水稻杂种后代籽粒直链淀粉含量选择与品质和产量性状的关系

 选用4个稻米直链淀粉含量有显著差异的粳稻品种配制两个杂交组合（系选1号×通769和东农423×藤系180）,研究其杂交后代籽粒直链淀粉含量选择对品质和产量性状的影响。结果表明,籽粒直链淀粉含量选择对杂种后代蒸煮食味品质和产量相关性状有不同程度的影响,其影响程度因杂交组合及性状不同而异;在蒸煮食味品质性状中,淀粉黏滞性谱的崩解值和消减值受直链淀粉含量选择的影响较大,而在产量相关性状中抽穗期、单株有效穗数、结实率、单株粒重等受直链淀粉含量选择的影响相对较大;通过直链淀粉含量的连续定向选择可以从杂种后代中分出直链淀粉含量不同的后代,粳稻杂种后代低直链淀粉含量的定向选择效果优于高直链淀粉含量的选择效果,更容易得到超低亲的变异类型;直链淀粉含量的选择对杂种后代产量性状的影响较复杂,存在有利或不利的影响,低直链淀粉含量的选择将会导致单株粒重的下降。     

Genetic analysis of rainfed lowland rice drought tolerance under naturally-occurring stress in eastern India: Heritability and QTL effects

Drought tolerance is an important rainfed rice breeding objective, but because the heritability (H) of yield under drought stress is thought to be low, secondary physiological traits are considered better targets for selection than yield under stress per se. This assumption has rarely been tested, and there are no reports on H for yield under drought stress from experiments repeated over seasons in rainfed lowland rice. To assess the potential for improving yield under drought stress via direct selection, and to identify associated quantitative trait loci (QTL), doubled haploid lines with a narrow range of flowering dates, derived from the population CT9993-5-10-1-M/IR62266-42-6-2, were screened under full irrigation and severe drought stress induced by draining the paddy before flowering in 2000–2002 at Raipur, India. Drought stress reduced mean yield by 80%. H was similar in stress and non-stress trials, as was the relative magnitude of the genotype and genotype × year variances. The genetic correlation between yield in stress and non-stress conditions was 0.8, indicating that about 64% of the genetic variation for yield under stress was accounted for by differences in yield potential also expressed in irrigated environments. These results indicate that direct selection for yield under drought stress can produce yield gains under stress without reducing yield potential. There was no secondary trait for which selection resulted in greater predicted response in yield under stress than direct selection for stress yield per se. A QTL was detected on chromosome 1 near sd1 that explained 32% of the genetic variation for yield under stress, but only 4% under non-stress. Its effect was consistent across years. This QTL accounted for much of the variation in drought yield not accounted for by variation in yield potential.     

旱稻数量性状的遗传参数分析

从广义遗传力、遗传相关、遗传进度和选择指数等几个方面,分析了57份旱稻品种的株高、有效穗数、主穗长度、主穗粒数、千粒重、单株粒重和剑叶长/宽7个主要数量性状的遗传潜力和选择效果.分析结果表明：株高、剑叶长/宽、单株粒数、主穗长度、千粒重的广义遗传力较高,有效穗数、单株粒重的广义遗传力偏低;单株粒数、单株粒重、有效穗数3个主要产量构成因素的遗传变幅较大,在该群体中对这3个性状进行选择的潜力较大;产量性状中的单株粒数和千粒重与单株粒重本身均有一定的遗传潜力,预期遗传进度也较大,特别是单株粒数的预期遗传进度较大;单株粒重与单株粒数、千粒重间存在显著或极显著的遗传正相关,主穗长度与有效穗数间存在极显著的遗传负相关,因此可以通过提高单株粒数和千粒重来间断增加单株产量;用单株粒重与单株粒数、千粒重和有效穗数构成的选择指数进行综合选择,相对效率高达219.34%,比直接选择单株粒重提高了119.34%,显著高于对单株粒重的直接选择,因此采用这个指数对单株粒重进行间接选择效果较为理想.     

Use of Selection Indices Based on Multivariate Analysis for Improving Grain Yield in Rice

In order to study selection indices for improving rice grain yield, a cross was made between an Iranian traditional rice (Oryza sativa L.) variety, Tarommahalli and an improved indica rice variety, Khazar in 2006. The traits of the parents (30 plants), F1 (30 plants) and F2 generations (492 individuals) were evaluated at the Rice Research institute of Iran (RRII) during 2007. Heritabilities of the number of panicles per plant, plant height, days to heading and panicle exsertion were greater than that of grain yield. The selection indices were developed using the results of multivariate analysis. To evaluate selection strategies to maximize grain yield, 14 selection indices were calculated based on two methods (optimum and base) and combinations of 12 traits with various economic weights. Results of selection indices showed that selection for grain weight, number of panicles per plant and panicle length by using their phenotypic and/or genotypic direct effects (path coefficient) as economic weights should serve as an effective selection criterion for using either the optimum or base index.     

Progress in ideotype breeding to increase rice yield potential

The ideotype approach has been used in breeding programs at the International Rice Research Institute (IRRI) and in China to improve rice yield potential. First-generation new plant type (NPT) lines developed from tropical japonica at IRRI did not yield well because of limited biomass production and poor grain filling. Progress has been made in second-generation NPT lines developed by crossing elite indica with improved tropical japonica. Several second-generation NPT lines outyielded the first-generation NPT lines and indica check varieties. China's “super” rice breeding project has developed many F₁ hybrid varieties using a combination of the ideotype approach and intersubspecific heterosis. These hybrid varieties produced grain yield of 12 t ha⁻¹ in on-farm demonstration fields, 8–15% higher than the hybrid check varieties. The success of China's “super” hybrid rice was partially the result of assembling the good components of IRRI's NPT design in addition to the use of intersubspecific heterosis. For example, both designs focused on large panicle size, reduced tillering capacity, and improved lodging resistance. More importantly, improvement in plant type design was achieved in China's “super” hybrid rice by emphasizing the top three leaves and panicle position within a canopy in order to meet the demand of heavy panicles for a large source supply. The success of “super” hybrid rice breeding in China and progress in NPT breeding at IRRI suggest that the ideotype approach is effective for breaking the yield ceiling of an irrigated rice crop.     

水稻粒形遗传与长粒型优质粳稻育种进展

水稻粒形遗传机制和粒形育种一直是水稻品质和产量研究的重要领域。在粳稻品种选育中,对长粒形遗传种质的选择,已经成为近年来一种新的育种趋势。我们在总结粒长及其相关性状的遗传研究进展和已知粒长相关基因功能的基础上,系统地介绍了南方稻区长粒粳稻的育种历程及其选育策略。同时,对以品种嘉禾218为代表的南方长粒晚粳稻系列品种农艺性状和品质特性进行了比较,在阐明长粒粳稻优质、高产的品种特点的同时,提出长粒晚粳育种中选择粒形、兼顾株型、保产提质的选育思路。     

不同类型亲本的杂交粳稻产量性状比较

收集不同熟期、不同类型的BT型粳稻不育系(保持系)和恢复系,对亲本分别按不同性状进行聚类,比较分析不同类型亲本配组杂种后代的性状表现,结果表明:1)不同类型亲本配组,杂种的性状一般表现为中间类型;2)亲本的抽穗期、株高对杂种单株穗数、每穗总粒数、每穗实粒数、单株产量、单株颖花量等多数产量性状无明显影响。亲本的穗粒结构对杂种的穗粒构成有明显影响,多穗型亲本间配组,杂种每穗总粒数及单株颖花量、产量潜力均较小;大穗型亲本间配组,杂种每穗总粒数及单株颖花量、产量潜力均较大;3)以多穗型不育系与大穗型恢复系配组,产量较高,是现有亲本配制杂交粳稻一种较好的配组方式;4)直立穗不育系与弯曲穗恢复系配组,杂种单株颖花量最多,产量潜力最大,而且株叶形态较好,如筛选到结实率高的组合,该配组方式的杂种具有较高的增产潜力。     

珍汕97/明恢63重组自交系群体根系性状对产量的影响

在群体水培条件下,以珍汕97/明恢63重组自交系群体的204个株系(F12,F13)为供试材料,研究重组自交系群体抽穗期根系有关性状与产量的关系,以期为水稻根系改良和根系数量性状基因定位提供依据.结果表明,影响产量的主要根系性状为单株根系活性、颖花根活量、每株根干重、最长不定根长、众数根长、每条不定根长及每条不定根粗,其中以单株根系活性对产量的影响最大;增加单株根系活性、每株根干重、最长不定根长和每条不定根粗能显著提高产量,增加颖花根活量、每条不定根长和众数根长将使产量显著下降.增加高产类型水稻抽穗期的每株根干重、每条不定根重、单位长度根重及单株根系活性能显著提高产量.每株根干重与高产水稻关系密切,而每株不定根数则与低产水稻关系密切.颖花根活量的增加对高产水稻株系的产量有提高作用,对中低产水稻则有负面影响.     

Yield vs. morphophysiological trait-based criteria for selection of durum wheat in a semi-arid Mediterranean region (northern Syria)

The value of germplasm-specific and general indexes of selection based on morphophysiological traits was assessed as an alternative to conventional yield-based selection for grain yield improvement of durum wheat in a semi-arid Mediterranean region. General indexes were developed from the evaluation of a collection of 503 landrace accessions. Specific indexes were also defined for each of the durum wheat types mediterraneum typicum and syriacum as well as for a third germplasm group including mostly Mediterranean material pertaining to neither of these types. Indexes included two or three traits among the following: displacement from optimal heading date (difference in absolute value of days from the mean heading date of three control cultivars), early growth vigour, kernels per spike and kernel weight, the two yield components being alternative to each other. The efficiency of selection criteria was assessed in another set of 64 entries in terms of predicted yield responses and actual yield gains over target environments other than that of selection. Each of the three environments acted by turns as the selection environment and the remaining two as the target environments. These environments allowed for the assessment of selection criteria over a wide range of seasonal rainfall and mean yield levels. Large genotype×environment interaction was observed for yield and early vigour. Ranking of selection indexes for predicted and actual yield responses were fairly consistent, indicating an advantage of general indexes. The best among them, including heading displacement and kernels per spike, was, on the average, 20% and 11% more efficient than yield-based selection in terms of predicted and actual responses, respectively. The advantage of this index was the consequence of the absence of covariation and the moderate to high values of genetic correlation with yield over target environments, heritability and ratio of genotypic to genotype×environment interaction variance of its component traits.     

Cultivar evaluation and trait analysis of tropical early maturing maize under Striga-infested and Striga-free environments

Striga hermonthica is a major constraint to maize (Zea mays L.) production in sub-Saharan Africa. The use of secondary traits that have high heritability and genetic correlation with grain yield can improve the precision with which Striga resistant genotypes are identified. Fifteen early cultivars were evaluated under Striga-infested and Striga-free conditions for 2 years at Mokwa and Abuja, Nigeria. The objective was to examine their performance based on multiple traits under stress and non-stress conditions and analyze the interrelationship among traits using genotype-by-trait (GT) biplot so as to assess the value of traits used in the base index for selection for Striga resistance and improved grain yield (YLD). TZE-W DT STR C₄ had the best performance based on multiple traits while TZE-W DT STR C₄, TZE-Y DT STR C₄, Multicob Early DT, and TZE-W DT STR QPM C₀ were the closest to the ideal cultivar when Striga infested. Ears per plant, Striga damage at 8 and 10 weeks after planting, and ear aspect (EASP) were the most reliable traits for selecting for resistant genotypes. Striga emergence count at 8 and 10 weeks after planting were not among the reliable traits identified for selection for improved grain yield and their inclusion in the base index needs to be further verified. EASP had high correlation with grain yield and was one of the most reliable traits for selection for increased grain yield under Striga infestation and should be included in the index.     

玉米开花期耐旱相关性状的遗传及育种策略

玉米对干旱的反应取决于新陈代谢能力、形态结构和生育阶段.开花期逢遇干旱使玉米产量下降幅度最大.随着产量下降,环境方差所占比例增大,遗传力降低,直接选择效率不高.在干旱条件下,寻找遗传力高且与产量高度相关的第二类性状,构建选择指标,可提高耐旱选择效率.雌雄开花间隔天数(ASI)和单株穗数是可供利用的第二类性状,对其选择所获得的产量增益,在干旱和正常水分条件下均可表现出来.耐旱育种目的在于改变基因型对干旱环境的反应,实现耐旱丰产目标.根据目标环境特征,设计适宜的耐旱选择程序,结合分子标记辅助选择技术,鉴定和利用现有优良耐旱种质和CIMMYT耐旱群体,是我国进行耐旱育种和种质改良的可选途径。     

Response to two cycles of divergent selection for grain yield under drought stress in four rice breeding populations

Drought is a major production constraint in rainfed rice (Oryza sativa L.). Lack of effective selection criteria is a major limitation hampering progress in breeding for drought tolerance. In an earlier report, we showed in two populations that one cycle of direct selection was effective in increasing grain yield under stress. In the present study, we retested the efficiency of direct selection for grain yield under drought stress in rice using four populations derived from crossing upland-adapted, drought-tolerant varieties (Apo, Vandana) to high-yielding, lowland-adapted, drought-susceptible varieties (IR64, IR72). Each population was subjected to two cycles of divergent selection either under drought stress in upland or under nonstress conditions in lowland conditions. Following selection, approximately 40 high-yielding lines selected under each protocol from each population, along with a set of unselected lines, were evaluated in a series of selection response trials over a range of moisture levels. Significant response to direct selection under stress was realized in 9 out of 15 combinations of populations and stress environments, and in 6 of the 7 severe stress trials. Averaging over all the populations and stress environments, the stress-selected lines had a yield advantage of 25 and 37% over nonstress-selected and random lines, respectively. In contrast to this, under nonstress, the nonstress-selected lines had an average yield advantage of only 7 and 13% over stress-selected and random lines, respectively. Direct selection in managed stress trials during dry seasons gave significant response (25% on average relative to indirect selection in nonstress conditions) under naturally occurring wet season stress. In addition, direct selection under stress in upland gave an average gain of 16 and 45% over nonstress-selected and random lines, respectively, under stress in lowland. The yield advantage of the stress-selected lines appears to result mainly from maintenance of higher harvest index. These results show that direct selection for grain yield under stress is effective and does not reduce yield potential. Overall, this is the first report in rice demonstrating that (a) selection under managed drought stress in the dry season can result in yield gains under natural stress in the wet season, and (b) that selection under upland drought stress can, at least under the conditions of the present study, result in gains under lowland drought conditions.     

Relationship Between Plant Type and Grain Quality of Japonica Hybrid Rice in Northern China

Plant type and grain quality are two major aspects in rice breeding. Using canonical correlation analysis and canonical redundancy analysis, the relationship between plant type traits and rice grain quality traits was studied with 100 crosses derived from 10 sterile lines × 10 restorer lines. There was a complex relationship between parts of the traits of the two aspects. The angle of the 2nd leaf from the top and single panicle weight played important roles in plant type system and amylose content and grain length in grain quality system. The angle of the 2nd leaf from the top, plant height and single panicle weight had a great effect on grain quality traits, and amylose content, brown rice rate and translucency were easily influenced by plant type traits. Selection index model indicated that japonica hybrid rice in Northern China with good quality was characterized by broad flag leaf and 2nd leaf from the top, narrow and short 3rd leaf from the top, low plant height, short culm, long and more panicles and low single panicle weight.     

Use of Major Quantitative Trait Loci to Improve Grain Yield of Rice

Further improvement of rice productivity remains a challenge. Breeding is perceived as an important option to increase rice yield. However, the genetic progress of grain yield in most rice breeding programs was slow in the last decades. Although great progress in rice genomics and molecular biology has been achieved, the effect of such technological innovations on rice breeding is far small. Marker-assisted selection （MAS） for a few target quantitative trait loci （QTLs） has significant effects in improving qualitative traits, such as disease resistance. The success of MAS has therefore motivated breeders to identify and use major QTLs for yield and yield component traits. In this review, we summarized the recent methods in QTL identification, including novel statistical methods for linkage and association mapping, special population types, and whole-genome sequencing. We reviewed the successful application of marker-assisted gene introgression and gene pyramiding to improve grain yield and discussed the design of efficient MAS schemes to further increase the success rate of breeding programs. The use of well-characterized major QTLs through introgression and gene pyramiding is proven effective in improving grain yield, particularly yield under abiotic stress. Major QTLs that are stable across genetic background and growing environments are often found in less adapted germplasms, such as landraces and wild relatives. Advanced backcross QTL analysis and introgression lines, which integrate QTL discovery and utilization, are important methods for exploiting major QTLs contained in such germplasms. Next-generation sequencing substantially increases mapping resolution and accelerates the identification of casual genes underlying major QTLs. Practical guidelines derived from theoretical and empirical studies are given to guide the design of efficient marker-assisted gene introgression and pyramiding schemes.     

Parental Selection in Rice Cultivar Improvement

The evaluation of rice (Oryza sativa L.) cultivars assists breeders in identifying useful trait relationships and in selecting parents as donors of specific traits. This study was conducted to compare long-grain rice cultivars using genotype × trait (GT) biplot analysis and determine potential donors of traits related to grain yield and quality. Seventeen cultivars in the 2005 and 2006 Uniform Regional Rice Nursery in Beaumont, Texas, USA were analyzed for 20 traits using GT biplot analysis. The GT biplots showed the diversity among cultivars with regards to yield-related traits. Cultivars recommended as donor parents were: Trenasse, Spring, Presidio, and Cocodrie for high grain yield and head rice rate; Trenasse and Presidio for semi-dwarfness; Banks for tall plant height; Wells for high flag leaf area, panicle weight, and number and mass of filled grains per panicle; Hidalgo for high tiller density; Francis for high number of spikelets per panicle; Spring and Trenasse for short flowering duration; Cheniere for more days to heading and maturity and Spring for less days; and Spring and Hidalgo for high grain weight. Breeders can use these cultivars with specific traits to increase grain yield and quality.     

Breeding for drought tolerance: Direct selection for yield, response to selection and use of drought-tolerant donors in upland and lowland-adapted populations

Drought is the most important constraint reducing rice yield in rainfed areas. Earlier efforts to improve rice yield under drought mainly focused on improving secondary traits because the broad-sense heritability (H) of grain yield under drought stress was assumed to be low, however gains in yield by selecting for secondary traits have not been clearly demonstrated in rice. In present study, the effectiveness of direct selection for grain yield was assessed under lowland reproductive stage stress at Raipur in eastern India and under upland reproductive stage drought stress at IRRI. The selection under severe stress (in both upland and lowland trials) resulted in greater gains under similar stress levels (yield reduction of 65% or greater under stress) in evaluation experiments than did selection under non-stress conditions, with no yield reduction under non-stress conditions. We observed similar H of grain yield under stress and non-stress conditions, indicating direct selection for yield under drought will be effective under both lowland and upland drought stresses. None of the secondary traits (panicle exsertion, harvest index, leaf rolling, leaf drying) included in our study showed a higher estimate for H than grain yield under stress. Secondary traits as well as indirect selection for grain yield under non-stress situation were predicted to be less effective in improving yield under drought in both lowland and upland ecosystem than direct selection for grain yield under the respective stress situations. The low, but positive values observed for genetic correlation (r_G) between yield under stress and non-stress indicated that it is possible to combine drought tolerance with high-yield potential but low values also indicated that selection for grain yield needs to be carried under stress environments. The study also indicated that under lowland drought stress, the use of highly drought-tolerant donors, as parents in crosses to high yielding but susceptible varieties resulted in a much higher frequency of genotypes combining high-yield potential with tolerance than did crosses among elite lines with high-yield potential but poor tolerance. Breeding strategies that use drought-tolerant donors and that combine screening for yield under managed drought stress with screening for yield potential are likely to result in the development of improved cultivars for drought-prone rainfed rice producing areas.     

Comparing decentralized participatory breeding with on-station conventional sorghum breeding in Nicaragua: I. Agronomic performance

Few studies have assessed the effective gains achieved by collaborative decentralized participatory breeding, in terms of yield and other agronomic traits, in comparison with centralized conventional breeding using the same breeding schemes. Our study concerned an experience of participatory improvement of tortillero sorghum for low-input cropping systems in northern Nicaragua. It set out to compare the effect of two breeding schemes simultaneously managed on-station and on-farm. Two synthetic populations were used as sources of genetic variability. The study was designed to distinguish between three “selection modes”: farmers’ selection on-farm (FoF), breeder’ selection on-station (BoS) and breeder's selection on-farm (BoF). After two selection cycles, we found that FoF selection reduced phenotypic variability as much as BoS selection. In general, BoS selection produced higher-yielding lines under the target on-farm conditions. But FoF selection was more effective in promoting lines with higher values for an index of agronomic suitability (IAS), expressing a better balance between earliness, plant height, grain size and yield. Such genotypes might cope more easily with local environmental constraints and farmers’ preferences. BoF selection did not prove to be effective for either yield or IAS. This research shows the need for close collaboration between farmers and breeders as well as complementarities between the selection phases managed on-farm and on-station, to make breeding for difficult environments fully efficient.     

再生稻肥料管理对不同品种产量和品质的影响

【目的】探明肥料管理、品种及其互作对再生稻头季和再生季产量和品质的影响,为再生稻高产优质育种和栽培提供理论依据。【方法】采用大田试验的方法,以4个华中地区主推的再生稻品种为材料,设置4种肥料管理方法,分别测定水稻的产量和产量构成因素、稻米品质(加工品质和外观品质)、干物质生产及相关农艺性状等。【结果】相比推荐施肥对照(CK),全生育期施用再生稻专用缓释肥(SRF)使两季施肥的次数从5次减少到3次,而且产量在头季和再生季分别达8.86和6.39 t/hm ²,较CK仅降低了6.2%和9.1%。SRF在头季减产主要归因于较低的结实率,而在再生季减产是每穗颖花数和总颖花数共同下降的结果。促芽肥施与不施对再生季产量没有影响。再生稻两季的加工品质和外观品质主要受品种的影响,肥料处理及其与品种的互作影响很小。相比其他3个品种,甬优4949的头季和再生季产量最高,加工品质和外观品质最好。【结论】施用专用缓释肥和省施促芽肥均能够在不大幅损失稻谷产量的同时减少施肥次数促进再生稻轻简化栽培。     

Molecular Improvement of Grain Weight and Yield in Rice by Using GW6 Gene

Molecular design breeding is one of straightforward approaches to break yield barriers in rice. In this study, GW6 gene for grain length and width from Baodali was transferred into an indica recurrent parent 9311 and a japonica variety Zhonghua 11 （ZH11） using marker-assisted backcross （MAB）. One and three introgression lines were selected for phenotypic analysis from 9311 and ZH11 genetic backgrounds, respectively. SSL-1, an improved 9311 near isogenic line with GW6 performed 11%, 19% and 6.7%higher of grain length, 1000-grain weight and single plant yield, respectively, as compared with 9311. All the three improved ZH11-GW6 lines, R1, R2 and R3, had more than 30% increase in grain weight and about 7%higher in grain yield. Seed plumpness of R1, R2 and R3 was improved synchronously because the three ZH11-GW6 lines contained GIF1 （Grain Incomplete Filling 1）, a dominant grain filling gene. Thus, GW6 has high potential in increasing the yield of inbred lines through MAB, making it an important genetic resource in super hybrid rice breeding. This study provides insights in the utilization of GW6 for large grain and high yield rice breeding via molecular design breeding.     

利用分子标记辅助选择改良温敏核不育系GD-8S的稻瘟病抗性

以含有广谱稻瘟病抗性基因Pi 1的籼稻材料BL122为供体,优质感病温敏核不育系GD 8S为受体,通过杂交、多次回交和自交结合分子标记辅助选择技术,将Pi 1基因导入GD 8S中。综合目标基因的分子检测、育性镜检、田间农艺性状表现以及遗传背景的回复率,筛选获得5个改良株系RGD8S 1、RGD8S 2、RGD8S 3、RGD8S 4和RGD8S 5。采用广东省具有代表性的33个菌株进行人工接种抗性鉴定,5个改良株系的抗性频率为75.76%~100.00%,而对照仅为9.09%。农艺性状分析表明,除剑叶长和每株穗数外,其余性状改良株系与对照无显著差异。这些改良株系可用于进一步测配选育高抗稻瘟病杂交稻新组合。