Protocol for the Quality Control of Azospirillum Spp. Inoculants

Azospirillum has been one of the most studied genera of plant growth promoting rhizobacteria (PGPR) worldwide over the past 50 years. The use of these microorganisms in agriculture practices has been adopted due to their ability to associate in rhizospheric, epiphytic, or endophytic ways with roots and promote whole plant growth or crop productivity. The biological treatment of seeds (inoculation) in more than a hundred species of economic or ecological interest has become a common practice in many countries. In Argentina, the Az39 strain of Azospirillum brasilense, belonging to the Culture Collection of the Instituto de Microbiologia y Zoologia Agricola (IMYZA) of INTA Castelar, was selected in the 1980s after an intensive program to isolate and identify microorganisms for agriculture, according to their agronomic behavior. Since then, its ability to cover the premise for which it was selected has determined that Az39 is largely adopted by inoculant companies in Argentina with the aim of producing biological products for the treatment of several crops. In this chapter, those methods developed and standardized by the network Red de Control de Calidad de Inoculantes (REDCAI) of the Asociacion Argentina de Microbiologia (AAM) have been adapted as a guide for the quantification of Azospirillum spp. and the detection of contaminating microorganisms in biological products, as two of the most basic and important quality control parameters of inoculants.