首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 203 毫秒
1.
An invasive plant species may restrict its spread to only one type of habitat,or,after some time,may continue to spread into a different,often stressful,secondary,habitat.The question of whether evolution is required for an invasive species to spread from one habitat to another is currently hotly debated.In order for local adaptation to occur,genetic variation must be present within invasive populations.In this paper,I focus on the effect of habitat on the maintenance of genetic variation during the lag phase,the phase of population stability prior to expansion.Genetic diversity in invasive plant populations accumulates through multiple introductions,gene flow,mutation,and hybridization,but diversity is maintained by population level processes influencing effective population size(Ne).I show that when the plastic response to the environment results in little variation in reproductive output among individuals,Ne is maximized and genetic variation is maintained.Established models of plant competition show that below-ground competition reduces the variation in reproductive output,whereas competition for light increases variation in reproductive output.The same environments that maintain high Ne also reduce the opportunity for selection and minimize the response to selection,and thus the effects of the environment are synchronized to prevent genetic purges.When the primary invasion habitat supports high Ne,conditions are ripe for local adaptation to a secondary habitat,particularly if the secondary habitat has high opportunity for selection.When the primary invasion habitat supports low Ne,genetic diversity is less likely to be sufficient for local adaptation to secondary habitat to occur.  相似文献   

2.
 Eight hundred twenty four nit mutants were induced from 73 strains of Fusarium oxysporum f. sp. vanillae, and classified into four phenotypes by their abilities to utilize different nitrogen sources. Among these mutants, 64.9% were characterized as nit 1, 24.3% as nit 3, 9.8% as nit M, 1.0% as nit X. Based on complementary pairing tests of different nit mutants on the medium MM, 44 isolates belonged to 8 different VCGs, 29 isolates were classified into single and different VCGs. These results indicated that there was significant VCG diversity in Fusarium oxysporum f. sp. vanillae population. VCGs might be correlated with geographic origin of strains, but no close correlation was found between VCGs and pathogenicity.  相似文献   

3.
Many riparian(Tugai) forests growing along rivers in arid and hyper-arid regions of Central Asia are dominated by the Euphrates poplar(Populus euphratica). Besides generative reproduction, which is only possible upon flooding events and at a distance to the groundwater of less than 2 m, this phreatophytic tree species also reproduces vegetatively by forming clones that can cover land surface areas of several hectares. Along a gradient of groundwater distances, we investigated whether the fraction of clones in P. euphratica stands(1) increases with increasing distance to the water table;(2) is higher if supplied with water via river cut-offs; and(3) approaches 100% at a short distance to the groundwater, but at high salt concentrations in the upper soil layers, which would prevent germination and establishment of seedlings. AFLP(Amplified Fragment Length Polymorphism) analyses were conducted on leaf samples taken from mature P. euphratica trees growing at the fringes of the Taklimakan Desert in stands with different distances(2–12 m) to the groundwater at two plots at the middle and the lower reaches of the Tarim River and in a stand close to Ebinur Lake, Xinjiang, China. Genetic diversity was large among plots, but considerably smaller within plots. We found the highest genetic diversity(caused by regeneration from seeds) at plots that have a short distance to the groundwater or are supplied with additional water. There was no significant relationship between groundwater distance and clonal fraction. All investigated trees at the saline Ebinur Lake site belonged to one single clone. Our results demonstrate that the genetic pattern of this widespread species is not easily predictable even over small distances as it is a result of a complex interplay of stand history and dispersal of propagules(pollen, seeds, and vegetative diaspores) by wind and water. In conservation and restoration schemes, P. euphratica stands with a high genetic diversity and stands that grow at short distances to the water table and are regularly subjected to flooding(which favors generative over clonal reproduction) should be prioritized.  相似文献   

4.
Understanding variability in seed germination among populations is essential for planning an effective germplasm collection for restoration and conservation purposes.The knowledge of germination and dormancy patterns among populations of desert grasses is crucial for determining the potential of the species and populations to be used for restoration and conservation as well as forage production.Variability in seed germination of Panicum turgidum Forssk and Pennisetum divisum(Gmel.)Henr.in the desert of Kuwait was evaluated in different populations in May 2017.Experiment of seed germination(25 seeds and 4 replicates)was conducted for each population at night/day temperatures of 15℃/20℃and 20℃/30℃under the following light condition:continuous darkness or 12 h/12 h light/dark.Results showed that seed masses of both species strongly varied according to their seed provenances,and both species produced heavier seeds in population with a higher soil electrical conductivity.Seed germination percentage considerably varied between two species,and the variation in P.turgidum was greater(17%–49%)than that of P.divisum(72%–93%).Germination percentage in P.turgidum was greater at high temperature(20℃/30℃)than at low temperature(15℃/20℃).However,temperature regimes had no effect on germination percentage of P.divisum seeds.Mean germination time of both species exhibited significant inter-population variability.This result is especially relevant to assure the selection of the best population of each species and the regeneration success of the species.Besides this,inter-population variability also provides valuable information for enhancing our understanding of the mechanisms that regulate seed germination and how they might be related to seed provenance.  相似文献   

5.
 The investigation showed that stem-pitting Citrus tristeza virus (CTV)occurred commonly in citrus production areas in several varieties of Hunan Province. Accurate detection of CTV strains was performed by p23/PCR method, PCR and the results indicated that the most samples were infected with several CTV isolates. Three mild strains were isolated and their pathogenicity was identified by biological identification, it indicated that p23/PCR groups had uniformity with the pathogenicity of CTV isolates. Furthermore, three mild isolates were tested in the cross protection by analysis of biological symptoms and composition of p23 gene. Different protecting effects were observed among these strains and W17 mild isolate was effective.  相似文献   

6.
Eremosparton songoricum (Litv.) Vass. is a clonal shrub that reproduces both asexually by under-ground rhizomes and sexually by seeds. It is now a rare species with a narrow distribution in fragmented habitat patches in the Gurbantunggut Desert of Xinjiang, China. The objective of this study was to determine the spatial pattern or structure of genetic variation within population. The within-populations genetic structure of E. songoricum in a plot (10 m×10 m) was analyzed using inter simple sequence repeats (ISSR) markers. Correlograms of Moran's I showed significant positive value was about 7 m, but changed into a negative correlation with the increase of distance, indicating strong genetic structure. The natural character of clonal reproduction, restricted seed and pollen dispersal were the main factors of influencing the spatial pattern. The knowledge of clonal structures within populations was crucial for understanding evolutionary processes and ecological adaptation. This study provided basic data for the conservation and management of E. songoricum, especially for sampling strategies for ex situ conservation.  相似文献   

7.
 The pathogen of Siraitia grosvenorii wilt was identified.Six strains were isolated from diseased plants of S.grosvenorii collected from Yongfu County in Guangxi.By using bacteriological identification,pathogenicity tests assay,16S rDNA sequence analysis,the S.grosvenorii wilt was caused by Ralstonia solanacearum.The results of pathogenicity and carbohydrate utilized test demonstrated that the pathogen belonged to race 1 and biovarⅢ of R.solanacearum.  相似文献   

8.
Urban development in arid and semi-arid regions is largely constrained by fragile physical environments.The characteristics of an urban settlement are different from those in other regions of China.This paper analyses the coupling characteristics and spatio-temporal variations for oasis urban development and water-land resources at the northern slopes of the Tianshan Mountains by principal component analysis and a coupling degree model.The result shows that the degree and change in regional use of water and land resources are different among the studied cities/counties during their development.The built-up areas of these cities/counties have changed little with increasing populations and urbanization levels,which well reflects that the urban development in arid and semi-arid regions is limited by oasis areas.Per capita amount of water supplied,however,presented a trend of slowed growth with increasing levels of urbanization.Water consumption gradually increased with urban development and the improvement of people's living standards,accompanied by enhanced water use efficiency. The level of urbanization can be assessed through the coupling degree between oasis urban development and the use of water and land resources.A high coupling degree represents a high level of comprehensive urban development and use of water-land resources.Alternatively,a low coupling degree denotes a low level of urban development and water-land resource use.  相似文献   

9.
小麦-滨麦易位系M8657-1抗条锈病基因遗传分析和分子标记   总被引：3，自引：0，他引：3  
 M8657-1, one of the wheat translocation lines derived from Leymus mollis Trin. Hara, is possessed of effective resistance at all stages to Su-ll and other dominant races of Puccinia striiformis f. sp. tritici in China. Seedlings of the parents, F1, and F2 progeny derived from the cross of M8657-1 (resistant) Mingxian169 (susceptible) were inoculated with Su-ll in greenhouse to identify and map the probable new stripe rust resistance gene. The results suggested that the stripe rust resistance in M8657-1 was conferred by a pair of recessive genes. Simple sequence repeat (SSR) technique was used to detect molecular marker associated with the resistance gene:208 pairs of wheat SSR primers were used to screen the two parents, as well as resistant and susceptible bulks and then three SSR markers were selected for genotyping the F2 population. The geue, temporarily designated as YrLml, was found to be located on the chromosome 7DL and flanked by three SSR markers GDM67, WMC150 and WMC671, with the genetic distance of 5.0, 9.7 and 11.8cM, respectively.  相似文献   

10.
进境澳大利亚油菜籽中茎基溃疡病菌的检测   总被引：1，自引：0，他引：1  
 41 fungal isolates with similar morphological characteristics to Leptosphaeria maculans were obtained by the deep-freezing filter paper method from 2100 seeds of Brassica napus imported from Australia.The isolate 8129-5 showed a slower growth on PDA at 20℃with growth rate of 2.8 mm/day.The colonies on PDA at 20℃ had an irregular or regular margin with white or grayish white compact aerial mycelium.No diffusible pigment was produced on PDA at 31℃ or in liquid Czapek-Dox media at 20℃.PCR detection showed that the isolate 8129-5 could be amplified by L.maculans-specific primers LmacF/LmacR and got expected product of 331 bp.The sequence analysis revealed that the ITS sequence of isolate 8129-5 had 99.8% identity with L.maculans.Pathogenicity of the isolate 8129-5 was confirmed on cotyledons of rape seed by artificial inoculation compared with typical symptom of L.maculans.Based on the morphological characteristics, PCR detection and the result of pathogenicity test, the isolate 8129-5 was identified as L.maculans.  相似文献   

11.
 选用16对毒性相关基因特异性引物对四川和重庆9个县(市)分离到的200个稻瘟病菌单孢菌株进行PCR扩增,并采用最长距离法进行聚类分析,结果显示各引物均能扩增出其目的条带,多态位点百分率(P)高达93.75%,扩增频率差异较大;200个菌株可归为70个不同的单元型,其中单元型SCH13为优势单元型;在0.86遗传相似水平上,200个菌株可划分为27个遗传宗谱,包括1个优势宗谱,3个亚优势宗谱,14个次要宗谱,9个小宗谱,层次丰富;在群体平均水平上,病菌群体具有丰富的遗传多样性(H=0.324 4,I=0.484 2),且群体间差异较大;9个种群在遗传距离为0.05水平上可分为4个类群,种群遗传谱系与地理区域分布呈一定相关性。同时,该地区的群体存在一定的遗传分化(HT=0.320 0),群体内多样性大于群体间多样性(Hs=0.179 6,Dst=0.140 4),总遗传变异的56.13%存在于群体内(Gst=0.438 7),群体间基因流动性较小(Nm=0.639 6)。本研究揭示了四川和重庆部分区域稻瘟病菌群体遗传结构、遗传多样性及其与地理分布之间的关系,为抗病育种和品种布局奠定了基础。  相似文献   

12.
引起油茶炭疽病胶孢炭疽菌种群遗传结构研究   总被引：2，自引：0，他引：2  
 胶孢炭疽菌是引起油茶炭疽病的主要病原之一。目前对于该病原菌种群的遗传结构尚未见报道。研究病菌种群的遗传结构对制定科学的防治方法具有重要意义。本研究比较中国6个省12个不同地区的126个胶孢炭疽菌的ITS序列的差异,以期研究各不同群体的单倍体型多样性,不同地区群体之间的遗传关系,以及遗传距离与地理距离的线性关系。遗传分析发现,得到的126个胶孢炭疽菌样品ITS序列可定义为27种单倍体型。27种单倍体型中,一个主要的单倍体型(Haplotype12)含有78个样品,且基本上每个样品采集地都有分布。遗传分化指数(Fst)表明病菌不同地理种群间的遗传分化较大。AMOVA分析显示,种群间的遗传变异占总变异的6%,种群内部变异占总变异的94%。Mantel测试显示地理距离与遗传距离没有显著的线性关系。对所有地理种群病原菌ITS序列的核苷酸不配对进行分析,发现油茶炭疽病菌未经历过大规模的种群扩张过程。系统发育分析表明,来自不同地区的油茶炭疽病菌散乱的分布在系统树中。研究结果表明油茶炭疽病菌种群具有丰富的遗传多样性。  相似文献   

13.
 为了明确我国落选短体线虫群体的遗传多样性,利用mtCOI基因标记对落选短体线虫9个地理群体的遗传结构及遗传分化进行分析。结果显示,9个地理群体中共得到101条mtCOI序列,发现28个碱基变异位点,形成14个单倍型。其中,H1单倍型最常见,为7个地理群体的59个个体共有,推测其可能为祖先单倍型。全部地理群体在物种水平呈现中等遗传多样性(HT = 0.706±0.131),聚类分析显示其可分为类群Ⅰ与类群Ⅱ两个类群,AMOVA分析揭示落选短体线虫整体水平的遗传分化主要来源于种群间。Mantel检验表明落选短体线虫群体的遗传距离与地理距离存在正相关性,但是不同种群之间的遗传分化程度与地理距离没有显著关系。中性检验和错配分布检验均揭示落选短体线虫在整体水平和两个类群上的群体历史动态都处于相对稳定的状态。  相似文献   

14.
The random amplified polymorphic DNA (RAPD) method was used to investigate the genetic variability and population structure of Fusarium culmorum isolated from wheat stem bases. A total of 108 isolates, representing seven geographically distinct populations, was collected from five climatic regions in Tunisia. Pseudo-allelic frequencies were estimated at each of the 25 putative RAPD loci analyzed by scoring for the presence or absence of amplified fragments; 92 haplotypes were found among the 108 strains. The analysis of the population structure did not reveal any trend with regard to geographic origin. Total gene diversity (HT * = 0.318) was mostly attributable to diversity within populations (HS * = 0.308). Analysis of molecular variance confirmed that most of the genetic variability was within populations. Genetic differentiation among populations was low to moderate (GST * ranged from 0 to 0.190 and averaged 0.041 over all loci). Cluster analysis with UPGMA using genetic distances did not reveal any spatial clustering of the isolates collected from the different geographic regions. Based on these results, we conclude that the F. culmorum isolates recovered from different regions in Tunisia might be part of a single population pool.  相似文献   

15.
 为明确山西省玉米丝黑穗病菌群体的遗传结构,为该病害的综合防控提供理论依据。采用SSR标记方法对山西省不同地区玉米丝黑穗病菌进行检测。结果显示,12个SSR分子标记在118株玉米丝黑穗病菌中共检测出30个等位基因,平均等位基因数(Na)、有效等位基因数(Ne)、Shannon's 信息指数(I)、等位基因丰度(Ar)分别为2.5、1.768 6、0.614 4和2.175。平均观测杂合度(Ho,0.163 2)低于平均期望杂合度(He,0.396 5),且近交系数(Fis,0.522 1)大于0。说明本试验检测到的等位基因数较少,但分布比较均匀,且由于群体内的杂合子缺失导致病原菌群体显著偏离了Hardy-Weinberg。6个地理群体的遗传分化处于中等水平(FST = 0.050~0.055),群体间基因交流频繁(Nm = 1.563~121.109)。AMOVA分析结果进一步显示,遗传分化主要存在于群体内个体间(94.80%),群体间的变异仅占5.2%。UPGMA 聚类结果表明,供试群体可被划分为遗传分化明显的两个亚群,其中位于晋东南地区的晋城群体和长治群体聚为一个组群,位于晋中和晋北地区的其余4个群体聚为另一组群,与遗传结构分析结果一致,推断山西省玉米丝黑穗病菌群体可能来自于2个祖先亚群,且大多数菌株的遗传组分单一。  相似文献   

16.
安徽省水稻条斑病菌群体遗传结构分析   总被引：1，自引：0，他引：1  
 水稻条斑病菌是近年来影响安徽水稻生产的主要有害生物。本研究利用rep-PCR指纹技术分析了来自安徽11个不同县市的水稻条斑病菌群体遗传结构。用引物BOX、REP和ERIC分别对94个菌株的基因组DNA进行了PCR扩增,结果表明3组引物共扩增出了49条指纹条带,且所扩增出的DNA条带均为多态带。在群体平均水平上,安徽省水稻条斑病菌群体Nei’s基因多样性指数(H)为 0.32,Shannon 信息指数(I)为 0.49,表明安徽省水稻条斑病菌的遗传多样性丰富,但病菌的遗传多样性在地区间存在差异。UPGMA聚类分析表明,来自毗邻地区的水稻条斑病菌种群大都聚为一类,水稻条斑病菌种群遗传谱系与地理区域分布呈现一定相关性。同时,安徽省水稻条斑病菌群体存在一定的遗传分化,遗传变异主要来源于群体内部。  相似文献   

17.
小麦孢囊线虫病(CCN,Heterodera avenae)已成为山东省小麦生产上的一种重要病害,研究CCN群体间和群体内的遗传多样性可以为其综合防治提供理论依据。本实验研究了山东省17地市34个群体的r DNA-ITS区,并采用ISSR分子标记技术对其中10个地市的27个种群做了遗传多样性分析。结果表明,在r DNA-ITS系统发育树中,山东省34个小麦孢囊线虫群体与H.pratensis、H.australis及中国H.avenae群体亲缘关系较近。3个ISSR引物共扩增出31条条带,多态性条带百分率(PPB)为100%。菏泽、潍坊、烟台群体遗传多样性较高,枣庄、威海、淄博、滨州群体遗传多样性相对较低。M antel检测和聚类结果表明,群体间的遗传分化与地理距离并无显著的相关性,AM OVA分析结果显示,在总的遗传变异中17.7%的变异发生在群体间,82.3%的变异发生在群体内。研究结果显示山东省H.avenae具有较高的遗传多样性,且群体间已发生了一定程度的遗传分化。  相似文献   

18.
四川西南部小麦白粉菌群体毒性及遗传多样性分析   总被引：3，自引：2，他引：1  
为明确四川西南部白粉菌群体毒性及其遗传变异情况,本文将2011年采自四川西南部的小麦白粉病标样进行单孢子堆分离纯化,共获得48个白粉菌菌株,并将其按采集地划分为4个地理群体。利用28份已知抗白粉病基因材料测定了群体的毒性频率,并运用SRAP分子标记技术探讨了其遗传多样性。毒性测定结果表明,白粉菌群体毒性较强,群体间毒性结构存在差异。供试群体对Pm1、Pm3a、Pm3b、Pm3d、Pm5a、Pm6、Pm19的平均毒性频率达50%以上,而Pm13、Pm XBD、Pm5b、Pm2+6、Pm5+6抗性保持良好,平均毒性频率在10%以下。群体间毒性遗传距离与地理距离之间有一定的相关性,但未达到显著水平。用筛选出的10对SRAP引物共获得160个清晰、稳定的扩增位点,多态性频率为50.63%;白粉菌群体遗传多样度(h)、Shannon信息指数(I)分别为0.198 8、0.322 7,遗传变异主要源于群体内部。群体间基因流数值均在6.50以上,说明四川西南部白粉菌群体间菌源迁移频繁,基因交流较为充分。M antel Test分析表明SRAP标记解释的群体遗传多样性与地理距离、毒性多样性间的相关性未达到显著水平。  相似文献   

19.
由丁香假单胞菌猕猴桃致病变种Pseudomonas syringae pv. actinidiae (Psa)侵染引起的猕猴桃细菌性溃疡病(kiwifruit bacterial canker)是全球猕猴桃生产上最具毁灭性的细菌病害。为探明福建、安徽、四川和陕西4省Psa菌株的生物型和遗传多样性,用5对PCR特异性引物PsaJ-F/-R、PsaK-F/-R、Tac-F/-R、Con002-F/-R和avrRps4-F1/-R2检测Psa菌株的生物型;用4对PCR引物27F/1492R、PsaF1/PsaR2、gapA-Fps/Rps和rpoD+364s/-1222ps分别扩增16S rRNA、ITS、gapA和rpoD基因,进行多基因联合分析Psa菌株的遗传多样性。结果表明,特异性引物Tac-F/-R从47株Psa菌株中均能扩增出一条545 bp的特异条带,其他4对引物未扩增出任何条带,说明供试Psa菌株的生物型均为biovar 3。多基因联合分析表明,4省Psa存在丰富的遗传多样性,4个群体共检测出27个单倍型,单倍型多样性为0.955。安徽、福建、四川和陕西群体的单倍型数差异较大,分别为1、8、12个和12个。4个群体的多态性位点数、核苷酸多样性和平均核苷酸差异数差异极显著(P<0.01),其中福建群体的多态性最丰富,而安徽群体的多态性最低。AMOVA分析表明,3.6%的遗传变异来源于种群间,而96.4%的遗传变异来源于种群内,说明种群内变异是遗传变异的主要来源。遗传分化分析表明,安徽省Psa群体与其他3个群体间的遗传分化极高(Fst>0.175),福建、四川和陕西群体间的遗传分化水平较低(Fst<0.017)。研究结果有利于了解福建省Psa的来源,为阻断Psa的传播和猕猴桃细菌性溃疡病的长期可持续控制提供了理论参考。  相似文献   

20.
云南元阳哈尼梯田稻瘟病菌遗传多样性分析   总被引：7，自引：0，他引：7  
 利用12对SSR引物,对来自云南元阳哈尼梯田不同海拔高度、不同水稻品种上的稻瘟病菌菌株进行遗传多样性分析,并运用日本清泽建立的鉴别品种对其中62个菌株进行生理小种鉴定。结果显示:稻瘟病菌总体遗传多样性水平较高(He=0.57±0.27,I=1.17±0.60)。聚类分析表明,在80%相似水平下菌株可划分为9个多样性群体。供试菌株划分为16个生理小种,其中002、000和006为优势小种。分离的不同海拔稻瘟病菌生理小种和遗传多样性存在差异。海拔1600~1700m生理小种最丰富,达9个生理小种;海拔1500~1600m、1400~1500m和1700~1800m,生理小种分别为6、5和4个;遗传多样性分析表明,从海拔1400~1500m分离的菌株遗传多样性水平最高(He=0.57±0.24),并划分为6个群体。综合分析表明,在元阳哈尼梯田系统中,栽培传统品种遗传多样性越丰富的区域,其稻瘟病菌群体多样性和生理小种也越丰富。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号