as a top dressing and irrigation techniques during the reproductive stage are prompt types which may function to lower the canopy temperature by enhancing evapotranspiration. Trials combining the different types of techniques will contribute towards obtaining more efficient and steady countermeasures against heat damage under conditions of climate change.

The palatability and physicochemical properties of milled rice for each grain-thickness group

Abstract We examined the palatability and physicochemical properties of milled rice for each grain-thickness group, and examined the influence of physicochemical properties on the grain-thickness-dependent differences of the evaluation of palatability. The thicker the grain, the higher the palatability. However, the palatability of the grains thicker than 2.0 mm did not vary with the grain thickness. For the grains thinner than 2.0 mm, the thinner the grain, the lower the evaluated value of palatability, and the palatability values were very low in the grains thinner than 1.9 mm. The thinner the grain, the higher the protein content. On the contrary, the thinner the grain, the lower the amylose content. The maximum viscosity and breakdown values in angiographic characteristics decreased with decreasing grain thickness. Hardness/adhesion (H/-H) ratio in textural characteristics tended to increase with decreasing grain thickness. The palatability of the cooked rice grains in each grain-thickness group showed a negative correlation with the protein content and H/-H ratio, and strong positive correlation with the amylose content and maximum viscosity. These results indicate that the lowering of palatability with decreasing grain thickness is due to the increase in protein content, the decrease in amylose content, and the decrease in amylographic and textural characteristics. The standard partial regression coefficients against palatability were the highest for the maximum viscosity in Koshihikari, for H/-H ratio in Nipponbare and for protein content in Hinohikari. Thus, in rice cultivated under a certain cultivation condition, physicochemical factors involved in the grain-thickness-dependent difference of palatability are suggested to vary with the cultivar.

Validation of QTLs for Eating Quality of Japonica Rice 'Koshihikari' Using Backcross Inbred Lines

Abstract Using backcross inbred lines (BILs) derived from a cross between temperate japonica rice cultivars, Moritawase and Koshihikari, we validated the major quantitative trait loci (QTL) for eating quality and textural characteristics on chromosomes (Chr) 1, 2, 3, 6, 7, 10, and 12. Significant genetic differences in eating quality among BILs were detected at the QTL on Chr 3 and corresponded to the differences between the parents. Although differences in eating quality on the other chromosomes were not significant by t-test, cluster analysis and principal component analysis clearly showed that the genetic effects of the QTLs on Chr 6, 7, and 10 were similar to that on Chr 3, but the genetic effects of QTLs on Chr 1, 2, and 12 were entirely different from that on Chr 3. We previously identified that textural characteristics were highly correlated with eating quality. In this study, genetic differences in textural characteristics were similar to the genetic differences in eating quality among BILs. These results reveal major QTLs for eating quality of Koshihikari on Chr 3, 6, 7, and 10. The QTL on Chr 3 contributed most to the improvement of eating quality and textural characteristics.

Comparison of physicochemical properties of the grains between old- and new-types of rice cultivars in Japan.

Abstract The physicochemical properties of the grains of 16 old- and 21 new-type rice cultivars in Japan were investigated in 1995 and 1996. Among the old- and new-type cultivars, we found a similar pattern of varietal differences in physicochemical properties in both years, and in both the fields with and without nitrogen fertilizer applied. Between the two types, no significant differences in the mean protein and amylose contents in the rice grain were observed. The old-type rice cultivars tended to be lower in mean maximum viscosity and breakdown values than the new- type cultivars, although the difference was not significant. Cooked rice of the old-type cultivars tended to be higher in mean hardness/adhesion ratio (H/-H) and hardness/adhesiveness ratio (H/A3) than that of the new -type cultivars. The physicochemical properties which showed superior values in the standard partial regression coefficients against the taste of cooked rice were the protein content, breakdown value and H/-H. These, physico-chemical properties can be efficient indicators for evaluating the taste of cooked rice. The coefficient of parentage of each cultivar to cultivar Koshihikari showed tight negative correlations with amylose content, H/-H and H/A3, and tight positive correlations with maximum viscosity and breakdown values. The coefficients showed a loose positive correlation with protein content. However, Sasanishiki, Domannaka, Chiyonishiki, Nakate shinsenbon and Rikuu 132 were superior in their physicochemical indicators, in spite of their small coefficients of parentage to Koshihikari. This suggests that a highly palatable cultivar that is widely different from Koshihikari can be developed by utilizing genetic resources with superior physicochemical indicators.

Close association between aleurone traits and lipid contents of rice grains observed in widely different genetic resources of Oryza sativa.

Abstract We investigated 321 varieties to identify the aleurone traits that are closely related to the lipid content of rice. Brown rice seeds were cut crosswise near the center with a razor blade and the cut surface was stained with Oil Red O, and then observed under integrated fluorescence microscope (BZ9000). We found wide variations among varieties in the area stained, but the japonica group contained many varieties with a large stained area. We selected 17 representative varieties covering the whole range of stained areas and confirmed the thickness of aleurone layer using Kawamoto’s film method (micro-thin sections that were created with cryomicrotome). Aleurone traits were examined under a light microscope and measured. We found a strong correlation between the area of the aleurone layer and the stained area (r = 0.799***) and between the thickness of the aleurone layer and the thickness of the stained region (r = 0.543*). The area of the stained region therefore provides a fast and effective indicator for selecting varieties for the thickness of the aleurone layer. We also measured the amount (mg per 100 seeds) and proportion of triacylglycerols (TAGs) to 1 g of seed (mg g-1) in brown rice seeds without embryos. The amount and proportion of TAG to 1 g of seed were both significantly correlated with the area, average thickness and percentage of aleurone layer. This suggests that the aleurone traits will be good indicators for the selection of varieties with high levels of TAG.

Productivity of the Soybean Seeds Stored for Various Periods

Abstract The growth characters and productivity of the soybean plants that developed from seeds stored for various periods at 5°C and 40% relative humidity, but having 80% or higher germinability were examined in comparison with those of newly harvested seeds (new seeds). The seedlings at one month after sowing from the very old seeds (stored for 10 years and 7 months) showed morphological characters significantly different from those from the new seeds, but not those from the moderately old seeds (stored for 2 years and 7 months) or the old seeds (stored for 7 years and 7 months). In the plants from the old seeds, the mean emergence date, flowering date, maturing date, length of the main stem, yield components, seed yield, and inspection-grade or protein content of seed were not significantly different from those in the plants from the new seeds. On the other hand, in the plants from the very old seeds, the mean emergence date, length of main stem, yield components and seed yield were significantly different from those in the plants from the new seeds. We concluded that the seeds of soybean stored for 2 years and 7 months, or 7 years and 7 months having a germinability of higher than 80% are practically useful, and show normal growth characters and productivity. However, it should be noted that the seed storage for over 10 years had inferior grain yield.

An Efficient Method for Evaluating the Palatability Deterioration During Storage in Rice

Abstract 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.

Confirmation of the Productivity of the Stored Seeds of Wheat and Two-Rowed Barley

Summary To confirm the excellence in productivity of the stored seeds of wheat and two-rowed barley, we examined the growth characters and productivity of the plants developed from the seeds stored at 5°C and 40% relative humidity for various periods but showed a 80% or higher germination percentage, in comparison with those of newly harvested seeds (new seeds). The cultivars of stored seeds were identified by the random amplified polymorphic DNA (RAPD) method. There were no differences in the morphological characters of the seedlings 3 months after emergence between the new seeds and the old seeds (stored for 2 years and 5 months) or the very old seeds (stored for 10 years and 5 months or 16 years and 5 months). On the other hand, there was a positive correlation between the top dry weight at 3 months after emergence and 1,000-grain weight of the seed. In the plants from the old seeds, no significant differences from those from new seeds were observed either in the mean heading date, maturing date, culm lengths, ear length, yield components, grain yield or inspection-grade. On the other hand, in the plants from the very old seeds, the mean heading date, maturing date, culm lengths, yield components and grain yield were significantly different from those in the new seeds in some cultivars. The results of RAPD analysis showed that the band pattern of the very old seeds was the same as that of the new seed in each cultivar. We concluded that the seeds of wheat and two-rowed barley stored for 2 years and 5 months with a germination percentage of higher than 80% are practically useful, showing normal growth characters and productivity. However, it should be noted that some cultivars had inferior grain yield after the seed storage for over 10 years.

Selection Effectiveness of Lodging Tolerance by using Pushing Resistance for Improving Rice Cultivar adapted to Direct Sowing Culture in Flooded Paddy Fields

This study was undertaken to find the selection effectiveness of lodging tolerance by using pushing resistance for improving rice cultivar adapted to direct sowing culture in flooded paddy fields. The lines used in the experiment ware F4 and F5 breeding lines of Aoinokaze // Lemont / Hinohikari; 47 lines and Yumehikari // Lemont / Hinohikari; 29 lines that ware medium maturity lines. There was a significant negative correlation between the pushing resistance of F4 lines in transplanting culture and lodging degree of F5 lines in direct sowing culture. Even though the selection rate of pushing resistance in F4 was changing from 10% to 40%, thre was a distinct difference in lodging degree under direct sowing culture in F5. A few F5 lines selected by using pushing resistance in transplanting culture ware superior in lodging tolerance and yielding ability under direct sowing culture. There ware comparatively few deviations of yielding ability and grain quality by using pushing resistance for the selection of lodging tolerance in an early generation. These results lead to the conclusion that it is possible to breed high lodging tolerance cultivar adapted to direct sowing culture by using pushing resistance under transplanting culture in an early generation.