Rizobactérias promotoras do crescimento de mudas de Theobroma cacao L.

Abstract

The agricultural production is influenced by a series of factors, such as microbial activity, devaluing the quality of products or causing losses. However, microorganisms can be use in agricultural production. An example of significant contribution is given by the use of fixative bacteria of nitrogen in soy and sugar-cane, but other bacteria can also contribute to the increase of vegetable production, as by example, the Plant-Growth-Promoting-Rhizobacteria (PGPR) in the commercial commercial production of seedlings. Although the mechanisms of action of the PGPR still are going to be better cleared, already is consensus that the production of regulating of the growth vegetable, as Indol Acetic Acid (IAA), and the inhibition of the action of patógenos, be for competition or by straight antagonism due to secretion of antibiotics, are two examples of possible mechanisms involved in the promotion of the growth vegetable. The nutrition of the plants is another example of possible mechanism of advantage. The most classic example of that is the solubilization of mineral phosphates. Considering the fact then, in 2002, the federal government demonstrated interest in promoting the recuperation of the cacao tilling stimulating the adoption of resistant variety to the witch´s broon (Crinipellis perniciosa (Stahel) Singer), was prepared a project with objective to isolate PGPR be having potential for application in the process of commercial production of seedlings of cocoa tree. The justification at the time, was it of that the results might favor the development of process of production, of seedlings of cocoa tree with quality in less time in nursery, reducing so the costs of production. The screening tests were executed using seedlings of cocoa tree like plants traps for capture of PGPR. The seedlings of cocoa tree were cultivated in substrates formed from samples of soils collected in five sites representing three different ecosystems with historical of cocoa cultivation. A total of two hundred an ninety four (294) isolated was obtained from capture tests, of which eighteen (18) ones were identified as producers of quitinases, four (4) as producer of phosphatases, and five (5) as producers of AIA. Eleven (11) isolated were used in two tests to checking their effects on seedlings of cocoa tree. However, none presented effects of promotions of growth statistically add to ten per cent (10%) was observed when compared to seedlings cultivated without inoculation. Though, isolated with pointed characteristics related whit capacity of promotion of growth have also been tested, significant results were not obtained to indicated a potential of commercial use. However, is possible to conclude that the use of PGPR in the process of commercial production of seedlings of cocoa may be viable, but identification of isolated with this potential depends on more detailed works.