分子标记育种在我国的研究进展

现代生物技术的发展为利用外源基因培育优良作物品种提供了新的途径。简要综述了分子标记育种在我国研究的总体情况以及我国在分子标记育种领域取得的成就,并对分子标记育种的前景进行了展望。     

用SSR标记鉴定大豆杂交组合F1的方法研究

为建立鉴定大豆杂种的方法,采用亲本间有多态性的3对SSR引物,对148个耐盐与盐敏感大豆品种正反交F1植株进行分子鉴定,结果表明,有81．8％的F1为真杂种,且3对多态性SSR引物检测结果一致;在亲本基因型纯合的情况下,采用1对在亲本间有多态性的SSR引物即可对F1真伪进行准确判断;亲本间分子量差异大的SSR位点可用高浓度琼脂糖电泳进行快速鉴定。利用该方法对2007年参加国家大豆区试的大豆杂交种品系H02—286的50粒种子进行纯度鉴定,进一步验证了SSR标记检测杂种真伪的可行性。     

Determination of the effectiveness of Pseudorabies marker vaccines in experiments and field trials

The aim of vaccination in an eradication campaign is not only to induce clinical protection, but primarily to stop transmission of infections within and between herds by inducing herd immunity. Consequently, vaccines should be evaluated for their capacity to reduce virus transmission in the population. Glycoprotein E (gE) negative marker vaccines against Pseudorabies virus (PRV) infections in pigs have been evaluated this way in experiments and field studies. PRV infection in groups of (vaccinated) pigs was determined by measuring antibodies against gE of PRV from regularly taken serum samples. For the statistical analysis of the experiments a stochastic susceptible-infectious-removed (SIR) model was used. A measure for the transmission of virus is the reproduction ratio R, which is defined as the average number of secondary cases caused by one typical infectious individual. This implies that an infection will always fade out in a population when R < 1, but the infection can spread massively when R > 1. From several experiments it was shown that R < 1. Field studies showed that the R within herds was still > 1, but by reducing further contacts the R could be reduced to a value below one. This would imply that PRV could be eradicated by means of vaccination. In The Netherlands, an eradication campaign was launched in 1993, and in 2002 the virus was eradicated, as shown by a negligible number of gE-positive pigs. Farmers' organizations have to decide whether or not to stop vaccination.     

Mapping minor QTL for increased stearic acid content in sunflower seed oil

Increased stearic acid (C18:0) content in the seed oil of sunflower would improve the oil quality for some edible uses. The sunflower line CAS-20 (C18:0 genotype Es1Es1es2es2), developed from the high C18:0 mutant line CAS-3 (C18:0 genotype es1es1es2es2; 25% C18:0), shows increased C18:0 levels in its seed oil (8.6%). The objective of this research was to map quantitative trait loci (QTL) conferring increased C18:0 content in CAS-20 in an F₂ mapping population developed from crosses between HA-89 (wild type Es1Es1Es2Es2; low C18:0) and CAS-20, which segregates independently of the macromutation Es1 controlling high C18:0 content in CAS-3. Seed oil fatty acid composition was measured in the F₂ population by gas-liquid chromatography. A genetic linkage map of 17 linkage groups (LGs) comprising 80 RFLP and 19 SSR marker loci from this population was used to identify QTL controlling fatty acid composition. Three QTL affecting C18:0 content were identified on LG3, LG11, and LG13, with all alleles for increased C18:0 content inherited from CAS-20. In total, these QTL explained 43.6% of the C18:0 phenotypic variation. Additionally, four candidate genes (two stearate desaturase genes, SAD6 and SAD17, and a FatA and a FatB thioesterase gene) were placed on the QTL map. On the basis of positional information, QTL on LG11 was suggested to be a SAD6 locus. The results presented show that increased C18:0 content in sunflower seed oil is not a simple trait, and the markers flanking these QTL constitute a powerful tool for plant breeding programs.     

’Forrest’ resistance to the soybean cyst nematode is bigenic: saturation mapping of the Rhg1and Rhg4 loci

Field resistance to cyst nematode (SCN) race 3 (Heterodera glycines I.) in soybean [Glycine max (L.) Merr.] cv ’Forrest’ is conditioned by two QTLs: the underlying genes are presumed to include Rhg1 on linkage group G and Rhg4 on linkage group A2. A population of recombinant inbred lines (RILs) and two populations of near-isogenic lines (NILs) derived from a cross of Forrest×Essex were used to map the loci affecting resistance to SCN. Bulked segregant analysis, with 512 AFLP primer combinations and microsatellite markers, produced a high-density genetic map for the intervals carrying Rhg1 and Rhg4. The two QTLs involved in resistance to SCN were strongly associated with the AFLP marker E_ATGM_CGA87 (P=0.0001, R²=24.5%) on linkage group G, and the AFLP marker E_CCGM_AAC405 (P=0.0001, R² =26.2%) on linkage group A2. Two- way analysis of variance showed epistasic interaction (P=0.0001, R² =16%) between the two loci controlling SCN resistance in Essex×Forrest recombinant inbred lines. Considering the two loci as qualitative genes and the resistance as female index FI <5%, jointly the two loci explained over 98% of the resistance. The locations of the two QTLs were confirmed in the NILs populations. Therefore SCN resistance in Forrest×Essex is bigenic. High-efficiency marker-assisted selection can be performed using the markers to develop cultivars with stable resistance to SCN. Received: 5 November 2000 / Accepted: 23 January 2001     

A Protocol for Genetic Induction and Visualization of Benign and Invasive Tumors in Cephalic Complexes of Drosophila melanogaster

Drosophila has illuminated our understanding of the genetic basis of normal development and disease for the past several decades and today it continues to contribute immensely to our understanding of complex diseases ^1-7. Progression of tumors from a benign to a metastatic state is a complex event ⁸ and has been modeled in Drosophila to help us better understand the genetic basis of this disease ⁹. Here I present a simple protocol to genetically induce, observe and then analyze the progression of tumors in Drosophila larvae. The tumor induction technique is based on the MARCM system ¹⁰ and exploits the cooperation between an activated oncogene, Ras^V12 and loss of cell polarity genes (scribbled, discs large and lethal giant larvae) to generate invasive tumors ⁹. I demonstrate how these tumors can be visualized in the intact larvae and then how these can be dissected out for further analysis. The simplified protocol presented here should make it possible for this technique to be utilized by investigators interested in understanding the role of a gene in tumor invasion.     

Study of molecular genetic diversity and evolutionary history of medicinally important endangered genus Chlorophytum using DNA barcodes

This study was aimed to authenticate and present phylogenetic relationship among 19 species of genus Chlorophytum using DNA barcoding. In all, 107 accessions were analyzed with eight plastid (matK, rbcL, trnH-psbA, rpoC1, ycf5, rpoB, atp and psbK-psbI) and six nuclear (ITS) markers. The matK and rbcL were found to be ideal markers for identification and discrimination of Chlorophytum species. Phylogenetic analysis based on matK and rbcL sequences resolved the species in two major clades. All markers, except matK and rbcL, showed ambiguous reads and paralogy in analysis. DGGE analysis showed the presence of pseudogenes and/or co-amplification in these markers, which caused poor sequence quality. Phylogeny and probable evolution of genus Chlorophytum was proposed on the basis of cytological, morphological and genetic information.     

水稻抗性基因定位及相关分子标记研究进展

水稻是一种重要的粮食作物。而选育高抗性良种是有效防治病虫的危害,增加水稻单位面积产量的一项关键措施。了解水稻本身抗性的遗传信息是进行抗性育种的基础。现代生物技术的发展为抗性育种提供了新途径。本文较系统地概述了水稻对稻瘟病、白叶枯病、稻飞虱、稻叶蝉抗性基因定位及相关分子标记研究的最新发展,为利用分子标记进行水稻抗性育种及抗性基因克隆提供参考文献。     

Association analysis for agronomic traits in wheat under terminal heat stress

Terminal heat stress causes irreversible damage to wheat crop productivity. It reduces the vegetative growth and flowering period that consequently declines the efficiency to capture available stem reserves (carbohydrates) in grains. Markers associated with thermotolerant traits ease in marker assisted selection (MAS) for crop improvement. It identifies the genomic regions associated with thermotolerant traits in wheat, but the scarcity of markers is the major hindrance in crop improvement. Therefore, 158 wheat genotypes were subjected to genotyping with 165 simple sequence repeat markers dispersed on three genomes (A, B and D). Allelic frequency and polymorphic information content values were highest on genome A (5.34 (14% greater than the lowest value at genome D) and 0.715 (3% greater than the lowest value at genome D)), chromosome 4 (5.40 (16% greater than the lowest value at chromosome 2) and 0.725 (5% greater than the lowest value at chromosome 6)) and marker xgwm44 (13.0 (84% greater than the lowest value at marker xbarc148) and 0.916 (46% greater than the lowest value at marker xbarc148)). Bayesian based population structure discriminated the wheat genotypes into seven groups based on genetic similarity indicating their ancestral origin and geographical ecotype. Linkage disequilibrium pattern had highest significant (P < 0.001) linked loci pairs 732 on genome A at r² > 0.1 whereas, 58 on genome B at r² > 0.5. Linkage disequilibrium decay (P < 0.01 and r² > 0.1) had larger LD block (5–10 cM) on genome A. Highly significant MTAs (P < 0.000061) under heat stress conditions were identified for flag leaf area (xwmc336), spikelet per spike (xwmc553), grains per spike (cxfa2147, xwmc418 and xwmc121), biomass (xbarc7) and grain yield (xcfa2147 and xwmc671). The identified markers in this study could facilitate in MAS and gene pyramiding against heat stress in wheat.     

Accuracy map of an optical motion capture system with 42 or 21 cameras in a large measurement volume

Optical motion capture is commonly used in biomechanics to measure human kinematics. However, no studies have yet examined the accuracy of optical motion capture in a large capture volume (>100 m³), or how accuracy varies from the center to the extreme edges of the capture volume. This study measured the dynamic 3D errors of an optical motion capture system composed of 42 OptiTrack Prime 41 cameras (capture volume of 135 m³) by comparing the motion of a single marker to the motion reported by a ThorLabs linear motion stage. After spline interpolating the data, it was found that 97% of the capture area had error below 200 μm. When the same analysis was performed using only half (21) of the cameras, 91% of the capture area was below 200 μm of error. The only locations that exceeded this threshold were at the extreme edges of the capture area, and no location had a mean error exceeding 1 mm. When measuring human kinematics with skin-mounted markers, uncertainty of marker placement relative to underlying skeletal features and soft tissue artifact produce errors that are orders of magnitude larger than the errors attributed to the camera system itself. Therefore, the accuracy of this OptiTrack optical motion capture system was found to be more than sufficient for measuring full-body human kinematics with skin-mounted markers in a large capture volume (>100 m³).