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Previous issue date: 2014-08-22 / Fundação de Amparo à Pesquisa do Estado de Minas Gerais / A murcha bacteriana, causada por Ralstonia solanacearum, causa perdas diretas e indiretas na produção de várias culturas. Apesar de o uso de variedades resistentes ser a melhor opção para o manejo da doença, nãoraro encontram-se relatos de suplantação da resistência. O primeiro relato de murcha bacteriana no Brasil é antigo, porém pouco se conhece sobre os biovares, filotipos, sequevares e variabilidade genética do patógeno. Por essa razão realizou-se o presente estudo. Isolados brasileiros de R.solanacearum foram caracterizados como biovar 1, 2 e 3, filotipo II, que está disperso por todo o país e filotipo I, que encontra-se predominantemente na região Norte. Sete sequevares foram identificados: 1, 4, 18, 27, 28, 41 e 50. Além disso, nós classificamos quatro novos sequevares no filotipo IIB como sequevar 53, 54, 55 e 56. Inicialmente, utilizou-se rep-PCR para estimar a variabilidade. Obtiveram- se 282 haplótipos. Uma possível explicação para o alto número de haplótipos é a ocorrência de recombinação. Isolados das regiões Sul, Sudeste e Central formam um grande grupo genético, enquanto aqueles das regiões Norte e Nordeste formam outro grupo. Tal fato evidencia fluxo gênico entre essas regiões, provavelmente mediado pelo transporte de tubérculos e mudas contaminadas. Detectou-se diferenciação genética entre isolados de tomate e batata coletados na região Sul-Sudeste-Central. Os mecanismos evolutivos foram parametrizados a partir de análises de genealogia de genes por processo coalescente utilizando sequências parciais de sete genes. Detectou- se evidência de subdivisão dos filotipos I, IIA e IIB, mas não subdivisão por hospedeiro. O fluxo gênico é mais intenso da região Sul para a região Norte. O filotipo II é uma linhagem ancestral que teve origem no Brasil e o filotipo I foi recentemente introduzido, possivelmente por ação antropogênica. O filotipo IIA deu origem ao filotipo IIB e essa diferenciação ocorreu possivelmente devido a fatores ecológicos que precisam ser eBacterial wilt, caused by the Ralstonia solanacearum, cause direct and indirect losses in several crops. Planting of resistant varieties is the best option for disease management, but reports of resistance breakdown are commonly found in the literature. Although many years have passed after the first report of this pathogen in Brazil, information on biovars, phylotypes, sequevars and genetic variability of the pathogen is scarce. In the present study isolates were characterized as biovar 1, 2 and 3. Phylotype II is spread throughout Brazil and phylotype I is predominantly found in the North. Seven sequevars were identified: 1, 4, 18, 27, 28, 41 and 50. Moreover, we classified four new sequevars in the phylotype IIB as sequevar 53, 54, 55 and 56. Initially, we used rep-PCR to estimate the variability of the pathogen and 282 haplotypes were obtained. The high number of haplotypes could be due to the occurrence of recombination. Isolates of the South/Southeast/Central regions formed a genetically related cluster. Isolates from the North/Northeast regions formed another group. Gene flow occurs through the transportation of contaminated tubers and seedlings. Genetic differentiation was detected among isolates from tomato and potato collected in the South/Central/Southeast regions. In addition, gene genealogies based on the coalescent process were used to infer about evolutionary mechanisms. We detected evidence of subdivision of phylotypes I, IIA and IIB, but no subdivision by hosts. The gene flow is predominantly from the southern to the northern regions. We confirmed that phylotype II is an ancestral lineage that originated in Brazil and probably phylotype I was recently introduced by anthropogenic actions. Phylotype IIA originated phylotype IIB and this difference was probably due to ecological factors that need to be studied in more detail. Mutation, migration, recombination and selection occur in the population of R. solanacearum in Brazil, however mutation is more important than recombination. We conclude that the use of resistant varieties is a major challenge in all regions and hosts.
studados com mais detalhes futuramente. Detectaram-se evidências de mutação, migração, recombinação e seleção na população de R.solanacearum no Brasil. Entretanto, mutação é mais importante que recombinação. Conclui-se que a utilização de variedades resistentes será uma grande desafio em todas regiões e hospedeiros. / Bacterial wilt, caused by the Ralstonia solanacearum, cause direct and indirect losses in several crops. Planting of resistant varieties is the best option for disease management, but reports of resistance breakdown are commonly found in the literature. Although many years have passed after the first report of this pathogen in Brazil, information on biovars, phylotypes, sequevars and genetic variability of the pathogen is scarce. In the present study isolates were characterized as biovar 1, 2 and 3. Phylotype II is spread throughout Brazil and phylotype I is predominantly found in the North. Seven sequevars were identified: 1, 4, 18, 27, 28, 41 and 50. Moreover, we classified four new sequevars in the phylotype IIB as sequevar 53, 54, 55 and 56. Initially, we used rep-PCR to estimate the variability of the pathogen and 282 haplotypes were obtained. The high number of haplotypes could be due to the occurrence of recombination. Isolates of the South/Southeast/Central regions formed a genetically related cluster. Isolates from the North/Northeast regions formed another group. Gene flow occurs through the transportation of contaminated tubers and seedlings. Genetic differentiation was detected among isolates from tomato and potato collected in the South/Central/Southeast regions. In addition, gene genealogies based on the coalescent process were used to infer about evolutionary mechanisms. We detected evidence of subdivision of phylotypes I, IIA and IIB, but no subdivision by hosts. The gene flow is predominantly from the southern to the northern regions. We confirmed that phylotype II is an ancestral lineage that originated in Brazil and probably phylotype I was recently introduced by anthropogenic actions. Phylotype IIA originated phylotype IIB and this difference was probably due to ecological factors that need to be studied in more detail. Mutation, migration, recombination and selection occur in the population of R. solanacearum in Brazil, however mutation is more important than recombination. We conclude that the use of resistant varieties is a major challenge in all regions and hosts.
| Identifer | oai:union.ndltd.org:IBICT/oai:localhost:123456789/6315 |
| Date | 22 August 2014 |
| Creators | Santiago, Thaís Ribeiro |
| Contributors | Lopes, Carlos Alberto, Oliveira, José Rogério de, Mizubuti, Eduardo Seiti Gomide |
| Publisher | Universidade Federal de Viçosa |
| Source Sets | IBICT Brazilian ETDs |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/doctoralThesis |
| Source | reponame:Repositório Institucional da UFV, instname:Universidade Federal de Viçosa, instacron:UFV |
| Rights | info:eu-repo/semantics/openAccess |
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