Caracterização de isolados de Streptomyces spp. como rizobactérias promotoras de crescimento e de resistência à Pectobacterium carotovorum subsp. brasiliensis em plantas de Solanum lycopersicum (L.)

• Autor(a) principal: Dias, Maila Pacheco
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da PUC_RS
• Texto Completo: http://tede2.pucrs.br/tede2/handle/tede/7325
• topic: Actinomycetes; Defesa Vegetal; Pectobacterium spp.; PGPR; Tomateiro; CIENCIAS BIOLOGICAS::BIOLOGIA GERAL

Solanum lycopersicum L., tomato, is an herbaceous plant belonging to the Solanaceae family. Its fruits are consumed worldwide, reaching the world production of 160 million tons per year. In Brazil, it is the second vegetable in economic importance. However, the tomato is attacked by numerous diseases that lead to loss of production and /or poor quality of the fruit, such as the hollow stem, the disease caused by Pectobacterium spp. Due to the large number of diseases caused by plant pathogens, the tomato is a culture in which a significant amount of agrochemicals is used. Therefore, this species is among the vegetables with the greatest amount of residual pesticides. Under these circumstances, it is essential to develop sustainable plant defense techniques in order to reduce the use of agrochemicals. Then, changes in plant metabolism related to defense must be understood so that new strategies and new products can be developed. Disease control using soil microorganisms has been considered as an alternative, since the rhizobacteria, in addition to promoting plant growth, may induce resistance as the result of activation of the natural plant defenses. These, calls plant growth promoting rhizobacteria (PGPR), has been explored for their biofertilizers, biopesticides and phyto-stimulating abilities. The aims of this study were to characterize biochemically the Streptomyces spp. isolates, to determine the antagonism against Pectobacterium carotovorum subsp. brasiliensis (Pcb), to determine the ability of Streptomyces spp. on promoting growth of tomato plants and to evaluate the modulation of the defense-related metabolism of tomato plants when treated with Streptomyces spp. The possible influence of Streptomyces spp. on reducing soft rot disease in tomato plants was also evaluated. Biochemical characterization was evaluated through the ability of Streptomyces spp. on producing siderophores, solubilizing phosphate, and activity of amylase and lipase, as well as volatile organic compounds (VOC) production. Antagonism of Streptomyces spp. against Pcb was determined by dual-culture method and I-plate for VOC effect analysis. Plant growth promotion was evaluated through VOC emission and by direct interaction with Streptomyces spp. isolates (PM1, PM3, PM4, PM5, PM6 e PM9). Enzymes related to plant defense were colorimetric analyzed in plants treated with isolates of Streptomyces spp. Evaluation of soft rot disease was performed on plants treated with Streptomyces spp. and challenged with Pcb through the area under the disease progression curve (AUDPC) and plant mortality. Isolates of Streptomyces spp. displayed characteristics of PGPR and 32 volatile compounds were identified from the different isolates. PM3 was the isolate showing efficient antagonism against Pcb. Most of the isolates promoted increase of root and shoot length of tomato plants by VOC although PM5 was efficient on promoting growth by direct interaction with Streptomyces spp. Treatment with Streptomyces spp. modulated the activity of defense-related enzymes and decrease incidence of soft rot disease.