Unweighted Pair-group Method With Arithmetic Averages Research Articles

Molecular characterisation of ancient Prunus avium L. germplasm using sweet cherry SSR markers

SummaryA collection of 60 accessions of Prunus avium L. from the sweet cherry germplasm repository of the Campania Region in Italy, together with seven reference accessions of P. avium, were screened to estimate genetic diversity and to identify genetic relationships among accessions using a set of 28 microsatellite (SSR) markers. Of the 28 primer pairs used, 27 generated polymorphic amplification products and one was found to be monomorphic. Between twoand 14 alleles were revealed for the polymorphic loci, and the expected heterozygosity (He) ranged from 0.031 to 0.822. The total probability of identity was 5.59 10–16. The population structure was investigated using a model-based inference framework. Among the 67 accessions studied, the presence of seven groups was inferred using genetic data, without using prior information on the origin of the accessions. The probabilities of assignment of individual accessions to cultivated gene pools with proportions of membership >0.90 indicated that two gene pools accounted for the genomic origin of 46% of all the P. avium accessions sampled. A dendrogram was generated using the unweighted pair group method with arithmetic averages (UPGMA) based on a ‘Nei72’ geneticdistance analysis. This dendrogram classified all 60 ancient sweet cherry genotypes into one well-defined group that revealed the autochthonous character of most of the varieties cultivated in the Campania Region of Italy.The information obtained from SSR fingerprinting will be useful for optimising the conservation of cherry genetic resources present in the Campania Region. Moreover, this approach can be applied to optimise the conservation of local genetic resources of other fruit tree species.

ISSR, anthocyanin content and antioxidant activity analyses to characterize strawberry genotypes

Data on molecular markers, anthocyanin contents and antioxidant activities are increasingly used in breeding programs of many horticultural crops. Inter simple sequence repeat (ISSR) analysis, anthocyanin contents and antioxidant activities were used to characterize 10 strawberry (Fragaria x ananassa Duch.) cultivars and nine breeding lines. Fifteen primers generated 240 polymorphic ISSR-PCR bands. Cluster analysis by the unweighted pair-group method with arithmetic averages (UPGMA) revealed a substantial degree of genetic similarity among the genotypes ranging from 45% to 73% that were in agreement with the principal coordinate (PCO) analysis. Wide genetic diversity was observed among the strawberry genotypes for anthocyanin contents and antioxidant activities. The ISSR analysis together with data for antioxidant activities and anthocyanin contents in strawberries could be used for germplasm management and more effi cient choices of parents in current strawberry breeding programs.

English

  The Random Amplification of Polymorphic DNA (RAPD) analysis was used to detect the genetic diversity among Ugandan isolates of Xanthomonas campestrispv. musacearum (Xcm), the causal agent of banana Xanthomonas wilt (BXW) disease. Seven random primers were used because of their ability to amplify reproducible and reliable fingerprints generated between 6 - 12 amplicons each from the Xcm isolates obtained from central core of pseudostems, peduncles, fruit peelings, sap, nectar, insects’ bodies and bacterial oozes. Regardless of the source and geographical origin, similar fingerprints were generated from the tested isolates. Using a similarity coefficient of 58%, the unweighted pair group method with arithmetic averaging (UPGMA) analysis did not reveal any significant differences in clustering, with exception of a single isolate that had unique fingerprints. Prior to the genetic analysis, all the isolates compared showed no significant difference (P = 0.92) with regard to incubation period for appearance of symptoms and the severity of symptoms in pathogenicity test. Thus, our data indicates that the population of Xcm in Uganda is clonal, that is, one uniform population being spread fast and efficiently, suggesting that there is a low likelihood of the current population to rapidly evolve, in the near future, into more virulent strains to overcome any resistance deployed.   Key words: Banana Xanthomonas wilt, DNA fingerprints, genetic diversity,Xanthomonas campestris pv. musacearum.

Genetic Characterization of Hazelnut (Corylus avellana L.) Cultivars from Turkey Using Molecular Markers

Genetic relationships among 18 Turkish hazelnut (Corylus avellana L.) cultivars were investigated using randomly amplified polymorphic DNA (RAPD), intersimple sequence repeat (ISSR), and amplified fragment length polymorphism (AFLP) markers. Twenty-five RAPD primers, 25 ISSR primers, and eight AFLP primer pairs generated a total of 434 polymorphic marker loci. The three marker systems were able to differentiate the cultivars. Genetic similarity index values ranged from a high of 0.96 for ‘Kan’ and ‘UzunMusa’ to a low of 0.73 for ‘Yassi Badem’ and ‘Kalinkara’. The genetic relationships were presented as an unweighted pair group method with arithmetic average (UPGMA) dendrogram and a three-dimensional principal coordinate analysis (PCoA) plot. The UPGMA dendrogram showed two main clusters, while PCoA analysis showed three groups. Cultivar-specific markers were produced by all marker systems for 10 cultivars. This study demonstrates the usefulness of molecular markers for identification of hazelnut cultivars.

Molecular assessment of Ficus species for identification and conservation

Ficus L. is widely distributed in all the climatic stages and is of great diversity. Molecular marker is used for identification of genetic resources. Inter-simple Sequence Repeat (ISSR) markers was used to assess the identification of 23 important Ficus species / varieties and determination of the genetic relationships among these species. Out of twenty one ISSR primers tested, five primers produced 116 detectable fragments, out of which 106 were polymorphic across the species/varieties. Each of the five primers produced fingerprint profile unique to each of the species/variety studied and thus could be solely used for their identification. Thirteen unique bands specific to nine species were detected. These may be converted into species-specific probes for identification purposes. Genetic relationships among these species/varieties were evaluated by generating a similarity matrix based on the Dice coefficient and the Unweighted Pair Group Method with Arithmetic Average (UPGMA) dendogram. The results showed a clear cut separation of the 23 Ficus varieties/species and were in broad agreement with the morphology. Both molecular and morphological markers will be useful for preservation of the Ficus germplasm. Key words: Inter simple sequence repeat (ISSR), phylogeny, Ficus species, fingerprinting.

Assessment of Genetic Relationship Among Landraces of Bangladeshi Ridge Gourd (Luffa acutangula Roxb.) Using RAPD Markers

Information on genetic relatedness among ridge gourd (Luffa acutangula) genotypes from Bangladesh is currently not reported. Twenty eight accessions collected from different parts of Bangladesh were studied using random amplified polymorphic DNA (RAPD) technique. Four selected decamer primers, out of sixteen screened, could generate a total of 27 RAPD fragments of which 22 were polymorphic (81.5%). The bands ranged from 50 to 1500 bp in size. Genetic variation statistics for all loci estimated the average gene diversity (h) value as 0.278 and the Shannon’s Information Index (I) as 0.415. Dendrogram based on unweighted pair-group method with arithmetic averages (UPGMA) segregated the accessions into five clusters. Cluster III was the largest with 13 members followed by cluster II, V, I and IV with 6, 4, 3 and 2 members, respectively. Accession LA27 and LA29 were found very close to each other with the highest inter-variety similarity index (96.05%) and the lowest genetic distance (0.077); whereas accession LA40 and LA72 were more distant to each other with the lowest inter-variety similarity index (44.43%) and the highest genetic distance (0.73). A DNA extraction method has been standardized. The marker was found to be useful tool for assessing genetic variations in Luffa acutangula. Keywords: Genetic relationship; Germplasm; Ridge gourd; Luffa acutangula; RAPD. © 2009 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v1i3.1968 J. Sci. Res. 1 (3), 615-623 (2009)

Genetic Diversity, Antioxidant Activities, and Anthocyanin Contents in Lingonberry

Lingonberry (Vaccinium vitis-idaea L.) wild clones and cultivars were assessed for antioxidant activities, anthocyanin content, and for genetic variability using inter-simple sequence repeat (ISSR) markers. Four ISSR primers generated 113 polymorphic bands in 34 clones and eight cultivars. Cluster analysis by the unweighted pair-group method with arithmetic averages (UPGMA) separated the 41 genotypes into three main clusters, and identified the one remaining clone as an outlier. Within one cluster, the genotypes tended to form subclusters that were in agreement with a principal coordinate (PCO) analysis. Geographical distribution based on country of collection explained 12% of the total variation as revealed by analysis of molecular variance (AMOVA). Antioxidant activity and anthocyanin content were higher in the berries of clones belonging to V. vitis-idaea ssp. minus than those of the V. vitis-idaea ssp. vitis-idaea cultivars. The UPGMA clustering for chemical markers with 11 clones and seven cultivars identified two major clusters and one outlier. The ISSR markers and analyses of antioxidant activities and anthocyanin contents detected a sufficient degree of polymorphism to differentiate among lingonberries, making this technology valuable for germplasm management, and more efficient choices of parents in current lingonberry breeding programs.

Genetic relationships among 23 Ficus accessions using inter-simple sequence repeat markers

Ficus genus is widely distributed in all the climatic stages and great diversity. The exploration of genetic diversity is a pre-requisite for genome organization in the wild species and the related domesticated ones. Inter-Simple Sequence Repeat (ISSR) markers were used to assess the identification of 23 important Ficus accessions and determination of the genetic relationships among these accessions. Out of 21 ISSR primers tested, five primers produced 116 detectable fragments, of which 106 (91.3%) were polymorphic across the accessions. Each of the five primers produced a fingerprint profile unique to each of the accessions studied, and thus could be solely used for their identification. Thirteen unique bands specific to nine species were detected. These may be converted into species-specific probes for identification purposes. Genetic relationships among these accessions were evaluated by generating a similarity matrix based on the Dice coefficient and the Unweighted Pair Group Method with Arithmetic Average (UPGMA) dendogram. The results showed a clear cut separation of the 23 Ficus accessions and were in broad agreement with the morphology. Both molecular and morphological markers will be useful for preservation of the Ficus germplasm.

ÜÇ YAPRAKLI (Poncirus trifoliata L.) VE ÜÇ YAPRAKLI MELEZLERİ GRUBU TURUNÇGİLLERİN GENETİK AKRABALIK VE FARKLILIKLARININ SSR MOLEKÜLER MARKIRLARLA TANIMLANMASI

In this study, genetic relationship and diversity were determined by SSR (simple sequence repeat) molecular markers technique among 59 Poncirus (Poncirus trifoliata L. Raf.) types/cultivars derived from selections, introduction and hybridization. In this work, 14 SSR primers (TAA1, CAC19, TAA45, CT21, CAC33, CAC39, TAA33, CCT01, CAG01, CAT01, ATC09, TAA52, TAA15 and CAGG9) of the used 26 SSR primers produced polymorphic fragments. Genetic relationship and distance were determined by using UPGMA (unweighted-pair group method with arithmetic average) and PCA (principal component analysis) analysis. The Dice’s similarity coefficient among Poncirus and their hybrids accessions ranged from 0.63 to 1.00 and matrix correlation was 0.84. While Poncirus Krides SRA 339 - M and Poncirus SEAB B 6C - BB1 (SRA) in a group; Poncirus Town (SRA) and Poncirus Jacobsen B 6C - Z19 (SRA) in a different group; Poncirus Dwarf (SRA) and Poncirus Yamaguchi B 6C - Z28 (SRA) in a different group with 100% genetic similarity were determined. On the contrary, Glenn citrangedin (CRC 3573) 63% genetic similarity is the farthest among 60 Poncirus.

Prunus avium: nuclear DNA study in wild populations and sweet cherry cultivars

The PCR-SSR technique was used to detect nuclear DNA diversity in five wild populations of Prunus avium from deciduous forests in Italy, Slovenia, and Croatia and 87 sweet cherry accessions from different geographical areas that have been maintained in the sweet cherry collection in Italy. This sweet cherry collection includes local accessions from the Campania Region as well as accessions from different countries. Twenty-eight microsatellites, previously developed in this species, generated polymorphic amplification products. Between 2 and 14 alleles were revealed for the polymorphic loci studied, with the expected heterozygosity ranging from 0.045 to 0.831. The total probability of identity was 56.94 x 10-18. A model-based Bayesian clustering analysis identified nine distinct gene pools in cultivated P. avium. The probability that wild populations were assigned to cultivated gene pools indicated that three gene pools accounted for the genomic origin of 53% of P. avium sampled. A dendrogram was generated using UPGMA (unweighted pair group method with arithmetic averages) based on Nei genetic distance analysis. This dendrogram classified most of the genotypes into one major group with an additional group of five accessions. The results indicate that this set of SSRs is highly informative, and they are discussed in terms of the implications for sweet cherry characterization.

Development of ISSR markers for genetic diversity studies in Vaccinium angustifolium

Understanding of the genetic relationship within wild lowbush blueberry (Vaccinium angustifolium Ait.) germplasm is important to establish a broad genetic base for safeguarding and for future use of the existing genetic resources. The objective of this study was to assess the genetic variability within 43 wild lowbush blueberry clones, collected from 10 communities of four Canadian provinces, and the cultivar ‘Fundy’ by using inter simple sequence repeat (ISSR) markers, with the hope to establish a reference set of lowbush blueberry germplasm for blueberry conservation, breeding and research. Thirteen primers generated 242 polymorphic ISSR‐PCR bands. A substantial degree of genetic similarity was found among the wild collections. Cluster analysis by the unweighted pair‐group method with arithmetic averages (UPGMA) separated the 41 genotypes into two main clusters, and identified the three remaining clones as outliers. Furthermore, within one main cluster, the genotypes tended to form sub‐clusters that were in agreement with the principal coordinate (PCO) analysis. Geographical distribution contributed to 27% of total variation as revealed by analysis of molecular variance (AMOVA). The ISSR‐PCR method was simple, fast and relatively inexpensive to produce useful DNA fragments and detected a sufficient degree of polymorphism to differentiate among lowbush blueberry clones, making this technology valuable for germplasm management and the more efficient choice of parents in current blueberry breeding program.

Genetic Diversity and Variation Among Botanical Varieties of Old Portuguese Wheat Cultivars Revealed by ISSR Assays

Inter-simple sequence repeats (ISSRs) were used for genetic diversity analyses of an Old Portuguese wheat collection. Eighteen primers produced 96.3 and 98.5% of ISSR polymorphism in bread and durum wheat cultivars, respectively. The unweighted pair group method with arithmetical averages (UPGMA) phenogram clearly split all cultivars based on their species/ploidy, reflecting a defined genetic structure. ISSRs revealed high genetic diversity at interspecific, intraspecific, and intercultivar levels. Thirty-three exclusive ISSR markers were found. Cultivars were clustered according to their botanical varieties and, in a few cases, with their homonym(s). No statistically significant differences were found between genetic diversity parameters of durum and bread wheat, probably due to high intraspecific diversity. Similar analyses were performed among botanical varieties, and their relationships were defined. Cladograms resembled UPGMA clustering. This highly genetically diverse Old wheat collection will be conserved and maintained, and it could be further used in breeding programs to widen the narrow genetic basis of modern wheat varieties and to avoid the loss of rare and unique alleles.

Culturable bacteria in the sediment of Lake Taihu (I):primary analysis of bacterial diversity

采用牛肉膏培养基培养,从不同深度的太湖沉积物中共分离得到603个菌落形态不同的菌株,通过数值分析比较了40个形态表征性状,以不加权平均连锁聚类(UPGMA)的方式进行簇群归类,在0.75水平上可分成4个聚类群和51个亚群.从51个亚群中各随机选取一个菌株,测定其16SrDNA部分序列(约540bp)并据此进行分析,表明这些菌株分别属于Firmicutes、Actinobacteria、γ-Proteobacteria这三大类群,与数据库中已知的芽孢杆菌属(Bacillus)、类芽孢杆菌属(Paenibacillus)、微球菌属(Micrococcus)、节杆菌属(Arthrobacter)、迪茨菌属(Dietzia)和假单胞菌属(Pseudomonas)细菌具有很高的相似性.其中迪茨菌属在国内淡水湖泊沉积物中为首次报道.;The sediment samples collected from the different sites of the Lake Taihu, 2006 were cultured on traditional nutrient medium. 603 bacteria strains were separated with 40 different morphological features, and were grouped into 4 clusters and 51 subclusters at the level of 0.75 with numerical classified based on the unweighted pair group method with arithmetic averages (UPGMA) algorithm. Based on the partial sequences of 16SrDNA (540bp) analysis, the bacteria strains sample chosen from each subclusters randomly were ranked into Firmicutes, Actinobacteria and γ-Proteobacteria three groups, and closely related to Bacillus, Paenibacillus, Micrococcus, Arthrobacter, Dietzia and Pseudomonas genera. The dietzia genera was reported in the sediment of freshwater lake in China for the first time.

Genetic Diversity of Wilt and Root Rot Pathogens of Chickpea, as Assessed by RAPD and ISSR

Intra- and interspecific polymorphisms among fungal pathogens that cause wilt and root rot on chickpea were investigated by using 30 RAPD (random amplified polymorphic DNA) and 20 ISSR (inter-simple sequence repeats) primers. UPGMA (unweighted pair group method with arithmetic average) cluster analysis of RAPD and ISSR datasets using Dice's coefficient differentiated all fungal isolates from each other and revealed considerable genetic variability between the isolates. The isolates that were not easily separable using morphological characteristics were classified again according to their branching in dendrograms. A partial correlation was observed between cluster analysis and geographic origin of Fusarium solani isolates. Additionally, high cophenetic correlation values for RAPD and ISSR data, using the MXCOPH algorithm, were observed (0.983 and 0.987, respectively). The results show that both analyses were suitable for the evaluation of genetic polymorphisms among fungal populations.

A high genetic diversity revealed between commercial rose cultivars by RAPD-PCR technique

Genetic diversity between fifteen commercial cultivars of rose were evaluated, using Ten decamer primers (A-J). All primers detected polymorphism among the cultivars. In total, 126 bands were produced, 73 of which were polymorphic. Primers E and F produced the highest, while primer H produced the lowest number of bands. The percentage of polymorphic bands ranged from 37% to 81% with an average of 63.9%. The average number of polymorphic bands produced was 7.3 per primer. Only the amplified DNA fragments ranging in size between 220 to 3000 bp were used for statistical analyses. Cluster analysis based on the presence or absence of bands was performed by Jaccard’s similarity coefficient, based on Unweighted Pair Group Method with Arithmetic Averages (UPGMA). Genetic similarity ranged between 0.12 to 0.53. The dendrogram revealed two main clusters. Each cluster was divided into subgroups. This investigation showed that genetic diversity was relatively considerable among these cultivars. Also, the results propose that RAPD marker is a useful tool for evaluation of genetic diversity and relationships amongst different rose cultivars.

Genetic diversity analysis and conservation of the Chinese herb Salvia miltiorrhiza collected from different geographic origins in China

Salvia miltiorrhiza is an economically important floral herb. However, little work has been conducted to further our understanding of the genetics of this herb. In this study, a representative set of germplasm of S. miltiorrhiza populations was used to analyze genetic diversity using amplified fragment length polymorphism (AFLP) methodology. Twenty seven S. miltiorrhiza geographical populations from ten provinces in China were selected based on morphological diversity and geographic origin. A total of 528 unambiguous bands were identified by ten primer combinations of EcoRI +3 and MseI +3. Of those, 476 showed a clear polymorphism, representing 90% of the total bands. The samples showed different levels of similarity ranging between 0.504 and 0.789. The unweighted pair-group method with arithmetic averaging (UPGMA) cluster analysis conducted on polymorphic AFLP markers revealed that all these S. miltiorrhiza populations could be clearly distinguished into eight distinct groups as well as an intermediate. The population genetic diversity of S. miltiorrhiza revealed here had clear implications for conservation, management and use of the S. miltiorrhiza germplasm.

A study of genetic diversity of sesame (Sesamum indicum L.) in Vietnam and Cambodia estimated by RAPD markers

Sesame (Sesamum indicum L.) is a traditional oil crop cultivated throughout South East Asia. To estimate the genetic diversity of this crop in parts at the region, 22 sesame accessions collected in Vietnam and Cambodia were analyzed using 10 RAPD markers. The 10 primers generated 107 amplification products of which 88 were polymorphic fragments (83%). Genetic diversity of all populations was Ht = 0.34 when estimated by Nei’s genetic diversity and species diversity was H′sp = 0.513 when estimated by Shannon diversity index. Genetic distance ranged from 0.03 to 0.43, with a mean genetic distance of 0.23. The unweighted pair group method with arithmetic averages (UPGMA) cluster analysis for the 22 accessions divided the material in four groups. The dendrogram revealed a clear division among the sesame accessions based on their geographical region. Interestingly, some geographically distant accessions clustered in the same group, which might indicate the human factor involved in the spreading of sesame varieties. The high level of polymorphism shown suggests that RAPD techniques can also be useful for the selection of parents in sesame (Sesamum indicum L.) breeding program and for cultivar differentiation.

Genetic diversity assessment in Portugal accessions of Olea europaea by RAPD markers

Eighty seven olive (Olea europaea ssp. sativa L.) cultivar accessions from Portugal were characterized by means of randomly amplified polymorphic DNA (RAPD) markers. Of the 11 arbitrary 10-mer primers tested a total of 92 polymorphic bands were obtained, representing 87.6 % of the total amplification products. Twenty nine different genotypes were clearly discriminated. Differences were not found among the amplification profiles from different individuals of the same cultivar. All the genotypes could be identified by the combination of three primers: OPR-1, OPK-14 and OPA-1, seven genotype-specific markers being detected. Genetic relationships were estimated by the unweighted pair-group method with arithmetic averaging (UPGMA). The genetic analysis of the results showed a gradual distance between the various cultivars, making it difficult to identify well-differentiated phylogenetic groups, although two clusters were distinguishable with 35 % similarity, in addition to three independent branches with lower similarity: Galega, Tentilheira and Redondal. The dendrogram reflect some relationships for most of the cultivars according to the use of the fruit and ecological adaptation.

Molecular characterization of Chaetomium species using URP-PCR

Chaetomium spp. are common colonizers of soil and cellulose-containing substrates. Seventeen isolates of Chaetomium spp., which included 15 isolates of C. globosum and one each of C. reflexum and C. perlucidum , were genetically characterized with universal rice primers (URP - primers derived from DNA repeat sequences in the rice genome) using polymerase chain reaction (URP-PCR). Out of the 12 URP's used in the study, nine primers were effective in producing polymorphic fingerprint patterns from DNA of Chaetomium spp . Analysis of the entire fingerprint profile using the unweighted pair-group method with arithmetic averages (UPGMA) clearly differentiated C. globosum isolates from C. perlucidum and C. reflexum . One of the primers, URP-2R, produced a uniform DNA band of 1.9 kb in all the isolates of C. globosum but not in C. perlucidum and C. reflexum , which can be used as molecular marker to differentiate C. globosum from other species. Our results indicate that URP's are sensitive and give reproducible results for assaying the genetic variability in Chaetomium spp.

Genetic diversity and structure of the invasive tree Miconia calvescens in Pacific islands

ABSTRACTAim This study investigates the amount and distribution of genetic variation within and among populations of the highly invasive tree, Miconia calvescens (Melastomataceae; hereafter miconia), in tropical island habitats that are differently impacted (distribution and spread) by this weed.Location Invasive populations were included from northern and southern Pacific islands including the Hawaiian Islands (Hawaii, Kauai and Maui), Marquesas Islands (Nuku Hiva), Society Islands (Tahiti, Tahaa, Moorea, Raiatea) and New Caledonia.Methods We used 9 codominant microsatellite and 77 highly variable dominant intersimple sequence repeat markers (ISSRs) to characterize and compare genetic diversity among and within invasive miconia populations. For the codominant microsatellite data we calculated standard population genetic estimates (heterozygosity, number of alleles, inbreeding coefficients, etc.) and described population genetic structure using AMOVA, Mantel tests (to test for isolation by distance), unweighted pair‐group method with arithmetic averages (UPGMA) cluster analysis and principal components analysis (PCA). We also tested for the presence of a population bottleneck and used a Bayesian analysis of population structure in combination with individual assignment tests. For the dominant ISSR data we used AMOVA, PCA, upgma and a Bayesian approach to investigate population genetic structure.Results Both markers types showed little to no genetic differentiation among miconia populations from northern and southern Pacific hemispheres (AMOVA: microsatellite, 3%; ISSR, 0%). Bayesian and frequency‐based analysis also failed to support geographical genetic structure, confirming considerable low genetic differentiation throughout the Pacific. Molecular data furthermore showed that highly successful miconia populations throughout the Pacific are currently undergoing severe bottlenecks and high levels of inbreeding (f = 0.91, ISSR; FIS = 0.27, microsatellite).Main conclusions The lack of population genetic structure is indicative of similar geographical sources for both hemispheres and small founding populations. Differences in invasive spread and distribution among Pacific islands are most likely the result of differences in introduction dates to different islands and their accompanying lag phases. Miconia has been introduced to relatively few tropical islands in the Pacific, and the accidental introduction of a few or even a single seed into favourable habitats could lead to high invasive success.