THE DEVELOPMENT OF AZOSPIRILLUM AS A COMMERCIAL INOCULANT FOR IMPROVING CROP YIELDS

Bacteria of the genus Azospirillum are nitrogen-fixing organisms that live in close association with plants in the rhizosphere. The Azospiri llum-plant association leads to the enhanced development and yield of different host plants under appropriate growth conditions. This increa se in yield is attributed mainly to an improvement in root development , an increase in the rate of water and mineral uptake by roots, and to a lesser extent, biological N-2 fixation, Worldwide data accumulated in the field over the past 20 years indicates that Azospirillum is cap able of promoting the yield of agriculturally important crops in diffe rent soils and climatic regions. A,brasilense shows both chemotaxis an d chemokinesis in response to temporal gradients of different chemoeff ectors, thereby increasing the chance of root-bacterial interactions, Phytohormones synthesized by Azospirillum influence the host root resp iration rate, metabolism and root proliferation and hence better the m ineral and water uptake in inoculated plants. Positive effects of comb ined inoculation with Rhizobium have been reported for different legum es and were related to the favorable influence of Azospirillum on the nodule number, plant development, dry weight, and N-2 fixation. Additi onally, A. brasilense produces the reserve material polyhydroxybutyrat e comprising up to 70% of the cell dry weight This substance has recei ved much attention recently as it can be extracted and formed into a b iodegradable thermoplastic