Genetic linkage map ofBrassica campestris L. using AFLP and RAPD markers

A genetic linkage map comprised of 131 loci was constructed with an F₂ population derived from an inter-subspecific cross betweenBrassica campestris L. ssp.chinensis cv. ‘aijiaohuang’ and ssp.rapifera cv. ‘qisihai’. The genetic map included 93 RAPD loci, 36 AFLP loci and 2 morphological loci organized into 10 main linkage groups (LGs) and 2 small groups, covering 1810.9cM with average distance between adjacent markers being approximately 13.8cM. The map is suitable for identification of molecular markers linked to important agronomic traits, QTL analysis, and even for marker-assisted selection in breeding programs of Chinese cabbage and turnip. Project (No. 39870509) supported by the National Natural Science Foundation of China     

高梁分子遗传图谱研究进展

本文从临时性作图群体和永久性作图群体两方面概述了高粱分子标记遗传图谱的研究进展,比较了不同分子标记和不同作图群体在高粱图谱构建上的差异,展望了高粱遗传图谱的研究方向.     

基于杨梅基因组鸟枪法测序开发的107个SSR标记及其在品系鉴定中应用

研究目的：开发多态性高的基因组简单重复序列（SSR）标记,为杨梅遗传多样性、遗传图谱构建及品种鉴定相关研究奠定基础。 创新要点：从杨梅全基因组鸟枪法测序数据中新开发了107个SSR标记,并应用于品种间遗传多样性分析及品系鉴定。 研究方法：应用生物信息学软件从基因组测序数据中搜索SSR位点并设计相应引物,添加通用的M13尾巴和荧光标识筛选多态性高的SSR标记。 重要结论：开发的107个基因组SSR标记可以广泛应用于杨梅种质资源和遗传育种研究,鉴定出三个杨梅新品系。     

水稻米香基因的初步定位

香味是水稻重要食味品质性状之一,但稻米香味的遗传甚为复杂.早有报道水稻米香基因位于第八条染色体上且与RFLP标记RG28紧密连锁.本实验通过水稻籼粳亚种之间的杂交,利用SSR(Simple Sequence Repeat)分子标记的方法对水稻米香基因进行初步定位.结果表明:稻米香味性状受一对隐性基因控制,且位于第八条染色体SSR标记RM8264和RM1109之间,其遗传距离大约2.1cM.这一结果将对于米香基因的精细定位提供了重要依据.     

Fine mapping of multiple interacting quantitative trait loci using combined linkage disequilibrium and linkage information

Quantitative trait loci (QTL) and their additive, dominance and epistatic effects play a critical role in complex trait variation. It is often infeasible to detect multiple interacting QTL due to main effects often being confounded by interaction effects. Positioning interacting QTL within a small region is even more difficult. We present a variance component approach nested in an empirical Bayesian method, which simultaneously takes into account additive, dominance and epistatic effects due to multiple interacting QTL. The covariance structure used in the variance component approach is based on combined linkage disequilibrium and linkage (LDL) information. In a simulation study where there are complex epistatic interactions between QTL, it is possible to simultaneously fine map interacting QTL using the proposed approach. The present method combined with LDL information can efficiently detect QTL and their dominance and epistatic effects, making it possible to simultaneously fine map main and epistatic QTL.     

A recessive gene controlling male sterility sensitive to short daylength/low temperature in wheat (Triticum aestivum L.)

Utilization of a two-line breeding system via photoperiod-thermo sensitive male sterility has a great potential for hybrid production in wheat (Triticum aestivum L.). 337S is a novel wheat male sterile line sensitive to both short daylength/low temperature and long daylength/high temperature. Five F₂ populations derived from the crosses between 337S and five common wheat varieties were developed for genetic analysis. All F₁’s were highly fertile while segregation occurred in the F₂ populations with a ratio of 3 fertile:1 sterile under short daylength/low temperature. It is shown that male sterility in 337S was controlled by a single recessive gene, temporarily designated as wptms3. Bulked segregant analysis (BSA) coupled with simple sequence repeat (SSR) markers was applied to map the sterile gene using one mapping population. The wptms3 gene was mapped to chromosome arm 1BS and flanked by Xgwm413 and Xgwm182 at a genetic distance of 3.2 and 23.5 cM, respectively. The accuracy and efficiency of marker-assisted selection were evaluated and proved essential for identifying homozygous recessive male sterile genotypes of the wptms3 gene in F₂ generation.     

Development of genic SSR markers from transcriptome sequencing of pear buds

研究目的：基于转录组数据开发具有扩增率高和跨物种转移性的基因组编码区内的SSR（genic-SSR）标记,为梨属植物的分子系统发育关系和遗传多样性相关研究提供新的方法。创新要点：首次利用梨属植物的转录组测序（RNA-seq）数据结合M-13荧光尾巴高效率地开发了104个genic-SSR标记,并成功将其应用于梨属植物的系统发育关系研究中。研究方法：应用生物信息学软件从转录组测序数据中搜索SSR位点和设计相应引物,结合高效的M-13荧光尾巴的方法筛选多态性高的SSR标记。重要结论：转录组数据能够为梨属植物分子系统发育关系和遗传多样性研究提供新的SSR标记来源。     

DNA分子标记及其在作物遗传育种中的应用

介绍了在作物遗传育种中常用的几种分子标记,并且概述了它们在作物遗传育种中应用的几个方面(1)分子标记遗传图谱的建立及基因定位;(2)分子标记的辅助选择;(3)亲缘关系和遗传多样性研究;(4)品种纯度鉴定.     

DNA标记及其在鱼类中的应用

DNA分子标记是继形态标记、细胞标记和生化标记之后发展起来的一种比较理想的遗传标记技术。本文简要介绍RFLP、RAPD、AFLP、SSR、SNP、EST、mtDNA等DNA分子标记的类型,基本原理和特点,以及分子标记技术在鱼类遗传图谱构建、基因定位和分子标记辅助育种等方面的应用前景予以展望。     

基于SSR分子标记的遗传学实验教学项目设计与探讨

该文利用科学研究中发现的全生育期黄绿叶突变体ygl4(t)为材料,整合水稻育苗及杂交技术、叶绿素含量测定、遗传分析及基于SSR标记的基因连锁分析等实验内容,设计了一个跨专业综合性实验。学生通过该实验可以观察水稻生长过程,了解化学诱变和SSR标记的重要应用价值,学会区分野生型与突变体的差异,理解基因型与表型的内在联系。该实验对培养学生将多专业知识及实验技能整合运用能力和创新研究能力具有重要作用。     

Determination of the genetic diversity of vegetable soybean [Glycine max (L.) Merr.] using EST-SSR markers

The development of expressed sequence tag-derived simple sequence repeats (EST-SSRs) provided a useful tool for investigating plant genetic diversity. In the present study, 22 polymorphic EST-SSRs from grain soybean were identified and used to assess the genetic diversity in 48 vegetable soybean accessions. Among the 22 EST-SSR loci, tri-nucleotides were the most abundant repeats, accounting for 50.00% of the total motifs. GAA was the most common motif among tri-nucleotide repeats, with a frequency of 18.18%. Polymorphic analysis identified a total of 71 alleles, with an average of 3.23 per locus. The polymorphism information content (PIC) values ranged from 0.144 to 0.630, with a mean of 0.386. Observed heterozygosity (H _o) values varied from 0.0196 to 1.0000, with an average of 0.6092, while the expected heterozygosity (H _e) values ranged from 0.1502 to 0.6840, with a mean value of 0.4616. Principal coordinate analysis and phylogenetic tree analysis indicated that the accessions could be assigned to different groups based to a large extent on their geographic distribution, and most accessions from China were clustered into the same groups. These results suggest that Chinese vegetable soybean accessions have a narrow genetic base. The results of this study indicate that EST-SSRs from grain soybean have high transferability to vegetable soybean, and that these new markers would be helpful in taxonomy, molecular breeding, and comparative mapping studies of vegetable soybean in the future.     

Assessment of genetic diversity by simple sequence repeat markers among forty elite varieties in the germplasm for malting barley breeding

The genetic diversity and relationship among 40 elite barley varieties were analyzed based on simple sequence repeat (SSR) genotyping data. The amplified fragments from SSR primers were highly polymorphic in the barley accessions investigated. A total of 85 alleles were detected at 35 SSR loci, and allelic variations existed at 29 SSR loci. The allele number per locus ranged from 1 to 5 with an average of 2.4 alleles per locus detected from the 40 barley accessions. A cluster analysis based on the genetic similarity coefficients was conducted and the 40 varieties were classified into two groups. Seven malting barley varieties from China fell into the same subgroup. It was found that the genetic diversity within the Chinese malting barley varieties was narrower than that in other barley germplasm sources, suggesting the importance and feasibility of introducing elite genotypes from different origins for malting barley breeding in China.     

水稻早世代稳定株系特有分子标记研究

SSR和ISSR分子标记已广泛应用于研究遗传行为和基因定位。在对水稻早世代稳定遗传特性的研究中,选用分布于水稻12条染色体上的168对多态性较好的SSR引物,对28个稳定株系的F_1、F_2、F_3及同组合的分离株系进行了SSR标记分析；选用26个多态性较好的ISSR引物对5个组合中出现的8个稳定株系及同组合的分离株系进行了ISSR分子标记。结果显示：稳定株系的标记带型出现三种类型：(1)母本带出现,父本带消失；(2)父本带出现,母本带消失；(3)出现非父母标记带型。分离株系表现为杂合标记带。推测水稻早世代稳定是在遗传因子作用下,在杂交受精或合子早期发育中发生了双亲染色体重排,形成纯合的F_1单株。     

Back to Africa: Tracing Dyslexia Genes in East Africa

A sample of Swahili-speaking probands with reading difficulties was identified from a large representative sample of 1,500 school children in the rural areas of Tanzania. Families of these probands (n = 88) were invited to participate in the study. The proband and his/her siblings received a battery of reading-related tasks and performance on these tasks was recorded and treated as phenotypic data. Molecular-genetic analyses were carried out with 47 highly polymorphic markers spanning three previously identified regions of interest harboring susceptibility loci for reading difficulties: 2p, 6p, and 15q (DYX1–DYX3). The analyses revealed the involvement of these regions in the development of reading difficulties in Swahili. The linkage signals are especially pronounced for time (compared with error) indicators of reading difficulties. These findings are easily interpretable because in transparent languages such as Swahili deficits in reading are more related to the rate/speed of reading and reading-related processes than to the number of errors made. In short, the study incrementally advances the field by adding an understudied language and an understudied population to the variety of languages and populations in the field of molecular-genetic studies of reading difficulties.     

Determination of genetic relationships between evergreen azalea cultivars in China using AFLP markers

Evergreen azaleas are among the most important ornamental shrubs in China. Today, there are probably over 300 cultivars preserved in different nurseries, but with little information available on the cultivar itself or relationships between cultivars. Amplified fragment length polymorphism (AFLP) markers were employed to determine the genetic relationships between evergreen azalea cultivars in China. One hundred and thirty genotypes collected from gardens and nurseries, including cultivars classified in the groups East, West, Hairy, and Summer, unknown cultivars, and close species, were analyzed using three primer pairs. A total of 408 polymorphic fragments were generated by AFLP reactions with an average of 136 fragments per primer pair. The average values of expected heterozygosity and Shannon’s information index were 0.3395 and 0.5153, respectively. Genetic similarities were generated based on Dice coefficients, used to construct a neighbor joining tree, and bootstrapped for 100 replicates in Treecon V1.3b. Principal coordinate analysis (PCO) was performed based on Dice distances using NTSYS-pc software. The AFLP technique was useful for analyzing genetic diversity in evergreen azaleas. Cluster analysis revealed that cultivars in the West and Summer groups were quite distinct from other groups in the four-group classification system and that the East and Hairy groups should be redefined.     

Identification of candidate genes for drought stress tolerance in rice by the integration of a genetic （QTL） map with the rice genome physical map

INTRODUCTION Drought stress is a major constraint to rice(Oryza sativa) production and yield stability in rainedecosystems (Dey and Upadhyaya, 1996). Rice mustbe made more drought tolerant, but this is a somewhatcontradictory objective considering that rice is mostcommonly grown under flooded conditions. Achiev-ing drought tolerance in rice will require a deeperunderstanding of the possible physiological mecha-nisms available for water stress tolerance and theidentification of favo…     

Map features and the recall of discourse

College undergraduates heard a 1760-word narrative which described events occurring on an imaginary island. As they listened, learners studied either a map of the island with features located spatially, a map—outline with features listed next to it, or just an outline without feature information. People who saw the map recalled more idea units and feature-related information on both free- and cued-recall tests. There was also a significant relation between correct recall and the ability of a subject to reconstruct the spatial relations on the map. The data were interpreted in terms of a feature-location model of map—discourse memory.     

Evaluation of the effect and profitability of gene-assisted selection in pig breeding system

Objective:To evaluate the effect and profitability of using the quantitative trait loci (QTL)-linked direct marker (DR marker) in gene-assisted selection (GAS). Methods: Three populations (100, 200, or 300 sows plus 10 boars within each group) with segregating QTL were simulated stochastically. Five economic traits were investigated, including number of born alive (NBA), average daily gain to 100 kg body weight (ADG), feed conversion ratio (FCR), back fat at 100 kg body weight (BF) and intramuscular fat (IMF). Selection was based on the estimated breeding value (EBV) of each trait. The starting frequencies of the QTL's favorable allele were 0.1, 0.3 and 0.5, respectively. The economic return was calculated by gene flow method. Results: The selection efficiency was higher than 100% when DR markers were used in GAS for 5 traits. The selection efficiency for NBA was the highest, and the lowest was for ADG whose QTL had the lowest variance. The mixed model applied DR markers and obtained higher extra genetic gain and extra economic returns. We also found that the lower the frequency of the favorable allele of the QTL, the higher the extra return obtained. Conclusion: GAS is an effective selection scheme to increase the genetic gain and the eco- nomic returns in pig breeding.