Rhizosphere bacteria from the Bolivian highlands improve drought tolerance in quinoa (Chenopodium quinoa Willd.)

Drought is one of the most destructive abiotic factors for agricultural production, causing considerable yield losses. Quinoa (Chenopodium quinoa Willd.) is cultivated worldwide in different environmental conditions due to its nutritional characteristics and ability to grow in harsh environments. This study aims to select drought stress tolerant rhizosphere bacteria from the Bolivian altiplano to evaluate their quinoa growth-promoting capacity, including in vitro germination, seedling growth under drought stress in greenhouse conditions and field studies.

Rhizosphere soil from the southern highlands of Bolivia was collected to isolate 164 drought-stress tolerant bacteria. From these, 28 strains were shown to produce indole acetic acid, and/or to possess nitrogen-fixing or phosphate solubilizing capacity under in vitro conditions. Furthermore, all strains were evaluated for improvement of in vitro quinoa seed germination. Based on these properties, nine bacterial strains were formulated in three different matrixes and evaluated for quinoa seedling growth promotion during drought stress in a 3-month greenhouse experiment. Three strains were shown to significantly (P < 0.05) increase root length of the quinoa seedlings. One strain was selected and shown to significantly (P < 0.05) increase leaf number in a field trial under semi-arid conditions in the southern altiplano in Bolivia. DNA sequencing and phylogenetic analyses of the 16S locus putatively identified the three strains with growth-promoting potential under drought stress as members of the genera Bacillus, Pseudomonas, and Serratia.

Microorganisms from the arid Bolivian altiplano constitute a potential biological source of bioinoculants to improve quinoa productivity and provide sustainable mitigation of climate change effects.