An AFLP-based linkage map of Zoysiagrass (Zoysia japonica)

To construct an amplified‐fragment length polymorphism (AFLP)‐based molecular linkage map of zoysiagrass, the selfed progenies of a clone consisting of 78 individuals were analysed using 471 AFLP markers derived from 126 PstI/MseI primer combinations. Of these markers, 364 were grouped into 26 linkage groups. The maps covered a total length of 932.5 cM, with an average spacing of 2.6 cM between markers. This information proves useful for gene targeting, quantitative trait loci mapping, and marker‐assisted selection in zoysiagrass.     

Density enhancement of a faba bean genetic linkage map (Vicia faba) based on simple sequence repeats markers

Genetic mapping for faba bean lags far behind other major crops. Density enhancement of the faba bean genetic linkage map was carried out by screening 5,325 genomic SSR primers and 2033 expressed sequence tag (EST)‐SSR primers on the parental cultivars '91825' and 'K1563'. Two hundred and fifteen genomic SSR and 133 EST‐SSR primer pairs that detected polymorphisms in the parents were used to screen 129 F₂ individuals. This study added 337 more SSR markers and extended the previous linkage map by 2928.45 cM to a total of 4516.75 cM. The number of SSR markers in the linkage groups varied from 12 to 136 while the length of each linkage group ranged from 129.35 to 1180.21 cM. The average distance between adjacent loci in the enhanced genetic linkage map was 9.71 cM, which is 2.79 cM shorter than the first linkage map of faba bean. The density‐enhanced genetic map of faba bean will be useful for marker‐assisted selection and breeding in this important legume crop.     

An SSR-based molecular genetic map of cassava

Summary Microsatellites or simple sequence repeats (SSR) are the markers of choice for molecular genetic mapping and marker-assisted selection in many crop species. A microsatellite-based linkage map of cassava was drawn using SSR markers and a F₂ population consisting of 268 individuals. The F₂ population was derived from selfing the genotype K150, an early yielding genotype from an F₁ progeny from a cross between two non-inbred elite cassava varieties, TMS 30572 and CM 2177-2 from IITA and CIAT respectively. A set of 472 SSR markers, previously developed from cassava genomic and cDNA libraries, were screened for polymorphism in K150 and its parents TMS 30572 and CM 2177-2. One hundred and twenty two polymorphic SSR markers were identified and utilized for linkage analysis. The map has 100 markers spanning 1236.7 cM, distributed on 22 linkage groups with an average marker distance of 17.92 cM. Marker density across the genome was uniform. This is the first SSR based linkage map of cassava and represents an important step towards quantitative trait loci mapping and genetic analysis of complex traits in M. esculenta species in national research program and other institutes with minimal laboratory facilities. SSR markers reduce the time and cost of mapping quantitative trait loci (QTL) controlling traits of agronomic interest, and are of potential use for marker-assisted selection (MAS).     

Genetic linkage map of cassava (Manihot esculenta Crantz) based on AFLP and SSR markers

To generate a genetic linkage map of cassava ( Manihot esculenta Crantz), 58 F₁ progenies from a cross between Rayong 90 (female) and Rayong 5 (male) were examined in amplification fragment length polymorphism (AFLP) and simple sequence repeat (SSR) analyses. A total of 469 polymorphic markers consisting of 378 AFLPs generated from 76 primer combinations and 91 SSRs were identified. These markers were analyzed using the joinmap ^® 3.0 package program to construct a genetic linkage map. A total of 33 linkage groups of a common map were constructed from 119 AFLPs and 18 SSRs, spanning 1095 cM with an average of 7.99 cM between markers. The genetic linkage map generated in this study will be useful for genetic studies in cassava particularly for the identification of genetic markers linked to traits of interest, although the complex cassava genome suggests that maybe a long term objective.     

Male and female genetic linkage map of hops, Humulus lupulus

A male and female linkage map of hop has been constructed using 224 DNA polymorphisms (106 amplified fragment length polymorphisms (AFLPs), three random amplified polymorphic DNAs (RAPDs), one RAPD‐sequence‐tagged‐site (STS), and three microsatellite (STSs) segregating in an F₁ population of the English cultivar ‘Wye Target’‐the German male breeding line ‘85/54/15’. Linkage between these loci was estimated using JOINMAP Version 2.0. The final map for the female parent consisted of 110 loci assigned to eight linkage groups covering a distance of 346.7 cM. For the male map, 57 loci could be mapped on nine linkage groups spanning over 227.4 cM. One of these male linkage groups (Gr09‐M) presumably represents the Y chromosome, since all markers assigned (10 AFLPs, three RAPDs and one STS) were closely linked to the male sex (M). Because of their sex‐specific segregation, 10 doubly heterozygous AFLPs spanning a distance of 18.7 cM could be identified as markers describing the X chromosome, which is part of the male and female map. Three STMSs, which had already proved useful in hop genotyping, could be integrated as codominant locus‐specific markers and thus allowed to produce reliable allelic bridges between the female and male counterparts.     

AFLP in Triticum aestivum L.: patterns of genetic diversity and genome distribution

The amplified fragment length polymorphism (AFLP) procedure was applied to a diverse panel of wheat (Triticum aestivum L. em. Thell.) accessions and sixty-nine of the recombinant inbred lines (RILs) from the widely used genetic mapping population derived from the cross of Opata 85 and W7984. Most (76.8%) bands were monomorphic among T. aestivum accessions. The majority of bands monomorphic in T. aestivum also were present in the synthetic wheat parent (W7984). Ten primer pairs generated 153 polymorphic AFLP bands, 140 of which could be assigned to a chromosome location and were relatively evenly distributed on the genetic linkage map. AFLP loci in T. aestivum were distributed throughout the genome; they generally have only one detectable sequence variant; and they exhibit monogenic dominant mendelian inheritance. Frequencies of polymorphic bands in the germplasm sampled are in the range that enables informative cluster analyses as well as map-based diversity and association analysis studies. AFLP bands mapped to individual loci in the Opata 85/W7984 RIL population will frequently be polymorphic in other crosses or germplasm, irrespective of whether the band arises from the T. aestivum parent or the synthetic wheat parent. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic analysis of Lolium. I. Identification of linkage groups and the establishment of a genetic map

A genetic map of Lolium has been produced using isozyme, restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) markers applied to a segregating family derived from an F₁ hybrid plant of L. perenne × L. multiflorum provenance, crossed on to a doubled haploid L. perenne. A total of 106 markers, out of a total of 160 polymorphic loci analysed, have been ascribed to seven linkage groups covering a map distance of 692cM, Two of these groups may be allocated to chromosomes 2 and 6 of the Lolium genome. The remaining unallocated markers, the majority of which showed severe segregation distortion, could be associated into small groups of two or three markers which showed no linkage with the main groups at a LOD of 2.8 or, if associated, could not be mapped in a satisfactory manner. This high incidence of disturbed segregations could be accounted for by the use of an interspecific hybrid between two species of differing genome size, with consequent cytological imbalance.     

A genetic map of sugar beet (Beta vulgaris) based on RAPD markers

Linkage analysis of sugar beet (Beta vulgaris L.) was performed with random amplified polymorphic DNA (RAPD)-markers. From three segregating populations, a combined genetic map was constructed which comprises 85 RAPD, five isozyme, one RFLP marker and the genes for resistance against the nematode Heterodera schachtii Schm., one restorer locus for male sterility and the genes for annuality and hypocotyl colour. For mapping of the two unlinked restorer genes a statistical model was developed based on the maximum-likelihood function.     

Clustering of amplified fragment length polymorphism markers in a linkage map of rye

Amplified fragment length polymorphisms (AFLPs) are now widely used in DNA fingerprinting and genetic diversity studies, the construction of dense genetic maps and in fine mapping of agronomically important traits. The AFLP markers have been chosen as a source to extend and saturate a linkage map of rye, which has previously been generated by means of restriction fragment length polymorphism, random amplified polymorphic DNA, simple sequence repeat and isozyme markers. Gaps between linkage groups, which were known to be part of chromosome 2R, have been closed, thus allowing the determination of their correct order. Eighteen EcoRI‐MseI primer combinations were screened for polymorphism and yielded 148 polymorphic bands out of a total of 1180. The level of polymorphism among the different primer combinations varied from 5.7% to 33.3%. Eight primer combinations, which revealed most polymorphisms, were further analysed in all individuals of the F₂ mapping population. Seventy‐one out of 80 polymorphic loci could be integrated into the linkage map, thereby increasing the total number of markers to 182. However, 46% of the mapped AFLP markers constituted four major clusters located on chromosomes 2R, 5R and 7R, predominantly in proximity to the centromere. The integration of AFLP markers caused an increase of 215 cM, which resulted in a total map length of almost 1100 cM.     

Integration of AFLP markers into an RFLP-based map of durum wheat

Amplified fragment length polymorphism (AFLP) is a powerful technique which can readily be applied to a wide range of species for mapping purposes. AFLPs were added to a linkage map of durum wheat constructed using restriction fragment length polymorphisms (RFLPs). The mapping population included 65 recombinant inbred lines derived from a cross between the durum wheat cultivar ‘Messapia’ and accession ‘MG4343’ of the wild Triticum turgidum ssp. dicoccoides (Körn.). Genomic DNA was digested with MseI (4‐cutter) and Sse83871 (8‐cutter). Using a silver‐staining protocol, 14 primer combinations revealed 421 clearly scorable amplicons including 100 polymorphisms. The presence of nine pairs of bands linked in repulsion phase with each pair generated by one primer combination suggested the presence of codominant alleles; sequence analysis of four band pairs confirmed their codominant nature. The integration of 80 AFLP loci extended the map in several telomeric regions, reduced the size of four large gaps present in the previous map, and eliminated one gap. The new map obtained after the inclusion of the 80 AFLP loci and eight additional RFLP loci spans 2063cM which represent a 52.6% increment compared with the previous map. Compared with the distribution of RFLPs, no significant clustering of AFLP markers was observed.     

栽培大豆×半野生大豆高密度遗传图谱构建及株高QTL定位

采用中SNP160K芯片对丰收24×通交83-611 F2群体252个植株及其亲本进行基因分型,构建了一张由5861个SNP标记组成的全长为3661.46 cM的高密度遗传连锁图谱。利用完备区间作图法(ICIM)定位到7个株高QTL,每个QTL可解释2.56%～10.41%的株高变异。qPH-6-1具有最高的表型变异贡献率和显性效应,可解释10.41%的株高变异,加性效应和显性效应分别为–1.72和18.94; qPH-18-1贡献率次之,可解释9.64%的株高变异,但具有最高的加性效应,达-12.42。在F2群体中筛选出11个qPH-6-1和qPH-18-1基因型为Q6Q6/Q18Q18的单株,平均株高167.00 cm;筛选出16个基因型为q6q6/q18q18的植株,平均株高为91.25 cm。在qPH-18-1定位区间内外增加23个SNP标记,将定位区间由766.97kb缩小至66.03kb,包含8个基因,结合基因注释和相对表达量差异分析,推测Glyma.18G279800和Glyma.18G280200可能与大豆的株高相关。本研究为大豆株型的改良提供了分子参考依据和遗传基础。     

利用双杂合位点标记资料构建芒果遗传图谱

为了建立芒果 (MangiferaindicaL )的分子标记遗传图 ,用 15对AFLP (AmplifiedFragmentLengthPolymorphism)引物组合扩增了芒果品种间杂交组合 (Keitt×Tommy Atkins)的 6 0个F1单株 ,获得了 191个多态性位点。它们的分离表现为双杂合 (Aa×Aa)和测交 (Aa×aa)分离两种类型 ,但前者占了 5 9 7%。为了充分利用双杂合位点分离所提供的遗传信息 ,我们根据群体中任意两个双杂合位点隐性个体出现的数目 ,利用二项式分布概率理论推断它们是否连锁以及它们彼此间的相引或相斥关系。在该芒果群体呈 3:1分离的 81个多态性标记中 ,39个被分为 14组 ,以此为基础构建了 15个连锁群 ;这些连锁群共覆盖了 35 4 1cM的芒果基因组。其中 ,最小与最大遗传距离分别为 3 7cM和 2 8 9cM。此外 ,对 18个 1∶1分离类型的标记 ,直接利用Mapmaker作图软件构建了两个芒果连锁群。本文对所提出的利用双杂合位点构建果树遗传图谱的策略进行了讨论。     

Construction of a genetic linkage map for witloof (Cichorium intybus L. var. foliosum Hegi)

A genetic linkage map based on an intraspecific cross between two inbred lines of witloof‐chicory (Cichorium intybus L. var. foliosum Hegi) has been constructed. In total, 129 RAPD markers were scored in 565 F₂ plants. Grouping of these markers at a LOD of threshold 4.0 resulted in nine linkage groups, which is equal to the chicory haploid genome. The nine linkage groups covered 609.6 cM. All 129 RAPD markers were linked to one of the nine groups. Three RAPD markers could not be mapped. Out of the 126 remaining RAPD markers, 18 showed segregation distortion with significance value of P < 0.01.     

A genetic linkage map of Spinacia oleracea and localization of a sex determination locus

A genetic map of Spinach (Spinacia oleracea) was constructed in a classical back cross population using 101 AFLP and 9 microsatellite markers. The map was divided into seven linkage groups with a total length of 585 cM and an average distance between the markers of 5.18 cM. The linkage map was constructed with LOD 3.5, but was quite stable with seven linkage groups remaining until LOD 7.0. Gender segregated 1 male to 1 female in the mapping population and was mapped to a small area of one linkage group with a distance of 1.9 cM to a microsatellite marker termed SO4. This small chromosomal region co-segregating with sex determination in the species is in contrast to previous reports on a heterologous XY chromosome system in spinach. Microsatellite markers used as anchors in the map construction were isolated from sequences of known nuclear encoded genes in spinach. This enabled simultaneous positioning on the map of these genes: Rubisco activase (Rca), Photosytem 1 subunit V (PsaG), Protein Kinase (Pk), Nitrate reductase (Nir), ferrodoxin:thioredoxin reductase (Ftr), Ribosomal protein L1 (Rps22), Choline monooxygenase (Cmo), Pseudogene for BZIP protein (Bzip), Glycerol-3-phosphate acyltransferase (Act1) and stromal ascorbate peroxidase, thylakoid-bound ascorbate peroxidase (Apx2). Spinach has a small genome, which makes it suitable for basic genomic studies and many physiologically important genes have been cloned from the species. The present map anchored with user friendly microsatellite markers will be useful for future studies of physiology and genetics of the species as well as studies of the nature of gender determination.     

An SSR-based genetic map of pepper (Capsicum annuum L.) serves as an anchor for the alignment of major pepper maps

Of the Capsicum peppers (Capsicum spp.), cultivated C. annuum is the most commercially important, but has lacked an intraspecific linkage map based on sequence-specific PCR markers in accord with haploid chromosome numbers. We constructed a linkage map of pepper using a doubled haploid (DH) population derived from a cross between two C. annuum genotypes, a bell-type cultivar ‘California Wonder’ and a Malaysian small-fruited cultivar ‘LS2341 ({"type":"entrez-nucleotide","attrs":{"text":"JP187992","term_id":"347495878"}}JP187992)’, which is used as a source of resistance to bacterial wilt (Ralstonia solanacearum). A set of 253 markers (151 SSRs, 90 AFLPs, 10 CAPSs and 2 sequence-tagged sites) was on the map which we constructed, spanning 1,336 cM. This is the first SSR-based map to consist of 12 linkage groups, corresponding to the haploid chromosome number in an intraspecific cross of C. annuum. As this map has a lot of PCR-based anchor markers, it is easy to compare it to other pepper genetic maps. Therefore, this map and the newly developed markers will be useful for cultivated C. annuum breeding.     

GBS高密度遗传连锁图谱定位甘蓝型油菜粉色花性状

甘蓝型油菜花瓣颜色是重要的观赏性状,花瓣颜色的选育和改良已成为材料创制的主要研究方向。目前对甘蓝型油菜粉色花性状定位研究未见报道。本研究以甘蓝型油菜纯系黄花62和甘蓝型油菜纯系粉花77为亲本构建双单倍体(doubled haploid,DH)群体。利用简化基因组测序技术(genotyping-by-sequencing,GBS)筛选出3253个单核苷酸多态性(single nucleotide polymorphism,SNP)标记,构建了全长1766.06 cM甘蓝型油菜连锁图谱,标记间平均遗传距离为0.54 cM;使用WinQTL Cartographer复合区间作图方法对粉色花性状进行数量性状座位(quantitative trait locus,QTL)定位,检测到位于A07和C03染色体上各1个QTL;将定位区间内基因与甘蓝和白菜同源基因进行线性比对,在这些区间中找到了一些存在于3个物种的同源基因;对粉色花定位区间内基因进行可变剪切分析发现,2个花色相关基因BnaA07g15980D和BnaA07g17500D在亲本粉色花瓣中发生内含子保留可变剪切。上述研究结果为甘蓝型油菜粉色花相关基因精细定位和分子连锁标记开发提供了更多线索。     

Development of EST-SSR markers and construction of a linkage map in faba bean (Vicia faba)

To develop a high density linkage map in faba bean, a total of 1,363 FBES (Faba bean expressed sequence tag [EST]-derived simple sequence repeat [SSR]) markers were designed based on 5,090 non-redundant ESTs developed in this study. A total of 109 plants of a ‘Nubaria 2’ × ‘Misr 3’ F₂ mapping population were used for map construction. Because the parents were not pure homozygous lines, the 109 F₂ plants were divided into three subpopulations according to the original F₁ plants. Linkage groups (LGs) generated in each subpopulation were integrated by commonly mapped markers. The integrated ‘Nubaria 2’ × ‘Misr 3’ map consisted of six LGs, representing a total length of 684.7 cM, with 552 loci. Of the mapped loci, 47% were generated from multi-loci diagnostic (MLD) markers. Alignment of homologous sequence pairs along each linkage group revealed obvious syntenic relationships between LGs in faba bean and the genomes of two model legumes, Lotus japonicus and Medicago truncatula. In a polymorphic analysis with ten Egyptian faba bean varieties, 78.9% (384/487) of the FBES markers showed polymorphisms. Along with the EST-SSR markers, the dense map developed in this study is expected to accelerate marker assisted breeding in faba bean.     

Present position regarding breeding of mango (Mangifera indica L.) in India

Summary Progress of hybridization work at various centres in India is reviewed. With the improved technique of mango hybridization and the report of self-incompatibility in mango, it will be possible to evolve a larger number of hybrids for screening for desirable characters. Embryological studies have shown that in mango pollen tubes grow down the style and effect fertilization but the development of zygote is blocked leading to a sporophytic type of self-incompatibility. Hybrids recently evolved through the combinations of regular and commercial biennial bearing varieties indicate that largescale hybridization may offer a solution to the biennial bearing problem in mango.Paper read at the International Horticultural Congress, Maryland, Maryland, U.S.A., 1966.     

Numerical taxonomic studies of mango (Mangifera indica L.) varieties in Nigeria

Summary The major characters which account for the variation among the mango varieties in Nigeria were studied using PCA and SCLA. Thirty-one varieties were collected in all ecological zones of the country. Altogether 64 characters were observed and coded for analysis. The results from both methods divided the varieties into two or four groups. The PCA showed that the combination of qualitative and quantitative data as well as combination of few vegetative characters with many reproductive characters are important for mango classification. The primary and secondary characters in classification of mango varieties are discussed.