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1.
BMC Genomics ; 22(1): 843, 2021 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-34802418

RESUMO

BACKGROUND: Scab is the most important fungal disease of apple and pear. Apple (Malus x domestica Borkh.) and European pear (Pyrus communis L.) are genetically related but they are hosts of two different fungal species: Venturia inaequalis for apple and V. pyrina for European pear. The apple/V. inaequalis pathosystem is quite well known, whereas knowledge about the pear/V. pyrina pathosystem is still limited. The aim of our study was to analyse the mode of action of a major resistance gene of apple (Rvi6) in transgenic apple and pear plants interacting with the two scab species (V. inaequalis and V. pyrina), in order to determine the degree of functional transferability between the two pathosystems. RESULTS: Transgenic pear clones constitutively expressing the Rvi6 gene from apple were compared to a scab transgenic apple clone carrying the same construct. After inoculation in greenhouse with V. pyrina, strong defense reactions and very limited sporulation were observed on all transgenic pear clones tested. Microscopic observations revealed frequent aborted conidiophores in the Rvi6 transgenic pear / V. pyrina interaction. The macro- and microscopic observations were very comparable to the Rvi6 apple / V. inaequalis interaction. However, this resistance in pear proved variable according to the strain of V. pyrina, and one of the strains tested overcame the resistance of most of the transgenic pear clones. Comparative transcriptomic analyses of apple and pear resistant interactions with V. inaequalis and V. pyrina, respectively, revealed different cascades of molecular mechanisms downstream of the pathogen recognition by Rvi6 in the two species. Signal transduction was triggered in both species with calcium (and G-proteins in pear) and interconnected hormonal signaling (jasmonic acid in pear, auxins in apple and brassinosteroids in both species), without involvement of salicylic acid. This led to the induction of defense responses such as a remodeling of primary and secondary cell wall, lipids biosynthesis (galactolipids in apple and cutin and cuticular waxes in pear), systemic acquired resistance signal generation (in apple) or perception in distal tissues (in pear), and the biosynthesis of phenylpropanoids (flavonoids in apple but also lignin in pear). CONCLUSION: This study is the first example of a successful intergeneric transfer of a resistance gene among Rosaceae, with a resistance gene functioning towards another species of pathogen.


Assuntos
Ascomicetos , Malus , Pyrus , Fungos do Gênero Venturia , Malus/genética , Doenças das Plantas/genética , Pyrus/genética
2.
PLoS One ; 16(6): e0252865, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34111167

RESUMO

Apple scab caused by Venturia inaequalis is a serious disease of cultivated apple worldwide. In this study, we collected 132 V. inaequalis isolates from Shaanxi, Gansu, Xinjiang, and the U.K. and analyzed their genetic diversity by using 13 microsatellite markers. Cluster analysis based on population structure and genetic distances suggested high similarity among the four regions. Population differentiation values ranged from 0.044 to 0.155, indicating there is a high level of kinship among the four regions. All isolates could be divided into 5 lineages with a 0.76 similarity coefficient. Among the four regions, Shaanxi had only one lineage, Group II; Gansu had four lineages, Group I, Group II, Group IV, and Group V; Xinjiang had all five lineages, Group I, Group II, Group III, Group IV, and Group V; and the U.K. had three lineages, Group I, Group II and Group IV. High molecular variance was detected for populations in the four regions, with 91% of the variance occurring within the populations and 9% among the populations. Structure analysis there are three common ancestors of these four regions. The results of the present study shed light on the genetic diversity of V. inaequalis in Shaanxi, Gansu and Xinjiang, which will lead to the development of more effective management strategies and new resistant apple cultivars through molecular marker-assisted selection.


Assuntos
Fungos do Gênero Venturia/genética , Malus/microbiologia , Repetições de Microssatélites , China , DNA Fúngico/genética , Fungos do Gênero Venturia/classificação , Marcadores Genéticos , Variação Genética , Filogenia , Filogeografia , Doenças das Plantas/microbiologia , Reino Unido
3.
Mol Plant Microbe Interact ; 34(7): 852-856, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33656373

RESUMO

Venturia carpophila, the causal agent of scab disease on peach, is a host-specific fungus that is widely distributed around the world, including China. In our previous study, samples were collected from 14 provinces in China, and 750 isolates were obtained by single-spore separation. Here, we reported the first highly contiguous whole-genome sequence (35.87 Mb) of the V. carpophila isolate ZJHZ1-1-1, which included 33 contigs with N50 value of 2.01 Mb and maximum contig length of 3.39 Mb. The high-quality genome sequence and annotation resource will be useful to study the fungal biology, pathogen-host interaction, fungicide resistance, characterization of important genes, population genetic diversity, and development of molecular markers for genotyping and species identification.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.


Assuntos
Prunus persica , Fungos do Gênero Venturia , Genoma Fúngico/genética , Doenças das Plantas , Prunus persica/genética
4.
Int J Mol Sci ; 22(2)2021 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-33430246

RESUMO

Among the fungal diseases of apple trees, serious yield losses are due to an apple scab caused by Venturia inaequalis. Protection against this disease is based mainly on chemical treatments, which are currently very limited. Therefore, it is extremely important to introduce cultivars with reduced susceptibility to this pathogen. One of the important sources of variability for breeding is the process of polyploidization. Newly obtained polyploids may acquire new features, including increased resistance to diseases. In our earlier studies, numerous tetraploids have been obtained for several apple cultivars with 'Free Redstar' tetraploids manifesting enhanced resistance to apple scab. In the present study, tetraploids of 'Free Redstar' were assessed in terms of phenotype and genotype with particular emphasis on the genetic background of their increased resistance to apple scab. Compared to diploid plants, tetraploids (own-rooted plants) were characterized with poor growth, especially during first growing season. They had considerably shorter shoots, fewer branches, smaller stem diameter, and reshaped leaves. In contrast to own-rooted plants, in M9-grafted three-year old trees, no significant differences between diplo- and tetraploids were observed, either in morphological or physiological parameters, with the exceptions of the increased leaf thickness and chlorophyll content recorded in tetraploids. Significant differences between sibling tetraploid clones were recorded, particularly in leaf shape and some physiological parameters. The amplified fragment length polymorphism (AFLP) analysis confirmed genetic polymorphism of tetraploid clones. Methylation-sensitive amplification polymorphism (MSAP) analysis showed that the level of DNA methylation was twice as high in young tetraploid plants as in a diploid donor tree, which may explain the weaker vigour of neotetraploids in the early period of their growth in the juvenile phase. Molecular analysis showed that 'Free Redstar' cultivar and their tetraploids bear six Rvi genes (Rvi5, Rvi6, Rvi8, Rvi11, Rvi14 and Rvi17). Transcriptome analysis confirmed enhanced resistance to apple scab of 'Free Redstar' tetraploids since the expression levels of genes related to resistance were strongly enhanced in tetraploids compared to their diploid counterparts.


Assuntos
Fungos do Gênero Venturia/genética , Genoma/genética , Malus/genética , Doenças das Plantas/genética , Fungos do Gênero Venturia/patogenicidade , Duplicação Gênica/genética , Genótipo , Fenótipo , Melhoramento Vegetal , Doenças das Plantas/microbiologia , Tetraploidia
5.
Phytopathology ; 111(2): 408-424, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32748736

RESUMO

Scab (caused by Venturia carpophila) is a major disease affecting peach in the eastern United States. The aims of the study were to characterize the mating-type loci in V. carpophila, determine whether they are in equilibrium, and assess the population genetic diversity and structure of the pathogen. The mating-type gene MAT1-1-1 was identified in isolate JP3-5 in an available genome sequence, and the MAT1-2-1 gene was PCR amplified from isolate PS1-1, thus indicating a heterothallic structure. Mating-type loci structures were consistent with those of other Venturia spp. (V. effusa and V. inaequalis): the mating-type gene is positioned between APN2 encoding a DNA lyase and a gene encoding a Pleckstrin homology domain. Primers designed to each of the mating-type genes and a reference gene TUB2 were used as a multiplex PCR to screen a population (n = 81) of V. carpophila from various locations in the eastern United States. Mating types in five of the nine populations studied were in equilibrium. Among the 81 isolates, there were 69 multilocus genotypes. A population genetic analysis of the populations with >10 individuals (four populations) showed them to be genetically diverse. Linkage disequilibrium was found in five of nine populations with ≥4 isolates. A discriminant analysis of principal components indicated three genetic clusters, although extensive admixture was observed. Mating-type identification in V. carpophila provides a basis for understanding reproductive methods of the pathogen and can be a basis for further studies of the genetics of the peach scab pathogen.


Assuntos
Genes Fúngicos Tipo Acasalamento , Prunus persica , Fungos do Gênero Venturia , Genes Fúngicos Tipo Acasalamento/genética , Variação Genética , Doenças das Plantas , Análise de Sequência de DNA
6.
Pest Manag Sci ; 77(3): 1383-1391, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33098187

RESUMO

BACKGROUND: Peach scab, caused by Venturia carpophila, can significantly reduce both the yield and quality of peach fruit. It is difficult to distinguish peach scab from other peach diseases such as black spot and bacterial spot. An efficient assay is needed to identify V. carpophila in order to develop scientific management strategies. RESULTS: A set of loop-mediated isothermal amplification (LAMP) primers was designed based on the internal transcribed spacer (rDNA-ITS) sequence to detect V. carpophila. Compared with the conventional polymerase chain reaction (PCR) method, the LAMP method not only exhibited higher sensitivity and specificity in the detection of V. carpophila, but also required simpler equipment and less operational time. The minimum detectable concentration of V. carpophila genomic DNA with the LAMP method was 56.6 fg µl-1 , which was 100 times lower than with the conventional PCR method. When eight fungal species including V. carpophila (23 isolates from 14 provinces) and one bacterial species were used with LAMP detection, only V. carpophila showed a color change, from brown to yellowish green, and ladder-like bands in electrophoresis, indicating successful amplification. Moreover, when crude DNAs of peach fruit samples were used in LAMP detection, amplification was observed only from diseased fruits, and not from healthy fruits and the negative control. CONCLUSION: The LAMP assay shows simplicity, rapidity, high sensitivity and specificity, and will be useful in distinguishing scab caused by Venturia carpophila from other diseases with similar symptoms. © 2020 Society of Chemical Industry.


Assuntos
Prunus persica , Fungos do Gênero Venturia , Técnicas de Diagnóstico Molecular , Técnicas de Amplificação de Ácido Nucleico , Prunus persica/genética , Sensibilidade e Especificidade
7.
Phytopathology ; 111(2): 244-252, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33151825

RESUMO

Pecan scab, caused by Venturia effusa, is the most economically damaging disease of pecan in the southeastern United States, and annual epidemics are most effectively managed through multiple fungicide applications. The fungicide applications can be the single greatest operating cost for commercial growers and the return on that investment is impacted by fungicide resistance. V. effusa produces multiple generations of conidia per season, exhibits substantial genetic diversity, overwinters as stromata in the tree, and is under immense selection from the applied fungicides, all of which lead to a high risk for developing fungicide resistance. Since the mid-1970s, resistance or reduced sensitivity has been observed in isolates of V. effusa to the methyl benzimidazole carbamates, demethylation inhibitors, quinone outside inhibitors, organotin compounds, and the guanidines. Over the last 10 years, several studies have been conducted that have improved both scab management and fungicide resistance management in V. effusa. The aim of this review is to summarize recent developments in our understanding of fungicide resistance in V. effusa in the context of scab management in southeastern pecan orchards. The history, modes of action, general use of the labeled fungicides, and mechanisms and stability of fungicide resistance in V. effusa are discussed; conclusions and future research priorities are also presented.


Assuntos
Ascomicetos , Carya , Fungicidas Industriais , Fungos do Gênero Venturia , Fungicidas Industriais/farmacologia , Doenças das Plantas , Sudeste dos Estados Unidos
8.
Pest Manag Sci ; 77(2): 844-850, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32926586

RESUMO

BACKGROUND: Myclobutanil is one of the most widely used demethylation inhibitor (DMI) fungicides for the management of apple scab, caused by Venturia inaequalis. Strains of V. inaequalis resistant to myclobutanil have been reported across the world. Tebuconazole, another DMI fungicide, has been proposed as an alternative to myclobutanil, and the extent of cross-resistance with myclobutanil therefore needs to be evaluated. The sensitivity to tebuconazole and myclobutanil of a total of 40 isolates was determined. Half the isolates came from an isolated orchard which had never been sprayed with fungicides and half from orchards sprayed regularly with myclobutanil, but still with disease control problems. The progeny of a tebuconazole resistant (R) × sensitive (S) V. inaequalis cross were analyzed in order to improve understanding of the genetic control of tebuconazole sensitivity. RESULTS: There is cross-resistance between myclobutanil and tebuconazole (r = 0.91; P < 0.001). Sensitivity to tebuconazole of the progeny of a R × S cross varied quantitatively in a pattern which implied at least two gene loci differing between the parental strains. In addition, the asymmetric distribution of the sensitivity in the progeny implied possible epistatic effects. CONCLUSION: Resistance to myclobutanil and tebuconazole is strongly correlated. At least two genes are involved in the control of tebuconazole resistance in V. inaequalis.


Assuntos
Ascomicetos , Ascomicetos/genética , Fungos do Gênero Venturia , Nitrilas , Doenças das Plantas , Triazóis
9.
Phytopathology ; 111(6): 990-1000, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32910743

RESUMO

Scab caused by Venturia nashicola is one of the most serious diseases of Asian pears, including Japanese pear (Pyrus pyrifolia var. culta) and Chinese pears (P. bretschneideri and P. ussuriensis). Breeding scab-resistant pear cultivars is essential to minimize fungicide use and development of fungicide resistance. A survey of pathogenic specialization in V. nashicola is needed to ensure durable scab resistance in cultivated pears. V. nashicola race 1, 2, and 3 isolates, each differing in pathogenicity to Japanese pear cultivar Kousui and Asian pear strain Mamenashi 12, have been reported in Japan. In this study, isolates collected from scabbed pears in China and Taiwan were classified as V. nashicola based on conidial size and mating ability. However, various isolates had pathogenicity distinct from races 1, 2, and 3 according to tests on seven differential host genotypes of pear cultivars from Japan (Kousui and strain Mamenashi 12), China (Jingbaili, Yali, Linyuli, and Nanguoli), and Taiwan (Hengshanli). These new races were designated as races 4 to 7. Progenies characteristic of race 3 isolates were produced using a cross between race 1 and race 2 isolates, suggesting the possible role of sexual recombination in the emergence of novel races. Japanese pear cultivar Kinchaku and Chinese P. sinkiangensis 'Xiangli' (a Korla fragrant pear grown in China) did not show visible symptoms after inoculation with any of the seven races. Broad scab resistance in Kinchaku and Xiangli makes them a promising genetic resource for resistance breeding programs.


Assuntos
Ascomicetos , Pyrus , Fungos do Gênero Venturia , Melhoramento Vegetal , Doenças das Plantas
10.
Plant Dis ; 105(2): 377-383, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32729799

RESUMO

An 18-ha commercial pecan orchard was sampled over 3 years to study the spatial and temporal variation in fungicide sensitivity of Venturia effusa, cause of pecan scab. The orchard was divided into a two-dimensional, 8 × 8 grid of 64 quadrats, each containing nine trees (unless there were missing trees), and samples were collected once per year from each quadrat to be tested for sensitivity to fentin hydroxide, propiconazole, and thiophanate-methyl. Averaged across the orchard, insensitivity to all three fungicides was significantly lower in 2016 compared with 2015, but significantly greater for fentin hydroxide and thiophanate-methyl in 2017. Although significant spatial autocorrelation was observed for sensitivity to propiconazole in 2017 and for thiophanate-methyl in 2015 and 2017, indicating clustering, all other fungicide-by-year combinations were not significant. Omnidirectional spatial dependence was observed for sensitivity to propiconazole and thiophanate-methyl in 2017. In both instances, the semivariance increased linearly with lag distance; however, the range of spatial dependence was >276.5 m and could not be estimated accurately. Additionally, a separate sampling was conducted in all 3 years to identify an appropriate sampling size and pattern for fungicide sensitivity screening. A leaflet sample size of 165 in 11 groups of 15 allowed for accurate sensitivity testing for the three fungicides in all 3 years; however, a sample size of 45 leaflets in three groups of 15 was sufficient for quantifying sensitivity for propiconazole and thiophanate-methyl, in most cases. These results indicate that considerable biological variation in fungicide sensitivity exists in orchard-scale populations of V. effusa and that the spatial characteristics of those populations may differ in two-dimensional space depending on the growing season.


Assuntos
Ascomicetos , Carya , Fungicidas Industriais , Fungos do Gênero Venturia , Fungicidas Industriais/farmacologia , Tiofanato
11.
Mol Ecol ; 29(24): 4925-4941, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-33031644

RESUMO

Secondary contact between crops and their wild relatives poses a threat to wild species, not only through gene flow between plants, but also through the dispersal of crop pathogens and genetic exchanges involving these pathogens, particularly those that have become more virulent by indirect selection on resistant crops, a phenomenon known as "pestification." Joint analyses of wild and domesticated hosts and their pathogens are essential to address this issue, but such analyses remain rare. We used population genetics approaches, demographic inference and pathogenicity tests on host-pathogen pairs of wild or domesticated apple trees from Central Asia and their main fungal pathogen, Venturia inaequalis, which itself has differentiated agricultural and wild-type populations. We confirmed the occurrence of gene flow from cultivated (Malus domestica) to wild (Malus sieversii) apple trees in Asian forests, potentially threatening the persistence of Asian wild apple trees. Pathogenicity tests demonstrated the pestification of V. inaequalis, the agricultural-type population being more virulent on both wild and domesticated trees. Single nucleotide polymorphism (SNP) markers and the demographic modelling of pathogen populations revealed hybridization following secondary contact between agricultural and wild-type fungal populations, and dispersal of the agricultural-type pathogen population in wild forests, increasing the threat of disease in the wild apple species. We detected an SNP potentially involved in pathogen pestification, generating an early stop codon in a gene encoding a small secreted protein in the agricultural-type fungal population. Our findings, based on joint analyses of paired host and pathogen data sets, highlight the threat posed by cultivating a crop near its centre of origin, in terms of pestified pathogen invasions in wild plant populations and introgression in the wild-type pathogen population.


Assuntos
Malus , Fungos do Gênero Venturia , Fluxo Gênico , Genética Populacional , Malus/genética , Doenças das Plantas/genética
12.
Int J Mol Sci ; 21(16)2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32824325

RESUMO

There is an urgent need for novel, efficient and environmentally friendly strategies to control apple scab (Venturia inaequalis), for the purpose of reducing overall pesticide use. Fructans are recently emerging as promising "priming" compounds, standing out for their safety and low production costs. The objective of this work was to test a fructan-triggered defense in the leaves of apple seedlings. It was demonstrated that exogenous leaf spraying can reduce the development of apple scab disease symptoms. When evaluated macroscopically and by V. inaequalis-specific qPCR, levan-treated leaves showed a significant reduction of sporulation and V. inaequalis DNA in comparison to mock- and inulin-treated leaves, comparable to the levels in fosetyl-aluminum-treated leaves. Furthermore, we observed a significant reduction of in vitro mycelial growth of V. inaequalis on plates supplemented with levans when compared to controls, indicating a direct inhibition of fungal growth. Variations in endogenous sugar contents in the leaves were followed during priming and subsequent infection, revealing complex dynamics as a function of time and leaf ontogeny. Our data are discussed in view of the present theories on sugar signaling and fructan-based immunity, identifying areas for future research and highlighting the potential use of fructans in apple scab management in orchards.


Assuntos
Antifúngicos/farmacologia , Resistência à Doença , Frutanos/farmacologia , Fungos do Gênero Venturia/patogenicidade , Malus/microbiologia , Fungos do Gênero Venturia/efeitos dos fármacos , Fungos do Gênero Venturia/fisiologia , Malus/efeitos dos fármacos , Malus/imunologia , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/imunologia , Folhas de Planta/parasitologia , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/fisiologia
13.
Mycologia ; 112(4): 711-721, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32469692

RESUMO

Pecan scab, caused by Venturia effusa, is the most prevalent disease of pecan in the southeastern United States. Recent characterization of the mating type (MAT) distribution of V. effusa revealed that the MAT idiomorphs are in equilibrium at various spatial scales, indicative of regular sexual recombination. However, the occurrence of the sexual stage of V. effusa has never been observed, and the pathogen was previously considered to rely entirely on asexual reproduction. We were able to generate the sexual stage by pairing isolates of opposite mating types on oatmeal culture media. Cultures were incubated at 24 C for 2 mo to allow hyphae from isolates of each mating type to interact. Culture plates were then incubated at 4 C for 4 mo, after which immature pseudothecia were observed. Following exposure to a 12-h photoperiod for 2 wk at 24 C, asci and ascospores readily developed. Pseudothecium and ascospore production was optimal when incubated for 4 mo at 4 C. We utilized progeny from a cross of an albino isolate and wild-type (melanized) isolates to determine that recombination had occurred. Multilocus genotyping using 32 microsatellite markers confirmed that progeny were the result of recombination, which was further supported by segregation of mating types and culture pigmentation. Albino progeny were all confirmed to contain the same mutation in the polyketide synthase (PKS1) melanin biosynthesis gene as the albino parent. The results of this study demonstrate the heterothallic nature of V. effusa. The impact of determining the source of the overwintering ascostroma will aid in management decisions to reduce the primary inoculum in the disease cycle.


Assuntos
Carya/microbiologia , Fungos do Gênero Venturia/fisiologia , Doenças das Plantas/microbiologia , Fungos do Gênero Venturia/genética , Fungos do Gênero Venturia/crescimento & desenvolvimento , Genes Fúngicos Tipo Acasalamento/genética , Genótipo , Hifas/genética , Hifas/crescimento & desenvolvimento , Hifas/fisiologia , Melaninas/biossíntese , Melaninas/genética , Repetições de Microssatélites/genética , Mutação , Recombinação Genética , Esporos Fúngicos/genética , Esporos Fúngicos/crescimento & desenvolvimento , Esporos Fúngicos/fisiologia , Fatores de Tempo
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