Prospecção de bactérias promotoras de crescimento de plantas de uma lagoa temporária do semiárido tropical

Abstract

Aquatic ecosystems are important in semi-arid regions, such as the Caatinga’s biome. In this region, the temporary lagoon is characterized by flood and dry phases. In the dry season, the temporary lagoon is capable of sustaining high productivity and biodiversity. The legume tree, Mimosa bimucronata, is common in these environments because it is adapted to soils with poor drainage We guess that there is a strong contribution of the microbial symbionts in the tolerance to stresses supported by these plants in the lagoon environment. The bioprospection of plant-growth promoting bacteria (PGPB) have never been carried out in the temporary lagoon in a tropical semiarid. Our aim was to isolate PGPB associated with the rhizosphere and the adjacent soil of M. bimucronata, and characterize the main mechanisms of plant-growth promotion, and to evaluate the biotechnological potential of the isolates to promote Zea mays L. development under 30% and 80% of microcosm capacity (MC). We analyzed 355 bacterial isolates, which were separated as follows: 131 rhizospheric soil isolates (ISR); 97 isolates from adjacent soil (ISA); 104 rhizospheric soil endospore isolates (IFESR) and 23 adjacent soil endospores forming isolates (IFESA). Based on the phenotypic characterization, we choose 98 isolates for subsequent analysis. In that amount (98), all of them produced indole-acetic acid AIA, 35 solubilized bi-basic calcium phosphate, none solubilized aluminium phosphate, 94 produced exopolysaccharides (EPS) and 63 produced biofilm. Based on the last mechanisms, the best 30 isolates were selected, and in this amount (30), 17 were able to fix nitrogen, 24 produced 1-carboxylic acid-1-aminocyclopropane (ACC) deaminase, 8 grown in medium up to 0.844 water activity (Aw) and 14 produced chitinases. In addition, the isolates that presented the highest values of plant-growth promotion mechanisms were selected to perform a microbial consortium, which was inoculated in an experiment using Z. mays L. Among the consortia, the highlight was the C4, with a 65% increase of the dry biomass of the root when compared to the control without inoculation (CSI). Isolates 70 and 38 showed significantly effect when compared to the other isolates, mainly for the increase of the total leaf area. Regarding the dry root biomass (BSR), the isolates 28-7 and 28-10 were significantly different when compared to the other treatments under conditions of 80% pot capacity. Isolate 43 significantly enhanced the stem length, BSPA and BSR, demonstrating the potential to promote Z. mays L growth. under water stress (30% CP). These results indicate the potential of the native isolates obtained from M. bimucronata in a temporary lagoon in a tropical semiarid region for corn growth.