Abstract
The high Andean plateau of Peru is known to suffer harsh environmental conditions. Acidic soils containing high amount of heavy metals due to mining activities and withstanding very low temperatures affect agricultural activities by diminishing crop quality and yield. In this context, plant growth promoting rhizobacteria (PGPR) adapted to low temperatures and tolerant to heavy metals can be considered as an environment-friendly biological alternative for andean crop management. The aim of this work was to select and characterize psychrotrophic PGPR isolated from the rhizosphere of maca (Lepidium meyenii Walp.) a traditional andean food crop. A total of 44 psychrotrophic strains isolated from 3 areas located in the Bombon plateu of Junin-Peru were tested for their PGPR characteristics like indole acetic acid (IAA) production, phosphate solubilization and for their ability to improve seed germination. In addition, their capacity to grow in the presence of heavy metals like cadmium (Cd), lead (Pb), cobalt (Co) and mercury (Hg) was tested. Of the total number of strains tested, 12 were positive for IAA production at 22 °C, 8 at 12 °C and 16 at 6 °C. Phosphate solubilization activities were higher at 12 °C and 6 °C than at 22 °C. Red clover plant assays showed that 16 strains were capable to improve seed germination at 22 °C and 4 at 12 °C. Moreover, 11 strains showed tolerance to Cd and Pb at varying concentrations. This study highlight the importance of obtaining PGPRs to be used in high andean plateu crops that are exposed to low temperatures and presence of heavy metals on soil.
Highlights
The Bombon plateu is located on the high Andes of Junin, Peru
A total of 44 psychrotrophic strains isolated from 3 areas located in the Bombon plateu of Junin-Peru were tested for their plant growth promoting rhizobacteria (PGPR) characteristics like indole acetic acid (IAA) production, phosphate solubilization and for their ability to improve seed germination
Low temperatures and soil contamination are common problems which affect farmers of this region, together, these two factors diminish the yield of economically important crops such as maca (Lepidium meyenii Walp.) a Brassicaceae whose roots are used as food
Summary
The Bombon plateu is located on the high Andes of Junin, Peru. It is known for its dry climate, extremely low temperatures and acidic soils (pH < 5) with relatively high concentration of toxic heavy metals. Plant growth promoting rhizobacteria (PGPR) are considered of great importance due to their ability to solubilize inorganic phosphates, transport iron, produce phytohormones like indole acetic acid (IAA) [2] and fix atmospheric nitrogen [3]. These attributes allow those microbes to induce plant growth and development. PGPRs can be considered as a biological alternative to improve the yield and growth of crops growing in the high Andes under harsh environmental conditions In this context, the aims of this research were to select and characterize psychrotrophic bacteria isolated from maca rhizosphere by testing their plant growth promoting ability and tolerance to heavy metals. There are only few studies that explore the application of biofertilizers based on psychotrophic bacteria with PGPR characteristics, adapted to the harsh climatic conditions of the high Andean region and with potential to bioremediate soils contaminated with heavy metals
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