High-throughput bioassaying for the characterization of microbial-based biostimulants mode of action - a case study of Azospirillum

DE DIEGO, NURIA; LOPEZ, GASTON; SPÍCHAL LUKÁS; UGENA LYDIA; CASSAN, FABRICIO; ADELA HÝLOVÁ; MORA VERÓNICA

Congreso; Biostimulants World Congress; 2019

Biostimulants are products of biological origin that improve germination, growth, nutrient uptake and stress tolerance in plants. The majority of biostimulants have an undefined composition made by complex mixtures of compounds. As complex multicomponent product is very difficult to determine their mode od action, so they may be tested in wide range of concentractions and intensities of stresses. Here we present a screening pipeline for characterization of microbial-based biostimulatns using Azospirillum spp. (Az39) as example.A wild-type and two mutants strains (ipdC or Hpc-) were tested fot the inoculation effect on the germination and rosette growth caacity in Arabidopsis under salinity using multi-trait high-throughput screening method. The effect on transgenic Arabidopsis plants harboning hormone responsive reporters was also evaluated. We proved that the inoculation with Azospirillum spp. is a good biotechnological approach to improve plant growth and to cope with some stress conditions as salinity. This responde is mediate by activating the plant response through auxinas, but not cytokinins or abscisic acid. However, blocking the auxin signalling in the bacteria is not enough to remove the plant growth promotion. Azospirillum spp. also produce other compounds such as polyamines that crosstalk with phytohormones regulating many biological processes in plants. Thus, the interaction of the different compounds presented n the biostimulants is essential for their performance and it cannot be attributed to the activity of the individual components. However, the use of high-throughput screening systems can accelerate their characterizatin, giving additional information about the doses to be applied and plant growth conditions.