?Quorum sensing? e biofilme como estrat?gias para a sele??o de Pseudomonas sp. promotoras de crescimento

• Autor(a) principal: Pinton, Rachel
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFRRJ
• Texto Completo: https://tede.ufrrj.br/jspui/handle/jspui/4188
• topic: Auto- indutores; Rizobact?rias; Promo??o de crescimento; Couve; Autoinducers; Rhizobacteria; Growth promotion; Kale; Agronomia

Due to the need of developing agricultural management practices that could bring lower environmental negative impacts, researches have been investigating biological components of agro ecosystems in order to reach higher productivity and sustainability. Therefore, the present study was conducted with the purpose of prospecting plant growth promotion rhizobacteria and parameters for their selection. There were isolated 127 strains of rhizobacteria from rhizoplane of lettuce, kale, arugula and parsley. The plants were cultivated in King B media, modified for Pseudomonas, and its morphological characterization was made. There were set assays to detect ALH (acil homoserina lactone) production, an auto inducer present in ?quorum sensing? systems of gram- negative bacteria, with Agrobacterium tumefaciens. Among the 112 strains evaluated, 14 (12.5%) resulted positive for AHL production. From the 91 strains evaluated for biofilm formation, 87 (95.5%) showed positive. Three experiments were conducted using kale to verify the rhizobacteria capacity in promoting plant growth. In the first experiment, there were tested: 2 isolated strains, 5 inoculate doses, and 4 inoculation methods. After 30 days, the material was collected and the following parameters were evaluated: shoot fresh weight; shoot dry weight, and root dry weight. There was no difference between strains; however, there was difference among the inoculation methods, with better results when seedlings received inoculate than in the seeds. In the second experiment, 7 strains were used; with 2 inoculate concentrations, and one moment of inoculation, at the 10th day after planting. The treatments for both experiments were placed in vases with 1kg of substrate (soil from A horizon of a Fragiudult). After 55 days the plants were collected and the following parameters evaluated: shoot fresh weight, shoot dry weight, and root dry weight. The plants inoculated with R142 strain showed increment of 40% in shoot fresh weight, and 55% in root dry weight. In the third experiment, the same 7 strains used in the second assay were inoculated; with 2 inoculate concentrations, and 2 inoculation periods. The parcels were set in Styrofoam containers for plants with the substrate PLANTMAX (EUCATEX). The plants were collected 24 days after planting and there was no difference between strains, but there were differences among inoculate concentration (10 9 was better than 10 7), and the results were better when inoculated at the 6th day than at the 12th. The obtained data allow us to conclude that the R142 strain was efficient in promoting growth in kale, the inoculate dosage 10 9 was most appropriated, and the inoculation must be performed on seedlings.