Tomio Itani

Variation of 2-Acetyl-1-Pyrroline Concentration in Aromatic Rice Grains Collected in the Same Region in Japan and Factors Affecting Its Concentration

Abstract Aroma strength of aromatic rice varies with the genetic and environmental conditions. We determined the concentration of 2-acetyl-1-pyrroline (2AP), a key compound of the aroma of aromatic rice, in 62 samples of rice grains (brown rice) from‘Hieri’ produced by 17˜24 farmers in 3 years in the Kubokawa area of Kochi Prefecture, Japan. Many ofthem showed similar values and the standard deviations were 27˜31%. However, a few samples showed extremely high (200%) or low (60%) 2AP concentrations compared to the individual year averages (100%). The influence of harvest time and temperature during ripening on the 2AP concentration in the brown rice was also examined using two cultivars. During grain development in an early-heading cultivar ‘Miyakaori’ , the 2AP concentration in the brown rice reached a peakat 4 or 5 weeks after heading (WAH) and then decreased rapidly to 20% of the maximum at 7 or 8 WAH. In a late-heading cultivar ‘Hieri’, the 2AP concentration peaked at 4 WAH then gradually decreased to 40% of the maximum at 8 WAH.The 2AP concentration was higher in brown rice ripened at a low temperature (day : 25°C/night : 20°C) than that ripened at a high temperature (day: 35°C/night: 30°C) in both a short-grain cultivar ‘Hieri’ and a long-grain cultivar ‘Sari Queen’.

Anti-oxidative analysis, and identification and quantification of anthocyanin pigments in different coloured rice

Anthocyanin pigments in coloured rice cultivars were isolated and identified using high-performance liquid chromatography techniques. Two black rice cultivars (Asamurasaki, Okunomurasaki) contained three major anthocyanins: cyanidin-3-glucoside, peonidin-3-glucoside and malvidin. Chinakuromai (black) rice additionally contained a fourth anthocyanin, petunidin-3-glucoside. Four red rice cultivars contained only malvidin. The total anthocyanin content varied greatly among black rice cultivars (79.5-473.7 mg/100g), but was lower in red rice (7.9-34.4 mg/100g). Total phenolic content was similar between red (460.32-725.69 mg/100g) and black (417.11-687.24 mg/100g) rice. The oxygen radical absorbing capacity was ranked as follows: red (69.91-130.32 μmol Trolox/g)>black (55.49-64.85 μmol Trolox/g)>green (35.32 μmol Trolox/g)>white (21.81 μmol Trolox/g) rice. The antioxidant capacity resulted mainly from the seed capsule, not the endosperm. The anthocyanin pigments contributed little to the total antioxidant capacity of red (0.03-0.1%) and black (0.5-2.5%) rice cultivars. Hence, the antioxidant capacity is derived mainly from other phenolic compounds.

Umbelliferone released from hairy root cultures of Pharbitis nil treated with copper sulfate and its subsequent glucosylation

Hairy root cultures of Pharbitis nil treated with CuSO4 and methyl jasmonate (MeJA) produced umbelliferone (1) and scopoletin (2) in the culture medium, and skimmin (3), a β-D-glucopyranoside of 1, was isolated from the hairy roots. While 1 in the medium increased and reached a maximal level 16 h after the treatment with CuSO4, the amount of 3 in the hairy roots decreased, reaching a minimal level after 8 h, before recovering to a level higher than the basal level after 24 h and then continuously increasing. These observations suggest that 1 was released by the hydrolysis of 3. Umbelliferone (1) inhibited hairy root growth, while skimmin (3) did not. This result suggests that, after the release of 1 as a phytoalexin, the hairy roots glycosylated 1 for the detoxification and re-use of 3 as a source of phytoalexin.

Partitioning of 13C-labelled photosynthate varies with growth stage and panicle size in high-yielding rice

A super-high-yielding rice (Oryza sativa L.) cultivar, Takanari, and a traditional japonica rice cultivar, Nakateshinsenbon, were grown under field conditions to compare partitioning of 13C-labelled photosynthate to different plant organs during the period of reproductive development. The flag leaf and the two leaves immediately below it on the main culm were exposed individually to 13CO2 and the movement of the heavy carbon isotope to grains, hull, panicle branches and vegetative parts of plant was assessed. Also, the effect of a reduction of sink size on the partitioning of 13C to different organs was studied by removing some of the primary branches of the panicle. 13C taken up by the three leaves in the post-heading period, moved mostly to the grains and hull of the panicle. At this stage, the uppermost three leaves and the panicle consisted of a single source-sink unit. Partitioning of 13C to the rest of the vegetative structures of the plant was minimal. In the case of Nakateshinsenbon, the flag leaf supplied most of the carbon assimilates for the grains and contributions from the other two leaves were much smaller. However, in Takanari, the contribution of 13C to grains from the second leaf was equivalent to that of the flag leaf. In Takanari, removal of more than one third of the primary branches of the panicle significantly reduced partitioning from the third leaf of the culm, but partitioning from the flag leaf was not significantly changed. In contrast, branch removal treatment significantly depressed transport of carbon assimilates from the flag leaf in Nakateshinsenbon. The obligatory nature of the source-sink relationship in rice is discussed. It is concluded that in lower-yielding traditional rice, photosynthesis in the flag leaf supplies carbon assimilates to the developing grains. But in the super-yielding rice Takanari, the main source area is extended to include the two leaves below the flag leaf so as to sustain an extra large panicle. Even greater grain-filling is possible in super-yielding rice, if the source area is increased further.

Glucosylation of Phenolic Compounds by Pharbitis nil Hairy Roots: I. Glucosylation of Coumarin and Flavone Derivatives

Hairy roots of medicinal morning glory (Pharbitis nil) showed potent glucosylation activity against umbelliferone and aesculetin, so the glucosylation activity against several phenolic compounds was tested. Some coumarin derivatives and flavone derivatives having phenolic hydroxyl groups were incubated with the hairy roots. The coumarin derivatives and flavone derivatives almost disappeared from the culture medium in half a day. In the case of the coumarin derivatives, a 7-hydroxyl group was easily glucosylated. A methyl group at C-8 somewhat decreased the glucosylation to a hydroxyl group at C-7 of the coumarin skeleton. The 4-hydroxy coumarin derivatives were changed to acetophenone-type glucosides by incubation with the hairy roots through decarboxylation. Several flavonol derivatives were tested for glucosylation by the hairy roots. 3-Hydroxy flavone, 3.6-dihydroxyflavone and 3,7-dihydroxyflavone were glucosylated to give 3-glucosylated derivatives. Of these, 3,6-dihydroxyflavone was highly glucosylated, but not 3-hydroxyflavone or 3,7-dihydroxyflavone to the same degree. In the case of the flavones, a 3-hydroxy group could be predominantly glucosylated, and hydroxyl groups on the A and B ring of the flavones affected glucosylation by the hairy roots.

Difference in the physical properties of white-core and non-white-core kernels of the rice varieties for sake brewing is unrelated to starch properties.

Abstract This study was designed to determine whether or not the difference in the physical properties between white-core and non-white-core kernels of the rice varieties for sake brewing is associated with their starch properties. We used two rice cultivars for sake brewing, Senbon-nishiki and Yamada-nishiki, from three different plots in Hiroshima prefecture. Hardness values of kernels were significantly higher in non-white-core than in white-core kernels in both varieties. Vickers hardness (VH) values were lowest at the center of the kernel in both types of kernels. VH values of white-core tissues of white-core kernels were significantly lower than those of corresponding tissues of non-white-core kernels. No significant differences were observed between the two types of kernels in VH values of the surrounding translucent tissues and in the starch properties (amylose content, pasting properties analyzed using a rapid viscoanalyzer and gelatinization properties analyzed using a differential scanning calorimetry). These results suggest that the difference in physical properties between the two types of kernels of the rice varieties for sake brewing are associated with the difference in structure of endosperm cells and not in starch properties.

Genetic polymorphisms in Japanese fragrant landraces and novel fragrant allele domesticated in northern Japan

Rice fragrance is an important characteristic for Southeast Asian consumers, and fragrant landraces from Japan were first recorded in the 17th century. Principal component analysis clearly showed that Japanese fragrant landraces were genetically different from non-Japanese fragrant landraces. Japanese fragrant landraces were composed of six clades, none of which carried the most common fragrance mutation, an 8-bp deletion in exon 7 of Badh2. Fragrant landraces comprised two major groups carrying different Badh2 mutations. One group carried a known SNP at exon13 and the other a SNP at the exon1-intron1 junction as splicing donor site. The latter was considered to be a potential splicing mutant group as a novel allele at Badh2. Heterozygosity (He) scores in the two fragrant groups were not significantly different from non-fragrant landraces and modern cultivars. However, lower He scores were found around the Badh2 locus in the two groups. The potential splicing mutant group showed a more extended haplotype than the E13 SNP group. A likely causal factor responsible for loss of function is a novel splicing mutation allele that may have been generated quite recently. The fragrance allele has dispersed as a result of out-crossing under local environmental conditions.

Relationship between the Starch Properties of White-Core Tissue and Polishing Characteristics in Brewers’ Rice Kernels

References The kernels of Hattan-nishiki No. 1 and Kairyo-omachi have larger air spaces in the white-core tissue and are broken easily during the process of polishing when compared with those of Senbon-nishiki and Yamada-nishiki. The polishing characteristics of brewers’ rice kernels are closely related with the structure of the white-core tissue of kernels. In this study, the varietal differences in the starch properties of white-core tissue of brewers’ rice kernels on polishing characteristics were studied. The starch properties were studied by rapid visco analysis (RVA) and differential scanning calorimetry (DSC); the amylose content of the rice flour of each variety was also analysed. No significant differences were observed in the amylose content among the four varieties. The two RVA parameters, peak viscosity and breakdown, were higher in Hattan-nishiki No. 1 and no significant differences were observed in them among Senbon-nishiki, Yamada-nishiki and Kairyo-omachi. The DSC parameters, gelatinization onset and peak and conclusion temperatures, were higher in Hattan-nishiki No. 1, lower in Senbon-nishiki and Yamada-nishiki, and intermediate between them in Kairyo-omachi. These results suggest that the polishing characteristics of brewers’ rice kernels are related with not only the endosperm structure but also the starch property of white-core tissue, except for Kairyo-omachi.

Varietal Difference of Polishing Characteristics and Suitability for Sake Brewing in "Hattan-Type Varieties" of Rice Suitable for Brewing Original Hiroshima Sake

Abstract By successive crossing using Hattan-type varieties originating from “Hattanso” as a parent, “Hattan-type varieties” of rice suitable for brewing the original Hiroshima sake have been bred. The varieties were improved inheriting the flavor of Hattan-type sake, and Hattan-nishiki No.1 and No.2 were bred in 1984. However, neither variety was suitable for brewing high-grade sake such as Ginjoshu and Daiginjoshu, which require high-degree polishing of rice grains. Therefore, their parent cultivar, Hattan No. 35, is attracting attention for the production of high-grade sake. We have been trying to breed a new variety, which retains the sake-brewing suitability of Hattan-type varieties but can endure high-degree polishing. In this study, to establish a guideline for further breeding, we examined the polishing characteristics and suitability for sake brewing of six Hattan-type varieties derived from Hattanso. In the process of breeding of “Hattan-type varieties” of rice, grain size, white-core size and % of white-core grains increased resulting in an increased suitability for sake brewing, such as water absorptivity and digestibility, in Hattan No.35, Hattan-nishiki No.1 and Hattan-nishiki No.2. However, Hattan-nishiki No.1 and No.2 had many ellipsoidal-white-cores with large white tissue, which cause the grains to be easily broken during high-degree polishing. On the other hand, Hattan No.35, having grains with relatively many lined-white-cores with small white tissue, was superior for high-degree polishing. In the future, breeding of a new variety, which has the superior cultivation characteristics of Hattan-nishiki No.1 and No.2, but with improved white-core characteristics, is expected.

Allelopathic Potential of White, Red and Black Rice Cultivars

Abstract The inhibitory effect (allelopathic potential) of shoot, seed and root extracts of 8 white, 5 red and 5 black rice (Oryza sativa L.) cultivars was determined against the seedling growth of lettuce (Lactuca sativa L.) and white clover (Trifolium repens L.). All extracts inhibited hypocotyl and root growth of lettuce and white clover seedlings, and those inhibitory activities ranged from –1% – 96%. The average inhibitory activity of the extracts on the hypocotyl and root growth of lettuce and white clover was 42 – 88%. No apparent difference in the inhibitory activity was found either among the extracts of white, red and black rice, or among the extracts of shoots, seeds and roots. However, the red rice cultivar Tsushima-akamai marked the greatest inhibitory activity with an average of 88% growth inhibition on hypocotyls and roots of lettuce and white clover, followed by Souja-akamai and Koshihikari. These results suggest two red rice, Tsushima-akamai and Souja-akamai, may be potentially useful for weed management in agriculture.