scholarly journals Genetic Variability and Distribution of Mating Type Alleles in Field Populations of Leptosphaeria maculans from France

2006 ◽  
Vol 72 (1) ◽  
pp. 185-191 ◽  
Author(s):  
Lilian Gout ◽  
Maria Eckert ◽  
Thierry Rouxel ◽  
Marie-Hélène Balesdent
Keyword(s):  
Genetic Structure ◽  
Genetic Variability ◽  
Mating Type ◽  
Gene Diversity ◽  
Spatial Scales ◽  
Leptosphaeria Maculans ◽  
Genotypic Diversity ◽  
Stem Canker ◽  
Field Population ◽  
Sexual And Asexual Reproduction

ABSTRACT Leptosphaeria maculans is the most ubiquitous fungal pathogen of Brassica crops and causes the devastating stem canker disease of oilseed rape worldwide. We used minisatellite markers to determine the genetic structure of L. maculans in four field populations from France. Isolates were collected at three different spatial scales (leaf, 2-m2 field plot, and field) enabling the evaluation of spatial distribution of the mating type alleles and of genetic variability within and among field populations. Within each field population, no gametic disequilibrium between the minisatellite loci was detected and the mating type alleles were present at equal frequencies. Both sexual and asexual reproduction occur in the field, but the genetic structure of these populations is consistent with annual cycles of randomly mating sexual reproduction. All L. maculans field populations had a high level of gene diversity (H = 0.68 to 0.75) and genotypic diversity. Within each field population, the number of genotypes often was very close to the number of isolates. Analysis of molecular variance indicated that >99.5% of the total genetic variability was distributed at a small spatial scale, i.e., within 2-m2 field plots. Population differentiation among the four field populations was low (GST < 0.02), suggesting a high degree of gene exchange between these populations. The high gene flow evidenced here in French populations of L. maculans suggests a rapid countrywide diffusion of novel virulence alleles whenever novel resistance sources are used.

scholarly journals Occurrence of a New Subclade of Leptosphaeria biglobosa in Western Australia

2008 ◽  
Vol 98 (3) ◽  
pp. 321-329 ◽  
Author(s):  
L. Vincenot ◽  
M. H. Balesdent ◽  
H. Li ◽  
M. J. Barbetti ◽  
K. Sivasithamparam ◽  
...  
Keyword(s):  
Oilseed Rape ◽  
Mating Type ◽  
Western Australia ◽  
Leptosphaeria Maculans ◽  
Stem Canker ◽  
Tubulin Genes ◽  
Wide Scale ◽  
Scale Characterization ◽  
Leptosphaeria Biglobosa ◽  
Β Tubulin

Stem canker of crucifers is caused by an ascomycete species complex comprising of two main species, Leptosphaeria maculans and L. biglobosa. These are composed of at least seven distinct subclades based on biochemical data or on sequences of internal transcribed spacer (ITS), the mating type MAT1-2 or fragments of actin or β-tubulin genes. In the course of a wide-scale characterization of the race structure of L. maculans from Western Australia, a few isolates from two locations failed to amplify specific sequences of L. maculans, i.e., the mating-type or minisatellite alleles. Based on both pathogenicity tests and ITS size, these isolates were classified as belonging to the L. biglobosa species. Parsimony and distance analyses performed on ITS, actin and β-tubulin sequences revealed that these isolates formed a new L. biglobosa subclade, more related to the Canadian L. biglobosa ‘canadensis’ subclade than to the L. biglobosa ‘australensis’ isolates previously described in Australia (Victoria). They are termed here as L. biglobosa ‘occiaustralensis’. These isolates were mainly recovered from resistant oilseed rape cultivars that included the Brassica rapa sp. sylvestris-derived resistance source, but not from the susceptible cv. Westar. The pathogenicity of L. biglobosa ‘occiaustralensis’ to cotyledons of most oilseed rape genotypes was higher than that of L. biglobosa ‘canadensis’ or L. biglobosa ‘australensis’ isolates.

scholarly journals Population Genetic Structure of Tapesia acuformis in Washington State

2003 ◽  
Vol 93 (6) ◽  
pp. 650-656 ◽  
Author(s):  
G. W. Douhan ◽  
T. D. Murray ◽  
P. S. Dyer
Keyword(s):  
Genetic Structure ◽  
Mating Type ◽  
Asexual Reproduction ◽  
Permutation Test ◽  
Phylogenetic Analyses ◽  
Random Mating ◽  
Likelihood Ratio Statistic ◽  
Washington State ◽  
Homogeneous Population ◽  
Sexual And Asexual Reproduction

Eyespot of wheat is caused by Tapesia yallundae and T. acuformis. Historically, T. yallundae has been considered the more important causal agent of the disease in Washington state and consists of a large homogeneous population with a genetic structure consistent with both sexual and asexual reproduction. T. acuformis has increased significantly in Washington in the past 10 years and apothecia were found recently under natural field conditions, indicating that T. acuformis may have a more important role in eyespot of wheat than previously was thought. To determine the genetic structure of T. acuformis in Washington, 141 single conidial isolates were sampled from four subpopulations in the eastern wheat-growing region of the state. Isolates were scored for mating type and six amplified fragment length polymorphism markers. All markers segregated in a 1:1 ratio and were determined to be unlinked based on genetic analysis of 24 progeny from an in vitro cross. No significant differences in allele frequencies (0.127 < P < 0.809) were found among individual loci across the four subpopulations and over all loci based on contingency table analysis of the log-likelihood ratio statistic G2. Likewise, no overall differences between subpopulations were detected using the population differentiation statistic θ (θ = -0.004, P = 0.537). Random mating could not be rejected within each subpopulation or for the combined data using clone-corrected data sets based on (i) 1:1 ratio of mating-type, (ii) multilocus gametic disequilibrium analyses (index of association), (iii) phylogenetic analyses (parsimony tree length permutation test), and (iv) genotypic diversity analyses. T. acuformis has a genetic structure similar to that of sympatric populations of T. yallundae in Washington, with both sexual and asexual reproduction contributing to the structuring of this species.

scholarly journals Genetic Diversity and Differentiation inPhoma betaePopulations on Table Beet in New York and Washington States

Plant Disease ◽  
2019 ◽  
Vol 103 (7) ◽  
pp. 1487-1497 ◽  
Author(s):  
Lori B. Koenick ◽  
Niloofar Vaghefi ◽  
Noel L. Knight ◽  
Lindsey J. du Toit ◽  
Sarah J. Pethybridge
Keyword(s):  
Genetic Diversity ◽  
New York ◽  
Mating Type ◽  
Gene Diversity ◽  
Management Strategies ◽  
Allelic Diversity ◽  
Genotypic Diversity ◽  
Reproduction Mode ◽  
Inoculum Source ◽  
Seed Crops

Phoma betae is an important seedborne pathogen of table beet worldwide that is capable of causing foliar, root, and damping-off diseases. Ten microsatellite and mating type markers were developed to investigate the genetics of P. betae populations in table beet root crops in New York and in table beet seed crops in Washington, from where table beet seed is predominantly sourced. The markers were used to characterize 175 isolates comprising five P. betae populations (two from New York and three from Washington), and they were highly polymorphic with an allelic range of 4 to 33 and an average of 11.7 alleles per locus. All populations had high genotypic diversity (Simpson’s complement index = 0.857 to 0.924) and moderate allelic diversity (Nei’s unbiased gene diversity = 0.582 to 0.653). Greater differentiation observed between populations from the two states compared with populations within the same state suggested that an external inoculum source, such as windblown ascospores, may be homogenizing the populations. However, most genetic diversity (87%) was among individual isolates within populations (pairwise index of population differentiation = 0.127; P = 0.001), suggesting that local within-field inoculum source(s), such as infested field debris or infected weeds, may also be important in initiating disease outbreaks. Standardized index of association, proportion of compatible pairs of loci, and mating type ratio calculations showed evidence for a mixed reproduction mode in all populations. These findings could be useful in designing more effective management strategies for diseases caused by P. betae in table beet production.

Seasonal and annual genotypic variation and the effect of climate on population genetic structure of the cereal aphid Sitobion avenae in northern France

2007 ◽  
Vol 98 (2) ◽  
pp. 159-168 ◽  
Author(s):  
C.-A. Dedryver ◽  
J.-F. Le Gallic ◽  
L. Haack ◽  
F. Halkett ◽  
Y. Outreman ◽  
...  
Keyword(s):  
Genetic Structure ◽  
Spatial Scales ◽  
Genotypic Variation ◽  
Reproductive Mode ◽  
Genotypic Diversity ◽  
Theoretical Models ◽  
Sitobion Avenae ◽  
Cereal Aphid ◽  
Northern France ◽  
High Dispersal

AbstractChanges in the genetic structure and genotypic variation of the aphid Sitobion avenae collected from cereal crops in northern France were examined by analysing variation at five microsatellite loci across several years and seasons. Little regional and temporal differentiation was detected, as shown by very low FST among populations. Repeated genotypes, significant heterozygote deficits, positive FIS values and frequent linkage disequilibria were found in nearly all samples, suggesting an overall pattern of reproductive mode variation in S. avenae populations. In addition, samples from Brittany (Bretagne) showed greater signs of asexual reproduction than those from the north of France, indicating a trend toward increasing sexuality northward. These patterns of reproductive variation in S. avenae are consistent with theoretical models of selection of aphid reproductive modes by climate. Contrasting with little changes in allelic frequencies, genotypic composition varied substantially in time and, to a lesser extent, in space. An important part of changes in genotypic arrays was due to the variation in frequency distribution of common genotypes, i.e. those that were found at several instances in the samples. Genotypic composition was also shown to vary according to climate, as genotypic diversity in spring was significantly correlated with the severity of the previous winter and autumn. We propose that the genetic homogeneity among S. avenae populations shown here across large temporal and spatial scales is the result of two forces: (i) migration conferred by high dispersal capabilities, and (ii) selection over millions of hectares of cereals (mostly wheat) bred from a narrow genetic base.

scholarly journals Analisis keragaman genetik Phytophthora palmivora dari tanaman kakao di Indonesia menggunakan AFLP Genetic diversity analysis of Phytophthora palmivora from cocoa in Indonesia using AFLP

2016 ◽  
Vol 78 (2) ◽  
Author(s):  
Agus PURWANTARA ◽  
Abu UMAYAH
Keyword(s):  
Genetic Structure ◽  
Fragment Length ◽  
Theobroma Cacao ◽  
Genotypic Diversity ◽  
Stem Canker ◽  
Phytophthora Palmivora ◽  
Banding Patterns ◽  
Length Polymorphisms ◽  
Amplified Fragment Length Polymorphisms ◽  
High Degree

Abstract Phytophthora palmivora is the causal agent of pod rot, stem canker, seedling and leaf blight and cherelle wilt of cacao (Theobroma cacao) in Indonesia.  The genetic structure of the pathogen population across the country is unknown.  In this study, a population of 20 cultures of P. palmivora isolated from cocoa at six major cocoa producing provinces namely Sumatera Utara, Lampung, Jawa Barat, Jawa Timur, Sulawesi Selatan and Sulawesi Tenggara in Indonesia was evaluated for genotypic diversity using amplified fragment length polymorphisms (AFLP).  Ten primer combinations were used to evaluate all isolates, 68 out of 347 AFLP markers (19.6 %) produced were polymorphic.  Results of the AFLP analyses showed that the P. palmivora population in Indonesia possessed high degree of similarity (96 %). AFLP banding patterns indicated that the isolates form two distinct groups, but with no genetic differentiation based on geography, types of cocoa or the part of the tree from which the isolates were obtained.  These data suggest that frequent outbreaks of Phytophthora pod rot in various growing regions is probably resulted from changing of local climatic condition which is condusive for the disease epidemic rather than from different genetic structure or pathogenic populations of this pathogen, which would affect recommendations for disease management.Abstrak Phytophthora palmivora adalah penyebab penyakit busuk buah, kanker batang, hawar bibit dan daun, dan layu pentil pada tanaman kakao (Theobroma cacao) di Indonesia.  Struktur genetik dari populasi patogen di seluruh negeri belum diketahui.  Pada kajian ini, 20 kultur P. palmivora yang diisolasi dari berbagai bagian tanaman kakao dari enam provinsi penghasil kakao di Indonesia, yaitu Sumatera Utara, Lampung, Jawa Barat, Jawa Timur, Sulawesi Selatan dan Sulawesi Tenggara diuji keragaman genetiknya mengguna-kan amplified fragment length polymorphisms (AFLP). Sepuluh kombinasi primer digunakan untuk menguji semua isolat, 68 di antara 347 penanda AFLP (19,6 %) yang dihasilkan adalah polimorfik.  Hasil analisis AFLP menun-jukkan bahwa populasi P. palmivora di Indonesia mempunyai tingkat kekerabatan yang tinggi (96 %).  Pola pita AFLP menunjukkan bahwa kedua puluh isolat membentuk dua kelompok, tetapi tidak ada perbedaan berdasar letak geografis, tipe kakao atau bagian tanaman kakao asal isolat diperoleh. Data ini menunjukkan bahwa ledakan penyakit busuk buah Phytophthora yang sering terjadi di berbagai daerah diduga lebih diakibatkan oleh perubahan kondisi iklim setempat yang memicu terjadinya epidemi daripada karena perbedaan genetik atau patogenisitas dari populasi patogen, sehingga hasil ini dapat melengkapi saran-saran dalam pengelolaan penyakit.

scholarly journals Mating-Type Distribution and Genetic Diversity of Cercospora sojina Populations on Soybean from Arkansas: Evidence for Potential Sexual Reproduction

2013 ◽  
Vol 103 (10) ◽  
pp. 1045-1051 ◽  
Author(s):  
Hun Kim ◽  
Annakay D. Newell ◽  
Robyn G. Cota-Sieckmeyer ◽  
John C. Rupe ◽  
Ahmad M. Fakhoury ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Mating Type ◽  
Spatial Scales ◽  
Genotypic Diversity ◽  
The United States ◽  
Economic Losses ◽  
Mating Types ◽  
Cercospora Sojina ◽  
Single Leaf ◽  
Corrected Data

Cercospora sojina causes frogeye leaf spot of soybean, which can cause serious economic losses in the United States. In this study, 132 C. sojina isolates were collected from six fields (from two counties, Cross and Crawford) in Arkansas. To determine mating type, a multiplex polymerase chain reaction assay was developed with primers specific for C. sojina. Of the 132 isolates, 68 isolates had the MAT1-1-1 idiomorph and 64 isolates had the MAT1-2 idiomorph; no isolates possessed both idiomorphs. Both mating types were present in a variety of spatial scales, including separate lesions on individual leaves. Clone-corrected data from eight microsatellites indicated that mating-type loci were present in approximately equal proportions in all populations analyzed, which suggests that Arkansas populations of C. sojina are undergoing cryptic sexual reproduction. All six populations evaluated had high genotypic diversity of 26 to 79%. In addition, among strains isolated from a single leaf, multiple and distinct haplotypes were associated with both mating types, supporting the hypothesis that sexual reproduction occurs within the populations. Most populations showed significant gametic disequilibrium but levels of disequilibrium were relatively low, particularly in populations from Crawford County. A low differentiation index (GST) was observed for all simple-sequence repeat markers across all populations. Furthermore, the value of G statistics between populations suggests that significant genetic exchange exists among the populations. Taken together, these results demonstrate that C. sojina populations from Arkansas are genetically diverse and most likely undergoing sexual reproduction.

scholarly journals Some evidence for skewed mating type distribution in Iranian populations of Rhynchosporium commune, the cause of barley scald disease

2016 ◽  
Vol 56 (3) ◽  
pp. 237-243 ◽  
Author(s):  
Mahdi Arzanlou ◽  
Kaivan Karimi ◽  
Fariba Mirabi
Keyword(s):  
Mating Type ◽  
Spatial Scales ◽  
Genotypic Diversity ◽  
Sexual Cycle ◽  
Pcr Assay ◽  
Unequal Distribution ◽  
Equal Distribution ◽  
Multiplex Pcr Assay ◽  
The World ◽  
Mating Type Genes

AbstractRhynchosporium commune(formerly known asRhynchosporium secalis), the causal agent of scald disease on barley, is known to spread asexually by splash dispersed conidia. However, there are multiple lines of evidence for the possibility of a clandestine sexual cycle occurrence in this species including extensive genotypic diversity, equal distribution of mating type alleles across the world and expression of mating type genes. In the current study, the potential for the occurrence of a sexual cycle amongst the Iranian population ofR. communewas assessed by analyzing distribution and frequency of the mating type alleles at both micro and macro-spatial scales. A total of 95 single-conidialR. communeisolates were obtained from different barley fields in Kurdistan province. Previously designed primers were applied in a multiplex PCR assay to study distribution and frequency of the mating type alleles within and between populations. Totally, 67 isolates were determined asMAT1-1and the remaining 28 isolates asMAT1-2throughout the sampling counties. The results obtained at a macro-spatial scale revealed that unlike Kamyaran county (bothMAT1-1andMAT1-2at an equal ratio), an unequal distribution of mating type genes was dominant amongR. communeisolates in both Mariwan and Dehgolan counties. Our findings support a predominantly asexual reproduction for Mariwan and Dehgolan counties and the possibility of sexual stage occurrence in Kamyarna county.

scholarly journals Spatial Genetic Structure of a Vector-Borne Generalist Pathogen

2011 ◽  
Vol 77 (8) ◽  
pp. 2596-2601 ◽  
Author(s):  
Helvécio D. Coletta-Filho ◽  
Leonora S. Bittleston ◽  
Rodrigo P. P. Almeida
Keyword(s):  
Genetic Structure ◽  
Riparian Vegetation ◽  
Diversity Index ◽  
Gene Diversity ◽  
Isolation By Distance ◽  
Spatial Genetic Structure ◽  
Genotypic Diversity ◽  
Mantel Test ◽  
Content Type ◽  
Vector Borne

ABSTRACTVector-borne generalist pathogens colonize several reservoir species and are usually dependent on polyphagous arthropods for dispersal; however, their spatial genetic structure is generally poorly understood. Using fast-evolving genetic markers (20 simple sequence repeat loci, resulting in a total of 119 alleles), we studied the genetic structure of the vector-borne plant-pathogenic bacteriumXylella fastidiosain Napa Valley, CA, where it causes Pierce's disease when it is transmitted to grapevines from reservoir plants in adjacent riparian vegetation. Eighty-three differentX. fastidiosamultilocus microsatellite genotypes were found in 93 isolates obtained from five vineyards, resulting in an index of clonal fraction closer to 0 and a Simpson's genotypic diversity index (D) closer to a maximum value of 1. Moderate values of Nei's gene diversity (HNei; averageHNei= 0.41) were observed for most of theX. fastidiosapopulations. The low Wright's index of genetic diversity among populations calculated by the FSTAT software (Wright'sFSTindex) among population pairs (0.0096 to 0.1080) indicated a weak or absent genetic structure among the five populations; a panmictic population was inferred by Bayesian analyses (with the STRUCTURE and BAPS programs). Furthermore, a Mantel test showed no significant genetic isolation by distance when both Nei (r= −0.3459,P= 0.268) and linearized θ (r= −0.3106,P= 0.269) indices were used. These results suggest that the riparian vegetation from which vectors acquire the pathogen prior to inoculation of grapevines supports a diverse population ofX. fastidiosa.

scholarly journals Sexual Reproduction Plays a Major Role in the Genetic Structure of Populations of the Fungus Mycosphaerella graminicola

Genetics ◽  
1996 ◽  
Vol 142 (4) ◽  
pp. 1119-1127 ◽  
Author(s):  
Ruey-Shyang Chen ◽  
Bruce A McDonald
Keyword(s):  
Genetic Structure ◽  
Asexual Reproduction ◽  
Pathogenic Fungus ◽  
Random Mating ◽  
Genotypic Diversity ◽  
Mycosphaerella Graminicola ◽  
Dna Fingerprints ◽  
Genetic Structure Of Populations ◽  
Sexual And Asexual Reproduction ◽  
Single Field

Abstract The relative contributions of sexual and asexual reproduction to the genetic structure of populations can be difficult to determine for fungi that use a mixture of both types of propagation. Nuclear RFLPs and DNA fingerprints were used to make indirect and direct measures of departures from random mating in a population of the plant pathogenic fungus Mycosphaerella graminicola during the course of an epidemic cycle. DNA fingerprints resolved 617 different genotypes among 673 isolates sampled from a single field over a 3-month period. Only 7% of the isolates represented asexual clones that were found more than once in the sample. The most common clone was found four times. Genotypic diversity averaged 85% of its maximum possible value during the course of the epidemic. Analyses of multilocus structure showed that allelic distributions among RFLP loci were independent. Pairwise comparisons between individual RFLP loci showed that the majority of alleles at these loci were in gametic equilibrium. Though this fungus has the capacity for a significant level of asexual reproduction, each analysis suggested that M. graminicola populations maintain a genetic structure more consistent with random-mating over the course of an epidemic cycle.

scholarly journals Population Biology and Genetic Variation ofSpongospora subterraneaf. sp.subterranea, the Causal Pathogen of Powdery Scab and Root Galls on Potatoes in South Africa

2019 ◽  
Vol 109 (11) ◽  
pp. 1957-1965 ◽  
Author(s):  
Norman Muzhinji ◽  
Jacquie E. van der Waals
Keyword(s):  
South Africa ◽  
Genetic Structure ◽  
Population Biology ◽  
Gene Diversity ◽  
Random Mating ◽  
Management Strategies ◽  
Genotypic Diversity ◽  
Potato Production ◽  
Powdery Scab ◽  
Genetic Structure And Diversity

Spongospora subterranea f. sp. subterranea, causal agent of powdery scab and root galls of potatoes, occurs worldwide and is responsible for quality and yield losses in potato production in South Africa. Despite being one of the most important potato pathogens in South Africa, little information is available on the genetic structure and diversity of S. subterranea f. sp. subterranea, which could provide insight into the factors shaping its evolution and the role of inoculum sources in disease development. A total of 172 samples were collected from four potato growing regions in South Africa. An additional 27 samples obtained from Colombia were included for comparative purposes. The samples were screened against six informative microsatellite (simple-sequence repeat) markers. Of the 172 samples obtained from potato growing regions in South Africa, there were 75 multilocus genotypes (MLGs), only 16 of which were shared between potato growing regions, indicating substantial gene flow and countrywide dispersal of the pathogen. The presence of common MLGs among the root- and tuber-derived samples indicated a lack of specialization of S. subterranea f. sp. subterranea to either tuber or root infection. Nei’s unbiased estimates of gene diversity for the clone-corrected data were low and ranged from 0.24 to 0.38. Analysis of molecular variance and discriminant analysis of principal components showed no population differentiation between different potato growing regions in South Africa and between root- and tuber-derived genotypes. The presence of MLGs, high considerable genotypic diversity, and failure to reject the null hypothesis of random mating in most populations are indicative of some kind of recombination, either sexual or asexual, in these S. subterranea f. sp. subterranea populations. Information from this study provides new insights into the genetic structure and diversity of S. subterranea f. sp. subterranea in South Africa. Continuous monitoring of the pathogen population dynamics will be helpful in implementing effective region-specific management strategies for the pathogen, especially in the development of resistant potato cultivars.

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