Evaluation of the plant growth promoting properties under salt strees of bacteria isolated from Andean wetland

Abstract

Soil salinity is a severe problem affecting agricultural productivity in about 1/3rd of World?s irrigated lands. Our country presents 32 million hectares classified as Saline Soils and 53 million hectares as Sodic Soils, which means that we have 85 million hectares with salinity / sodicity problems.This problem has negative effects on the soil, such as the reduction of biological activity, the reduction in the availability of nutrients, the generation of changes in the structure, degradation and desertification of the land, which is limiting for the development of crops. Salinity changes the agronomically useful lands into unproductive areas, so that desertification of soils is a great concern and if we do not solve this problem we will soon face the situation of the lack of sufficient food in the world. Plant growth promoting bacteria (PGPB) are a useful alternative strategy for salt tolerance in plants. These bacteria are able to colonize the plant rhizosphere and confer beneficial effects by various direct and indirect mechanisms such as the production of indole-3-acetic acids (IAA), aminocyclopropane-1-carboxylate (ACC) deaminase, phosphate solubilization, among others. The use of halotolerant PGPB is environmental friendly and they are an inexpensive strategy for a better crop production and conservation in salt affected areas.The aim of this study was to evaluate the effect of saline stress in the promoting properties of PGPB isolated from Andean wetland. For this purpose, the tolerance to different NaCl concentrations (200, 700, 1000,1400,1700 and 2600mM) of thirteen strains was evaluated. Seven of them were able to grow at up to 1700mM of NaCl.The results of this research showed that the isolates retain its characteristics as promoting plant growth at 200 mM of NaCl. Under this saline stress they can produce IAA, ACC deaminase, N2-fixation and phosphate solubilization. At higher concentrations of NaCl (1400mM), only three strains maintained the ability to solubilize phosphate. Finally, the results showed that there are strains that are able to produce a greater concentration of AIA as the concentration of salt increases. These results encourage continued studies for the use of these microorganisms as an alternative to improve the response of crops affected by saline soils.