Dairyland populations of bur cucumber (Sicyos angulatus) as a possible seed source for riverbank populations along the Abukuma River,Japan

In 2006, the distribution of bur cucumber (Sicyos angulatus L.) along the river bank of the Abukuma River, Japan, was examined. Twenty‐six populations were found in the area surrounding the upper reach of the river and they were limited to dairy land. On the basis of polymerase chain reaction–restriction fragment length polymorphism analysis for four of the six polymorphic loci that were detected in 16 non‐coding regions of the chloroplast DNA from 300 samples, five multilocus haplotypes (A–E) were identified. Despite its smaller size, the surrounding area's population showed a higher genetic diversity at the haplotype level than did the riverbank population. The haplotype composition of the surrounding area's population was similar to that of the riverbank population in the upper‐stream region. The distribution of haplotype D was biased towards the upper reach of the river, possibly because of migration from the surrounding area's population. The distribution of haplotype E was biased towards the middle‐to‐lower reaches of the river and was associated with the existence of source populations other than the surrounding area's population. The results also showed that the estimated seed flow from another dairy land could transport seeds into the middle reach of the river at a high frequency, suggesting that dairy land is largely responsible for the development of the riverbank populations. The eradication of dairyland populations should be given priority in order to prevent future migration along the river bank and to protect the existing endangered wetland species from invasive S. angulatus.     

Genetic diversity of the annual weed Monochoria vaginalis in southern China detected by random amplified polymorphic DNA and inter-simple sequence repeat analyses

Two molecular genetic screening techniques, RAPD (random amplified polymorphic DNAs) and ISSR (inter-simple sequence repeats), were applied to detect the level and pattern of genetic diversity of Monochoria vaginalis, a common weed of rice fields, in seven populations from southern China. Among these populations, 116 bands were amplified by 18 RAPD primers, of which 34 bands (29.31%) were polymorphic, and 14 ISSR primers produced 111 bands with 87 polymorphic bands (78.38%). Within each population, a relatively low level of genetic diversity was detected by both RAPD and ISSR analyses, with a mean genetic diversity (H) of 0.0348 and 0.0551 respectively. Analysis of molecular variance of the data from the RAPD and ISSR markers detected that the majority of total genetic variation existed among populations (73.50% and 76.70% respectively) and only minor genetic variation within populations (26.50% and 23.30% respectively). Cluster analysis divided the seven populations into two groups, indicating that the genetic relationships among populations have relatively low correlation with their geographical distribution (Mantel test; r = 0.45 and 0.48 respectively). Our results indicated that both RAPD and ISSR markers were effective and reliable for accurately assessing the degree of genetic variation of M. vaginalis. Comparing the two techniques, ISSR markers were more efficient than the RAPD assay. The Mantel test gave r = 0.16, suggesting no correlation between these two molecular markers.     

Genetic diversity of Pueraria lobata (kudzu) and closely related taxa as revealed by inter-simple sequence repeat analysis

Kudzu (Pueraria lobata) is a noxious weed infesting some areas of the USA. Knowledge of its genetic variation in both native and invasive areas can lead to effective biological control measures. Inter-simple sequence repeat (ISSR) variations were studied in P. lobata and its four closely related congeneric species (P. edulis, P. montana, P. phaseoloides and P. thomsoni). ISSR results allowed a clear separation of these five species. For P. lobata, 108 plants from China and USA were analysed. The samples from the US were genetically closer to Chinese P. lobata populations than to other congeneric populations. High genetic differentiation was found for P. lobata, P. montana and P. thomsoni in Chinese samples. High genetic diversity and low population differentiation was found in P. lobata samples of the US. This supports the hypothesis of multiple introductions into the USA from different sources in Japan or China, followed by subsequent gene exchange and recombination.     

玉米根际球孢白僵菌群体遗传多样性的ISSR分析

为了明确玉米根际球孢白僵菌的遗传分化情况及亲缘关系,通过ISSR-PCR分子标记技术对分离自玉米根际的球孢白僵菌的遗传多样性进行了研究。从40个引物中共筛选出11个多态性高、稳定性好的引物用于正式的扩增分析,在37个菌株中共扩增出83条谱带,其中多态性条带占69条,多态性百分率为83.13%。平均每引物扩增条带在7.5条。群体的多态位点百分率(PPL)为83.13%,Nei基因多样性指数(H)为0.316 9,Shannon信息指数(I)为0.465 7。结果表明,分离自安徽省涡阳、萧县、蒙城三个地区的球孢白僵菌具有较高的遗传多样性。研究结果对进一步探讨玉米根际球孢白僵菌不同菌株的生防效果具有重要意义。     

我国烟草赤星病菌遗传多样性的ISSR分析

为明确我国烟草赤星病的2种主要致病菌链格孢菌Alternaria alternata和长柄链格孢菌A.longipes的地理差异与遗传结构,采用ISSR标记对分离自9个省市的135株烟草赤星病菌进行遗传多样性分析。结果显示,通过正交优化试验建立的烟草赤星病菌ISSR-PCR最佳反应体系稳定性较好,筛选出17条多态性高且稳定的引物,共扩增出192条谱带,其中有177条具有多态性,多态率为92.19%。UPGMA聚类分析结果显示,链格孢菌和长柄链格孢菌的遗传相似性系数分别在0.67~1.00和0.66~1.00之间,遗传相似性系数为0.83时可使链格孢菌和长柄链格孢菌分别划分为5个和6个亚群,其中前者不同地理种群间表现出地理相关性,后者不同菌株随机分组。烟草赤星病菌种群的基因多态性和遗传多样性丰富,链格孢菌和长柄链格孢菌的群体间遗传分化系数分别为0.36和0.37,均存在遗传分化;群居每代迁移数分别为0.89和0.85,不同地理种群间存在基因交流;2种烟草赤星病菌的遗传分化结构表现出相似性。表明我国烟草赤星病菌中的链格孢菌和长柄链格孢菌均存在丰富的遗传多样性,且二者进化方向相似,ISSR标记能较好地揭示烟草赤星病菌种群间的亲缘关系和遗传差异性,可用于其遗传多样性分析。     

Genetic structure of the invasive Chromolaena odorata in China

Chromolaena odorata is one of the world's worst tropical weeds, and it can be found in Guangdong, Guangxi, Hainan and Yunnan provinces in China. Genetic variation of 27 C. odorata populations sampled from across its invasive range in China was investigated using inter‐simple sequence repeats (ISSR) analysis. All populations exhibited low levels of genetic variation. On average, 2.35% of the ISSR loci were polymorphic, total genetic diversity (H_T) was 0.0406 and Shannon's information index (H_sp) was 0.0623. High genetic identities (I) between populations (0.9687 ± 0.01204) indicated low genetic differentiation. A frequent founder effect was interpreted as the main cause of the genetic structure observed in C. odorata.     

玉米圆斑病菌(Bipolaris zeicola)遗传多样性ISSR分析

利用简单序列重复间隔区(inter-simple sequence repeats,ISSR)标记对玉米圆斑病菌(Bipolaris zeicola)的遗传多样性进行了分析。筛选出9个扩增多态性好且稳定的通用引物,共扩增出47条DNA条带,大小分布于250~2 000bp之间,其中多态性条带为33条,为总条带数的70.21%。遗传距离为0.91处时,所有菌株被聚为6个组。ISSR标记可以揭示菌株间的亲缘关系及差异性,可用于玉米圆斑病菌遗传多样性研究。此外,通过分子标记划分的类群与利用寄主反应型之间存在一定相关性,但其关系并不密切。     

玉米大斑病菌ISSR反应体系的优化和遗传多样性分析

以玉米大斑病菌基因组DNA为模板,采用单因素水平优化的方法对DNA聚合酶的来源及浓度、引物浓度、dNTPs浓度、DNA模板浓度、Tm(退火温度)、PCR反应循环数等重要参数进行摸索和优化,建立了玉米大斑病菌ISSR-PCR优化反应体系,并从40条ISSR引物中筛选出9条多态性较好的ISSR引物。对来自河北、河南、辽宁等玉米主产区的44个菌株进行ISSR分析表明,ISSR标记在我国玉米大斑病菌中存在较高的多态性,多态性条带占40.3%。聚类分析显示,在阈值为0.8时菌株被分为7个类群。对ISSR揭示的玉米大斑病菌的遗传多样性与菌株交配型、地理来源之间的关系进行分析,结果显示菌株的遗传多样性与交配型间的关系密切,而与其地理来源无明显相关性。     

Genetic variation,vegetative compatibility,and aggressiveness diversity of Diplodia bulgarica isolates from apple orchards in West Azarbaijan province of Iran

This study investigated inter-simple sequence repeat (ISSR), vegetative compatibility, and aggressiveness diversity in 101 isolates of Diplodia bulgarica recovered from apple trees displaying symptoms of canker and decline in West Azarbaijan province of Iran. Marker analyses revealed high within population diversity, low genetic differentiation, high gene flow, and sharing of multilocus genotypes (MLGs) among geographic populations. Moreover, clustering and multivariate analyses identified two highly differentiated genetic clusters with limited admixture between them. These findings may suggest that the pathogen has been introduced from two genetically divergent sources and has been moved within the region through infected materials. The large number of MLGs, low clonal fraction, and absence of a widely distributed dominant genotype may explain the occurrence of recombination in this pathogen. However, significant linkage disequilibrium in the populations and limited admixture between genetic clusters may indicate the rare occurrence of recombination in D. bulgarica populations in West Azarbaijan, and that the pathogen has not been in the province long enough to reach equilibrium. Vegetative compatibility analyses revealed the occurrence of anastomosis between nonself pairings and high vegetative compatibility group diversity within populations. All studied MLGs produced necrotic lesions on detached shoots of Red Delicious apple but differed in their aggressiveness levels. Our results provide new insights into genetic and phenotypic variation of D. bulgarica that can assist in developing management strategies. Our findings also highlight the vital need for quarantine measures and the production of healthy plant materials to prevent the introduction and spread of the pathogen in Iran.     

Genetic diversity and population genetic differentiation in the endangered annual weed,Bidens cernua (Compositae), and two common congeners in Japan

In this study, we examined the genetic diversity in three populations of the critically endangered annual, Bidens cernua, in Japan by using inter‐simple sequence repeat markers and compared our data with those from two common congeners: Bidens radiata var. pinnatifida and Bidens tripartita. In contrast to our expectations, the degree of genetic diversity at the species level was higher in B. cernua than in B. radiata var. pinnatifida or B. tripartita. At the population level, the degree of genetic diversity was highest in B. cernua. These results may be ascribed to the mating system and method of seedbank formation in B. cernua. An analysis of molecular variance revealed relatively high genetic differentiation among the populations of all three species. We concluded that the distribution width could not be an index of genetic variability in Bidens examined in this study.     

Genetic diversity of Solanum elaeagnifolium,an invasive problematic weed in Jordan

Solanum elaeagnifolium (silverleaf nightshade) is a problematic weed that is common in Jordan and difficult to control. The weed exhibits distinct morphological variations in growth habit, leaf shape, leaf margins, flower colour and presence or absence of spines between individuals among and within populations suggesting genetic differences. Genetic variations among 61 samples of S. elaeagnifolium collected from heavily infested sites in the central Jordan Valley were investigated using six simple sequence repeat (SSR) markers and eight amplified fragment length polymorphism (AFLP) primer combinations. Results showed that 111 out of 675 AFLP bands were polymorphic generating polymorphism information content (PIC) of 38.0%, while 23 SSR polymorphic alleles were detected generating a PIC of 30.8%. Phylogenetic analysis using RaxML software identified four major clades with a clear clustering of the samples with their collection sites. Genetic analysis using both techniques revealed high level of genetic diversity among S. elaeagnifolium samples collected from a small geographical area indicating that a range of genetic diversity may be detected in weed populations across the country that may complicate its management.     

柑橘叶点霉属(Phyllosticta spp.)真菌的遗传多样性分析

利用筛选的11条ISSR引物对从我国柑橘主产区和国外收集的135株叶点霉属真菌菌株进行扩增,扩增产物进行凝胶电泳,扩增图谱用NTSYS-pc2.10软件进行群体聚类分析。结果显示,共扩增出116个DNA条带,其中多态性位点为112个,多态率为96.55%;平均每个引物可以扩增出10.55个条带,扩增产物大小在250~3 000 bp。聚类分析显示,中国柑橘叶点霉属真菌可以分为4个种,即P.citricarpa、P.citriasiana、P.capitalensis和P.citrichinaensis。以遗传相似性系数0.97为阈值时,柑橘黑斑病病原菌(P.citricarpa)种群可分为5个亚类,subclade-I的菌株来自中国的本地早、温州蜜柑、槾橘和南丰蜜橘,subclade-II的菌株均来自中国的砂糖橘,subclade-III的菌株来自非洲莫桑比克柠檬和葡萄柚、佛罗里达甜橙、南非甜橙和来自杭州市场上进口的澳橘,subclade-IV的菌株来自中国的甜橙,subclade-V的菌株来自中国的柠檬,表明我国柑橘黑斑病病原菌具有丰富的遗传变异,其遗传变异与寄主相关;我国与国外的柑橘黑斑病病原菌在起源上可能存在差异。P.citriasiana、P.capitalensis和P.citrichinaensis种群内也存在遗传变异,但其遗传变异与地理分布和寄主未发现相关性。该研究结果为研究柑橘叶点霉属真菌的遗传多样性奠定了基础。     

内蒙古亚洲小车蝗种群遗传多样性和遗传分化的ISSR分析

亚洲小车蝗Oedaleus asiaticus Bei-Bienko是我国北方草原和农牧交错区的主要害虫。为评价内蒙古地区亚洲小车蝗种群的遗传多样性和遗传分化,应用ISSR标记方法对内蒙古15个亚洲小车蝗种群遗传多样性及遗传分化进行了分析。结果表明,7条引物扩增出85条ISSR条带,均为多态性条带。多态性比例（P）、Nei''s遗传多样性指数（H）和香农多样性指数（I）分别为82.59%、0.2319和0.3421,表明亚洲小车蝗种群具有较高的遗传多样性。基因流（Nm）和基因分化系数（Gst）分别为1.2298和0.3352,表明亚洲小车蝗不同地理种群具有明显的遗传分化。遗传距离与地理距离呈极显著正相关关系。表明地理距离和地形差异可能是形成亚洲小车蝗种群遗传分化的主要原因。     

Genetic variation and structure of Solanum elaeagnifolium in Australia analysed by amplified fragment length polymorphism markers

Solanum elaeagnifolium is a weed of national significance in Australia. However, the genetic diversity of S. elaeagnifolium is poorly understood. Four amplified fragment length polymorphism primer combinations were utilised to investigate the genetic variation and structure of 187 S. elaeagnifolium individuals collected from 94 locations in Australia. High genetic diversity was found, with an average Jaccard's genetic similarity at 0.26. Individuals were assigned to two genetic clusters or considered as admixed according to their membership coefficient value (q) calculated by Bayesian model‐based genetic structure analysis. This suggested that Australian S. elaeagnifolium may have originated from two distinct gene pools. These results were further supported by principal co‐ordinates analysis. Large spatial groups of individuals assigning to these two gene pools were found in western Victoria and south‐western New South Wales (NSW) and northern NSW, which correlated well with the early records of S. elaeagnifolium in both regions. The high genetic diversity found here could add difficulties to effective control of S. elaeagnifolium across regions.     

Genetic diversity within and between sulfonylurea‐resistant and susceptible populations of Schoenoplectus juncoides in Japan

To reveal the effects of herbicide selection on genetic diversity in the outcrossing weed species Schoenoplectus juncoides, six sulfonylurea‐resistant (SU‐R) and eight sulfonylurea‐susceptible (SU‐S) populations were analysed using 40 polymorphic inter‐simple sequence repeat loci. The plants were collected from three widely separated regions: the Tohoku, Kanto and Kyushu districts of Japan. Genetic diversity values (Nei's gene diversity, h) within each SU‐S population ranged from h = 0.125 to h = 0.235. The average genetic diversity within the SU‐S populations was H_S = 0.161, and the total genetic diversity was H_T = 0.271. Although the H_S of the SU‐R populations (0.051) was lower than that of the SU‐S populations, the H_T of the SU‐R populations (0.202) was comparable with that of the SU‐S populations. Most of the genetic variation was found within the region for both the SU‐S and SU‐R populations (88% of the genetic variation respectively). Two of the SU‐R populations showed relatively high genetic diversity (h = 0.117 and 0.161), which were comparable with those of the SU‐S populations. In contrast, the genetic diversity within four SU‐R populations was much lower (from h = 0 to 0.018) than in the SU‐S populations. The results suggest that selection by sulfonylurea herbicides has decreased genetic diversity within some SU‐R populations of S. juncoides. The different level of genetic diversity in the SU‐R populations is most likely due to different levels of inbreeding in the populations.     

Genetic diversity of herbicide-resistant and -susceptible Avena fatua populations in North Dakota and Minnesota

Genetic diversity within and among 20 herbicide-resistant (HR) and 16 herbicide-susceptible (HS) Avena fatua multi-field populations was determined using 82 polymorphic loci resulting from two intersimple sequence repeat (ISSR) primers and one long-primer random amplified polymorphic DNA (LP-RAPD) primer. Collections from the Red River Valley of North Dakota and Minnesota, sampled in 1964 and 2000, represented A. fatua populations before and after intensive exposure to herbicides. A 1995 collection from south-west North Dakota represented A. fatua exposed to low herbicide selection. Despite differences in years of herbicide exposure among collections, both HR and HS populations from every collection maintained nearly similar levels of ISSR and RAPD diversity. Genetic differentiation among populations (G_ST) varied from 11% to 13% among HR populations and from 9% to 16% among HS populations, indicating that 84–91% of total variation remained within HS or within HR populations. Minimal difference in gene diversity between HR and HS is consistent with multiple origins of resistance, where HR A. fatua most likely evolved from diverse founding individuals.     

西双版纳自然保护区球孢白僵菌的遗传多样性

为了解西双版纳自然保护区球孢白僵菌Beauveria bassiana的遗传多样性,采用SSR分子标记技术对西双版纳自然保护区的240株球孢白僵菌的遗传结构、基因流、菌株分化以及遗传变异相关性进行了测定和分析。结果表明,9条引物扩增240株球孢白僵菌菌株多态位点数为77个,多态位点比率为97.40%。采集的240株球孢白僵菌的总体等位基因数、有效等位基因数、Nei’s基因多样性指数和Shannon信息多样性指数分别为1.97、1.31、0.18和0.29。从寄主居群来看,鞘翅目昆虫球孢白僵菌群体遗传多样性最高,螳螂目最低,其Nei’s基因多样性指数和Shannon信息多样性指数分别为0.20和0.30、0和0;总遗传变异的29.27%存在于寄主居群间。从生境水平来看,五十五生境中球孢白僵菌群体遗传多样性最高,丫口寨生境中最低,其Nei’s基因多样性指数和Shannon信息多样性指数最高分别为0.19和0.31、0.06和0.09;总遗传变异的14.92%存在于生境居群间。从季节水平来看,球孢白僵菌秋季居群的遗传多样性最高,夏季最低,其Nei’s基因多样性指数和Shannon信息多样性指数分别为0.20和0.32、0.17和0.26;总遗传变异的3.45%存在于季节居群间。表明西双版纳自然保护区球孢白僵菌在寄主昆虫、生境分布和季节间存在明显的遗传多样性,与寄主昆虫类群的关系密切。     

Multiple introductions are responsible for the disjunct distributions of invasive Parthenium hysterophorus in China: evidence from nuclear and chloroplast DNA

Parthenium hysterophorus is an invasive weed native to tropical and subtropical America. Since its introduction into China in 1926, this weed has been limited to southern areas (18°–25°N). However, new populations were recently reported in Shandong (35°N). The origin of this geographically isolated population remains unclear. In this study, we used inter simple sequence repeat and chloroplast DNA sequence markers ( trnQ-5'rps16 ) to investigate the genetic structure of 18 invading populations of P. hysterophorus and to examine the genetic relationship of Shandong and southern populations. Our data show that Shandong population is genetically different and has apparently higher levels of genetic diversity than most populations in southern China. Both neighbour-joining clustering and principal coordination analysis clearly separated Shandong from other populations. Chloroplast DNA sequence analysis further confirmed that the Shandong population was characterised by a unique haplotype that was not found in southern populations. We conclude that the population in Shandong may have been independently introduced from areas outside China. As P. hysterophorus has a broad potential distribution in China, attention should be paid to both international and domestic quarantine to prevent new introductions and curtail the possible hybridisation and gene flow between populations in different regions.