Azospirillum brasilense Az39 as a model of PGPR and field traceability

CONIGLIO, ANAHÍ; MORA, VERÓNICA; PUENTE, MARIANA; CASSÁN; FABRICIO

Microbial Probiotics for Agricultural Systems: Advances in agronomic use

Springer Nature

Año: 2019; p. 45 - 70

Azospirillum is one of the best studied genus of plant growth promotingrhizobacteria at present. These bacteria are able to colonize hundreds of plant speciesand significantly improve their growth, development and productivity underfield conditions. Besides nitrogen fixation, the most studied mechanism proposedfor Azospirillum to explain plant growth promotion of inoculated plants has beenrelated to its ability to produce several phytohormones, mainly auxins and particularlyindole-3-acetic acid. Although different capacities have been described toexplain the plant growth regulation by Azospirillum one single mechanism is notquite extensive to explain the full effect observed on inoculated plants. The bacterialmode of action is currently better explained as the result of additive and selectiveeffects. One of the most important achievements obtained thus far is the utilizationof azospirilla as commercial inoculants in approximately 7.0 million doses and 5.0million ha, mainly cultivated with cereal crops and legumes in South America.Different inoculation practices (farmer applied or industrial seed treatments, in-furrow,foliar or soil sprayed applications) have been developed and improved in thelast two decades for a wide range of crops, in field conditions. Particularly, thecombined inoculation of legumes with rhizobia and azospirilla, could over improvethe performance of the plants compared with a single inoculation, due to the complementarybiological processes of both microbes. The development and validationof specific novel methodologies for identification of A. brasilense, and particularlythe strain Az39 in both bio-products and inoculated samples (i.e. soil, rhizosphere,seeds or plant tissues) offer a precise tool to evaluate the functionality and traceability