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| Author(s): |
Daniele Bussioli Alves Corrêa
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia |
| Defense date: | 2015-07-24 |
| Examining board members: |
Suzete Aparecida Lanza Destéfano;
Fabiana Fantinatti Garboggini;
Ivan Paulo Bedendo;
Alessandra Alves de Souza;
Welington Luiz de Araújo
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| Advisor: | Suzete Aparecida Lanza Destéfano |
| Abstract | |
Potato scab is a widespread disease in growing areas in Brazil, becoming a limiting factor in potato production. This disease affects potato quality due to injuries on the tuber surface decreasing its market value or precluding its commercialization. Several species of the genus Streptomyces causing potato scab are known and the survey of pathogenic species present in the Brazilian producing areas is the most important factor for performing management measures. This study aimed to characterize 57 strains of Streptomyces, considered possible new species associated with potato scab in Brazil, through polyphasic taxonomy. The morphological, biochemical, pathogenic (nec1, tomA and txtAB genes and in vitro pathogenicity tests on radishes and potatoes) and molecular characterization (species-specific primers for S. acidiscabies, S. scabiei and S. turgidiscabies, PCR-RFLP of atpD gene, multilocus sequence analysis of atpD, gyrB, recA, rpoB and trpB genes and 16S rRNA gene sequence analysis) of the strains were performed. Using PCR-RFLP of atpD gene technique and sequence analysis of atpD and rpoB genes, the strains were initially separated into 20 genetic groups (G1 to G20). These groups showed high heterogeneity in their spore chains morphology, pigment production and the appearance and color of the colonies and spores, as well as the utilization of different carbon sources. From a total of 57 strains evaluated, 24 (35.3%) showed presence of the three pathogenicity genes, six (8.8%) showed no amplification of the genes and 38 (55.9%) showed absence of one or more genes. All strains were pathogenic on radish causing symptoms of necrosis, radial swelling and/or stunting of shoot and roots, however, they showed differences in virulence level. The most virulent strains were evaluated in pathogenicity test on potato tubers slices and the aggressiveness of the strains, determined by the extent and depth of necrosis, was dependent on the cultivar of potato used, and all evaluated varieties were susceptible. The phylogenetic relationship of the strains has been established with respect to the main species of plant pathogenic Streptomyces and most groups were allocated in different branches and/or with low sequence similarity values. G11 group was closely related to S. scabiei and its genomospecies and G7 was allocated with S. turgidiscabies/S. reticuliscabiei, but they showed no amplification in experiments using species-specific primers and different morphological features were observed. The molecular data, associated with morphological, biochemical and pathogenic characteristics of the strains, allowed confirmation that these genetic groups represent at least 34 new species of phytopathogenic Streptomyces in Brazil. The polymorphisms in the atpD gene sequences allowed the development of species-specific primers for S. caviscabies/S. setonii (Cavis1F/Cavis4R) and S. scabiei (ScADF2/ScADR1). The specificity of these primers was confirmed by amplification experiments using DNA from other Streptomyces species causing potato scab. Sensitivity level of the PCR technique using the Cavis1F/Cavis4R primers was 0.1 pg. Further, in AFLP analyzes, E21/M16 primers set was selected as molecular marker for taxonomic studies within the group of plant pathogenic species of Streptomyces (AU) | |
| FAPESP's process: | 11/02994-8 - Identification of new species of Streptomyces associated to potato scab in Brasil |
| Grantee: | Daniele Bussioli Alves Corrêa |
| Support Opportunities: | Scholarships in Brazil - Doctorate |