Rizobactérias produtoras de ácido indolacético como promotoras do crescimento de mudas micropropagadas de abacaxizeiro ‘brs imperial’

Abstract

ABSTRACT 1 = Given the negative environmental impact of artificial fertilizers and their increasing costs, the utilization of soil’s beneficial microorganisms such as rhizobacteria, because of its capability of association with roots, has been gaining attention for the low cost as well as for the easy production in artificial environments. These bacteria colonize the rhizosphere of plants and they have been studied to increment agricultural production for both plants growth and the biocontrol of phytopathogens. The production of micropropagated pineapple plantlets is a technique that is becoming more popular in the commercial market, however the use of this technique may be limited due to the high cost, mainly because of the long period of acclimatization. One of the alternatives to reduce this step may be the use of rhizobacteria with the capability of producing vegetal growth regulators. Considering this, the study aims to evaluate the effect of rhizobacteria in promoting the growth of micropropagated plants and pineapple plants. For this purpose, it was used plants derived from tissue culture. The samples were cultivated in vitro in commercial substrate, in which a solution containing the microorganism and kept under controlled conditions was added. After 45 days the samples were acclimatized and evaluated every 60 days up to 180 days. The results show that in the pre-acclimatization phase the bacteria had a positive effect on the plant growth, however in the acclimatization phase it was not as efficient. ABSTRACT 2 = The availability of quality plantlets has been one of the barriers to improve production and expand cultivated areas of pineapple. Thus, the micropropagation has been a strategy used to produce a large number of healthy plantlets, increasing or guaranteeing productivity of various crops. However, the pre-acclimatization step results in plants with low adaptation rates to the ex vitro conditions. Therefore, is required an acclimation step that for being long raises the plantlets cost. An alternative that has gained prominence is the use of plants growth promoting rhizobacteria, because they are capable of producing plant growth regulators. In this context, the objective of this study was to evaluate the effect of rhizobacteria in promoting growth of a pineapple variaty, both in the pre-acclimatization and in the ex vitro stage. In this regard, indoleacetic acid producing bacteria were selected after they had been added in test tubes containing the substrate for plants cultivation in vitro. The plants were produced in accordance with protocols that had been already established. After 60 days these plants were evaluated and the other plants were transplanted to a greenhouse where they were evaluated every 60 days for six months. The following variables were analyzed: height, D leaf length, number of leaves, fresh and dry weights of shoot and root, root length, number of stomata, photosynthetic rate, transpiration and stomatal conductance. According to the results, it was possible to verify that rhizobacteria isolates can promote plant growth in vitro in the pre-acclimatization phase. However, its effect on the ex vitro stage in greenhouses was not significant over time.