Complex constitutive nature of Japanese upland rice, Oryza sativa L.

Two rice ecotypes, the so-called lowland and upland populations, which carry different isozyme genotypes mostly at a single locus, are cultivated in Japan. The aim of this study was to examine the origin and the mechanism for keeping these genetic differences. The upland population is cultivated in upland fields and carries a different allele for a particular isozyme gene, Pgd-1, which has never been found in the lowland population. RFLP markers showed a weak trend for genetic differentiation between the two ecotypes. On the other hand, morphological, and physiological traits showed marked differences between the two ecotypes. Furthermore, based on the genotypic difference, two Japonica subgroups are defined in the upland population. Subgroup I is the minor group and carries key lowland characters, including the genotype for PGD. Subgroup II carries different traits and the genotype for PGD of the alternative subgroup. As an allelic difference for Pgd-1 is known to occur between the two ecospecies, Tropical (Tr) and Temperate (Tm) Japonicas, upland cultivars can be classified by diagnostic characters which distinguish a variety into Tr or Tm type. The upland population consists of three types of cultivars, Tr-, Tm- and intermediate-type. In contrast, the lowland population consists of a uniform Tm type Japonicas. As Japanese upland cultivars still have an isozyme allele specific to the Tr type, the upland population has a rather complex constitution which is presumably now being introgressed by lowland genetic material, but still represents a major difference at some genetic levels. Upland rice carries several stress-resistant genes which would be useful for lowland rice breeding. The genetic difference would be efficient for tagging upland specific traits by upland specific genetic markers. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic analysis of semidwarf mutants induced in indica rice (Oryza sativa L.)

The mode of inheritance of five semidwarf (SD) mutants and allelic relationship with DGWG (sd1) locus was studied. The five SD mutants viz., Basmati 370 (SD1), Basmati 370 (SD2), Basmati 370 (SD3), TCA 2 (SD) and TCA P2-5 (SD) when crossed with their tall parents exhibited monogenic inheritance of 3 tall: 1 semidwarf in the F2 progenies. The SD mutants were also crossed with semidwarf varieties (DGWG and Bala) possessing sd1 gene. Crosses between Basmati 370 (SD1) × Bala, Basmati 370 (SD3) × Bala and TCA 2 (SD) × DGWG produced tall F1 hybrids and in F2 generation, modified dihybrid ratios (9 : 6 : 1 and 9 : 7) were observed indicating that the mutants Basmati 370 (SD1), Basmati 370 (SD3) and TCA 2 (SD) are non-allelic to sd1 gene. Whereas, the mutants Basmati 370 (SD2) and TCA P2-5 (SD) when crossed with Bala produced semidwarf F1 hybrids and in F2 generation, segregation for plant height was not observed indicating that these mutants are allelic to sd1 gene. The three non-allelic SD mutants identified in the present study can be used in rice breeding as alternative gene sources for semidwarfism. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of amylose content in rice (Oryza sativa L.)

Summary The inheritance of low and very low amylose contents in six rice crosses and their reciprocals was studied by single grain analysis of parents F₁, F₂, B₁ and B₂ seeds. To minimize the environmental effects, the seeds of all generations of all crosses were produced in a single season. The results indicated different dosage effects in different crosses. One major gene was found to govern a difference of 6–12% in amylose content in low and intermediate amylose parents. Very low amylose content was similarly found to be governed by one major gene in crosses between very low- and low-amylose content parents. Minor genes and modifiers also seem to play some role. In the cross between two low amylose parents differing by about 2.5% in amylose content, the differences appeared to be controlled by some minor genes and modifiers. The selection program in different crosses has been suggested.     

Variation among progenies of diploid plants regenerated from haploid, microspore-derived cell-suspension protoplasts of rice (Oryza sativa L.)

Progenies of 110 diploid R₀ plants regenerated from haploid protoplasts derived from microspore callus cell suspension culture of rice (cv. Miara) were evaluated for 6 traits, along with control lines, in a replicated field trial. Complementary post-harvest observations were carried out for four panicle or grain characters. A wide range of variation was observed for all traits under study among the protoclonal lines. The mean of the protoclonal population was significantly different from that of the control for most traits and 64.5% of the lines differed from the control for at least one field-evaluated trait. A unidirectional shift towards later-maturing, taller, and lower-tillering lines was observed. Of all the lines, 39% were taller than the control by at least 10 cm, 31 % had flowering delayed by at least 5 days, and 13% exhibited significantly longer panicles (P = 0.05). As to the agronomical value of the lines, the variation resulted in a global negative drift although favourable variations were found in a few lines. All but two lines were homogeneous, suggesting that most variations existed in a homozygous form in the R₀ plants. R₂ lines grown from seeds of 17 R₁ protoclonal lines stably inherited the changes and did not segregate, thereby confirming that variations are fixed.     

The use of microsatellite polymorphisms for the identification of Australian breeding lines of rice (Oryza sativa L.)

Ten microsatellite loci were analysed for 43 cultivars or breeding lines of rice. Polymorphism-Information-Content values ranged from 0.62 to 0.92. The microsatellite markers were found to be useful for cultivar identification and assessment of genetic relationships. Most of the cultivars could be uniquely identified by at least one microsatellite marker. Genetic heterogeneity was detected within rice samples by amplification of microsatellites from DNA extracted from multiple individual plants and also from bulked DNA preparations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Agro-morphological characterization of ovary culture-derived plants of rice (Oryza sativa L.)

Plants derived from unpollinated ovary culture of ten rice genotypes showed significant variability in agro-morphological characteristics. The ovary-derived plant (H1) populations were completely haploid, doubled haploid or haploid-doubled haploid mixture. Haploids had very drastic reduction in plant height, panicle length, grain length, breadth and number and spikelet fertility (0.0%–2.1%). Doubled haploids from the hybrid of UPRI 95–121 × UPRI 95–165 were normal with fertility ranging between 69.6% and 97.7%. A genetic segregation in ratio of 1:1 was observed for five pigmentation characters in the H1 population derived from hybrid UPRI 95–122 × UPRI 95–165. Plant height showed the largest coefficient of variability (28.5%) followed by the number of spikelets per panicle (24.2%), number of grains per panicle (22.0%), percent seed set (9.2%) and panicle length (9.0%). The range of variation in the H1 population from fully fertile hybrid PMS 2A (CMS) × IR 31802 (restorer) was similar to its corresponding F2 population for plant height, spikelet fertility and number of grains/panicle. A single clone of plants from the cultivar BG 1321 exhibited complete male sterility but normal female fertility when pollinated with other varieties. Ovary-derived plants from the CMS lines PMS 2A and IR 58025A showed stable male sterility and those from thermosensitive genetic male sterile line UPRI 95–140 showed thermosensitive genetic male sterility. These lines have potential in the hybrid breeding program and are being currently exploited. This revised version was published online in July 2006 with corrections to the Cover Date.     

栽培稻的基因型差异程度和分类

本文利用来自一个籼/粳交(圭630/02428)的双单倍体(DH)系和由多种类型的籼、粳品种(系)组成的对照组,从分子水平上研究亚洲栽培稻的基因型差异。结果表明,栽培稻中存在两种主要的差异类型,即质的差异和量的差异。前者主要存在于籼、粳分化程度比较高的对照组中,85%以上的有关位点已经发生了籼或粳的分化趋向;后者主要存     

Chromosomal regions controlling anther culturability in rice (Oryza sativa L.)

Diallel analysis has revealed that anther culturability in rice (Oryza sativa L.) is a quantitative trait controlled by the nuclear genome. Mapping of anther culturability is important to increase the efficiency for green plant regeneration from microspores. In the previous study, we detected distorted segregation of RFLP markers in rice populations derived from the anther culture of an F₁ hybrid between a japonica cultivar ‘Nipponbare’ and an indica cultivar ‘Milyang 23’. To clarify the association between chromosomal regions showing distorted segregation and anther culturability, the anther culturability of doubled haploid lines derived from the same cross combination was examined, and the association between alleles of the RFLP markers, which exhibiting the most distorted segregation on chromosomes 1, 3, 7, 10 and 11, and the anther culturability was evaluated. One region on chromosome 1 was found to control callus formation from microspores, and one region on chromosome 10 appeared to control the ratio of green to albino regenerated plants. In both regions, the Nipponbare allele had positive effects. Three regions on chromosomes 3, 7 and 11, however, showed no significant effect on anther culturability. This revised version was published online in August 2006 with corrections to the Cover Date.     

A Functional Growth Analysis Model for Grain Development in Oryza sativa L.

The pattern of grain growth in two rice cultivars was assessed in terms of total dry weight of grain from anthesis upto maturity. Rice grain development followed a sigmoidal trend. Richards' function was found to more closely fie the data on grain growth and thus could serve as a suitable mathematical model for rice grain growth analysis.     

Genetic progress of upland rice (Oryza sativa L.) lines for disease resistance

The rice crop is affected by diseases throughout its cycle, impacting negatively on grain yield and quality. The control of the disease impact can be accomplished via crop breeding, using highly multiple resistant genotypes. This study aimed to evaluate the efficiency of multiple-character and specific selection of multiple resistance to major culture-associated diseases (neck blast, leaf scald and grain discoloration) in rice lines of the Upland Rice Genetic Breeding Program. The experiments were conducted in 35 sites during 12 agricultural years, where 124 lines were evaluated for the severity of fungal diseases, under natural field conditions. Multiple parameters were calculated based on the diseases´ scores: genetic, phenotypic and environmental variances, heritability, selection gain, renewal rate, and genetic and renewal progress. Genetic variance for the disease resistance was identified in the population, and the selection gain for multiple-character selection was of 3.16 year⁻¹ throughout the breeding process with a renewal rate of over 35%. The programme has showed efficiency in selecting multiple resistant genotypes to the mentioned diseases, highlighting genotypes with high potential for market release.     

粳稻和籼稻愈伤诱导和分化期间生理代谢差异初探

通过比较粳稻品种日本晴和籼稻品种9311成熟胚愈伤诱导和分化阶段,愈伤组织的基础生理代谢差异,探讨籼稻9311再生率低于粳稻日本晴的可能原因。研究表明,在愈伤诱导和分化的所有不同时期,在所有时期日本晴愈伤中的总氮和氨态氮含量均高于9311,在分化25天以前,硝态氮含量也高于9311。此外,在细胞代谢水平上,通过对可溶性蛋白含量的差异分析表明,在愈伤诱导一个月至分化15天时,日本晴的可溶性蛋白含量高于9311。     

Development of a technique for in vitro unpollinated ovary culture in rice, Oryza sativa L.

A simple and efficient technique for in vitro unpollinated ovary culture in rice which is also applicable for indica genotypes was developed for breeding and genetic studies. Sampling explants at the auricle distance of 7–12 cm between the two uppermost leaves of a tiller, providing a chilling pretreatment and ovaries with 1/3 of the hulls intact gave optimum response to culture. For callus induction with the spontaneous breaking of ovaries, N₆ media supplemented with NAA (2 mg/l) and DMSO (0.6–0.8%) gave a mean PCI value of 3.8% and range of 0.8–12.5% among genotypes. Media combining 2,4,5-T or 2,4-D with NAA in N₆ medium also has reasonably good callus induction. For calli induced inside, 2,4-D (0.2–0.5 mg/l), NAA (2 mg/l) and KT (1 mg/l) contained media were superior. The maximum green plant regeneration (PPR) of 77.3% was found with the medium containing NAA 0.25 mg/l, IAA 0.5 mg/l and KT 2.0 mg/l. Significant genotype, medium and their interaction effects for per cent ovary survival and callus induction were observed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Chromosomal localization of five mutant genes in rice, Oryza sativa, using primary trisomics

The chromosomal locations of five mutant genes in rice were determined by crossing the marker stocks with the 12 primary trisomics. Genetic segregation of each gene was studied in the F₂ or backcross populations. Out of the 60 possible cross combinations, 43 F₂ or BC₁ populations were studied. Segregation data indicated that spl11 was located on chromosome 12 while wp2 and eg2_(t) were located on chromosome 6. The genes v12_(t) and Bc₆ were located on chromosomes 8 and 9, respectively, which are sparsely populated with genetic markers.     

水稻圆粒基因RS的鉴定和定位

阐明水稻籽粒大小相关基因的遗传和分子机制对水稻产量形成具有重要意义。利用甲基磺酸乙酯(ethyl methanesulfonate, EMS)诱变粳稻品种宁粳3号筛选获得圆粒突变体round seed (rs)。遗传分析表明,突变体rs圆粒表型由单隐性核基因控制。颖壳扫描电镜观察发现,rs籽粒变圆主要是细胞数目改变导致的。在突变体rs中,细胞周期相关基因的表达较野生型显著升高。将RS定位在第3染色体短臂标记RM3413与N3-5之间,物理距离约589 kb。RS突变影响BR信号途径,改变了粒型相关基因的表达。本研究有助于阐明水稻籽粒发育的分子机制。     

Enhanced anther culture efficiency of indica rice (Oryza sativa L.) through modification of the culture media

The production of microspore-derived green plants from anther culture of indica rice is generally very low compared with japonica cultivars. A modified anther culture medium, consisting of a higher KNO₃ content (31 mm ) and casein hydrolysate (CH, 500 mg/1) but without ammonium salts, was tested in comparison with a medium consisting of the widely-used N6 medium nitrogen background, using four indica × indica F₁ hybrids as test materials. Green plant regeneration frequency was at least three-fold higher in the microspore-calli derived from the former medium than in those derived from the modified N6 medium. More than 700 microspore-derived plants were raised in the field. Another study was carried out using indica × japonica and indica × javanica F₁ hybrids. The results indicated that a medium with higher (3.5 mm ) ammonium sulphate may induce a higher frequency of anthers with microspore-calli but not necessarily lead to a larger number of green-plant regenerating calli. Subsequently, using the indica cv. ‘IR-43’ as the test material, use of a lower level (1.75 mm ) of (NH₄)₂SO₄, in addition to KNO₃ (31 mm ), was found to be better than CH (500 mg/l) for anther-response as well as green plant regenerability of the derived microspore-calli. Nitrate-nitrogen or ammonium-nitrogen alone elicited poor response. Twenty-five media involving combinations of KNO₃ (20–34 mm ) and (NH₄)₂SO₄ (1–3 mm ) were tested for their effects on anther response. Combinations involving KNO₃ (31–34 mM) and (NH₄)₂SO₄ (2.0–2.5 mm ) were found superior not only for achieving greater anther response but also, for subsequent green-plant regeneration. This contrasts with the 28 mm of KNO₃ and 3.5 mm of (NH₄)₂SO₄ in the widely-used N6 medium developed for japonica rice. Other than potassium nitrate and ammonium sulphate, and potassium phosphate to some extent, the levels of other inorganic salts tested did not make any significant difference to the process of anther response. Based on these results, modified media with three levels of ammonium sulphate were tested for anther culture efficiency of indica × japonica and indica × javanica derivatives (F₃s). Microspore-calli derived from a medium of a lower (1.75 mm ) level of (NH₄)₂SO₄ showed a higher regeneration potential overall than those derived from a higher (3.5 mm ) level. A revised medium has been suggested, on the basis of these results, for the realization of improved anther culture efficiency and, consequently, improved feasibility of using doubled haploids in genetic and breeding research with indica rice.     

Genetic diversity among parental lines of Indica hybrid rice (Oryza sativa L.) in China based on coefficient of parentage

Genetic diversity constitutes the raw material for plant improvement, and provides protection against genetic vulnerability to biotic and abiotic stresses. Diversity of parental lines of indica hybrid rice in China is not well‐characterized. The major objective of this study was to quantify genetic diversity of Chinese parental lines of hybrid rice via coefficient of parentage (COP). All 100 parental lines of hybrid rice widely used in hybrid breeding and commercial production during 1976–2003 were studied by COP analysis. The mean COP for the 100 parental lines was low (0.056), indicating a potentially high degree of diversity in Chinese hybrid rice breeding. Forty‐nine percent of all pairs of parental lines were completely unrelated by pedigree data. The low mean COP for the parental lines was attributed to a continual incorporation of exotic germplasm (wild rice, japonica and javanica etc.) into the genetic base over time, to the introduction of foreign germplasm from the Philippines (International Rice Research Institute), Korea, the United States, Thailand, and Guyana as breeding stock. The mean COP from 1976 to 1990 was twice as much as that from 1990 to 2003. Cluster analysis was an effective method to discriminate diversity, ten clusters were identified, and maintainer lines, restorer lines and other parental lines with special genetic background were clearly grouped. In addition, restorer lines were further divided into 11 sub‐clusters, which basically was in agreement with hybrid rice breeding. Among ten provinces, Hunan, Sichuan and Fujian were outstanding for breeding 54 of 100 parental lines in hybrid rice production, and the genetic diversity of parental lines in Fujian, Sichuan,Guangxi, Hunan and Jiangsu were all narrower than that in Hubei, Guangdong, Zhejiang and Jiangxi. The result of coefficient of parentage analysis for 100 parental lines may promote the management of parental diversity and hybrid rice breeding in China.     

水稻抗坏血酸氧化酶基因家族生物信息学分析

抗坏血酸氧化酶(ascorbic acid oxidase,AAO)是多铜氧化酶家族中的一员,在植物生长发育过程中起重要作用。为深入研究水稻AAO基因家族的功能特征及表达模式,采用生物信息学从Phytozome的水稻数据库鉴定出14个AAO成员,并对其染色体定位、蛋白理化性质及二级结构、基因结构、保守基序、系统发生树和表达模式等方面进行预测分析。结果显示,14个OsAAO不均匀地分布在8条染色体上,多为碱性蛋白;蛋白二级结构以无规则卷曲为主要组成部分;基因结构和保守基序分析表明,OsAAO内含子数目变化差异较大,但氨基酸序列具有较强的保守性;系统发生树可分为3个亚家族,OsAAOs与玉米、高粱簇在一起,亲缘关系较近;另外表达模式分析发现,OsAAO在不同的组织部位表达水平具有差异,这表明其行使功能不同。这些结果为今后研究该基因家族的生物学功能和培育耐旱品种提供理论依据。     

三氮苯类除草剂对水稻染色体结构、蛋白质含量及组分的影响

比较研究了不同浓度三氮苯类除草剂对水稻幼苗生长、叶绿素及可溶性蛋白质含量、根尖分生组织染色体结构、分生组织和叶绿体蛋白质组分的影响。结果表明,在0.1 mg /L Atrazine处理水稻后培养1周。幼苗高度由(10.8±1.7) cm（对照）降至 (8.2±0.7) cm,叶绿素含量由(1.07±0.013) mg/g FW（对照）降至(0.97±0.013) mg/g FW,