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。     

A genetic map of macadamia based on randomly amplified DNA fingerprinting (RAF) markers

The first genetic linkage map of macadamia (Macadamia integrifolia and M. tetraphylla) is presented. The map is based on 56 F₁ progeny of cultivars ‘Keauhou’ and ‘A16’. Eighty-four percent of the 382 markers analysed segregated as Mendelian loci. The two-way pseudo-testcross mapping strategy allowed construction of separate parental cultivar maps. Ninety bridging loci enabled merging of these maps to produce a detailed genetic map of macadamia, 1100 cm in length and spanning 70–80% of the genome. The combined map comprised 24 linkage groups with 265 framework markers: 259 markers from randomly amplified DNA fingerprinting (RAF), five random amplified polymorphic DNA (RAPD), and one sequence-tagged microsatellite site (STMS). The RAF marker system unexpectedly revealed 16 codominant markers, one of them a putative microsatellite locus and exhibiting four distinct alleles in the cross. This molecular study is the most comprehensive examination to date of genetic loci of macadamia, and is a major step towards developing marker-assisted selection for this crop. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular mapping of an aluminum tolerance locus on chromosome 4D of Chinese Spring wheat

Summary The tolerance of aluminum (Al) of disomic substitution lines having the chromosomes of the D genome of Triticum aestivum L. cv. Chinese Spring individually substituted for their homoeologues in T. turgidum L. cv. Langdon was investigated by the hematoxylin method. The disomic substitution lines involving chromosome 4D were more Al tolerant than Langdon. The tolerance was found to be controlled by a single dominant gene, designated Alt2, that is in the proximal region of the long arm of chromosome 4D. The locus was mapped relative to molecular markers utilizing a population of recombinant chromosomes from homoeologous recombination between Chinese Spring chromosome 4D and T. turgidum chromosome 4B. Comparison of the location of Alt2 in this map with a consensus map of chromosomes 4B and 4D based on homologous recombination indicated that Alt2 is in a vicinity of a 4 cM interval delineated by markers Xpsr914 and Xpsr1051. The Alt2 locus is distal to marker Xpsr39 and proximal to XksuC2. The Altw locus is also proximal to the Knal locus on chromosome 4D that controls K⁺/Na⁺ selectivity and salt tolerance. In two lines, Alt 2 and Knal were transferred on a single 4D segment into the long arm of T. turgidum chromosome 4B.     

An introduction to markers, quantitative trait loci (QTL) mapping and marker-assisted selection for crop improvement: The basic concepts

Recognizing the enormous potential of DNA markers in plant breeding, many agricultural research centers and plant breeding institutes have adopted the capacity for marker development and marker-assisted selection (MAS). However, due to rapid developments in marker technology, statistical methodology for identifying quantitative trait loci (QTLs) and the jargon used by molecular biologists, the utility of DNA markers in plant breeding may not be clearly understood by non-molecular biologists. This review provides an introduction to DNA markers and the concept of polymorphism, linkage analysis and map construction, the principles of QTL analysis and how markers may be applied in breeding programs using MAS. This review has been specifically written for readers who have only a basic knowledge of molecular biology and/or plant genetics. Its format is therefore ideal for conventional plant breeders, physiologists, pathologists, other plant scientists and students.     

Integration of AFLP markers into a linkage map of sugar beet (Beta vulgaris L.)

The AFLP (amplified fragment length polymorphism) technique has been applied in establishing an extended linkage map of sugar beet. A total of 120 AFLPs were integrated into an existing linkage map based on RFLP markers. Four primer combinations yielded between 19 and 40 polymorphic bands in an F₂ population consisting of 94 plants. The AFLP loci were evenly distributed over the nine linkage groups, with the exception of linkage group V where the number of AFLPs was significantly low. The AFLPs were found to be reproducible even against the background of different combinations of Taq DNA polymerases and buffers. However, the quantity of higher molecular weight fragments (>400 bp) was reduced when using plant DNA of poor quality as a template. The results of these experiments are discussed, together with possible applications of AFLPs in sugar beet breeding.     

RFLP/AFLP mapping of a brown planthopper (Nilaparvata lugens Stål) resistance gene Bph1 in rice

We have constructed a linkage map of the rice brown planthopper (BPH)resistance gene, Bph1. RFLP and AFLP markers were selected by thebulked segregant analysis and used in the mapping study of 262 F₂sthat were derived from a cross of `Tsukushibare', a susceptible japonica cultivar, and `Norin-PL3', an authentic japonicaBph1-introgression line. Twenty markers were mapped within a 28.9-cMregion containing the Bph1 locus on the long arm of rice chromosome12. Combining the result of segregation analysis of BPH resistance by themass seedling test and that of the markers, the Bph1 locus wasmapped within a 5.8-cM region between two flanking markers. The closestAFLP markers, em5814N and em2802N, was at 2.7 cM proximal to theBph1 locus. Together with the previously constructed high-resolutionmap of bph2 locating the locus at ca. 10 cM proximal to the Bph1 locus, this improved version of the linkage map would facilitatepyramiding these two important BPH resistance genes.     

QTL mapping of volatile compounds in ripe apples detected by proton transfer reaction-mass spectrometry

The availability of genetic linkage maps enables the detection and analysis of QTLs contributing to quality traits of the genotype. Proton Transfer Reaction Mass Spectrometry (PTR-MS), a relatively novel spectrometric technique, has been applied to measure the headspace composition of the Volatile Organic Compounds (VOCs) emitted by apple fruit genotypes of the progeny ‘Fiesta’ × ‘Discovery’. Fruit samples were characterised by their PTR-MS spectra normalised to total area. QTL analysis for all PTR-MS peaks was carried out and 10 genomic regions associated with the peaks at m/z = 28, 43, 57, 61, 103, 115 and 145 were identified (LOD > 2.5). We show that it is possible to find quantitative trait loci (QTLs) related to PTR-MS characterisation of the headspace composition of single whole apple fruits indicating the presence of a link between molecular characterisation and PTR-MS data. We provide tentative information on the metabolites related to the detected QTLs based on available chemical information. A relation between apple skin colour and peaks related to carbonyl compounds was established. The two authors contributed equally to this work.     

Genetical Studies on the Mode of Inheritance and Localization of the amo1 (High Amylose) Gene in Barley

In the high amylose starch mutant ‘Glacier AC38’, a single recessive gene designated amo1 is responsible for an amylose content of up to 45%. A rapid technique was established in order to evaluate the amylose/amylopectin ratio in half kernels. To localize this gene, crosses with multiple marker lines and trisormes were conducted. In addition, RFLP markers were used to determine their mapping distance to amo1. Two markers are located 2 cM and 7 cM, respectively, from amo1 on chromosome 5S (1HS). The relationship between the wx and amo1 genes was also examined and the role of the amo1 gene in starch synthesis is discussed.     

Molecular markers linked to rhizomania resistance in sugar beet, Beta vulgaris, from two different sources map to the same linkage group

Rhizomania, one of the most important diseases of sugar beet, is caused by beet necrotic yellow vein virus, a Furovirus vectored by the fungus Polymyxa betae Keskin. Reduction of the production losses caused by this disease can only be achieved by using tolerant cultivars. The objective of this study was the identification and mapping of random amplified polymorphic DNA (RAPD) markers linked to a rhizomania resistance gene. The RAPD markers were identified using bulked segregant analysis in a segregating population of 62 individuals derived by intercrossing plants of the resistant commercial hybrid GOLF, and the resistance locus was positioned in a molecular marker linkage map made with a different population of 50 GOLF plants. The resistance locus, Rr1, was mapped to linkage group III of our map of Beta vulgaris L. ssp. vulgaris, which consisted of 76 RAPDs, 20 restriction fragment length polymorphisms (RFLPs), three sequence characterized amplified regions (SCARs) and one sequence tagged site (STS). In total, 101 molecular markers were mapped over 14 linkage groups which spanned 688.4 cM with an average interval length of 8.0 cM. In the combined map, Rr1 proved to be flanked by the RAPD loci RA411₁₈₀₀ and AS7₁₁₀₀ at 9.5 and 18.5cM, respectively. Moreover, in our I₂ population, we found that a set of markers shown by Barzen et al. (1997) to be linked to the ‘Holly’ type resistance gene was also linked to the ‘GOLF’-type resistance gene. These results appeared to indicate that the rhizomania resistance gene present in the GOLF hybrid could be the same gene underlying resistance in ‘Holly’-based resistant genotypes. Two other explanations could be applied: first, that two different alleles at the same locus could have been selected; second, that two different genes at two different but clustered loci underwent the selection process.     

Molecular genetic mapping of peach

Summary A project to develop a linkage map of the peach (Prunus persica) genome is underway using an F2 population segregating for several morphological characters and pest resistance e.g., nectarine (g), weeping shape (pl) and aphid resistance (Rml). The RAPID technique was used to analyse 270 plants. Linkage analysis of the F2 population was performed using the MAPMAKER software. Eight linkage groups were established and RAPID markers flanking thepl gene were found.