EFFECT OF THE ASSOCIATION OF Rhizobium etli - Phaseolus vulgaris L. ON THE PLANT GROWTH AND THE PREFERENCE OF Bemisia tabaci

Abstract

Background. Cascading effects through tritrophic interactions (microorganisms, plants, herbivores) are basic components in ecosystems that are often influenced by force from bottom up or top down. One of the most important cases is the fixation of nitrogen through growth promoting bacteria of PGPR plants, which can alter the cascading effects in superior trophic interactions, through physical and chemical changes in the plants. Bacteria as growth promoters not only participate in growth, they are also considered the best biological control agents since they have the potential to suppress pathogenic microorganisms and induce systemic resistance against pest insects. Objective. This study aims to evaluate the contribution of the inoculation of the Rhizobium etli nitrogen fixing bacteria in the growth of Phaseolus vulgaris and the oviposition and preference of Bemisia tabaci. Methodology. Bean plants were established on sterilized soil, two batches of plants were formed: plants inoculated with R. etli and non-inoculated (control) plants. In the first experiment, were measured plant growth and characteristics related to defense against phytophages. In the second experiment, the preference and oviposition of Bemisia tabaci was evaluated by free choice and non-choice tests. Results. Inoculation with R. etli favored some specific growth characteristics, such as leaf area and root length. Phytophagous defense variables, as well as adult preference and oviposition of B. tabaci were not different between inoculated and non-inoculated plants. Implications. The main limitation of the use of PGPR depends on the type of soil and the variety of beans, so this inoculant could also be tested in cases where it has been proven that there is low natural colonization of Rhizobium in Phaseolus lunatus L. during its growth. Conclusion. Inoculation increased some growth variables; however, it did not affect the oviposition and preference of Bemisia tabaci. Additional work is required to assess the effects of factors, such as bean variety, synergy among rhizobacteria species, natural resistance of the host plant, environmental conditions and soil types.