Genetic enrichment of the arctic clonal plant Saxifraga cernua at its southern periphery via the alpine sexual Saxifraga sibirica

Isolation of populations at the margins of a species range may lead to decreasing genetic diversity via genetic drift and inbreeding. Hybridization between peripheral populations of two species can, however, counteract genetic impoverishment. The mainly clonal, polyploid plant Saxifraga cernua has a wide arctic distribution but also extends southwards into alpine sites. In the Ural Mountains, its peripheral distribution overlaps with that of its sexually reproducing, diploid relative Saxifraga sibirica, and fertile polyploids of more or less intermediate appearance are found in this overlap zone. We used amplified fragment length polymorphism (AFLP) analysis to address the potential impact of interspecific gene flow on genetic diversity in the peripheral populations. A total of 149 plants from 17 populations along a 1650 km south-north gradient were analysed for 253 markers. The results suggest that three Middle Ural populations containing fertile and morphologically more or less intermediate plants have been affected by hybridization. All of these plants formed a strongly supported (100%) group with S. cernua in a neighbour-joining tree, but their AFLP phenotypes assigned either to S. cernua or to artificial (simulated) F(1) hybrids between S. cernua and S. sibirica in multilocus assignment tests. The three populations were highly diverse with virtually every plant representing a distinct AFLP phenotype, providing additional evidence for formation of later-generation hybrids and/or backcrossing to S. cernua. In contrast, other peripheral populations of S. cernua were typically monoclonal, suggesting that hybridization with S. sibirica can increase genetic diversity in S. cernua at its southern periphery.     

Genetic diversity and population structure of Buddleja crispa Bentham in the Himalaya-Hengduan Mountains region revealed by AFLP

Buddleja crispa Benth. is one of the most morphologically variable species in genus Buddleja, and it is widely distributed in the Himalaya-Hengduan Mountains (HHM) region. This study used AFLPs as a tool to examine the genetic variation among and within 25 populations of B. crispa. Analysis of population genetics of the species aimed to clarify morphological variation, current distribution patterns, strong adaptability to habitats, and the effects of geological factors in the HHM region. The genetic structure results, based on PCoA and NJ cluster analyses, revealed that the populations of B. crispa were divided into two genetic groups. Furthermore, the peripheral populations had lower genetic diversity than the populations in the center of the distribution areas (Three Parallel Rivers). We conclude that the gene flow (predominantly seed and pollen flow) and the population differentiation of B. crispa might be more affected by the barriers formed by rivers and mountains than by geographic distance.     

毛竹7个新近发表种下类型的AFLP分析

为了解毛竹(Phyllostachys edulis)种下类型的遗传关系,对花龟竹(P.edulis‘Mira’)、斑毛竹(‘Porphyrosticta’)、安吉锦毛竹(‘Anjiensis’)、麻衣竹(‘Exaurita’)、黄皮毛竹(‘Holochrysa’)、绿槽龟甲竹(‘Lücaoguijiazhu’)、孝丰紫筋毛竹(‘Purpureosulcata’)等7个新近发表的种下类型进行了AFLP分子标记分析。结果表明,采用筛选的8对引物组合共扩增了1728条条带,多态性条带百分率达98.77%,检测到多态性位点881个。Nei’s遗传多样性指数(H)为0.2736,Shannon信息指数(I)为0.4291。这丰富了毛竹所有23个种下类型的分子亲缘关系研究数据。     

利用AFLP分析西南特色猕猴桃的遗传多样性

为分析西南地区特色猕猴桃(Actinidia Lindl.)的遗传多样性,建立并优化了猕猴桃DNA 多态性分析的AFLP 体系,AFLP 标记体系为300 ng 基因组DNA 用EcoR Ⅰ/Mse Ⅰ (15 U/5 U)于37℃下酶切2 h,加接头后的混合物稀释5 倍用于预扩增,预扩增产物再稀释10 倍后进行选择性扩增.结果表明,筛选的22 对引物进行扩增反应,共得到979 条条带,其中多态性条带为649 条.采用优化的AFLP 体系,对西南地区的10 种猕猴桃50 个样本进行了遗传多样性分析,包括普通品种中华猕猴桃、美味猕猴桃,及特色品种硬毛猕猴桃、毛被猕猴桃、革叶猕猴桃、四萼猕猴桃、狗枣猕猴桃、葛枣猕猴桃、京梨猕猴桃和紫果猕猴,结果表明种内和种间的聚类关系明显;斑果组(sect. Maculatae)和净果组(sect. Leiocarpae)的种间有聚类交叉,并呈现地理区域性分布.     

AFLP mapping of quantitative trait loci for yield-determining physiological characters in spring barley

 An amplified fragment length polymorphism (AFLP) map covering 965 cM was constructed using 94 recombinant inbred lines of a cross between the spring barley varieties Prisma and Apex. This map was employed to identify quantitative trait loci (QTLs) controlling plant height, yield and yield-determining physiological characters using an approximate multiple-QTL model, the MQM method. The seven physiological traits were parameters used in a process-based crop-growth model that predicts barley biomass production as affected by daily temperature and radiation. The traits were measured in experiments conducted over 2 years. Except for the relative growth rate of leaf area, all traits examined had at least one QTL in each year. QTLs and their effects were found to vary with developmental stages for one trait, the fraction of shoot biomass partitioned to leaves, that was measured at several stages. Most of the traits were associated, though to different extents, with the denso dwarfing gene (the height-reducing allele in Prisma) located on the long arm of chromosome 3. Some of the QTLs were mapped to similar positions in both years. The results in relation to effects of the dwarfing gene, the physiological basis for QTL×environment interaction, and the relative importance of the parameter traits with respect to yield, are discussed. Received: 17 September 1998 / Accepted: 28 December 1998     

香菇空间诱变突变体的分子生物学鉴定研究*

香菇Cr04菌株经空间诱变后从中筛选出了农艺性状明显改善的突变菌株Cr04DZ。本研究用RAPD和AFLP技术对Cr04DZ与其地面对照菌株Cr04进行了DNA指纹分析,找出了它们之间的DNA多态性,从而从分子水平上证实了香菇经空间诱变后遗传物质发生了变化。此外,还比较了AFLP与RAPD检测香菇DNA多态性的效率,优化了对食用菌进行RAPD与AFLP分析的反应条件。通过对Cr04DZ及其对照株Cr04的RAPD及AFLP分析,筛选出了突变体的3个RAPD及29个AFLP多态性产物,已完成了3个AFLP产物的克隆。     

51个春兰(Cymbidium goeringii)品种的AFLP遗传多样性分析

为了揭示春兰品种的遗传多样性和亲缘关系,为春兰种质资源的有效利用和开发提供依据,采用AFLP技术对51个春兰品种进行了遗传多样性分析,经筛选得到了8对条带清晰、多态性高的引物,共扩增出1315条DNA片段,其中多态性条带为1217条,平均1对引物扩增条带164条,多态性带152条,多态性位点频率为92.5%,表明春兰品种具有丰富的遗传多态性。49个品种含有特有带。51个品种间遗传相似系数变化范围为0.501~0.716,聚类分析表明,51个春兰品种共分为5个类群,来自同一地区的品种并没有聚在一起,表明春兰品种的遗传背景混乱。AFLP分子标记技术能有效地分析春兰品种的遗传多样性和亲缘关系。     

Genetic diversity within and among populations of Shorea leprosula Miq. and Shorea parvifolia Dyer (Dipterocarpaceae) in Indonesia detected by AFLPs

The genetic diversity within and among populations of Shorea leprosula and Shorea parvifolia from Indonesia was investigated using amplified fragment length polymorphisms (AFLPs). The results indicated that S. leprosula is genetically more variable than S. parvifolia. At the population level, a higher level of genetic diversity was revealed for S. leprosula with a percentage of polymorphic loci (PPL_p) of 53.32% and an expected heterozygosity (H _ep) of 0.16 in comparison with S. parvifolia showing PPL_p of 51.79% and H _ep of 0.14. At the species level, S. leprosula showed PPL_s of 92.86% and H _es of 0.21, while S. parvifolia showed PPL_s of 85.71% and H _es of 0.21. Genetic differentiation (G _st) indicated that 25 and 31% of total genetic diversity in S. leprosula and S. parvifolia, respectively, were attributed to the differences among populations. An analysis of molecular variance (AMOVA) at two hierarchical levels exhibited that most genetic variation resided within populations with proportion of 70.2% for S. leprosula and 66.2% for S. parvifolia. The AMOVA at three hierarchical levels performed for S. leprosula and S. parvifolia together revealed that the genetic difference between the two species was remarkably higher with a proportion of 44.1% than the differences within and among populations (38.1 and 17.8%, respectively). The genetic differentiation between islands was significant for S. leprosula but not for S. parvifolia. The observed genetic diversity agreed with the life history traits of Shorea species. Highly differentiating individual AFLP markers were found for each species, which will serve as diagnostic markers for the identification of wood of different species, from different islands and regions.     

’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     

AFLP在分子生物学研究中的应用

扩增片段长度多态性（AFLP）可靠性强,多态检出率高,因而被认为是最有效的DNA指纹分析技术。AFLP已广泛应用于分类学、病理学、种群遗传学、DNA指纹分析的研究和建立数量性状基因图谱,成为最主要的遗传标记。介绍了AFLP的原理、影响因素及其在分子生物学研究中的应用。