Classification of cultivated rices into indica and japonica types by the isozyme, RFLP and two milled-rice methods.

Four methods for classifying cultivated rices (Oryza sativa L.) (including IR varieties) into indica and japonica types - waxy gene product in endosperm starch, glutelin α3 molecular weight in milled rice, RFLP polymorphism at the Wx locus and Glaszmann's isozyme method - were compared. On the basis of the two endosperm traits and the RFLP method Glaszmann's group 1 (indica) was classified as mainly indica and intermediate groups 2, 3 and 4 as exclusively indica. However, the endosperm traits classified Glaszmann's group 5 as mainly indica, while the RFLP method classified it as japonica. The RFLP waxy gene probe was closest to the isozyme method in classifying group 6 as japonicas; the waxy gene product gave mainly indica reaction even in group 6, and the glutelin α3 method was intermediate. All IR rices were classified as being indica on the basis of Wx gene product and by Glaszmann's method, but a few were classified as japonica by the glutelin α3 method and by the RFLP waxy gene probe.

Protein and lysine digestibility and protein quality of cooked Filipino rice diets and milled rice in growing rats.

The protein quality of typical rice-based menu of Filipino preschool child and adult and cooked milled rice was assessed for true digestibility (TD), biological value (BV) and net protein utilization (NPU) in growing rats. Lysine and energy digestibilities were also determined. For the preschool child diet, TD was 88.8%, BV 90.0%, and NPU 79.9%. For the adult diet, TD was 87.3%, BV 86.6%, and NPU 75.5%, whereas cooked rice had 90.0% TD, 82.5% BV and 74.3% NPU. Lysine digestibility was 95.4% for preschool child diet, 95.7% for adult diet, and 100.0% for rice. Digestible energy was 91.3% for preschool child diet, 93.0% for adult diet, and 95.3% in rice. Amino acid scores were 100.0% for preschooler diet, 92.1% for adult diet, and 62.2% for rice. Protein quality based on amino acid score corrected for TD was 88.8% for preschool child diet. 80.4% for adult diet, and 56.0% for rice. If based on lysine digestibility instead of TD, protein quality would be 7.1% higher.

Rice varieties with similar amylose content differ in starch digestibility and glycemic response in humans.

Three high-amylose rice varieties, IR42, IR36, and IR62, with similar chemical composition including amylose content (26.7-27.0%), were cooked under the same conditions and tested for in vitro digestibility as well as blood glucose and insulin responses in healthy human volunteers. The starch-digestion rate and the glycemic and insulin responses were the highest in IR42, followed by IR36 and, then IR62. The differences were not due to unabsorbed carbohydrate but were related to their physicochemical properties, such as gelatinization temperature, minimum cooking time, amylograph consistency, and volume expansion upon cooking. When the three varieties were cooked for their minimum cooking time, they had the same degree of gelatinization and their starch-digestion rates and glycemic responses were similar. We conclude that amylose content alone is not a good predictor of starch-digestion rate or glycemic response. Rice varieties with similar high-amylose contents can differ in physicochemical (gelatinization) properties and this, in turn, can influence starch digestibility and blood glucose response.

Effects of nitrogen fertilizer treatment and source and season on grain quality of IR64 rice.

The effects of nitrogen fertilizer treatment and source (prilled urea, urea supergranule, fresh azolla, rice straw or sesbania or rice straw compost and their combinations) on grain quality were studied in the 1987 crops of variety IR64 at IRRI. Although fertilizer application improved grain yield, it improved protein content only in the case of urea supergranule, azolla and rice straw. Lysine contents of brown rice protein were similar in samples with no N fertilizer and those with the highest protein content in both seasons. Fertilizer treatment regardless of source tended to decrease weight and increase translucency of brown rice in both seasons. Effects on other grain properties were not consistent in both seasons. Season affected more grain properties than fertilizer treatment did, particularly translucency which was higher in the dry season than in the wet season.

Grain quality characteristics of rice in Madagascar retail markets.

A survey of rice in retail markets of Madagascar with emphasis on the surplus regions of Marovoay and Lac Alaotra and the deficient area, Antananarivo City showed rices of Madagascar to be predominantly medium-long, medium-shaped, with high apparent amylose content, low gelatinization temperature, and soft, hard or medium gel consistency. Mean protein content was 7.5%. Percent white grains among red and white grains ranged from 0 to 100% (mean 56%), head rice 0-94%, translucency 6-66%, and Kett whiteness 12-48%.

Effect of saline soil on grain quality of rices differing in salinity tolerance.

Four varieties of rice, differing in salinity tolerance and grown in saline soil (electrical conductivity 5-6 dS/m) at Sadhoke, Punjab, Pakistan, had lighter grain and higher Na content than control samples. Grains of three out of the four rices grown on saline soils had higher brown rice protein (higher nutritional value), less translucent grain, lower starch and amylose content, and lower K than their control samples, but these differences were not related to salinity tolerance. Alkali spreading value and gel consistency were not affected by culture in saline soil. Cooked rice Instron hardness increased in saline culture in two higher-protein samples of the four rices. Amylograph peak viscosity was suppressed by saline culture.

Grain quality of rices grown in irrigated and upland cultures.

Upland culture of nine varieties at Ivory Coast resulted in decreases in grain weight, brown and milled rice translucency, Chroma meter L* of rough rice, Chroma meter L* and b* of milled rice, milled rice protein, and Amylograph peak viscosity, and in increases in total phenolics of hull and brown rice, and Chroma meter a* of rough, brown, and milled rice of 5 to 8 of the varieties as compared with irrigated culture. Upland culture had no consistent effect on grain resistance to Angoumois grain moth (Sitotraga cerealella).

Olfactory sensitivity of two sympatric species of rice leaf folders (Lepidoptera: Pyralidae) to plant volatiles.

Electroantennograms (EAGs) were recorded from male and female moths of two sympatric leaf folder species,Cnaphalocrocis medinalis (Gue-née) andMarasmia patnalis Bradley (Lepidoptera: Pyralidae) to 91 volatile chemicals of plant origin. Responses of both leaf folder species were similar to all compounds except to three monoterpenes-ß-myrcene, menthone, and isomenthone- and two sesquiterpenes-cis-nerolidol and isophytol. Response ofM. patnalis, an oligophagous leaf folder, to these compounds was higher compared with that of polyphagousC. medinalis. EAG responses of males to saturated and unsaturated aliphatic aldehydes were significantly higher than those of conspecific females in both species. A higher response ofC. medinalis males also was observed for 1-nonanol, 3-nonen-2-one, andtrans, trans-2,6-dimethyl-2,4,6-octatriene. In contrast, females of both species responded more to monoterpenes, borneol, isoborneol, and fenchyl alchohol. Response ofC. medinalis female was higher for terpinen-4-ol, carveol, dihydrocarveol, (-)-myrtenal, and perillaldehyde. In both species and sexes, high EAG responses were recorded for compounds of the green leaf odor complex. EAG responses to nonanal and hexanal were maximum among the aliphatic aldehydes while 1-hexanol elicited the highest response among the alcohols tested. EAG responses to terpene compounds-citronellal,α-terpineol, and (-)-myrtenal-were equal to the response to 1-hexanol. While all compounds tested elicited a negative potential, thymol and carvacrol elicited a positive EAG potential. The EAG data are discussed with regard.

Properties of Thai cooked rice and noodles differing in glycemic index in noninsulin-dependent diabetics.

Glycemic index responses of two cooked rices and six types of cooked noodles consumed by eight noninsulin-dependent diabetics correlated positively with in vitro starch digestibility of food slurry and negatively with amylose content of the food. Glutinous (waxy) rice had the highest values, and mung bean noodles the lowest.

Variability in contents of thiamine and riboflavin in brown rice, crude oil in brown rice and bran-polish, and silicon in hull of IR rices.

Among 30 IR varieties, variety had greater effect on thiamine content of brown rice than season. Both season and variety affected riboflavin content. Purple- and red-pericarped Philippines rices had higher riboflavin and crude protein contents than IR rices. Crude oil contents of brown rice and bran-polish of 19 IR rices were significantly affected by variety, but only brown rice oil content was significantly affected by season. Bran-polish of waxy rice IR29 had the highest oil content. Silicon content of hull of 16 IR rices showed significant variation due to variety and season and tended to be higher in the dry season crop. Variety rankings in nutrient composition were not consistent for the two crops. The levels of nutrients of IR rices were within the range of values reported for other rices.

Protein and energy utilization of boiled rice-legume diets and boiled cereals in growing rats.

In growing rats, boiled milled rice-legume diets (2:1 N ratio) had lower energy digestibility than boiled milled rice and equal if not better true digestibility, biological value, and net protein utilization (NPU). Rice-soybean diets showed better NPU than the other rice-legume diets. Boiled whole-grain corn and sorghum had lower digestible energy and NPU than boiled milled rice. NPU of the diets did not follow strictly the trend of the amino acid score of the diets; phenol (tannin) content reduced energy and protein digestibility of all diets, but sugars reduced energy and protein digestibilities of rice-legume diets only.

Genetic analysis of waxy locus in rice (Oryza sativa L.).

Inheritance of waxy locus was studied in crosses of a waxy variety with four non-waxy parents having high-, intermediate-, low- or very low-amylose content. The analysis for amylose content was done on a single grain basis in parents, F1, F2, B1F1, and B2F1 seeds. The waxy parent lacking synthesis of amylose content was found to differ from the ones having high-, intermediate-, low- or very low-amylose content by one gene with major effect. Dosage effects for amylose content were observed to have great influence on segregation pattern and efficiency of selection. Selection efficiency for amylose content can be enhanced by selecting for endosperm appearance in early segregating generations.

Protein quality of high-protein and low-protein milled rices in preschool children.

High-protein (11.0%, IR480-5-9) and low-protein (7.1%, IR32) milled rices were compared with casein as a control when fed as the main source of dietary N to eight apparently normal Filipino children, 1.5 to 2.0 years of age. Daily diets were formulated to contain 250 mg N and 100 kcal/kg body weight. Apparent digestibility of 60.0% for high-protein rice was lower than for low-protein rice (66.2%), and higher values of 76.8 and 80.8% were obtained for the two casein control diets. Corresponding apparent retentions were similar for the two rices, at 23.4 and 26.9%, respectively, as compared to 25.0 and 38.6% for the two casein control diets. These results support previous data on children fed non-isonitrogenous rice-based diets indicating that an increase in protein content of milled rice results in only a slight decrease in its protein quality. The results were similar to those obtained with Peruvian children on a similar protocol.

Free sugars in relation to starch accumulation in developing rice grain.

The changes in sugars (water-soluble carbohydrates) were studied in the developing grain of rice (Oryza sativa L., variety IR28 and IR29) in relation to the role of these sugars as precursors of ADP glucose in starch accumulation. The levels of total sugars, total reducing sugars and free glucose, sucrose and other nonreducing sugars, maltooligosaccharides, and total and nonsucrosyl fructose followed closely the changes in the rate of starch accumulation, in both IR28 and 29; the peak value occurred 9 days after flowering. The level of soluble carbohydrates remained high in the caryopsis and also in milled rice after starch accumulation, suggesting that the supply of sugar precursors does not limit starch accumulation in the rice grain. Because of a higher level of reducing sugars, the level of free sugars in the grain of waxy rice IR29 was higher than that of nonwaxy IR28.

Some properties of 3-phosphoglycerate phosphatase from developing rice grain.

Some properties of 3-P-glycerate phosphatase from developing caryopsis of rice (Oryza sativa L., variety IR26) were studied. The enzyme was found to be soluble and not bound to starch, and concentrated mainly in the pericarp-aleurone layer; its maximum activity was at 12 to 14 days after flowering. Contents of 3-P-glycerate and chlorophyll were highest in the grain at 7 to 8 days after flowering when starch synthesis was at a maximum. The enzyme was purified about 100-fold by precipitation with 50 to 80% ammonium sulfate, followed by chromatography through Sephadex G-200 and CM-Sephadex C-50. The pH optimum was from 5.7 to 6 and no cation was required for activity. The purified preparation had an apparent Km of 2.85 mm and was inhibited by Cu(2+), Hg(2+), Zn(2+), Fe(3+), molybdate, and F(-). The enzyme also exhibited high activity toward UTP, ATP, and p-nitrophenyl phosphate; moderate activity toward other phosphates; but no activity toward phytate. A molecular weight of about 23,000 was obtained for the 3-P-glycerate peak during gel filtration on Sephadex G-200, which corresponded to a value of 26,000 for the major protein fraction by thin layer gel filtration on Sephadex G-150. Zymograms of the whole extract and semipurified preparations showed two phosphatase bands with 3-P-glycerate as substrate.

Aspects of nitrogen metabolism in the rice seedling.

The effects of nitrogen source NO(3) (-) or NH(4) (+) on nitrogen metabolism during the first 2 weeks of germination of the rice seedling (Oryza sativa L., var. IR22) grown in nutrient solution containing 40 mug/ml N were studied. Total, soluble protein, and free amino N levels were higher in the NH(4) (+)-grown seedling, particularly during the 1st week of germination. Asparagine accounted for most of the difference in free amino acid level, in both the root and the shoot. Nitrate and nitrite reductase activities were present mainly in the shoot and were higher in the NO(3) (-)-grown seedling, whereas the activity of glutamate dehydrogenase and glutamine synthetase in the root tended to be lower than that of the NH(4) (+)-grown seedling during the 1st week of germination. Glycolate oxidase and catalase activities were present mainly in the shoot. Maximum activity of the above five enzymes occurred 7 to 10 days after germination. Differences in the zymograms of nitrate reductase, glutamate dehydrogenase, and catalase were mainly between shoot and root and not from N source. Nitrite reductase bands were observed only in plants grown in plants grown in NO(3) (-).Ten-day-old seedlings of three rices differing in level of grain protein did not differ in the level of N fractions and of enzyme activities, which were consistent with their differences in grain protein content.

Enzymes of carbohydrate metabolism in the developing rice grain.

The levels of reducing and nonreducing sugars, starch, soluble protein, and selected enzymes involved in the metabolism of sucrose, glucose-1-P, and glucose nucleotides were assayed in dehulled developing rice grains (Oryza sativa L. line IR1541-76-3) during the first 3 weeks after flowering. The level of reducing sugars in the grain was highest 5 to 6 days after flowering. The level of nonreducing sugars and the rate of starch accumulation were maximum 11 to 12 days after flowering, when the level of soluble protein was also the highest. The activities of bound and free invertase, sucrose-UDP and sucrose-ADP glucosyltransferases, hexokinase, phosphoglucomutase, nucleoside diphosphokinase, and UDP-glucose and ADP-glucose pyrophosphorylases were high throughout starch deposition, and were maximum, except for nucleoside diphosphokinase which did not increase in activity, between 8 and 18 days after flowering. Soluble primed phosphorylase and ADP glucose-alpha-glucosyltransferase (starch synthetase) were both present during starch accumulation. Phosphorylase activity was at least 2-fold that of soluble starch synthetase but the synthetase followed more closely the rate of starch accumulation in the grain. The activity of starch synthetase bound to the starch granule also increased progressively with increased starch content of the grain.