Diversidade populacional de Ralstonia solanacearum em pimentão no Estado de Pernambuco e controle da murcha bacteriana

• Autor(a) principal: GARCIA, Alessandra de Lima
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFRPE
• Texto Completo: http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/6479
• topic: Ralstonia solanacearum; Murcha bacteriana; Controle de doença; Pimentão; FITOSSANIDADE::FITOPATOLOGIA

Bacterial wilt caused by Ralstonia solanacearum is important worldwide mainly due to the great losses it causes in a large and diverse host range and its difficult control. In Brazil, bacterial wilt in solanaceous mainly occurs in Northeastern, North and Southeastern regions and may cause 100% losses. In the state of Pernambuco, bacterial wilt may be destructive to bell pepper in the producing counties of Mesorregiões Agreste and Mata. This work aimed: (i) to analyze 78 bacterial strains obtained from wilted bell pepper plants at producing counties of the state of Pernambuco, Brasil identified as R. solanacearum by multiplex PCR with reference to biochemical, virulence, molecular and genotypic diversity, and (ii) to evaluated the commercial disinfectant product Kilol- L® and its components, the ascorbic, citric and lactic acids for disease control. In the first paper the biochemical analysis characterized biovars and biotypes. The virulence studies included analysis of disease severity, area under disease progress curve and incubation period after inoculation of bell pepper, tomato, eggplant and tobacco plants by root wounding and inoculum drenching. The molecular characterization was performed by multiplex PCR, Rep-PCR and ISSR. The genotypic diversity was studied considering the number of observed genotypes and how they distributed by population differing in richness, evenness and diversity. There was predominance (97. 44%) of strains belonging to biovar 3, biotype 8 and phylotype I, but also were found biovar 1, biotypes 3 and 6, and phylotype II. The multivariate analysis performed with UPGMA and using the pool of the virulence data permitted the separation of R. solanacearum strains in 12 similarity groups, pointing out high variability, with strains of different areas in the same group. The Rep-PCR with REP and BOX markers and ISSR showed similarity among most of the R. solanacearum strains, although they did not separate strains belonging to biovars, biotypes, phylotypes, or from distinct areas. The genotypic diversity analysis evidenced moderate diversity in the total population but high variability among strains from the same county. In the second paper, initially it was evaluated in vitro the sensitivity of R. solanacearum to Kilol-L® (0.4, 0.8, 2.5, 5, 10 and 100%) and its components the ascorbic, citric and lactic acids (0.25, 0.5, 1, 2.5, 5 and 10%). After the phytotoxicity test in bell pepper cv. Atlantis, the concentrations Kilol-L® 0.8% and ascorbic, citric and lactic acids 1% were selected and tested for bacterial wilt severity reduction, by spraying of shoots or immersion of roots both using 21days-old plants. Ralstonia solanacearum strain CGH41 was inoculated by wounding roots and pouring inoculum. According to the analysis of the inhibition halos R. solanacearum showed high sensitivity to lactic acid 10% and medium sensitivity to lactic acid 5 and 2.5 %, ascorbic and citric acids 10% and Kilol-L® 100%. The immersion of roots in lactic acid 1% controlled bell pepper bacterial wilt by 100% however without difference from ascorbic and citric acids 1%. The method of root immersion differed from the shoot spray for most of the treatments. The unique significant effect of Kilol-L® was to elevate de incubation period when applied by shoot spraying.