Genetic and clonal diversity in Korean populations ofVitex rotundifolia (Verbenaceae)

Vitex rotundifolia L.f. is a woody perennial and has sexual and asexual modes of reproduction. Allozyme study was conducted on 550 plants in 13 Korean populations. The levels of genetic variability and divergence within and among populations, respectively, are considerably lower and higher than the mean values for woody plants with similar life history tralts. Mean percentage of polymorphic loci (P _P), mean number of alleles per locus (A _P), and mean genetic diversity (He _P) within populations ofV. rotundifolia were: 16.7%, 1.21, and 0.047. On average, about 79% of the total variation inV. rotundifolia was common to all populations (meanG _ST=0.208). In addition, significant differences in allele frequencies among populations were found in all polymorphic loci examined (P<0.001). On the other hand, levels of genotypic diversity within and among populations were moderate. About 44% (18/41) of multilocus genotypes were “local genotypes” (genotypes occurring in only one population), whereas only one “widespread genotype” (genotypes occurring in more than 75% of the populations) were detected. The mean number of multilocus genotypes per population (G) and mean genotypic diversity index (D _G) were 8.4 and 0.74, respectively. Most common multilocus genotypes found in populations were homozygous for five polymorphic loci. The abundance of ramets of these genets is responsible for the low levels of expected heterozygosity within populations. The results indicate that clonal reproduction may act as an enhancer of genetic drift by reducing effective size of local populations ofV. rotundifolia.     

GENETIC DIVERSITY AND CLONAL STRUCTURE IN A COLUMNAR CACTUS,LOPHOCEREUS SCHOTTII

In southern Arizona the columnar cactus, Lophocereus schottii, inhabits desert riparian environments. Reproduction in this part of its range is predominantly asexual and occurs by either the dispersal of stems in the immediate vicinity of parents or the long-distance transport of detached stem pieces downstream by floodwaters. Genetic diversity and clonal structure of eight populations of L. schottii in Organ Pipe Cactus National Monument, Arizona, were examined. In all populations ramets were mapped and stem tissue from each ramet was examined electrophoretically. At the species level, 44.4% of the loci were polymorphic and the genetic diversity was 0.145. Within populations, the mean proportion of polymorphic loci and genetic diversity were 34.4% and 0.126%, respectively. Although most of the allozyme variation was within populations, appreciable heterogeneity was found among populations (G_ST = 0.130). Genetic and genotypic diversity was greatest in three of the four populations located in the principal area of L. schottii occurrence in the monument. Genotypic diversity was lowest in the smallest population and in the most isolated population. Ramets in all populations were spatially aggregated. Plant pairs with identical multilocus genotypes were usually ≤ 10 m apart, but some widely separated individuals had identical genotypes. Occasional long-distance dispersal of stems and the periodic recruitment of seedlings have caused genets to intermingle, promoting outcrossing and maintaining genetic diversity.     

Population genetic analysis of Elliottiaracemosa (Ericaceae), a rare Georgia shrub

Genetic and genotypic diversity found within populations of threatened plant species can have important implications for their conservation and management. In this study we describe genetic and genotypic diversity found within 10 populations of the endemic shrub Elliottiaracemosa (Ericaceae), the Georgia plume. E. racemosa is a threatened species known from fewer than 50 locations, all within the state of Georgia, USA. Seedset is limited to nonexistent in some E. racemosa populations and sexual recruitment has not been documented. However, the species is known to spread vegetatively via root-sprouts. Twenty-one allozyme loci were resolved for E. racemosa, nine of which were polymorphic. Compared with other woody taxa, E. racemosa has low genetic (i.e. allelic) diversity within populations (H_ep = 0.063) and at the species level (H_es = 0.091). Most of the genetic variation (82%) was found within populations, and genetic identities between populations were high (mean I = 0.96). However, genotypic diversity (i.e. the number of multilocus genotypes) differed markedly among populations. Two of the 10 populations consisted almost entirely of single multilocus genotypes, whereas more than 20 multilocus genotypes (in samples of 48 stems) were detected at three sites. Sites in which few multilocus genotypes were detected have low seedset, suggesting that the lack of clonal diversity limits reproduction in some populations of this reportedly self-incompatible species.     

Low Levels of Genetic Diversity within Populations of Hosta clausa (Liliaceae)

Abstract Genetic diversity of Korean populations in Hosta clausa was investigated using starch gel electrophoresis. Hosta clausa is widespread, grows only along streamsides, and has both sexual and asexual reproduction. Populations of the species are small and isolated. Thirty-two percent of the loci examined were polymorphic, and mean genetic diversity within populations (He_p=0.082) was lower than mean estimates for species with very similar life history characteristics (0.131), particularly for its congener H. yingeri (0.250). The mean number of multilocus genotypes per population was 8.7, and genotypic diversity index (D_G) was 0.84. Significant differences in allele frequencies among populations were found in all seven polymorphic loci (P < 0.001). About one-fifth of the total allozyme variation was among populations (G_ST=0.192). Indirect estimate of the number of migrants per generation (Nm=0.48, calculated from mean G_ST) and nine private alleles found indicate that gene movement among populations was low. The low levels of genetic diversity within populations and the relatively high levels of genetic diversity among populations suggest that strong moist habitat preferences, clonal reproduction, low level of gene flow among populations, genetic drift, and historical events may have played roles in the genetic structuring of the species.     

Genotyping the clonal structure of a gorgonian coral, Junceella juncea (Anthozoa: Octocorallia), using microsatellite loci

The identification of different clones is fundamental to the study of population structure among organisms with mixed reproductive modes such as cnidarians. However, due to the low genetic variation of coral mtDNA and contamination by zooxanthellate DNA, very few molecular markers are available for studying the clonal structure of cnidarians. Herein we used four polymorphic loci of microsatellite DNA isolated from a zooxanthellae-free octocoral, Junceella juncea, to study its clonal structure in seven populations collected from three localities in Taiwan. In total, 40 multilocus genotypes were found among 152 colonies, and the number of genotypes (clones) identified in the seven populations ranged from 2 to 16. Each of the 40 multilocus genotypes was restricted to a single population, even where adjacent populations were only 100 m distant. The ratio of observed to expected genotypic diversity (G_o:G_e) ranged from 0.217 to 0.650, and G_o showed a significant departure from G_e (p<0.05) at each site indicating that asexual fragmentation may play a major role in the maintenance of established populations. Mean relatedness (R) values showed that genotypes within reefs were more closely related than those between regions. The results indicate that microsatellites are useful for discerning the clonal structures among and within populations at different spatial scales. Electronic supplement: Unique multilocus genotypes (clones) revealed by 4 polymorphic loci for Junceella juncea colonies collected from Xiashuijui (Reefs A, B, C, Transplant, Transect), Nanwan and Shicheng     

Genetic variation in Pueraria lobata (Fabaceae), an introduced, clonal, invasive plant of the southeastern United States

Pueraria lobata (kudzu), a clonal, leguminous vine, is invading the southeastern United States at a rate of 50 000 ha per year. Genetic variability and clonal diversity were measured in 20 southeastern U.S. populations using 14 allozyme loci. Within its U.S. range, 92.9% of the loci were polymorphic and overall genetic diversity was 0.290. Such high levels of genetic diversity are consistent with its history of multiple introductions over an extended period of time. The average proportions of polymorphic loci and genetic diversity within populations were 55.7% (range = 28.6–85.7%) and 0.213 (range = 0.114–0.317), respectively. The proportion of total genetic diversity found among populations was similar to species with equivalent life history characters (G_ST = 0.199). No regional patterns of variation were seen. The number of putative genotypes in each population ranged from 2 to 26. Mean genotypic diversity was 0.694, ranging from 0.223 to 0.955. Such high levels of genotypic diversity indicate that local sites are often colonized by several propagules (most likely seeds) and/or that sexual reproduction occurs within populations after establishment. An excess of heterozygosity was observed in populations with few unique genets, implying that selection for highly heterozygous individuals may occur in populations of P. lobata.     

REDUCED GENETIC DIVERSITY AND INCREASED POPULATION DIFFERENTIATION IN PERIPHERAL AND OVERHARVESTED POPULATIONS OF GIGARTINA SKOTTSBERGII (RHODOPHYTA,GIGARTINALES) IN SOUTHERN CHILE1

This study assesses two hypotheses on the genetic diversity of populations of Gigartina skottsbergii Setchell et Gardner (Rhodophyta, Gigartinales) at the border of the species distribution: 1) peripheral populations display a reduced genetic diversity compared with central populations, and 2) genetic differentiation is higher among peripheral than among central populations. Two peripheral and four central populations were sampled along the Chilean coast and 113 haploid individuals were analyzed using 17 random amplification of polymorphic DNA loci. The genetic diversity was estimated by allele diversity (H_e), allele richness (Â), and the mean pair‐wise differences among multilocus genotypes. All three estimates consistently and significantly indicated a lower genetic diversity within the peripheral than within the central populations. Genetic differentiation between the two peripheral populations was stronger (F_ST=0.35) than between central populations at similar spatial scales (F_ST ranging from 0 to 0.25). In addition, it appeared from the distribution of pair‐wise differences that peripheral populations are in demographic expansion after a recent bottleneck. The results are discussed in the specific context of potential overharvesting of these wild populations.     

Characterisation and inheritance of nuclear microsatellite loci for use in population studies of the allotetraploid <Emphasis Type="Italic">Salix alba</Emphasis>–<Emphasis Type="Italic">Salix fragilis</Emphasis> complex

We present nine polymorphic di- and tri-nucleotide repeat nuclear microsatellite markers selected specifically for their use in high throughput studies concerning the dioecious allotetraploid Salix alba–Salix fragilis willow complex. These taxa and their hybrids are difficult to discriminate using morphological characters. Thus, multiplex reactions were developed for these microsatellite loci and their effectiveness to distinguish individuals, especially hybrids, and their inheritance patterns in controlled crosses were determined. All loci displayed disomic–monogenic inheritance which allowed for the genotype data to be analysed as for a diploid organism. The nine loci produced a total of 67 alleles (mean, 7.4 alleles per locus; range, 3–11 alleles) in a reference panel of 57 individuals from two germplasm collections and natural populations. Gene diversity values (as measured by the expected heterozygosity) ranged from 0.000–0.820. A total of 53 distinct multilocus genotypes were observed, and ordination analysis revealed three separate clusters corresponding to S. alba, S. fragilis and hybrids. The microsatellite loci described here will be used in population genetic studies to investigate genetic variation, gene flow, levels of hybridisation and the extent of introgression in natural populations of the S. alba–S. fragilis complex. They are also useful for clonal identification, conservation and sustainable management of germplasm collections, genetic mapping and the selection of individuals and/or certification of controlled crosses for breeding programmes.     

POPULATION VARIATION,OUTCROSSING, AND COLONIZATION OF DISTURBED AREAS BY CALAMAGROSTIS CANADENSIS: EVIDENCE FROM ALLOZYME ANALYSIS

Calamagrostis canadensis (a rhizomatous grass) exists in temperate forest sites of different successional age. It can rapidly colonize disturbed sites to form dense swards. We examined allozyme variation in: four populations (mature forest, intermediate aged forest, forest cutblock, wetland); nine small plots (2 m × 4 m) within the cutblock; and progeny of several families from three populations; in order to assess the mode of colonization of disturbed areas and the effect of successional changes on population genetic structure. All four populations showed equal and extensive genetic variation (1.5 to 1.7 alleles per locus [K], 41.7% to 50% polymorphic loci [PPL], H_st = 0.155 to 0.208) and were not genetically differentiated (G_st = 0.0193, 1 = 0.986 to 0.997). The cutblock subpopulations also showed considerable genetic variation (K = 1.6 to 1.8, PPL = 50% to 58.3%, H_st = 0.151 to 0.278) and no microdifferentiation (G_st = 0.034, I = 0.967 to 0.997). We found 14 different genotypes among the 30 individuals sampled from the cutblock as a whole (based on five polymorphic loci). The cutblock subpopulations had from nine to 14 different genotypes each (same five loci, 18 individuals per subpopulation). Seed produced was primarily outcrossed (multilocus estimate 0.888 to 0.900). We concluded that disturbed sites are colonized primarily by sexually produced seedlings. Potential genetic drift and natural selection, which occur during subsequent successional changes, do not result in reduced genetic variation or population differentiation.     

Conservation genetics of the endangered endemic Sambucus palmensis Link (Sambucaceae) from the Canary Islands

Five polymorphic microsatellites (simple sequence repeat; SSR) markers were used to estimate the levels of genetic variation within and among natural populations from different islands of the endangered endemic from the Canary Islands Sambucus palmensis Link (Sambucaceae). Genetic data were used to infer potential evolutionary processes that could have led to present genetic differentiation among islands. The levels of genetic variability of S. palmensis were considerably high; proportion of polymorphic loci (P = 100%), mean number of alleles per locus (A = 6.8), average expected heterozygosity (He = 0.499). In spite of its small population size and endemic character, 58 different multilocus genotypes were detected within the 165 individuals analyzed. All samples located in different islands always presented different multilocus genotypes. Principal Coordinates Analysis, genetic differentiation analysis (F _ST and G _ST ′) and Bayesian Cluster Analysis revealed significant genetic differences among populations located in different islands. However, this genetic differentiation was not recorded among Tenerife and La Gomera populations, possibly revealing the uncontrolled transfer of material between both islands. AMOVA analysis attributed 77% of the variance to differences within populations, whereas 8% was distributed between islands. The levels of genetic differentiation observed among populations, and the genetic diversity distribution within populations in S. palmensis, indicate that management should aim to conserve as many of the small populations as possible. Concentrating conservation efforts only on the few large populations would result in the likelihood of loss of genetic variability for the species.     

Genetic diversity and multilocus genetic structure in the relictual endemic herb<Emphasis Type="Italic"> Japonolirion osense</Emphasis> (Petrosaviaceae)

Plant clonality may greatly reduce effective population size and influence management strategies of rare and endangered species. We examined genetic diversity and the extent of clonality in four populations of the monotypic herbaceous perennial Japonolirion osense, which is one of the most rare flowering plants in Japan. Allozyme analysis revealed moderate levels of genetic variation, and the proportion of polymorphic loci (P=66.7%) was higher than the value for species with similar life-history traits. With four polymorphic loci, 19 multilocus genotypes were observed among 433 aerial shoot samples and 10 (52%) were found only in single populations. The proportion of distinguishable genotypes (PD=0.10) and Simpson's index of diversity (D=0.52) also exhibited moderate levels of genotypic diversity compared to other clonal plants, with genotype frequencies at Hardy-Weinberg equilibrium. The distributions of genotypes were often localized and they were mostly found within a radius of 5 m. Spatial autocorrelation analysis showed that shoot samples located 4 m apart were expected to be genetically independent. The results suggest that the spatial extent of genets was relatively narrow and thus the clonality was not extensive.     

Genetic variation and genotypic diversity in Epipactis helleborine populations from NE Poland

Enzyme electrophoreses were used to estimate genetic variation in five populations of Epipactis helleborine from two National Parks (Biebrza and Wigry) in northeast Poland. It has been proved that populations from these two regions differed in genetic structure, with the populations belonging to the Biebrza group having a higher level of genetic variation than those from Wigry. The number of polymorphic loci (P) ranged from 18.2% to 40.9% and the mean number of alleles per polymorphic locus (Ap) from 2.25 to 2.80. Although the observed heterozygosity (H_o) was lower than the expected one (H_e) in each population, the values of H_o and H_e were 2–3 times lower in the populations from Wigry than in those from Biebrza. Excluding the LUK population with the smallest genotypic diversity, the majority of 345 distinct multilocus genotypes occurred only once, sporadically 2–4 times in each population and their frequency ranged from 0.2% to 3.7%. Moreover, factors shaping genetic structure of E. helleborine and their intensity varied in the populations studied. Reproduction from seeds seems to influence greatly the genetic variation of the populations from the Biebrza National Park, while an assortative mating between related individuals or population size appears to be more important in the case of the populations from the Wigry National Park.     

Genetic Variation and Clonal Diversity of Psammochloa villosa(Poaceae) Detected by ISSR Markers

Genetic variation and clonal diversity of seven Psammochloavillosa(Poaceae) populations from northwest China were investigatedusing inter simple sequence repeat (ISSR) markers. Of the 84primers screened, 12 produced highly reproducible ISSR bands.Using these primers, 173 discernible DNA fragments were generatedwith 122 (70.5%) being polymorphic, indicating considerablegenetic variation at the species level. In contrast, there wererelatively low levels of polymorphism at the population levelwith the percentage of polymorphic bands (PPB) ranging from6.1 to 26.8. Analysis of molecular variance (AMOVA) showed thata large proportion of genetic variation (87.46%) resided amongpopulations, while only 12.54% resided among individuals withinpopulations. Clonal diversity was also high with 98 genets beingdetected from among 157 individuals using 12 ISSR primers. Theevenness of distribution of genotypes in P. villosa populationsvaried greatly, with all of the genotypes being local ones.No significant differences in genetic or clonal diversity werefound between populations in mobile or fixed dunes. The mainfactor responsible for the high level of differentiation amongpopulations and the low level of diversity within populationsis probably the clonal nature of this species, although selfingmay also affect the population genetic structure to some extent.The efficiency of ISSRs in identifying genetic individuals wasmuch higher than that of allozymes. An approximately asymptoticcorrelation was found between the number of genets detectedand the number of polymorphic loci used, suggesting that useof a high number of polymorphic bands is critical in genet identification.Copyright 2001 Annals of Botany Company Psammochloa villosa, ISSRs, genetic variation, clonal diversity     

Genic Heterozygosity and Protein Polymorphism among Local Populations of OENOTHERA BIENNIS

Twenty enzyme loci were studied in 44 Illinois populations of Oenothera biennis; four were polymorphic. Most of the variation was distributed between populations. Fifty-nine percent of the populations had one genotype, 27% two genotypes and the remaining 16% from three to five genotypes; the average was 1.50. The proportion of genetic diversity present in single populations is.38 of that present in the state. Members of single populations were uniformly heterozygous for 1 to 4 loci. The mean heterozygosity per population ranged from 0 to 20%. For Illinois populations collectively, heterozygosity averaged 4.5%. There was much gene frequency heterogeneity between populations. The true standardized genetic variance among populations for alleles at polymorphic loci varied from.40 to.78. Populations from Cook County were much more similar inter se than those downstate, had fewer genotypes and polymorphic loci, and had less heterozygosity than downstate populations. The mean normalized genetic identity among Cook County populations was.987 versus.947 for downstate populations. The mean number of genotypes per population in Cook County was 1.06 versus 2.40 in downstate populations. There was only one polymorphic locus in Cook County, VLP. The genetic structure of Oe. biennis suggests that single populations are colonized by one, or at best a few individuals. Cook County populations are judged to be less variable than downstate populations because the mean age of the populations probably is less than that of those downstate.     

Genetic variation and clonal diversity of <Emphasis Type="Italic">Bromus ircutensis</Emphasis> Kom. in the Otingdag sandy land detected by <Emphasis Type="Italic">ISSR markers</Emphasis>

Genetic variation and clonal diversity of nine populations of Bromus ircutensis Kom. from the Otingdag sandy land were investigated using Inter Simple Sequence Repeat (ISSR) markers. A total of 102 bands were amplified by using 11 ISSR primers chosen for the study. Among those 99% were polymorphic indicating high level of genetic variation at the species level with a mean genetic diversity (H) of 0.292 and Shannon information index (I) of 0.450. Percentage of polymorphic loci (PPL) of nine populations was 76.48% on average, which provides more evidence of considerable genetic variation at the population level. AMOVA analysis revealed that total genetic variation was higher within populations (87.06%) than between populations (12.94%), which is mainly the result of the extensive gene flow (Nm = 1.682) among B. ircutensis populations. UPGMA cluster analysis divided the nine populations into two groups. There was significant or moderate negative correlations between genetic diversity parameters (PPL, H, I) and longitude or latitude. Mantel test also showed a significant correlation between geographical distance and genetic distance (r = 0.681, p = 0.002). Our findings indicated that distribution of B. ircutensis populations was influenced by geographical and ecological factors. Clonal diversity was also high with 108 individuals identified by 11 ISSR primers being all of different genets. Our results provide a molecular basis for sustainable management and conservation of B. ircutensis in the study area.     

Genetic diversity of the expansive grass Brachypodium pinnatum in a changing landscape: Effect of habitat age

Perennial grasses constitute a major group of species showing a dramatic decline of biodiversity in successional plant communities. Using AFLP markers, we examined 12 populations of the expansive grass Brachypodium pinnatum differing in habitat age (30–50, ca. 100 and >300 years old) in order to determine whether clonal diversity of populations, genetic variation, and the relative importance of clonal propagation versus sexual reproduction change with grassland age. Five AFLP primer combinations gave a total of 517 bands, 79% of which were polymorphic. 314 different multilocus lineages were distinguished among the 453 samples analyzed. The number of genotypes (G) and clonal richness (R) decreased with habitat age, while the distribution of the frequency of genets changed from many clones of similar size to dominance by one or a few large clones. We consider these results to give evidence of significant role of sexual reproduction in the early phases of colonization and prevalence of clonal growth and competitive exclusion of less adapted genotypes in the later ones. However, habitat age had only marginal effect on genetic diversity, as percentage of polymorphic loci (PPL) within all the populations analyzed was similar, viz. 38.6–43.5%.     

Allozyme diversity in the federally threatened golden paintbrush, <Emphasis Type="Italic">Castilleja levisecta</Emphasis> (Scrophulariaceae)

Castilleja levisecta (Scrophulariaceae), the golden paintbrush, is an insect-pollinated herbaceaous perennial found in the Pacific Northwest. Currently restricted to two island populations off British Columbia and nine populations (eight on islands) in Washington, C. levisecta is a rare species threatened with extinction. Allozymes were used to describe genetic diversity and structure in these eleven populations. Despite its threatened status and small geographic range, exceptionally high levels of genetic diversity are maintained within C. levisecta. All sixteen of the loci resolved were polymorphic within the species (P_s=100%), while the mean percentage of loci polymorphic within populations (P_p) was 65.7%. The mean number of alleles per polymorphic locus (AP_s) was 2.94 within the species and averaged 2.38 within populations (AP_p). Genetic diversity (H_es) was 0.285 for the species, whereas mean population genetic diversity (H_ep) was 0.213. Smaller populations had, on average, fewer observed alleles and less genetic diversity. A significant negative correlation (r = –0.72) was found between genetic identity and geographic distance, indicating reduced gene flow between distant populations. The most geographically isolated population was one of the larger populations, one of the most genetically diverse and the most genetically divergent. A wide range of pairwise population genetic identities (I = 0.771 – 0.992) was found, indicating considerable genetic divergence between some populations. Overall, 19% of the total genetic diversity was distributed among populations. Results of this survey indicate that genetic augmentation of existing populations is unnecessary. The high allelic diversity found for the species and within its populations holds promise for conservation and restoration efforts to save this rare and threatened plant species.     

Isolation and characterization of microsatellite loci from mother‐of‐millions,Bryophyllum delagoense (Crassulaceae), and its hybrid with Bryophyllum daigremontianum, ‘Houghton's hybrid’

Nine microsatellite loci were developed, and are transferable, across the Madagascan succulents Bryophyllum daigremontianum, Bryophyllum delagoense (mother‐of‐millions) and their horticultural hybrid (Houghton's), from enriched libraries of the later two species. For B. delagoense, a tetraploid, three to 13 alleles per locus were found for native Madagascan (H_O = 0.4–1.0), and one to nine in invasive Australian (H_O = 0.0–1.0) samples. In addition for 91 Australian samples, only five multilocus genotypes were found (95% of individuals were of two genotypes), suggesting extensive clonality in its introduced range. These loci will be used to examine genetic diversity, hybrid origin and mating system in natural and introduced populations.     

Genetic variability and bottleneck detection of four Tricholoma matsutake populations from northeastern and southwestern China

The excessive commercial collection of matsutake mushrooms can lead to extreme reduction of population size, which may cause genetic bottleneck and decrease genetic diversity of Tricholoma matsutake. Here, six polymorphic microsatellite loci markers were used to examine the genetic diversity of four natural T. matsutake populations from two main producing regions of China. The minimum combinations of four loci were able to discriminate total 86 sampled individuals with distinctive multilocus genotypes. Our analysis of molecular variance (AMOVA) revealed that about 80% and 20% of the overall genetic variation were respectively partitioned within and among populations. The principal‐coordinate analyses (PCA) distinguished the four tested populations into three genetic clusters, each of which was correlated with respective endemic host plants on a geographical basis. The AMOVA, PCA and pairwise population F_ST estimates consistently displayed the same genetic divergence patterns and spatial structure of T. matsutake mediated by host plants in China. The significant heterozygosity excesses demonstrated that a recent genetic bottleneck occurred in each population tested. The complementary M‐ratio test indicated past genetic bottleneck events over longer periods. Only four individuals were identified as putative first generation migrants within northeastern China, which implies restricted interpopulation gene flow in T. matsutake. We discuss that the significant genetic differentiation among populations of T. matsutake is most likely a function of host adaptation, host specificity, genetic bottleneck, limited dispersal and habitat fragmentation.     

Microsatellite Markers Reveal Genetic Variation within Sclerotinia sclerotiorum Populations in Irrigated Dry Bean Crops in Brazil

Microsatellites are powerful markers to infer population genetic parameters. We used 10 microsatellite loci to characterize the genetic diversity and structure of 79 samples of Sclerotinia sclerotiorum isolated from four Brazilian dry bean populations and observed that eight of them were polymorphic within populations. We identified 102 different haplotypes ranging from 6 to 18 per locus. Analyses based on genetic diversity and fixation indices indicated variability among and within populations of 28.79% (F_ST = 28793) and 71.21%, respectively. To examine genetic relatedness among S. sclerotiorum isolates, we used internal spacer (ITS1‐5.8S‐ITS2) restriction fragment length polymorphism (PCR‐RFLP) and sequencing analysis. PCR‐RFLP analysis of these regions failed to show any genetic differences among isolates. However, we detected variability within the sequence, which does not support the hypothesis of clonal populations within each population. High variability within and among populations may indicate the introduction of new genotypes in the areas analysed, in addition to the occurrence of clonal and sexual reproduction in the populations of S. sclerotiorum in the Brazilian Cerrado.