水稻QTL定位研究进展

水稻的许多重要农艺性状均属于数量性状,研究水稻数量性状遗传对水稻育种具有十分重要的意义。近年来大量的研究揭示了水稻QTL的基本特征,剖析了重要农艺性状的遗传基础,给水稻遗传改良带来了新策略,不断深入的研究已经完成了水稻特定数量基因的精细定位和克隆,到目前为止已经有一万多个水稻QTL进行了定位,其中有19个进行了克隆,这对水稻育种具有十分重要的意义。本文主要综述了QTL定位的理论基础,水稻QTL定位的研究进展,并对水稻QTL研究的趋势进行了展望。     

Identification of Quantitative Trait Loci Affecting Grain Fat Content in Rice (Oryza sativa L.)

Fat content (FC) partially determines rice grain quality. The objective of this study was to identify stably expressed quantitative trait loci (QTL) for FC. A total of 85 inbred lines derived from the backcross between Sasanishiki (japonica, as the recurrent parent) and Habataki (indica) were used to detect QTLs for rice fat content. Seven QTLs (denoted as qFC‐1, qFC‐2, qFC‐3, qFC‐6, qFC‐10, qFC‐11, and qFC‐12) were detected on chromosomes 1, 2, 3, 6 10, 11, and 12, respectively, using inclusive composite interval mapping (ICIM) method. Among them, three major QTLs (qFC‐3, qFC‐6, and qFC‐11) with large effect were further confirmed across two different environments using some chromosome segment substitution lines (CSSLs), where Habataki was used as the donor parent and Sasanishiki as the recurrent parent. Further experiments showed that one of the major QTLs (qFC‐11) could increase fat content, fat index, and grain yield together. To our knowledge, qFC‐11 is a newly detected stable QTL that will provide new opportunities for improving rice fat content through marker‐assisted selection.     

Diversity in Antioxidant Capacity,Phenolic Contents,and Flavonoid Contents of 42 Edible Beans from China

Edible beans are among the most important grain legumes consumed by humans. To provide new information on the antioxidant phenolics of edible beans, the antioxidant capacity, total phenolic content (TPC), and total flavonoid content (TFC) in both soluble and bound fractions of 42 edible beans from China were systematically evaluated, with main phenolic compounds identified and quantified in 10 beans possessing the highest TPC. Edible beans contained a wide range of total antioxidant capacity and TPC generally comparable with common grains, fruits, and vegetables, and their bound fractions had significant antioxidant capacity, TPC, and TFC. Red sword bean was found for the first time to show extremely high total antioxidant capacity (ferrous[II] at 235 ± 13.2 μmol/g and Trolox at 164 ± 10.5 μmol/g) and TPC (1767 ± 58.3 mg of GAE/100 g). Phenolic compounds such as catechin, ferulic acid, gallic acid, p‐coumaric acid, and protocatechuic acid were widely detected in selected beans. A positive correlation was found between antioxidant capacity (ferric‐reducing antioxidant power [FRAP] and Trolox equivalent antioxidant capacity [TEAC] values) and TPC, with correlation coefficient r = 0.974 (FRAP value versus TPC) and r = 0.914 (TEAC value versus TPC). Therefore, beans with high antioxidant capacity and phenolic content can be valuable sources of dietary natural antioxidants for the prevention of oxidative stress‐related chronic diseases.     

Effect of Milling on the Color,Nutritional Properties,and Antioxidant Contents of Glutinous Black Rice

Dehulled glutinous black rice (cv. Kam Doi Saket) was abrasively milled (0–60 s) to make a degree of milling (DOM) curve. The curve showed a nonlinear relationship between milling time and DOM. The slope sharply increased in the first 20 s; after this point, the increase was moderate. The redness of grain and flour surprisingly increased after milling, and the highest value was found at 20 s of milling. Protein, fat, and crude fiber were not uniformly distributed in the dehulled rice kernel. The rice retained only 76.95, 32.79, 20.24, and 36.57% of protein, fat, crude fiber, and ash, respectively, after milling for 60 s. Anthocyanins, γ‐oryzanol, and α‐tocopherol decreased by 74.49, 55.35, and 70.36%, respectively, after 10 s of milling. The scavenging activity decreased sharply when milling was carried out for longer than 30 s. The methanolic extract from rice milled for 60 s showed the lowest activity, which was 21.1 times lower than that of the dehulled rice extract. It was concluded that milling for 20 s was sufficient to remove most of the bran layer of the black rice sample, but 10 s of milling retained higher contents of nutritional components and rice antioxidants.     

Contents of Antioxidant Compounds in Turkish Oats: Simple Phenolics and Avenanthramide Concentrations

Antioxidant products such as simple phenolic compounds and avenanthramides in oat (Avena sativa L.) may have health‐promoting effects on humans. Therefore, it is very important to determine simple phenolics and avenanthramide concentrations of different genotypes of oats from different regions of the world. The aim of this research was to determine the concentrations of simple phenolics and avenanthramides of Turkish oat genotypes. According to the results, Turkish oat genotypes were significantly different for three major avenanthramides (Bc, Bp, and Bf) and the simple phenolic, ferulic acid (FA), while not significantly different for p‐coumaric acid (PCA). Ferulic acid concentrations of Turkish oat genotypes were higher than a standard U.S. cultivar, Belle. However, the major avenanthramide concentrations of Turkish oat genotypes were significantly lower than Belle.     

Quantitative Trait Loci for Seed Dormancy in Wild Barley (Hordeum spontaneum C. Koch)

A quantitative trait locus analysis was carried out to unravel the genetic basis of dormancy in wild barley (Hordeum spontaneum) from Israel. Two accessions, Ashkelon and Mehola, from divergent environments were crossed to produce a mapping population. A linkage map was produced from the F₂ population, and F₄ seeds were used for germination experiments. Five quantitative trait loci (QTL) were detected for dormancy across the different germination experiments. These QTL were found on chromosomes 1, 2, 5, 6 and 7. The variation explained by each QTL varied between 8 and 25%. Ashkelon alleles increased the germination except for the QTL on chromosome 5. Three out of these five QTL co-locate with QTL found earlier in cultivated barley crosses, although this does not necessarily imply that they would be the same loci. The level of dormancy is much higher in wild barley than in cultivated barley and wild barley may have alleles that have not yet been utilised in breeding for optimally dormant barley.     

Germinated Brown Rice Enhances Antioxidant Activities and Immune Functions in Aged Mice

The present work was designed to obtain information on the effect of germinated brown rice (GBR) that has undergone different germination times (zero, one, two, three, and four days) on antioxidant activities and immune functions in aged mice. White rice (WR) was also investigated as a comparison. Chemical analysis of rice samples showed that the amounts of most nutritional and bioactive components increased significantly after two days of germination and were much higher in GBR and brown rice (BR) than in WR. Animal feeding experiments showed that dietary GBR and BR performed much better than WR in enhancing antioxidant activities and improving immune function in aged mice, and dietary GBR from three to four days of germination overall exhibited a better effect than GBR from zero to two days of germination.     

Antioxidant Capacity of Newly Developed Pigmented Rice Cultivars in Korea

The antioxidant capacity of newly developed and highly popular pigmented rice cultivars (black rice, Galsaekchalmi, Jeoktomi, Hongchalmi, and Nogwonmi) in South Korea was analyzed. The rice grains were ground into powder, extracted with 70% ethanol, filtered, and concentrated with a rotary evaporator. The samples were analyzed for phenolic, flavonoid, and phytic acid contents, free radical scavenging activity, reducing power, ferrous ion chelating ability, lipid peroxidation inhibition, and superoxide dismutase‐like activity. The ethanolic extracts from pigmented rice cultivars showed greater antioxidant activity than that of the normal white rice. The black rice exhibited the highest free radical scavenging activity, ferrous chelating ability, and total phenolic and flavonoid contents. The reducing power and phytic acid content were found to be highest in Hongchalmi cultivar. The inhibition of lipid peroxidation was markedly higher in Jeoktomi compared with the other rice samples. The Nogwonmi rice showed the lowest antioxidant activity among the pigmented varieties analyzed. These findings provide valuable information on the antioxidant potential of newly developed pigmented rice varieties and may assist plant breeders in the selection of cultivars for the development of new lines of rice with enhanced functional quality.     

Quantitative Trait Loci (QTL) of Seed Zn Accumulation in Barley Population Clipper X Sahara

There is little information regarding the chromosomal regions conferring zinc (Zn) accumulation in barley. With the aim of developing markers for Zn accumulation, 150 lines derived from cross between ‘Clipper’ (low-Zn-accumulator) and ‘Sahara’ (high-Zn-accumulator) were screened. In field-grown plants, two regions located on 2HS and 2HL were associated with seed Zn concentration and content. 2HS was flanked by Xbcd175 and Xpsr108; 2HL was flanked by vrs1 and XksuF15 markers. These two regions accounted for 45% of total variation in seed Zn concentration and 59% of total variation in seed Zn content. In a glasshouse experiment, 2HS and 2HL were also associated with seed Zn concentration and content, and explained 37% and 55% of the total variation in seed Zn concentration and content, respectively. The identification of these Quantitative Trait Loci (QTL) provides an important starting point for transferring and pyramiding genes that may contribute to the improvement of barley productivity and nutritional quality in Zn-deficient environments.     

Cooking Quality,Antioxidant Properties,and Starch Digestibility of Wheat Noodles Substituted with Extruded Brown Rice Flour

The effect of extruded brown rice flour (EBR) contents (0–50%) on antioxidant activity, phenolics, in vitro digestibility, color, and cooking quality of noodles containing mixtures of wheat and EBR was investigated. The antioxidant activity and phenolic content increased, especially ferulic and coumaric acids in bound forms, whereas the in vitro glycemic index, optimal cooking time, water absorption, hardness, and color were diminished in noodles with the addition of EBR; cooking loss increased as a function of the EBR percentage. The partial replacement of wheat flour with EBR can be favorably used in the wheat noodle formulation. The results provide the basis for the development of staple foods with nutritional characteristics for today's functional food markets.     

Variation of Phenolics,Tocols, Antioxidant Activities,and Soluble Sugar Compositions in Red and Black Rice (Oryza sativa L.) During Boiling

This study systematically examined hydrothermal effects of antioxidant substances, such as total phenolic (TPC), flavonoid (TFC), and proanthocyanidin (TPAC) contents, cyanidin‐3‐O‐glucoside (C3G), peonidin‐3‐O‐glucoside (P3G), α‐, γ‐, and δ‐tocopherols, and α‐, γ‐, and δ‐tocotrienols, as well as antioxidant activities, color parameters, and soluble sugar compositions in red and black rice. It showed that color differences (ΔE ) of black rice were higher than those of red rice caused by boiling. The processed red and black rice exhibited significantly (P < 0.05) lower TPC, TFC, TPAC, C3G, P3G, and antioxidant activities compared with the raw rice except bound TPC and bound antioxidant activity. Interestingly, soluble free p‐coumaric and ferulic acids had higher contents in cooked red rice, and soluble free protocatechuic, vanillic, and sinapic acids had higher contents in cooked black rice. Boiling caused significant decreases of soluble conjugated phenolic acids and significant increases of insoluble bound phenolic acids in both red and black rice. Increases of total free tocol, glucose, and fructose contents were observed in most red and black rice. To increase the contents of some soluble free and insoluble bound phenolic acids, free vitamin E, and monosaccharides in red and black rice, boiled rice might be a good choice.     

Effect of Processing Conditions on Color Change of Brown and Milled Parboiled Rice

The effects of the soaking and steaming steps in rice parboiling on color changes and the levels of reducing sugars in rice were studied. Brown rice was soaked to different moisture contents (MC, 15, 20, 25, and 30%). The L*, a*, b* color parameters of the Commission Internationale de L'Eclairage (CIE 1976) indicated that during soaking, red and yellow bran pigments diffused from the bran into the endosperm. The increase in brightness brought about by soaking rice was attributed to migration of rice compounds (e.g., lipids) from the inner to the outer bran layers (rice surface). The levels of reducing sugars in brown and milled soaked rice samples increased with increasing brown rice MC after soaking. The total color difference (ΔE) between parboiled and nonparboiled rice increased with increasing MC after soaking and depended on the intensity of the steaming conditions as reflected in the degree of starch gelatinization. Parboiling affected yellowness more than redness in mildly steamed brown rice and most in intermediately steamed brown rice. Severe steaming of brown rice affected redness more than yellowness. All three parboiling conditions equally affected the yellow color more than the red color in milled rice. Linear regression analyses indicated that parboiling had a larger effect on ΔE of milled parboiled rice than of brown parboiled rice. Furthermore, the linear relationship between the level of gelatinized starch and ΔE of the milled parboiled rice samples showed that both parameters are indicators for the degree of parboiling. Reducing sugars were formed and lost during steaming, suggesting Maillard reactions during steaming.     

Comparison of Composition,Protein, Pasting,and Phenolic Compounds of Brown Rice and Germinated Brown Rice from Different Cultivars

Physical characteristics, amino acids composition, protein profiling, pasting characteristics, and phenolic compounds of brown rice (BR) and germinated brown rice (GBR) from different paddy cultivars (PB1, PS44, PB1509, PB1121, and PS5) were investigated. L* (lightness) decreased, but a* (redness and greenness) and b* (yellowness and blueness) increased with germination. Protein and ash content increased, whereas fat and amylose contents decreased with germination. GBR showed lower hardness and gumminess than BR. Foam stability and water absorption capacity from GBR flour were higher compared with BR flour. Accumulation of γ‐aminobutyric acid, histidine, arginine, proline, methionine, and acidic amino acids increased significantly with germination, and increase was related to change in accumulation of glutelin and prolamins. The accumulation of prolamins and glutelin acidic and basic subunits decreased with germination. GBR flour showed lower pasting viscosities compared with BR flour. Ferulic acid, p‐coumaric acid, and quercetin were present in both fractions of the bound form. GBR showed improved nutritional quality that varied in different cultivars. PB1121 was observed to be the best for producing GBR owing to greater changes brought in protein content, essential amino acids, catechin, chlorogenic acid, protocatechuic acid, vanillic acid, and foam stability.     

利用三重测交群体剖析玉米苗期性状杂种优势的遗传学基础

为了探讨玉米苗期性状及其杂种优势形成的遗传学基础,以强优势玉米(Zea maysL.)杂交种组合豫玉22及其重组近交系为基础材料,采用三重测交(triple testcross,TTC)遗传交配设计,组配了包含312个测交后代的TTC群体,通过复合区间作图法检测到了30个控制发芽后第4天的最长根长、苗高、初生根数、根干重及叶干重的QTLs,并且在第2、3和7染色体上存在4个同时控制不同苗期性状的QTL区域。分析发现,在利用Z1和Z2数据定位出的22个QTLs中,以超显性位点最多(11个),加性(5个)和部分显性较少(5个),而显性最少(1个)。另外,还检测到8个QTLs与遗传背景之间的互作和16对不同标记间的互作。据此,我们提出超显性和上位性是玉米苗期性状及其杂种优势形成的主要遗传学基础。关键词玉米,苗期性状,三重测交,杂种优势,QTL定位     

绵羊产肉性能主效基因及QTL的研究进展

绵羊的产肉性能受某些控制肌肉生长发育的主效基因或QTL(数量性状位点)的影响，对这些相关基因的研究成为近年来遗传学家和动物育种学家研究的热点。本文就近年来国内、外对控制绵羊肉用性状的主效基因或QTL的研究现状进行了概括总结，对当前相关研究领域存在的问题给出了拟解决的方法，并提出了一些自己的见解。     

Effect of Parboiling on Milling,Physicochemical, and Textural Properties of Medium‐ and Long‐Grain Germinated Brown Rice

Germinated brown rice is considered a more nutritious and palatable cooked product than conventional brown rice. However, germination usually decreases rice milling yield and alters some physicochemical properties. Parboiling is commonly used to increase milling yield and retain nutrients, but it also changes rice color and texture. The objective of this study was to investigate the effect of parboiling on milling, physicochemical, and textural properties of a medium‐grain and a long‐grain rice after germination at varying durations. Germinated rice samples of three germination durations were prepared with one germination time before the optimum time at which 70% of rice revealed hull protrusion, the optimum time, and one time after. Germinated rice was then immediately parboiled at 120°C for 20 min and was then immediately dried. The milling, physicochemical, and textural properties of parboiled germinated rice from both cultivars were determined. Parboiling significantly decreased the percentage of brokens, whiteness, and the apparent amylose content and increased γ‐aminobutyric acid content (GABA) in the nongerminated rice and rice at the first germination duration for both cultivars. Parboiling reduced pasting viscosities for both cultivars, but Jupiter still exhibited higher pasting viscosities than Wells. Cooked parboiled germinated rice was overall softer than nonparboiled rice because of kernel splitting, but Wells remained harder and less sticky than Jupiter. In conclusion, it is beneficial to combine parboiling with germination to enhance nutritional values and improve milling properties without affecting textural properties for both rice cultivars.     

Enhancement of Nutritional and Antioxidant Properties of Brown Rice Flour Through Solid‐State Yeast Fermentation

This study investigated the effect of solid‐state yeast fermentation on the nutritional and antioxidant properties of brown rice flour (BRF). Three brands of commercial baker's yeast (Eagle, Saf‐levure, and Mauripan) were used to ferment BRF at 25°C for 12 h. There were significant increases in protein, ash, insoluble and soluble fiber, phosphorus, zinc, magnesium, calcium, and iron contents after yeast fermentation. Fermented BRF with Eagle yeast possessed the highest contents of protein, ash, zinc, and calcium. Fermentation of BRF with Eagle yeast was more effective in increasing antioxidant activity and total phenolic contents from 1.01 to 1.54 mmol of Trolox equivalents per gram and from 1.09 to 1.21 mg of gallic acid equivalents per gram, respectively. Yeast fermentation reduced phytic acid content of BRF (124.59 ± 0.48 µg/g), and the Eagle yeast‐fermented sample had the lowest value (36.55 µg/g) compared with the other fermented samples. Fermented flour with Eagle yeast also had the highest α‐amylase activity, because it recorded the lowest stirring number. Solid‐state fermentation with commercial yeast, particularly Eagle yeast, was effective in improving the nutritional and antioxidant properties of underutilized BRF as a food ingredient.     

Influence of Cadmium Toxicity on Growth and Antioxidant Enzyme Activity in Rice Cultivars with Different Grain Cadmium Accumulation

Abstract

The effect of cadmium (Cd) toxicity on growth, lipid peroxidation, and antioxidant enzymes was studied using two rice cultivars, Bing 97252 with low and Xiushui 63 with high grain Cd accumulation. Plants were exposed to 0–5 μ M Cd in hydroponic culture. Cadmium stress inhibited plant height and chlorophyll content and altered melondialdehyde (MDA) content and the activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). Roots and shoots responded differently to Cd in terms of antioxidant enzyme activity. Generally, the activities of SOD, POD, and CAT decreased with increase in Cd level, while the activity of MDA increased with increase in Cd level. With the increase in Cd concentration in nutrient solution, MDA content in shoots and roots of Xiushui 63 increased at a much higher rate than did that of Bing 97252 at both growth stages. At booting stage, a decrease of 46%–52% in SOD activity was noted in plant roots grown under 5 μ M Cd, while at tillering stage the decrease was 13%–19% compared with the control. A significant decrease in chlorophyll content and plant height was noted under higher Cd treatment (1.0 and 5.0 μ mol) at two stages. The higher MDA and lower chlorophyll content in the cultivar Xiushui 63 showed that it is more sensitive to Cd than the cultivar Bing 97252.     

Extraction,Quantification, and Characterization of Phenolics Extracted with the Aid of Sonication from Rice Bran

Phenolics are phytochemicals extensively distributed among plants that have been receiving great deal of attention for their functionality. Rice bran is a good source of phenolics, especially hydroxycinnamates. Although chemicals are commonly employed to isolate phenolics, the use of physical treatments such as sonication is still limited. This study was conducted to optimize a procedure to isolate phenolics from rice bran using sonication as a preextraction treatment. Sonication was optimized by varying output, time, and temperature. Extraction was optimized by varying solvent, extraction time, temperature, and sample-to-solvent ratio. After an optimum procedure was established, HPLC analyses were conducted to identify and quantify the major individual phenolic acids extracted. The optimum conditions for extracting phenolics from rice bran were sonication with water (1:100 sample-to-solvent ratio) for 1 min; output intensity of 10; holding at ambient temperature; and autoclave treatment for 20 min at 121°C. This procedure extracted 8.85 ± 0.18 mg of phenolics/g of dried rice bran. Benzoic, p-coumaric, and trans-ferulic acids were the major phenolics identified in the extract. The proposed procedure will be valuable in obtaining phenolics for increasing product functionality such as lipid oxidation inhibitors in food systems.