INOCULANTS OF AZOSPIRILLUM-BRASILENSE - BIOMASS PRODUCTION, SURVIVAL AND GROWTH PROMOTION OF SETARIA-ITALICA AND ZEA-MAYS

We grew Azospirillum brasilense biomass in fed-batch culture for 28 h using succinic acid as a C source and liquid NH3 as N source. Viable c ell concentration reached 1-3 x 10(10) CFU ml(-1) after 28 h. Ground o r granular peat, serving as carriers for the bacteria, maintained the highest number of A. brasilense compared to vermiculite, talcum powder , basalt granules or bentonite. A. brasilense viable counts declined f rom about 10(10) CFU g(-1) peat to 10(5)-10(6) CFU g(-1) peat after 6 months. A pot system for evaluating the effect of A. brasilense inocul ants on plant growth in greenhouses demonstrated that application of p eat-carrier containing 10(8) CFU g(-1) peat, significantly increased p anicle length and dry weight of Setaria italica and ear and kernel wei ght of maize (Zea mays L). Highest growth promotion effects on maize w ere observed when using A. brasilense cells containing 40% polyhydroxy butyrate (PHB) and by applying the pear inoculant 2 cm below the maize seed.