The plant pathogen Phytophthora andina emerged via hybridization of an unknown Phytophthora species and the Irish potato famine pathogen, P. infestans

Emerging plant pathogens have largely been a consequence of the movement of pathogens to new geographic regions. Another documented mechanism for the emergence of plant pathogens is hybridization between individuals of different species or subspecies, which may allow rapid evolution and adaptation to new hosts or environments. Hybrid plant pathogens have traditionally been difficult to detect or confirm, but the increasing ease of cloning and sequencing PCR products now makes the identification of species that consistently have genes or alleles with phylogenetically divergent origins relatively straightforward. We investigated the genetic origin of Phytophthora andina, an increasingly common pathogen of Andean crops Solanum betaceum, S. muricatum, S. quitoense, and several wild Solanum spp. It has been hypothesized that P. andina is a hybrid between the potato late blight pathogen P. infestans and another Phytophthora species. We tested this hypothesis by cloning four nuclear loci to obtain haplotypes and using these loci to infer the phylogenetic relationships of P. andina to P. infestans and other related species. Sequencing of cloned PCR products in every case revealed two distinct haplotypes for each locus in P. andina, such that each isolate had one allele derived from a P. infestans parent and a second divergent allele derived from an unknown species that is closely related but distinct from P. infestans, P. mirabilis, and P. ipomoeae. To the best of our knowledge, the unknown parent has not yet been collected. We also observed sequence polymorphism among P. andina isolates at three of the four loci, many of which segregate between previously described P. andina clonal lineages. These results provide strong support that P. andina emerged via hybridization between P. infestans and another unknown Phytophthora species also belonging to Phytophthora clade 1c.     

Phenotypic and Genotypic Changes in the Phytophthora infestans Population in Taiwan – 1991 to 2006

Late blight, caused by Phytophthora infestans , is one of the most destructive diseases of tomato in Taiwan. A total of 655 isolates of P. infestans , including 29 isolates from potato, was collected from major tomato and potato production areas of Taiwan during 1991 to 2006. Isolates were characterized for their pathogenicity, mating type, in vitro metalaxyl sensitivity and molecular genotype (including allozyme pattern, mitochondrial genomic haplotype and DNA fingerprint) to monitor population changes in P. infestans . The population of P. infestans in Taiwan underwent a dramatic genetic shift in the 1997–1998 cool growing season. Isolates collected from tomato before 1997 were aggressive to tomato but not potato; most isolates obtained after 1998, were aggressive to both hosts. Metalaxyl sensitivity of isolates changed from sensitive/intermediate before 1997 to resistant since 1998. Similarly, the isolates obtained before 1997 were all US-1 clonal lineage (including variants US-1.1, US-1.2, US-1.3 and US-1.4). During the 1997–1998 cool growing season, the US-11 clonal lineage and the TW-1 genotype appeared, possibly introduced on imported table potatoes. The US-11 lineage spread rapidly and since 1999 has almost completely displaced the old population in Taiwan. Mating type determined by pairing with A1 and A2 reference isolages of P. parasitica , showed all isolates were of the A1 mating type, suggesting that the A2 mating type had not become established in Taiwan. The increasing percentage (up to 42.3% in 2006) of the US-11 variants (including US-11.l, US-11.2, US-11.3 and US-11.4) implied that genomic diversity of the pathogen is changing quickly. Therefore, it is important to continuously monitor the population changes of P. infestans and develop an integrated management strategy for this disease.     

Genotypic Analysis of Russian Isolates of Phytophthora infestans from the Moscow Region, Siberia and Far East

Phytophthora infestans samples were collected during 1997 and 1998 at multiple sites in Russia from Sakhalin Island in the Far East across Siberia (nine sites, 160 isolates) to the Moscow region (four sites, 325 isolates). In addition, 12 isolates that were obtained previously were included. All isolates were analysed for mating type, and sensitivity to metalaxyl. Isolates from within any of the nine sites outside of the Moscow region were monomorphic for mating type and nearly monomorphic for metalaxyl resistance. In contrast, both A1 and A2 isolates were detected in the Moscow region, and these isolates were also polymorphic for metalaxyl resistance. In two sites in Siberia only A2 mating type strains were detected, in the other six sites in Siberia and in Sakahlin Island, only A1 mating types were detected. A subset of isolates ( n =191) was also analysed for pathotype (virulence to 10 R-genes, each in a distinct differential genotype). All isolates were highly complex (mean number of virulences approximately 8.4 of a maximum number of 10). All isolates ( n =43) from Sakahlin Island were virulent to all 10 of the R-genes tested. A further subset of isolates ( n =70, including 12 isolates collected before 1997) was analysed for genotype at the Glucose- 6-phosphate isomerase and Peptidase loci, mtDNA haplotypes, and RFLP pattern using the RG57 probe. The US-1 clonal lineage (previously dominant) was not detected in the 1997–98 sample. The populations of P. infestans near Moscow in 1997 and 1998 was highly diverse with 15 unique genotypes (including both mating types) among a sample of 18 isolates. In contrast, the populations of P. infestans in Siberia had limited diversity, with only three multilocus genotypes detected and most populations were dominated by the SIB-1 clonal lineage. This lineage accounted for 31 of the 39 strains collected in Siberia that were assayed for multilocus genotype.     

Relationships Among Group IV Phytophthora Species Inferred by Restriction Analysis of the ITS2 Region

The polymerase chain reaction (PCR) was used to amplify the ITS2 region of nuclear ribosomal DNA from six Phytophthora species which comprise taxonomic Group IV. Digestion of the ca. 600 bp PCR product with restriction enzymes Alu I, Dra I, Hha I, Hinf I, Msp I, and Taq I revealed variation which allowed relationships among the species to be assessed. P. infestans , P. mirabilis and P. phaseoli were indistinguishable from one another with all enzymes tested. With Alu I and Taq I. P. ilicis , P. colocasiae . and P. hibernalis each showed unique banding patterns different from the common banding pattern shared by P. infestans . P. mirabilis . and P. hibernalis . Dra I allowed differentiation of P. ilicis and P. colocasiae from P. infestans , P. mirabilis , P. phaseoli , and P. hibernalis . all of which shared a common banding pattern. Hha I allowed differentiation of P. colocasiae and P. hibernalis from P. infestans, P. mirabilis, P. phaseoli , and P. ilicis . Hinf I allowed differentiation of P. ilicis and P. hibernalis , (each of which showed a unique banding pattern) from P. infestans, P. mirabilis, P. phaseoli , and P. colocasiae . Msp I allowed differentiation of P. hibernalis from the other five species. Species groupings determined by restriction analysis of ITS2 were consistent with those based on morphological criteria. These results show that restriction analysis of PCR-amplified TS2 regions can be useful as an adjunct to morphological criteria in Phytophthora species identification.     

Species tree estimation for the late blight pathogen, Phytophthora infestans, and close relatives

To better understand the evolutionary history of a group of organisms, an accurate estimate of the species phylogeny must be known. Traditionally, gene trees have served as a proxy for the species tree, although it was acknowledged early on that these trees represented different evolutionary processes. Discordances among gene trees and between the gene trees and the species tree are also expected in closely related species that have rapidly diverged, due to processes such as the incomplete sorting of ancestral polymorphisms. Recently, methods have been developed for the explicit estimation of species trees, using information from multilocus gene trees while accommodating heterogeneity among them. Here we have used three distinct approaches to estimate the species tree for five Phytophthora pathogens, including P. infestans, the causal agent of late blight disease in potato and tomato. Our concatenation-based "supergene" approach was unable to resolve relationships even with data from both the nuclear and mitochondrial genomes, and from multiple isolates per species. Our multispecies coalescent approach using both Bayesian and maximum likelihood methods was able to estimate a moderately supported species tree showing a close relationship among P. infestans, P. andina, and P. ipomoeae. The topology of the species tree was also identical to the dominant phylogenetic history estimated in our third approach, Bayesian concordance analysis. Our results support previous suggestions that P. andina is a hybrid species, with P. infestans representing one parental lineage. The other parental lineage is not known, but represents an independent evolutionary lineage more closely related to P. ipomoeae. While all five species likely originated in the New World, further study is needed to determine when and under what conditions this hybridization event may have occurred.     

Mitochondrial and Nuclear DNA Restriction Enzyme Analysis of the Closely Related Phytophthora Species P. infestans, P. mirabilis, and P. phaseoli

To determine relatedness of the phytopathogenic fungi Phytophthora infestans , P. mirabilis , and P. phaseoli restriction fragment patterns of mitochondrial DNAs of several isolates and hybridization patterns of nuclear DNAs after Southern hybridization with a specific homologous probe were analyzed.
All but two isolates of P. infestans and P. mirabilis show very similar restriction fragment patterns differing only in the length of one fragment due to small insertion/deletion(s). Two isolates of P. mirabilis have one additional site for Scr FI. On the contrary at least six sites differ in P. phaseoli when compared to the other two species. The mitochondrial genome of P. phaseoli is considerably smaller (approx. 6 kbp) than those of P. infestans and P. mirabilis .
A cloned 430 bp multicopy DNA sequence, derived from P. infestans , hybridized specifically with P. infestans, P. mirabilis , and P. phaseoli out of 61 species of Peronosporales ( Phytophthora, Halophytophthora, Pythium, Albugo, Bremia, Peronospora, Plasmopara ) tested and therefore has potential as a diagnostic probe. Restriction patterns revealed by this probe are invariant intraspecifi-cally but differ between the three species.
We consider P. mirabilis a forma specialis of P. infestans because of the very high similarly in its mitochondrial DNA restriction patterns.     

Phytophthora infestans isolates from Northern China show high virulence diversity but low genotypic diversity

Phenotypic and genotypic characteristics of 48 Phytophthora infestans isolates , collected in five provinces in Northern China between 1997 and 2003, were determined and compared with reference isolates. Characterisation included mating type, virulence, mitochondrial DNA (mtDNA) haplotype and DNA fingerprinting patterns based on simple sequence repeats (SSR) and amplified fragment length polymorphisms (AFLP). All isolates had the A1 mating type, mtDNA haplotype IIa and an identical SSR genotype (designated as SG-01-01) that differed from SSR genotypes found in the reference isolates, including those representing the 'old' US-1 lineage that dominated the P. infestans population worldwide prior to 1980. In contrast, the virulence spectra were highly variable and virulence to all resistance genes present in the standard differential set ( R1 to R11 ) was found. AFLP analysis revealed some diversity; eight different AFLP genotypes were found that could be grouped into two major clusters. This study shows that there is very little genotypic diversity in the P. infestans population in Northern China. The occurrence of many different races within this rather uniform population is discussed in the framework of recent insights into the molecular determinants of avirulence in potato– P. infestans 'gene-for-gene' interactions.     

Diversity in and evidence for selection on the mitochondrial genome of Phytophthora infestans

Two extant nomenclature systems were reconciled to relate six mitochondrial DNA (mtDNA) haplotypes of Phytophthora infestans, the oomycete pathogen causing late blight disease on potato and tomato. Carter's haplotypes I-a and I-b were included in Goodwin's haplotype A, while Carter's haplotypes II-a and II-b were included in Goodwin's haplotype B. In addition, haplotypes E and F were included in Carter's haplotype I-b. The mutational differences separating the various haplotypes were determined, and we propose that either haplotype I-b(A) or haplotype I-a(A) is the putative ancestral mtDNA of P. infestans, because either can center all the other haplotypes in a logical stepwise network of mutational changes. The occurrence of the six haplotypes in 548 isolates worldwide was determined. Haplotypes I-a and II-a were associated with diverse genotypes worldwide. As previously suggested, haplotype I-b was found only in the US-1 clonal lineage and its variants (n = 99 isolates from 16 countries on 5 continents), and haplotype II-b was limited to the US-6 clonal lineage and its derivatives (n = 36). In a confirmation of a previous suggestion, the randomly mating population in the Toluca Valley of central Mexico (n = 78) was monomorphic for mtDNA haplotype I-a(A). We hypothesize that selection there may be driving the dominance of that single mtDNA haplotype.     

Mitochondrial DNA sequence variation among geographical isolates of Opisthorchis viverrini in Thailand and Lao PDR, and phylogenetic relationships with other trematodes

The present study compared the genetic variation among 14 different geographical isolates of Opisthorchis viverrini sensu lato from Thailand and Lao PDR using sequence data for 2 mitochondrial DNA genes, the subunit 1 of NADH dehydrogenase gene (nad1) and cytochrome c oxidase gene (cox1). Four different nad1 haplotypes were detected among isolates, all of which were identical at the amino acid sequence level. Nucleotide sequence variation among 14 isolates ranged from 0 to 0.3% for nad1. Two different cox1 haplotypes were detected among isolates. These two haplotypes differed at 2 nucleotide positions, one of which resulted in a change in the amino acid sequence. Nucleotide sequence variation among isolates for cox1 ranged from 0 to 0.5%. Comparison of cox1 sequences of O. viverrini to those of other trematodes revealed nucleotide differences of 13-31%. A phylogenetic analysis of the cox1 sequence data revealed strong statistical support for a clade containing O. viverrini and 2 other species of opisthorchid trematodes; O. felineus and Clonorchis sinsensis.     

RAPD fingerprinting for the distinction of Prevotella intermedia sensu stricto from Prevotella nigrescens

A collection of 70 oral strains including reference strains and clinical isolates identified as Prevotella intermedia sensu lato was constituted to cover a large clinical and geographical diversity. Electrophoresis of the enzyme malate dehydrogenase allowed the identification of the 70 study strains as Prevotella intermedia sensu stricto (n= 36), Prevotella nigrescens (n= 31) and three unclassified strains. By using four primers, DNA fingerprints were generated from 20 strains as random amplified polymorphic DNA (RAPD). Matching co-migrating amplicon positions by pairwise comparison allowed the clustering of the fingerprints as two groups coincident with the P. intermedia/P. nigrescens assignment by enzyme electrophoresis of malate dehydrogenase. Our data suggest that isolates identified asP. intermedia sensu lato by conventional criteria can be speciated asP. intermedia sensu stricto or P. nigrescens by RAPD fingerprinting.     

Chromosomal deletion in isolates of Phytophthora infestans correlates with virulence on R3, R10, and R11 potato lines.

In Phytophthora infestans, a cluster of three dominant avirulence genes is located on the distal part of linkage group VIII. In a mapping population from a cross between two Dutch field isolates, probe M5.1, derived from an amplified fragment length polymorphism (AFLP) marker linked to the Avr3-Avr10-Avr11 cluster, hybridized only to DNA from the parent and F1 progeny that is avirulent on potato lines carrying the R3, R10, and R11 resistance gene. In the virulent parent and the virulent progeny, no M5.1 homologue was detected, demonstrating a deletion on that part of linkage group VIII. P. infestans is diploid, so the avirulent strains must be hemizygous for the region concerned. A similar situation was found in another mapping population from two Mexican strains. The deletion was also found to occur in many field isolates. In a large set of unique isolates collected in The Netherlands from 1980 to 1991, 37% had no M5.1 homologue and the deletion correlated strongly with gain of virulence on potato lines carrying R3, R10, and R11. Also, in some old isolates that belong to a single clonal lineage (US-1) and are thus highly homogenous, deletions at the M5.1 locus were detected, indicating that this region is unstable.     

The R3 resistance to Phytophthora infestans in potato is conferred by two closely linked R genes with distinct specificities

The R3 locus of potato (Solanum tuberosum L.) confers full resistance to avirulent isolates of Phytophthora infestans, the causal agent of late blight. R3 resides in the distal part of chromosome 11 and segregates in a potato mapping population, from which a well-saturated amplified fragment length polymorphism map is available. Using a population of 1,748 plants, we constructed a high-resolution genetic map at the R3 locus. Using the combination of fine mapping and accurate disease testing with specific P. infestans isolates, we detected that the R3 locus is composed of two genes with distinct specificities. The two genes R3a and R3b are 0.4 cM apart and have both been introgressed from S. demissum, the 'donor' species of most characterized race-specific R genes to P. infestans. A natural recombinant between R3a and R3b was discovered in one accession of S. demissum. The synteny between the R3 locus and the tomato I2 locus is discussed.     

Genetic Diversity of Phytophthora infestans (Mont.) de Bary in the Eastern and Western Highlands of Uganda

Eight isolates of Phytophthora infestans were recovered from late blight infected samples collected from the districts of Mbale and Mbarara in the Eastern and Western highlands of Uganda in 2001 and analysed using mitochondrial deoxyribonucleic acid (DNA) haplotype and Amplified Fragment Length Polymorphism (AFLP) markers. Polymerase chain reaction amplification with the P2 primer followed by digestion with MspI yielded a three‐fragment pattern characteristic of isolates belonging to the US‐1 clonal lineage; the polymorphism was confirmed by DNA sequencing. AFLP analysis yielded 60 markers, analysis of which clustered the Ugandan isolates with reference to US‐1 isolates (US930258 and US940501). These results suggest that the examined Ugandan isolates belong to the US‐1 clonage lineage.     

Molecular definition and the ubiquity of species in the genus Naegleria

To investigate the variability within species of the genus Naegleria, the ITS1,5.8S and ITS2 rDNA were sequenced of several strains of N. lovaniensis and its Western Australian variants, N. australiensis, N. fowleri, N. andersoni, N. jamiesoni, N. tihangensis, N. pringsheimi, N. pagei, N. gruberi sensu lato and a Naegleria lineage that lost a group I intron from the SSUrDNA twintron. As a result, it is possible to define a molecular species within the Naegleria genus. In addition, one strain of each different allozyme cluster was sequenced to investigate whether they belong to described species or should be treated as distinct new species. This leads to the proposal of eleven new species. The sequencing results from those Naegleria spp. of which several strains are available indicate that these species are ubiquitous. The only exception might be the species represented by the WA variants. However, there are still many Naegleria spp. for which only one strain has been isolated, hence, it is important that the search for more isolates should be continued worldwide.     

Phylogenetic relationships of Pythium and Phytophthora species based on ITS rDNA, cytochrome oxidase II and beta-tubulin gene sequences

Fifty-eight isolates representing 39 Pythium species and 17 isolates representing nine Phytophthora species were chosen to investigate intra- and intergeneric relationships with sequence analysis of three genomic areas. The internal transcribed spacer regions (ITS1 and ITS2), including the 5.8S gene of the ribosomal DNA were PCR amplified with the universal primers ITS1 and ITS4. On the other hand 563 bp of the cytochrome oxidase II (cox II) gene was amplified with the primer pair FM66 and FM58 for Pythium and FM75 and FM78 for Phytophthora. The 658 bp partial beta-tubulin gene was amplified with the forward primer BT5 and reverse primer BT6. Maximum parsimony analysis of the three DNA regions revealed four major clades, reflective of sporangial morphology. Clade 1 was composed of Pythium isolates that bear filamentous to lobulate sporangia. Clade 2 represents Pythium isolates that bear globose to spherical zoosporangia or spherical hyphal swellings. Meanwhile Phytophthora isolates were lumped into Clade 3 wherein the papillate, semipapillate and nonpapillate species occupied separate subclades. Lastly, Clade 4 was composed of Pythium species that bear subglobose sporangia resembling the papillate sporangia observed in Phytophthora. Hence a number of species (Ph. undulata, P. helicoides, P. ostracodes, P. oedochilum and P. vexans) have been proposed to be the elusive intermediate species in the Pythium-to-Phytophthora evolutionary line.     

Characterization of diversity in Colletotrichum acutatum sensu lato by sequence analysis of two gene introns, mtDNA and intron RFLPs, and mating compatibility

A diverse collection of isolates identified as Colletotrichum acutatum, including a range of fruit-rot and foliar pathogens, was examined for mtDNA RFLPs and RFLPs and sequence variation of a 900-bp intron of the glutamine synthetase (GS) gene and a 200-bp intron of the glyceraldehyde-3-phosphate dehydrogenase (GPDH) gene. RFLPs of mtDNA, RFLPs of the 900-bp GS intron and sequence analysis of each intron identified the same seven distinct molecular groups, or clades, within C. acutatum sensu lato. Sequence analysis produced highly concordant tree topologies with definitive phylogenetic relationships within and between the clades. The clades might represent phylogenetically distinct species within C. acutatum sensu lato. Mating tests also were conducted to assess sexual compatibility with tester isolates known to outcross to form the teleomorph Glomerella acutata. Mating compatibility was identified within one clade, C, and between two phylogenetically distinct clades, C and J4. The C clade represented isolates from a wide range of hosts and geographic origins. J4 clade contained isolates from Australia or New Zealand recovered from fruit rot and pine seedlings with terminal crook disease. That isolates in two phylogenetically distinct clades were capable of mating suggests that genetic isolation occurred before reproductive isolation. No other isolates were sexually compatible with the mating testers, which also were in groups C and J4. Certain clades identified by mtDNA and intron analysis (D1, J3 and J6) appeared to represent relatively host-limited populations. Other clades (C1, F1 and J4) contained isolates from a wide range of hosts. Isolates described as C. acutatum f. sp. pineum were clearly polyphyletic.     

Molecular systematics of the neotropical shovelnose catfish genus Pseudoplatystoma Bleeker 1862 based on nuclear and mtDNA markers

Pseudoplatystoma is a commercially important genus of Neotropical migratory catfishes widely distributed in all major river basins of South America. Historically, only three species were recognized, but a recent revision proposed eight putative morphospecies for the genus. A molecular study based on mitochondria DNA (mtDNA) provided support for recognition of only some of the species and raised questions about species boundaries in this group. We present a more encompassing analysis based on mtDNA (cytochrome b, 818bp) and nuclear DNA-based phylogenies (Rag1 intron 1, 664bp and S7 intron 1, 635bp) for a more extensive sampling (279 individuals from 42 localities) of all putative species in all major river basins. Patterns generated by individual gene genealogies and a multispecies coalescent analysis provided evidence to suggest recognition of only four distinct species in this genus: Pseudoplatystoma magdaleniatum, Pseudoplatystoma corruscans, Pseudoplatystoma tigrimun (sensu lato) and Pseudoplatystoma fasciatum (sensu lato). The species phylogeny places P. magdaleniatum as the sister group to all the other species in the genus, but the relationships among P. fasciatum s.l, P. tigrimum s.l., and P. corruscans could not be resolved with confidence.     

Loss of the mitochondrial cox2 intron 1 in a family of monocotyledonous plants and utilization of mitochondrial intron sequences for the construction of a nuclear intron

The intron content of plant organellar genes is a useful marker in molecular systematics and evolution. We have tested representatives of a wide range of monocotyledonous plant families for the presence of an intron (cox2 intron 1) in one of the most conservative mitochondrial genes, the cox2 locus. Almost all species analyzed were found to harbor a group II intron at a phylogenetically conserved position. The only exceptions were members of a single monocot family, the Ruscaceae: representatives of all genera in this family were found to lack cox2 intron 1, but instead harbor an intron in the 3' portion of the cox2 coding region (cox2 intron 2). The presence of cox2 intron 1 in families of monocotyledonous plants that are closely related to the Ruscaceae suggests that loss of the intron is specific to this family and may have accompanied the evolutionary appearance of the Ruscaceae. Interestingly, sequences that are highly homologous to cox2 intron 2 are found in a nuclear intron in a lineage of monocotyledonous plants, suggesting that the originally mitochondrial group II intron sequence was transferred to the nuclear genome and reused there to build a spliceosomal intron.     

Oospore Germination and Formation by the Late Blight Pathogen Phytophthora infestans in vitro and under Field Conditions

The ability of the late blight pathogen Phytophthora infestans to form oospores in leaves of seven potato cultivars was examined at different incubation temperatures under controlled environmental conditions and under field conditions. At 10°C, the oospore formation in three intermediate-resistant cultivars all differed significantly from each other (P < 0.05), with the lowest amount formed in cv. Asterix. This latter cultivar did not form oospores at any other temperature. Under field conditions oospores were formed abundantly in a naturally infected field. A significant date by cultivar interaction showed that P. infestans increased the oospore formation in foliage by time in cvs Columbo, Hertha and Matilda, whereas no significant differences between dates were found for other cultivars. The genetic structure of P. infestans in the naturally infected field plot, where oospores formed abundantly, was studied by using amplified fragment length polymorphism and a high genetic diversity was revealed. Oospore germination from two Scandinavian (A1 and A2) P. infestans isolates was stimulated in visible light and in 1 : 2 and 1 : 10 soil extract. The effect of light and nutrients on oosporogenesis is discussed.     

致病疫霉有性生殖诱导及F1代遗传多样性

致病疫霉Phytophthora infestans为马铃薯晚疫病的重要病原菌。通过从昆明市寻甸县采集110P和H-6两株致病疫霉,明确其染色体倍性、交配型、线粒体单倍型、毒性和甲霜灵敏感性,经对峙培养,利用改良的卵孢子萌发方法获得有性生殖F1代群体POP1（60株）,并对POP1进行表型和基因型测定。结果表明：冷冻处理24h为最佳条件,卵孢子萌发率达5.09%±0.15%;POP1的交配型、毒性和甲霜灵敏感性均发生了分离,其中交配型分离比为A1:A2:A1A2:自育型（SF）=16:5:17:22,毒性分离比为抗性（R）:敏感性（S）=11:49,甲霜灵敏感性分离比为抗性（R）:敏感性（S）=2:58;3个表型的分离均偏离孟德尔单基因显性遗传特点。基于8对SSR多态性引物对POP1基因型分析表明,遗传相似系数为0.98时,可将所有菌株分为14个基因型;遗传相似系数为0.95时,可将POP1分为6个分支,其中优势群体为S1,占分离群体的61.67%。关联分析进一步表明,8对SSR所代表的基因型和几个重要表型有显著相关性（R2=0.6667）。本研究建立了高效的致病疫霉卵孢子萌发体系,解析了有性生殖后代群体遗传结构特点,为深入探索致病疫霉的变异规律及病害流行趋势提供了理论基础。