Hideki Sasahara

Quantitative trait loci analysis of blast resistance in Oryza sativa L. ‘Hokuriku 193’

To investigate the genetic background responsible for blast resistance in Oryza sativa L. ‘Hokuriku 193’, QTL analysis was conducted using the F3 lines from the cross [ms-bo] Nekken 2 × Hokuriku 193 that were artificially infected with rice blast fungus (Magnaporthe grisea). QTLs were detected on chromosomes 1, 4, 6 and 12 that correlated with greater blast resistance in the Hokuriku 193-type lines. Notably, the QTL on chromosome 12 had a major effect and localized to the same region where Pi20(t), a broad-spectrum blast resistance gene, is positioned, suggesting strongly that the blast resistance of Hokuriku 193 was controlled by Pi20(t). Also, QTL analysis of the lines found to have no Pi20(t) detected two QTLs on chromosome 4 (qBR4-1 and qBR4-2) and one QTL on chromosome 6 (qBR6), of which qBR4-2 and qBR6 correlated with higher percentages of resistant plants in the Hokuriku 193-type lines. The blast susceptibility of BR_NIL (a NIL of Hokuriku 193 from which Pi20(t) was eliminated) was greater than that of Hokuriku 193, suggesting that elimination of Pi20(t) may markedly increase blast susceptibility. The disease severity of BR_NIL was mild, which might be the effect of qBR4-2 and/or qBR6.

The Effect of High-Temperature Stress Applied to the Root on Grain Quality of Rice

Abstract We verified the effect of high-temperature stress applied to the root on the occurrence of white immature kernels (WIKs) in order to breed rice (Oryza sativa L.) cultivars tolerant to the high temperature during the ripening period. The plants were grown in control and warmed pools after the heading date. The WIK percentages in the warmed pool were higher than those in the control pool. This suggests that high-temperature stress applied to the root increases the occurrence of WIKs. On the other hand, the WIK percentages correlated positively and significantly with the 1000 kernel weight and kernel width, suggesting that rice cultivars with high-temperature tolerance might have a smaller and/or thinner grain.

Anthocyanin and proanthocyanidin contents, antioxidant activity, and in situ degradability of black and red rice grains

Objective An experiment was conducted to assess the antioxidant contents and activities of colored rice grains and to evaluate their nutritive characteristics in terms of chemical composition and in situ ruminal degradation. Methods Ten cultivars of colored rice grains (Oryza sativa L.) collected from several areas of Japan were studied, and control rice without pigment, maize, barley, and wheat grains were used as control grains. Their chemical compositions, pigment, polyphenol contents, total antioxidant capacity (TAC), and degradation characteristics were determined. Results The starch contents of the colored rice grains were in the range of 73.5% to 79.6%, similar to that of the control rice grain. The black and red rice grains contained anthocyanin (maximum: 5,045.6 μg/g) and proanthocyanidin (maximum: 3,060.6 μg/g) at high concentrations as their principal pigments, respectively. There were significantly (p<0.05) positive relationships among the pigment contents, polyphenol content, and TAC values in the colored and control rice grains, indicating that the increase in pigment contents also contributed to the increased polyphenol content and TAC values in the colored rice grains. The dry matter and starch degradation characteristics, as represented by c (fractional degradation rate of slowly degradable fraction) and by the effective degradability, of the colored rice grains and the control rice grain were ranked as follows among commonly used grains: wheat>barley ≥rice>maize. The colored rice grains also included the most-digestible starch, since their potential degradable fraction and actual degradability at 48 h incubation were almost 100%. Conclusion Colored rice grains have high potential to be used as antioxidant sources in addition to starch sources in ruminants.

Improvement of seed shattering and dormancy in Oryza sativa L. ‘Hokuriku 193’ based on genetic information

In this study, we investigated the genetic basis of seed shattering and dormancy in Hokuriku 193 and bred an NIL improved these traits. Analysis of an F3 population from Hokuriku 193 × Koshihikari revealed a general correspondence between seed shattering and genotypes at the qSH1 locus, suggesting a strong influence of this locus on the seed shattering in Hokuriku 193. An F2 population from [ms-bo] Nekken 2 × Hokuriku 193 was also analyzed to identify quantitative trait loci (QTLs) for seed dormancy as measured by germination rate in the first December and March after seed harvest. The results revealed a concurrence QTLs of on chromosomes 1, 3, and 6 (qSDo1, qSDo3, qSDo6). In particular, qSDo1 and qSDo6 were considered regions worthy of active modification because they were QTL regions that promoted seed dormancy when carrying Hokuriku 193 genome regions around. SSDo_NIL, a near isogenic line (NIL) derived from Hokuriku 193 by introgressing Nekken 2 alleles only at the qSH1 locus and qSDo1, did not shatter, and its germination rate was significantly higher than that of Hokuriku 193. Yield performance was similar between SSDo_NIL and Hokuriku 193, suggesting that improvement of seed shattering and dormancy does not affect yield.

Quantitative trait loci analysis of grain appearance in Oryza sativa L. 'Emi-no-kizuna'

A quantitative trait locus (QTL) analysis was conducted on grain appearance in Emi-no-kizuna, a rice cultivar that has superior and stable appearance of the brown rice grain and high tolerance to high temperature stress, by using F3 lines derived from Emi-no-kizuna and Tomohonami. The investigation was performed 2013 and 2015. In summer 2013 the air temperature was higher and the larger differences in grain appearance were observed. In the QTL analysis, a highly contributing locus, qGA8, was detected at the end of the short arm of chromosome 8. Because trends of reduced the occurrence of white immature kernel and increased the percentage of perfect grain were observed in Emi-no-kizuna genotype in both years, qGA8 is likely to be an important QTL that is dominant in the superior grain appearance of Emi-no-kizuna. Also, qGA8 was linked to a QTL associated with days to heading. Another QTL, qGA7, associated with grain appearance was detected on chromosome 7 in 2013. Because no negative correlation was found between the genotype of qGA8 and thousand grain weight, it should be possible to breed cultivars that possess Emi-no-kizuna genotype qGA8 without a decrease in thousand grain weight.

A new rice variety “Nagomi-Risotto” suitable for Italian rice dish Risotto with extra-large grain

米穀安定供給確保支援機構の調査(2017)によると, 精米消費量の約 3割が家庭外,すなわち外食・中食で消 費されている.特に外食では,白飯以外の様々な料理で 提供される場合も多く,実需者からは,それぞれの料理 に合わせた業務用米への要望が高まっている.従来,業 務用米は食味の異なる複数品種のブレンド等で様々な用 途に対応していたが,主食用品種の食味の画一化が進ん だこともあり,最近は料理に合わせた品種が育成されて いる.例えば,表面の粘りは少なく硬いが,米飯全体は 柔らかく,日本人の嗜好に合ったカレー向き品種の「華 麗舞」(重宗ら 2011),粘りが少なく寿司に向く「笑みの 絆」(笹原 2012),「東北 194号(愛称「ささ結」など)」 (永野ら 2017)など,日本の米料理に適した品種が育成 されている. イタリアの米料理であるリゾットは,カレー,寿司の ように国内で日常的に食されるものではないが,イタリ ア料理の普及に伴い,各地の専門店で提供されている. リゾットは,バターなどの油脂で米を炒めた後に,熱し たブロード(ブイヨン)を加えながらアルデンテ(歯ご