Long-term development of Heterobasidion annosum in basidiospore-infected Sitka spruce stumps

The extent of colonization by Heterobasidion annosum was measured in 1989 in Sitka spruce stumps that had been inoculated with basidiospores in 1981 and assessed for infection in 1983. Only stumps that had infection in the sapwood in 1983 contained the fungus in 1989. There was a significant positive correlation between the sapwood area colonized in 1983 and the total area colonized in 1989. Between 1983 and 1989, H. annosum spread within the body of stumps and into most primary roots. There were significant correlations between the stump area colonized in 1983 and 1989 and the percentage of stump and root volume colonized in 1989. Roots of 26 excavated stumps were in contact with an average of two roots on each of two living trees. Fourteen roots on eight living trees became infected, and H. annosum spread proximally an average of 126 cm into trees. We believe that this is the first report of the transfer of H. annosum from spruce stumps inoculated with basidiospores to adjacent live trees.     

Number of Heterobasidion annosum vegetative compatibility groups in roots of basidiospore-infected stumps

Heterobasidion annosum was isolated from colonized parts of Sitka spruce stumps in Dundeugh Forest, Scotland and amabilis fir stumps in River Jordan, Vancouver Island, British Columbia. Isolates from each stump were paired in all combinations on malt extract agar and their interactions were scored according to established criteria. As many as ten vegetative compatibility (VC) groups were detected among isolates from the roots of a single stump. In four stumps that were intensively studied, about one-half of the VC groups in the roots were not detected in the upper part of the stump. Transfer of VC groups of H. annosum from stump roots to tree roots was observed.     

Genetic Structure of Heterobasidion annosum in White Fir Mortality Centers in California

ABSTRACT The structure of Heterobasidion annosum populations was studied in 15 mixed-conifer sites in central and northern California. Study sites displayed mortality of white fir trees in enlarging discrete patches (mortality centers). At each site, fungal genotypes were defined by somatic compatibility tests. In two sites, further genetic and molecular analyses were performed on field genotypes and on homokaryons obtained by dedikaryotization of field heterokaryons. Isolates were found to be colonizing mostly the roots and the bole sapwood of white fir trees, and no significant infections of other tree species were observed. Each mortality center was characterized by the presence of several fungal genotypes, all belonging to the S intersterility group. Both homokaryotic and heterokaryotic strains were present in all sites. Multiple genotypes were retrieved in individual trees or stumps. Out of 228 fungal genotypes, 86% were found only within a single tree or stump, while 14% had spread to adjacent trees. The two largest genotypes had diameters of 9 and 10 m, and had colonized five and nine trees, stumps, or both, respectively. The maximum distance between two adjacent trees colonized by the same genotype was 6 m, and a highly significant correlation was found between tree diameter and distance of fungal "vegetative" spread. The largest clones were found in areas characterized by high tree and stump densities, and secondary spread of the fungus was more significant in denser stands. In most cases, original infection courts of existing genotypes could be traced to standing trees and not to stumps. The genetic analysis performed in two mortality centers revealed that most local genotypes had different mating alleles, and thus originated from unrelated basidiospores. In a few cases, the same mating allele was shared by two heterokaryons (n+n genome) or by a homokaryon (n genome) and a heterokaryon. Molecular analysis showed that nuclei bearing the same mating allele were identical, providing evidence that the two nuclei forming heterokaryons can act independently in the field and can be shared among isolates, presumably via di-mon mating or by separate matings of different portions of widespread homokaryons.     

Spread of Heterobasidion annosum in Christmas Tree Plantations of the United States Pacific Northwest

ABSTRACT The population structure of Heterobasidion annosum in the Pacific Northwest (PNW) Christmas tree plantations was estimated at two spatial scales to assess the relative importance of primary and secondary infection, colonization, and spread of the pathogen. Ninety-three isolates from single trees in 27 discrete mortality pockets and 104 isolates from 12 individual root systems of noble and Fraser fir trees were sampled near Mossyrock, Washington. Isolates were genotyped using somatic compatibility assays and microsatellite markers to determine the spatial scale at which dispersal of single genotypes (genets) was occurring. All isolates sampled from different trees in discrete mortality pockets had distinct genotypes, whereas the root systems of single trees were dominated by one or two genotypes. These results suggest that infection of PNW Christmas trees results from frequent primary infection events of adjacent stumps and localized secondary spread within root systems rather than clonal spread of the pathogen between adjacent trees. We hypothesize that mortality pockets may be due to availability of infection courts and/or variation in inoculum levels during selective harvesting of patches of mature trees.     

Melanotus proteus: a newly recorded colonist of Sitka spruce stumps in Britain and a potential competitor for Heterobasidion annosum

The widespread occurrence in Scotland of M. proteus. which was previously regarded as rare, is reported. It is a common colonist of Sitka spruce stumps which merits consideration as a potential biological control agent against the tree-root pathogen H. annosum. There is some evidence that it may act as a decay organism in wounded Sitka spruce.     

Microsatellite DNA variation within and among invasive populations of Ambrosia artemisiifolia from the southern Pannonian Plain

Although the Pannonian Plain presents one of the areas in Europe most highly infested by Ambrosia artemisiifolia, previously reported population genetic studies of the invasive species have included only a few populations from this region. Our goal was to determine the level of genetic diversity and genetic structure of A. artemisiifolia populations from the southern Pannonian Plain using microsatellite DNA markers. We documented a high level of genetic diversity within the Pannonian populations, as compared with the genetic diversity parameters previously published for the other invasive populations of A. artemisiifolia in Europe. The mean number of alleles per locus (N_A) ranged between 6.8 and 9.4, allelic richness (r) between 6.59 and 8.53 and mean number of rare alleles per locus (N_R) ranged between 3.4 and 6.4 per analysed population. A low level of among‐population differentiation was detected, with percentage of variation between populations of 3.3%, generally low pairwise F_ST values (ranged from ?0.007 to 0.152) and also according to principal coordinate analysis. A Bayesian approach revealed that most individuals did not strongly associate with any single genetic cluster, confirming a lack of genetic structuring in the analysed region. Together with the results of quantification of the level of gene flow (N_m = 5.671), these observations indicated a presence of extensive gene exchange and admixture between the populations. Therefore, A. artemisiifolia in the Pannonian Plain region has the potential for rapid expansion.     

The identification of three new viruses isolated from Wisteria and Pisum in The Netherlands,and the problem of variation within the potato virus Y group

Three new legume diseases in The Netherlands are described:Wisteria vein mosaic, pea necrosis, and pea leafroll mosaic. In particle size and morphology and in host reaction the virus isolates resembled bean yellow mosaic virus (BYMV), but they were readily distinguishable in several test plants.In recent years several new legume viruses related to BYMV and bean common mosaic virus have been described. Besides, more and move viruses of the potato virus Y group are proving to be naturally infectious to legumes, e.g. lettuce mosaic virus, beet mosaic virus, watermelon mosaic virus, and even turnip mosaic virus, all of which are somehow related to BYMV. To investigate the nature and degree of these relationships, the virus isolates causing the three new legume diseases were compared with a normal strain of BYMV and with pea mosaic virus, clover yellow vein virus, cowpea aphidborne mosaic virus, two isolates of beet mosaic virus, and lettuce mosaic virus.They were all found to have several hosts and symptoms in common. The differences observed showed a range of gradations only. Unexpectedly, BYMV was found to infect 17 out of 20 non-legumes tested. TheWisteria isolate and lettuce mosaic virus did not produce inclusion bodies, whereas all others did. Often nucleoli were very much enlarged or contained crystals. The pea necrosis isolate produced many nucleoar crystalline needles.Cross-protection tests were of little help in determining mutual relationships.Antisera prepared against theWisteria isolate, the pea necrosis isolate, and BYMV, and an antiserum against bean common mosaic virus, revealed definite relationships, but also substantial differences.By using the electron microscope the three new isolates were indistinguishable from BYMV, whereas the particle lengths of two isolates of beet mosaic virus were considerably shorter. The isolate of pea mosaic virus had much longer (840 m) and more rigid particles.Thus, the more that known viruses are studied in detail, and the more new viruses and strains are described, the more borderlines supposed to exist between the different viruses of a morphological group disappear. The fading away of biological borderlines as described here, throws new light on the intergrading serological relationships between viruses of a morphological group as reported in the literature. Thus, extreme variation of viruses may make it impossible to define a species concept for viruses. Borderlines have to be drawn arbitrarily. The incitants ofWisteria vein mosaic, pea necrosis, and pea leafroll mosaic are here considered different viruses, although closely related to bean yellow mosaic and bean common mosaic viruses.Samenvatting Drie nieuwe in Nederland voorkomende ziekten van vlinderbloemigen worden beschreven, te wetenWisteria-nerfmozaïek, dat vrij algemeen bij de sierplant blauwe regen voorkomt (Fig. 1), erwtenecrose, slechts éénmaal geconstateerd (Fig. 2), en een met zaad overgaand, waarschijnlijk niet zeldzaam erwterolmozaïek (Fig. 3). In deeltjesgrootte en-vorm leken de betrokken virusisolaten op bonescherpmozaïekvirus, maar ze konden in verscheidene toetsplanten gemakkelijk worden onderscheiden.In de laatste jaren zijn talrijke nieuwe virussen van vlinderbloemigen beschreven die verwant zijn aan het bonescherpmozaïekvirus en het bonerolmozaïekvirus (Table 1). Bovendien blijkt dat een toenemend aantal virussen uit de aardappel-Y-virusgroep, zoals slamozaïekvirus, bietemozaïekvirus, watermeloenemozaïekvirus en zelfs een knollemozaïekvirus (turnip mosaic virus), in staat is onder natuurlijke omstandigheden vlinderbloemigen aan te tasten. Op de een of andere wijze zijn al deze virussen verwant aan het bonescherpmozaïekvirus. Om een inzicht te krijgen in de aard en mate van deze verwantschappen zijn de drie nieuw ontdekte isolaten vergeleken met een normale stam van het bonescherpmozaïekvirus en met erwtemozaïekvirus en verder met clover yellow vein virus, cowpea aphid-borne mosaic virus, twee isolaten van het bietemozaïekvirus en slamozaïekvirus (Tabel 2). Ze bleken alle ettelijke waardplanten en symptomen gemeen te hebben (Tabel 3, Fig. 4–14), waaronder erwte- en bonerassen (Tabel 4 en 5). Onderlinge verschillen waren slechts van graduele aard. Talrijke niet-vlinderbloemigen reageerden op de te identificeren isolaten, vooral op het erwtenecrosevirus (o.a. Fig. 13). Geheel onverwacht werd gevonden dat zelfs de normale stam van het bonescherpmozaïekvirus 17 van de 20 getoetste niet-vlinderbloemigen kon infecteren. Met moeite ging het virus lokaal over op biet, en spinazie werd zelfs systemisch geïnfecteerd. Bij nader inzien blijken in de literatuur meer verspreide meldingen van infectie van niet-vlinderbloemigen voor te komen (Tabel 12). De vorming van celinsluitsels en zelfs van vergrotingen van de nucleolus is niet beperkt tot bonescherpmozaïekvirus en tabaks-etsvirus, een andere vertegenwoordiger uit de Y-virusgroep. Ze werden alleen niet gevonden bij hetWisteria-virus en bij slamozaïekvirus. Het erwtenecrosevirus veroorzaakte vergrote en zeer opvallend van talrijke naalden voorziene nucleoli.Gegevens uit de literatuur en uit dit onderzoek over het niet vatbaar zijn van bepaalde plantesoorten zijn van betrekkelijke waarde, omdat de resultaten afhankelijk zijn vanhet ras of type van de getoetste plantesoort en de omstandigheden, alsmede van de kwaliteit van het inoculum en van de combinatie donor-acceptor (virusbrontoetsplant) (Tabel 6).De gevonden verschillen in bestendigheid van het infectievermogen in uitgeperst sap waren voor enkele isolaten slechts gering (Tabel 7). Premunitieproeven bleken nauwelijks te helpen bij het bepalen van onderlinge verwantschappen (Tabel 8 en 12).De in samenwerking met de heer D. Z. Maat bereide antisera tegen de isolaten uitWisteria en necrotische erwt en de normale stam van het bonescherpmozaïekvirus, alsmede een beschikbaar antiserum tegen bonerolmozaïekvirus toonden het bestaan van duidelijke verwantschappen, maar ook van niet geringe verschillen aan (Tabel 9).In de elektronenmicroscoop waren de drie nieuwe virusisolaten niet van bonescherpmozaïekvirus te onderscheiden terwijl beide isolaten van bietemozaïekvirus belangrijk korter waren (Tabel 10). Merkwaardigerwijs had het erwtemozaïekisolaat vrijwel rechte deeltjes van aanzienlijk grotere lengte (840 m).Uit dit onderzoek en uit gegevens uit de literatuur kan worden geconcludeerd dat naarmate de bekende virussen meer in detail worden bestudeerd en meer nieuwe virussen en virustammen worden beschreven de grenzen die men lange tijd veronderstelde te bestaan tussen verschillende virussen van een morfologische groep geleidelijk vervagen. Het hier vooral beschreven vervagen van biologische grenzen werpt nieuw licht op het reeds langer bekende bestaan van graduele serologische verwantschappen tussen virussen van een morfologische groep. Hiermee zitten we midden in het probleem van de variabiliteit van de virussen dat ook geldt voor de meer intrinsieke viruseigenschappen. De laatste zijn overigens ook al van betrekkelijke waarde voor de identificatie van virussen, omdat slechts een deel van de totale hoeveelheid genetische informatie van invloed is op deeltjesvorm, deeltjesgrootte en serologische eigenschappen. Biologische eigenschappen zullen daarom van waarde blijven voor de identificatie van virussen.Virussen schijnen zich overwegend of uitsluitend ongeslachtelijk te vermeerderen of vermeerderd te worden. Daardoor kan iedere mutant, indien ontstaan of terechtgekomen onder selectieve omstandigheden leiden tot een nieuw biotype. Door de enorme variabiliteit der virussen zal het vermoedelijk onmogelijk zijn ooit een soortsbegrip voor virussen te omschrijven. Toch moeten uit praktische overwegingen kunstmatige grenzen worden getrokken. Daar de geconstateerde verschillen tussen de verwekkers van de drie nieuwe ziekten en het bonescherpmozaïekvirus niet onderdoen voor die tussen laatstgenoemd virus en bonerolmozaïekvirus en tussen de nauw aan tabaks-etsvirus verwante virussen, worden de nieuwe verwekkers als aparte virussen beschouwd, hoewel ze onderling en aan het bonescherpmozaïekvirus nauw verwant zijn.     

Viruses of the tobacco rattle virus group in Northern Italy: Their vectors and serological relationships

Four species ofTrichodorus have been found in northern Italy, viz.Trichodorus viruliferus, T. teres, T. nanus and an undescribed species. In seven cases tobacco rattle virus (TRV) was isolated from soil samples by means of bait seedlings and in three of these cases the vector was found to beT. viruliferus. The seven virus isolates reacted with an antiserum against a Dutch TRV isolate and were divided into two groups according to their reaction with this serum. One isolate from each group was subjected to a more detailed examination. Of these, one was found to be closely related to a Dutch isolate from gladiolus with notched leaf symptoms, while the other showed a distinct relationship to the pea early-browning virus found in Britain. One of the isolates proved to be more closely related to the Dutch TRV than is the Dutch gladiolus isolate.     

Population variation of apple scab (Venturia inaequalis) within mixed orchards in the UK

Apple scab, caused by Venturia inaequalis, is one of the most important apple diseases worldwide. To investigate between- and within-orchard fungal variability, 212 isolates were sampled from two mixed orchards, one of 10?years of age and the other of 45?years of age, in the UK and genotyped with AFLP and SSR markers. Populations of isolates from the two orchards did not differ significantly in terms of allele frequencies at the screened AFLP and SSR loci. However, groups of isolates from individual cultivars differed significantly within each orchard and there were also significant differences between groups of isolates from individual trees of the same cultivar in the same orchard. These differences were less pronounced in the younger mixed orchard than in the older one. The existence of tree-to-tree fungal variability indicates a possible role for conidia as a source of primary inoculum. Non-random mating may be one of the factors causing the significant differences among fungal populations from different cultivars. These results suggest that apparently ??susceptible?? cultivars have different background genetic resistance factors, which can be exploited for disease management in mixtures.     

松材线虫组DNA条形码筛选

本文基于Gen Bank中登录的14种松材线虫组线虫的28S、18S和ITS部分基因DNA序列,利用遗传距离法及分子生物学方法评价其各自作为松材线虫组DNA条形码序列的适用性。结果显示,28S(拟松材线虫不分亚种)、28S(拟松材线虫分亚种)、18S和ITS的基因序列种内成对遗传距离平均值分别为0.0071、0.0030、0.0007、0.0043,种间成对遗传距离平均值分别为0.0476、0.0454、0.0052、0.1556,其中28S、18S基因序列种内及种间距离存在一定程度的重叠,ITS具有一定程度的Barcoding gap。3个基因序列构建的NJ进化树显示,28S、ITS构建的系统进化树具有较高的节点支持率,可以有效将14个松材线虫组线虫分离成独立分支,而且28S可以有效鉴别出拟松材线虫的2个亚种;基于18S基因构建的进化树不能对吉拉尼伞滑刃线虫、日本冷杉伞滑刃线虫、拟松材线虫进行有效区分。因此,28S、ITS区具有一定的遗传距离间隔以及相对较高的物种识别率,可以作为松材线虫组线虫候选条形码基因。     

Multiplex real-time PCR assays for the detection and identification of Heterobasidion species attacking conifers in Europe

Four species of the destructive forest pathogen Heterobasidion annosum sensu lato (s.l.) are present in Europe: H. annosum sensu stricto (s.s.), H. abietinum and H. parviporum are native species, while H. irregulare is a non-native invasive species currently reported only in Italy, yet recommended for regulation throughout Europe. In this study, real-time PCR detection tests were developed for each of the four species, which can be used simultaneously or individually thanks to probes labelled with species-specific fluorescent dyes. The different performance criteria of each assay were evaluated, and it was determined that they were theoretically capable of detecting amounts of DNA corresponding to 311, 29 and 29 cell nuclei in H. annosum s.s., H. irregulare and H. parviporum, respectively. The specificity of each assay was assessed with a wide set of strains. Real-time PCR tests successfully detected Heterobasidion species from 36 fruiting bodies taken from the forest, as well as from artificially inoculated or naturally infected wood samples. The multiplex real-time PCR assays developed in this study could have practical applications both in forest management and in phytosanitary monitoring.     

Zearalenone production in Fusarium culmorum after transformation with DNA of F. graminearum

Total DNA from a cycloheximide-resistant mutant of Fusarium graminearum producing zearalenone was incubated with the protoplasts of a non-zearalenone-producing cycloheximide-susceptible isolate of F. culmorum. The regenerated protoplasts were inoculated on a 5-mM cycloheximide medium. The cultures which developed were examined for zearalenone production. Sixty-five cycloheximide-resistant isolates, including two isolates producing zearalenone, were obtained from approximately 3.6 × 10⁴ viable F. culmorum protoplasts. Similar incubations with homologous F. culmorum DNA and non-fungal DNA did not elicit zearalenone production. The results suggest the transformation of F. culmorum by the genetic factors responsible for cycloheximide resistance and zearalenone production from F. graminearum. The epidemiological and taxonomic significance of these observations is discussed.     

Phenotypic variation within a clonal lineage of Phytophthora infestans infecting both tomato and potato in Nicaragua

Late blight caused by Phytophthora infestans (Mont.) de Bary is a constraint to both potato and tomato crops in Nicaragua. The hypothesis that the Nicaraguan population of P. infestans is genotypically and phenotypically diverse and potentially subdivided based on host association was tested. A collection of isolates was analyzed using genotypic markers (microsatellites and mitochondrial DNA haplotype) and phenotypic markers (mating type, virulence, and fungicide sensitivity). The genotypic analysis revealed no polymorphism in 121 of 132 isolates of P. infestans tested. Only the Ia haplotype and the A2 mating type were detected. Most of the tested isolates were resistant to metalaxyl. The virulence testing showed variation among isolates of P. infestans. No evidence was found of population differentiation among potato and tomato isolates of P. infestans based on the genotypic and phenotypic analysis. We conclude that the Nicaraguan population of P. infestans consists of a single clonal lineage (NI-1) which belongs to the A2 mating type and the Ia mitochondrial DNA haplotype. Moreover, based on the markers used, this population of P. infestans does not resemble the population in countries from which potato seed is imported to Nicaragua or the population in neighboring countries. The data presented here indicate that the NI-1 clonal lineage is the primary pathogen on both potato and tomato, and its success on both host species is unique in a South American context.     

Pathogenicity variation and DNA polymorphism of Bipolaris sorokiniana infecting winter wheat in the Huanghuai floodplain of China

Wheat root rot, caused by Bipolaris sorokiniana, has led to severe losses of wheat products worldwide. To evaluate the pathogenicity and genetic variation of B. sorokiniana, diseased wheat samples were collected from 97 locations in the Huanghuai floodplain of China in 2014 and 2015 for analysis. A total of 673 isolates were obtained, 262 of which were identified as B. sorokiniana. Pathogenicity analysis of the isolates revealed variation in pathogenicity, which was not directly correlated with geographic region. Large variations in pathogenicity were also found within geographic groups. To determine the genetic structure of the populations, PCR was performed with universal rice primers (URP). Cluster analysis based on amplification patterns showed that the classified groups were correlated with geographical regions. Thus, analysis of the genetic diversity of the population indicated a negative correlation with geographic origin, that is, the greater the distance between sites, the lower the genetic variation similarity coefficient. Identification of wheat germplasm resistance showed that resistant cultivars accounted for a low percentage, while susceptible and highly susceptible cultivars were in the majority. Overall, these results are meaningful for developing strategies to prevent and control wheat root rot.     

我国梭梭林地理分布和适应环境及种源变异

提要:综合国内对梭梭的研究成果,阐述了我国梭梭林的地理分布、群落特征、林分结构、适生环境、种源变异,并提出了今后的研究方向和保护策略,为梭梭的推广应用和生产经营提供借鉴。     

Generation of a ribosomal DNA probe by PCR and its use in identification of fungi within the Gaeumannomyces-Phialophora complex

The polymerase chain reaction (PCR) was used to amplify a ribosomal DNA fragment from Gaeumannomyces graminis. This fragment was labelled and tested for its usefulness as a probe in restriction fragment length polymorphism (RFLP) studies of fungi within the Gaeumannomyces-Phialophora complex. When the probe was hybridized to Eco RI digests of DNA from these fungi, there were consistent band pattern differences between the three varieties of G. graminis ( tritici, avenae and graminis ). This method of probe production, which is more rapid than many others currently used, has considerable potential for use in the identification of these organisms, and may also be applicable to other groups of fungi.     

山西省非物质文化遗产空间分布格局及影响因素探析

文中运用核密度估算法、区位熵等研究方法,对山西省非物质文化遗产的规模、结构、空间分布格局及影响机理进行了解析,研究表明:1)山西省非物质文化遗产项目类型分布结构层级分明,以传统技艺为主,民俗、传统美术、传统舞蹈与传统戏剧次之;2)山西省非物质文化遗产空间分布不均衡,呈以太原盆地和临汾盆地双核心集聚带状分布格局,中部、西南地区集聚明显,东南、北部地区分布较少;3)通过从地形、水系、交通等层面进行空间分析发现山西省非物质文化遗产主要聚集在中南部带状低海拔区域,与主要水系分布空间耦合良好,且与主要交通干线空间分布关联度较高;4)地形地貎、水系因素、交通因素、经济和社会文化等多种因素对山西省非物质文化遗产空间格局产生重要影响。     

Virulence variation and DNA polymorphism in Sphaerotheca fuliginea, causal agent of powdery mildew of cucurbits

Strains of Sphaerotheca fuliginea, one of the causal agents of powdery mildew of cucurbits, were examined for differences in virulence, mating type and DNA polymorphism. The 28 strains were chosen to be diverse according to host and geographic origin. Characterization of virulence phenotypes was based on the expression of symptoms on 4 species of cucurbits and 6 cultivars of melon. Two pathotypes, capable of attacking either cucumber cv. Marketer and melon cv. IranH and squash cv. Diamant or cucumber cv. Marketer and melon cv. IranH were observed. Tests on melon cultivars revealed 3 races. In tests of sexual compatibility with reference strains, heterothallism was observed for all isolates. Frequency of the two mating types differed significantly in the population. DNA polymorphism was determined both by restriction fragment length polymorphism (RFLP) of the ribosomal internal transcribed spacers (ITS) and 5.8S DNA amplified by the polymerase chain reaction and by random amplified polymorphic DNA (RAPD). For any one of the 11 restriction enzymes tested all strains presented an identical pattern of ITS RFLP. RAPD analysis, using 22 primers which provided reproducible patterns, revealed a relatively low degree of polymorphism. Furthermore, cluster analysis based on RAPD data (152 markers) did not separate groups within the species S. fuliginea. No association could be found between virulence, mating type, geographical and host origin and RAPD patterns. The lack of association between phenotypic and molecular markers and the close fit to linkage equilibrium for the characters examined suggest that recombination may play a role in populations of S. fuliginea.