Construction of a genetic map and location of quantitative trait loci for dwarf trait in maize by RFLP markers

Using F₂ population derived from the cross of tall inbred 7922 by dwarf inbred 5003, an RFLP linkage map of maize has been constructed, on which 85 markers are distributed among 10 linkage groups and span maize genome about 1827.8 cM with an average distance (24.4 cM) between markers. 106 F_2:3 lines of the population were grown in a 10 × 11 simple rectangular lattice design of one-raw plots with two replications and evaluated for plant height (PH). With interval mapping procedure, 5 QTLs controlling plant height have been identified and their genetic effects and gene action determined. 2 major QTLs with opposite effect have been discovered. One for increasing plant height isph1 which is located at chromosome 2 and accounts for 51.8% of the total phenotypic variation; the other for decreasing plant height isph3 which is located at chromosome 5 and accounts for 38.6% of the total phenotypic variation. The chromosomal location ofph3 might be the same as or close to the position ofbv1, a dwarf mutant of maize.     

春小麦重组自交系及多种SSR标记构建遗传图谱

 以春小麦重组自交系(RIL)宁春4 号×宁春27 号为作图群体,利用SSR 标记构建小麦遗传连锁图谱。结果表明,用1001对SSR 引物选出亲本间表现多态性的引物307 对,多态性频率为30.7%。利用307 对多态性引物对RIL 群体进行分析,共检测到266 个多态性标记位点。通过χ²检测(P<0.05),有147 个SSR 标记表现为偏分离,偏分离率为55.3%,129 个偏向母本宁春4号,其偏分离位点主要分布在B 和D 基因组上。用Mapmaker 3.0 和Mapdraw 2.1 软件将266 个SSR 位点绘制在小麦遗传连锁图上,该图谱覆盖小麦基因组全长2187.79 cM,标记间的平均遗传距离为8.22 cM。     

QTL mapping of resistance to sheath blight in maize（Zea mays L.）

Maize sheath blight (Rhizoctonia Solani) is a widely occurring fungus disease with great harm to corn-pro- ducing regions in the world. The first happening of sheath blight in China was reported in Jilin Province as early as in 1966[1]. Since the 1970s, the enlargement of corn- growing regions, the application of maize hybrids, the increasing use of fertilizers, especially the nitrogenous fertilizer, and a higher growth-density, all have caused a quick spread of sheath blight, the occurring …     

Construction of a genetic map with SRAP markers and localization of the gene responsible for the first-flower-node trait in cucumber (Cucumis sativus L.)

Cucumber (Cucumis sativus L.) is an annualclimber originated from the tropic rain forest area inthe south of Himalayas, which belongs to the Cucur bitaceae family. Cucumber is one of the importantvegetables in the world, and its planting area is sec ond only to that of tomato[1]. However genetics re search on cucumber obviously drops behind that of thelatter. The classic genetic map of cucumber, with sixlinkage groups, is composed of more than 100 genesfor color, morphology, and dise…     

Mapping and characterization of a tiller-spreading mutant<Emphasis Type="Italic">lazy-2</Emphasis> in rice

Tiller angle of rice is an important agronomic trait that contributes to breed new varieties with ideal architecture. In this study, we report mapping and characterization of a rice mutant defective in tiller angle. At the seedling stage, the newly developed tillers of the mutant plants grow with a large angle that leads to a “lazy“ phenotype at the mature stage. Genetic analysis indicates that this tillerspreading phenotype is controlled by one recessive gene that is allelic to a reported mutant la. Therefore, the mutant was named la-2 and la renamed la-1. To map and clone LA, we constructed a large mapping population. Genetic linkage analysis showed that the LA gene is located between 2 SSR markers RM202 and RM229. By using the 6 newly-developed molecular markers, the LA gene was placed within a 0.4 cM interval on chromosome 11, allowing us to clone LA and study the mechanism that controls rice tiller angle at the molecular level.     

Fine mapping of the dominant glandless Gene Gl2^e in Sea-island cotton （Gossypium barbadense L.）

Gle2 is a mutant gene that controls glandless trait in cotton plants and seeds. It is an important gene resource to gossypol-free cottonseed breeding. The objective of this research was to develop SSR markers tightly linked with Gle2 by using the F2 segregating population containing 1599 plants derived from the cross of G. hirsutum genetic standard line TM-1 and G. barbadense glandless mutant line Hai-1. Genetic analysis suggested that the Gle2 was an incomplete dominant gene. Based on the backbone of genetic linkage map from G. hirsutum × G. barbadense BC1 published by our laboratory,Gle2 was lo-cated between CIR362 and NAU2251b,NAU3860b,STV033,with a genetic distance 9.27 and 0.96 cM,respectively. This result is useful for cloning Gle2 gene by map-based cloning method.     

Construction of AFLP-based genetic linkage maps for the Chinese shrimp Fenneropaeneus chinensis

Fenneropaeneus chinensis is an important species in marine fishery resources and aquaculture in China. A genetic linkage map is essential for improving the efficiency of its breeding by marker-as- sisted selection and identifying commercially important genes. Linkage maps of F. chinensis were constructed with an F2 mapping population (110 progenies) using amplified fragment length polymor- phic (AFLP) marker in this study. Fifty-five AFLP primer combinations produced 532 AFLP markers fitting for map strategy in mapping family. The markers with 3:1 segregating ratios were analyzed using F2 intercross model for the common linkage map, while the markers with 1:1 ratio were analyzed using the pseudo-testcross strategy. The maps of male, female and common were constructed. The female map included 103 markers that formed 28 linkage groups, covering a total length of 1090 cM. All mark- ers were linked with the linkage groups. Segregation distortion was observed for 6 of 103 markers in the female map. The average distance between markers was 14.53 cM and ranged from 4.4 to 24.8 cM. The male map included 144 markers that formed 35 linkage groups. Ten markers remained unlinked in male map. Segregation distortion was observed for 7 of 144 markers in the male map. The total dis- tance of male map covered 1617 cM. The average distance between markers was 16.36 cM. The male map was 32.6% longer than the female map, which may reflect sex-specific recombination rates in Chinese shrimp. The common map was composed of 216 markers, including in 44 linkage groups covering a total distance of 1772.1 cM. Two markers remained unlinked. No distorted markers of 216 markers were shown in the common map. The distance between markers was 10.42 cM. An average estimated genome size for the Chinese shrimp was 2420 cM, which was consistent with the relative size of the Penaeid genome. The distribution of AFLP markers was relatively even in chromosomes of Chi- nese shrimp maps. The linkage analysis presented in this work provided some insight into the level of polymorphism and genetic variation of Chinese shrimp.     

Fine mapping of a semidwarf gene sd-g in indica rice（Oryza sativa L.）

The semidwarf gene sd-g which has been usedin indiea rice breeding in southern China is a new one, non-allelic to sd-1. To map sd-g, an F2 population derived fromthe cross between Xinguiaishuangai and 02428 was con-structed. The sd-g was roughly mapped between two mi-crosatellite markers RM440 and RM163, with genetic dis-tances of 0.5 and 2.5 cM, respectively. Then nine new poly-morphic microsatellite markers were developed in this region.The sd-g was further mapped between two microsatellitemarkers SSR5-1 and SSR5-51, with genetic distances of 0.1and 0.3 cM, respectively, while cosegregated with SSR418. ABAC contig was found to span the sd-g locus, the region be-ing delimited to 85 kb. This result was very useful for cloningof the sd-g gene.     

Construction of AFLP-based genetic linkage maps for the Chinese shrimp Fenneropaeneus chinensis

Fenneropaeneus chinensis is an important species in marine fishery resources and aquaculture in China. A genetic linkage map is essential for improving the efficiency of its breeding by marker-assisted selection and identifying commercially important genes. Linkage maps of F. chinensis were constructed with an F2 mapping population （110 progenies） using amplified fragment length polymorphic （AFLP） marker in this study. Fifty-five AFLP primer combinations produced 532 AFLP markers fitting for map strategy in mapping family. The markers with 3：1 segregating ratios were analyzed using F2 intercross model for the common linkage map, while the markers with 1：1 ratio were analyzed using the pseudo-testcross strategy. The maps of male, female and common were constructed. The female map included 103 markers that formed 28 linkage groups, covering a total length of 1090 cM. All markers were linked with the linkage groups. Segregation distortion was observed for 6 of 103 markers in the female map. The average distance between markers was 14.53 cM and ranged from 4.4 to 24.8 cM. The male map included 144 markers that formed 35 linkage groups. Ten markers remained unlinked in male map. Segregation distortion was observed for 7 of 144 markers in the male map. The total distance of male map covered 1617 cM. The average distance between markers was 16.36 cM. The male map was 32.6% longer than the female map, which may reflect sex-specific recombination rates in Chinese shrimp. The common map was composed of 216 markers, including in 44 linkage groups covering a total distance of 1772.1 cM. Two markers remained unlinked. No distorted markers of 216 markers were shown in the common map. The distance between markers was 10.42 cM. An average estimated genome size for the Chinese shrimp was 2420 cM, which was consistent with the relative size of the Penaeid genome. The distribution of AFLP markers was relatively even in chromosomes of Chinese shrimp maps. The linkage analysis presented in this work provided some insight     

Verification and fine-mapping of QTLs conferring days to flowering in soybean using residual heterozygous lines

The results of QTL mapping based on a primary mapping population should be further verified and refined for its real utilization in marker-assisted selection or map-based cloning.The primary mapping population contains 114 BC1F1 plants of the backcross between Essex (maturity group V,MG V) as the donor parent and ZDD2315 (MG II) as the recurrent parent.In this study,a genetic linkage map with 250 SSR markers spanning a total length of 2963.5 cM on 25 linkage groups (LG) was constructed using software MAPMAK...     

Construction of a genetic map and localization of QTLs for yield traits in tomato by SSR markers

Using an F2 population derived from the hybrid of Lycopersicon esculentum Mill. ‘XF 98-7’× Lycopersicon pimpinellifolium LA2184, a SSR genetic linkage map of tomato is constructed. The map contains 112 markers and spans 808.4 cM with an average distance of 7.22 cM between loci. Two quantitative trait loci (QTLs) for first flower node on chromosomes 5 and 11, two QTLs for number of flowers per truss on chromosomes 2 and 5, and five QTLs for fruit weight on chromosomes 1, 2, 3, 9 and 12 are identified.     

Chicken QTL mapping by multiplex PCR

To facilitate rapid determination of the chromosomal location of quantitative trait loci' the current approaches to gene mapping are improved using a multiplex PCR technique. The high-throughput linkage analysis method described here allows selection of 178 from 328 microsatellite markers through the multiplex PCR method combined with the semi-automatic fluorescence-labeled DNA analysis technology. Those polymorphism markers are distributed on 23 autosomes and one sex chromosome (chromosome Z). covering 3080cM genetic distance. The average marker density is 18cM. dispersed into 30 different sets. These selected polymorphism microsatellite markers segregate with the family members, following the Mendel's heritage laws, and are very useful for chicken linkage map analysis as well as for the research on some important economic quantitative characters of chicken.     

利用DNA微卫星标记定位水稻的抗稻瘟病基因

利用回交育种中产生的回交群体结合前人的研究结果构建了Pil基因区域的局部分子标记连锁图，通过BC1F2家系的接种结果判断其基因型，将Pil定位在RFLP标记RZ536与SSR标记RM144之间，图距分别为9．7、6．8cm，从而建立了一套完整的以PCR为基础的分子标记辅助选择体系。     

Construction of a BAC library from cucumber (Cucumis sativus L.) and identification of linkage group specific clones

A bacterial artificial chromosome (BAC) library consisting of 19,200 clones with an average insert size of 105 kb has been constructed from a cucumber (Cucumis sativus L.) inbred line S94; derived from a cultivar in North China. The entire library was equivalent to approximately 5 haploid cucumber genomes. To facilitate chromosome engineering and anchor the cucumber genetic linkage map to its chromosomes, 15 sequence-characterized amplified regions (SCAR) and seven simple sequence repeats (SSR) markers from each linkage group of cucumber were used to screen an ordered array of pooled BAC DNA with polymerase chain reaction (PCR). Fifteen markers gave at least two positive clones. As a result, 32 BAC clones representing 7 linkage groups of cucumber were identified, which further validated the genome coverage and utility of the library. This BAC library and linkage group specific clones provide essential resources for future research of the cucumber genome.     

Construction of a BAC library from cucumber (Cucumis sativus L.) and identification of linkage group specific clones

A bacterial artificial chromosome (BAC) library consisting of 19,200 clones with an average insert size of 105 kb has been constructed from a cucumber (Cucumis sativus L.) inbred line S94; derived from a cultivar in North China. The entire library was equivalent to approximately 5 haploid cucumber genomes. To facilitate chromosome engineering and anchor the cucumber genetic linkage map to its chromosomes, 15 sequence-characterized amplified regions (SCAR) and seven simple sequence repeats (SSR) markers from each linkage group of cucumber were used to screen an ordered array of pooled BAC DNA with polymerase chain reaction (PCR). Fifteen markers gave at least two positive clones. As a result, 32 BAC clones representing 7 linkage groups of cucumber were identified, which further validated the genome coverage and utility of the library. This BAC library and linkage group specific clones provide essential resources for future research of the cucumber genome.     

Construction of a BAC library from cucumber （Cucumis sativus L.） and identification of linkage group specific clones

A bacterial artificial chromosome （BAC） library consisting of 19,200 clones with an average insert size of 105 kb has been constructed from a cucumber （Cucumis sativus L.） inbred line S94, derived from a cultivar in North China. The entire library was equivalent to approximately 5 haploid cucumber genomes. To facilitate chromosome engineering and anchor the cucumber genetic linkage map to its chromosomes, 15 sequence-characterized amplified regions （SCAR） and seven simple sequence repeats （SSR） markers from each linkage group of cucumber were used to screen an ordered array of pooled BAC DNA with polymerase chain reaction （PCR）. Fifteen markers gave at least two positive clones. As a result, 22 BAC clones representing 7 linkage groups of cucumber were identified, which further validated the genome coverage and utility of the library. This BAC library and linkage group specific clones provide essential resources for future research of the cucumber genome.     

Physical location of terminal markers belonging to five linkage groups in maize RFLP map using in situ hybridization

Ten terminal or subterminal RFLP markers belonging to linkage groups 1, 3, 5, 6, and 10 in maize RFLP map were physically locted onto maize mitotic chromosomes with in situ hybridization. All biotinylated probes from 600 to 2 250 bp were detected by DAB staining. The markers belonging to linkage groups 1, 3, 5, 6, and 10 correspondingly located at the chromosomes 1, 3, 5, 6, and 10. All of the tested markers except bnl6.25 and umc44 were duplicated sequences. Each of them was also labeled on another chromosome besides on the chromosome corresponding to its linkage group. The marker bnl3. 04 was triplicated sequences and the signals were detected on three nonhomologous chromosomes. In the tested ten markers, there were only four located at the ends of corresponding chromosomes. Others were located at sites midway along the chromosome arms or near the centromeres. The region covered by two terminal or subterminal markers in each of linkage groups 1, 3, 5, and 6 occupied 80.02%, 38.25%, 82.30% and 51.16% of the region of both short and long arms in chromosomes 1, 3, 5, and 6 respectively. Only two terminal markers of linkage group 10 covered the whole chromosome 10. In some linkage groups, two terminal or subterminal markers covered a short genetic distance but were physically distant, while two covering a longer genetic distance were physically closer. Supported by The National Natural Science Foundation of China and the Doctorate Vesting Point Foundation of the Education Committec of the People's Republic of China Mao Ninghui: born in 1986, used to be an MS student of Wuhan University in 1992–1995 and now is working in Fudan University, Shanghai 200433     

Genetic and physical mapping of AvrPi7, a novel avirulence gene of Magnaporthe oryzae using physical position-ready markers

Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most devastating crop diseases worldwide. The avirulence gene corresponding to rice blast resistance gene Pi7 in field isolate CHL346 was inherited as a single gene, designated AvrPi7, in a segregating population consisting of 189 ascospore progenies derived from a cross between field isolates CHL346 and CHL42. In order to determine the chromosomal location of the AvrPi7 locus, a total of 121 simple sequence repeat (SSR) markers were developed based on the whole-genome sequence of reference isolate 70-15 of M. oryzae. Linkage analysis of the locus with these SSR markers showed that eight SSR markers on chromosome 1 were linked to the locus, among which the closest flanking markers MS1-9 and MS1-15 were 3.2 and 16.4 cM from the locus, respectively. For fine mapping, additional PCR-based makers including eight SSR markers and three candidate avirulence gene (CAG) markers were developed in the region flanking both markers. The AvrPi7 locus was genetically delimited within a 1.6-cM region flanked by markers MS1-21 and MS1-22, and co-segregated with the marker CAG2. To construct a physical map of the AvrPi7 locus, molecular markers linked to the Avr gene were mapped on the supercontigs of the ref-erence isolate 70-15 through bioinformation analysis (BIA). Consequently, the AvrPi7 locus was delim-ited to a 75-kb interval flanked by markers MS1-21 and MS1-22 based on the reference sequence. Merodiploids observed in this study are also discussed.     

Fine mapping of an incomplete recessive gene for leaf rolling in rice （Oryza sativa L.）

Genetic analysis and fine mapping of genes controlling leaf rolling were conducted using two backcrossed generations （BC4F2, BC4F3） derived from a cross between QMX, a non-rolled leaf cultivar as a recurrent parent, and JZB, a rolled leaf NIL of ZB as a donor parent. Results indicated that leaf rolling was mainly controlled by an incompletely recessive major gene, namely rl（t）, and at the same time, affected by quantitative trait loci （QTLs） and/or the environment. A genetic linkage map was constructed using MAPMAKER/EXP3.0 with eight polymorphic markers on chromosome 2, which were screened by BAS method from 500 SSR markers and 15 newly developed insertion/deletion （InDel） markers. The position of rl（t） was estimated with composite interval mapping （CIM） method using WinQTLcart2.5. Gene rl（t） was mapped between markers InDel 112 and RM3763, and 1.0 cM away from InDel 112 using 241 plants in BC4F2 population. To fine map r（t）, one BC4F3 line with 855 plants was generated from one semi-rolled leaf plant in BC4F2. Four new polymorphic InDel markers were developed, including InDel 112.6 and InDel 113 located between markers InDe1112 and RM3763. Based on the information of recombination offered by 191 rolled leaf plants and 185 non-rolled leaf plants from the BC4F3 line ,we mapped r（t） to a 137-kb region between markers InDel 112.6 and InDel 113. Homologous gene analysis suggested that r（t）was probably related to the process of leaf development regulated by microRNA.     

Cytogenetic Mapping of Disease Resistance Genes and Analysis of Their Distribution Features on Chromosomes in Maize

0　IntroductionMaizeisamongthemostintensivelystudiedspeciesingeneticsandoneofagronomicallythemostimportantplants.Therearemanydis easemicrobesandpeststoattackmaize,whichre sultsinlowproductionandbadquality .Withthedevelopmentofverydensegeneticmapconstruc tion ,avarietyoftheimportantdiseaseresistancegenesofmaizeincludingHelminthosporiumtur ciumPassresistancegenesHt1,Htn1andHt2 ,HelminthosporiummaydisNisikresistancegenesRhm1andRhm2 ,maizedwarfmosaicvirusresis tancegeneMdm1,wheatstreakmosaicvi…