Eurypsychrophilic Pseudomonas spp. isolated from Venezuelan tropical glaciers as promoters of wheat growth and biocontrol agents of plant pathogens at low temperatures

Abstract

Andean tropical glaciers are disappearing rapidly and, consequently, the microbes immured in these frozen environments will be lost forever. Some of these microbes are thought to be potentially useful to develop biotechnological products or processes. Among these microbes, plant-growth promoting (PGP) bacteria have been proposed as valuable tools to develop cold-active biofertilizers and/or biopesticides. A few years ago, we hypothesized that bacteria immured within glacial ice could be effective in promoting plant growth and/or in protecting plants from pathogen infection, at low temperatures. In this study, we aimed at testing some of these traits, with a suitable plant model (Triticum aestivum). In the present study, from a collection of bacteria isolated from Venezuelan tropical glaciers, we selected four Pseudomonas isolates and tested their PGP effects at low temperatures, both in vitro and on wheat plantlets. The isolates grew well over a wide range of low temperatures and were thus classified as eurypsychrophilic. They also displayed well-known PGP traits: solubilization of inorganic phosphates, production of phytohormones and antagonism against a phytopathogenic oomycete (Pythium ultimum). Inoculation of T. aestivum seeds with some of these Pseudomonas spp. isolates promoted a significant elongation of their roots and shoots. This was also the case when wheat plantlets were grown in sterile sand or soil, at 15 °C. Inoculation of wheat seeds also protected plantlets against the damage caused by P. ultimum. Together, our results suggest that some of these Pseudomonas spp. isolates could act as cold-active biofertilizers and/or biocontrol agents.