Effects of antagonistic Fusarium oxysporum on functional groups of indigenous bacteria in soil

Abstract Before planning the commercial use of microorganisms, genetically manipulated or not, in agricultural environments, their behavior and potential impact on soil ecosystems should be carefully studied as part of risk assessment. The influence of added inoculum of antagonistic Fusarium oxysporum strains, genetically manipulated (T26/6) or not (233/1) on nitrogen and carbon functional groups were evaluated in three soils from different sites at Albenga in Northwestern Italy, one natural and two other previously solarized, and in a fourth soil obtained from a site at Carignano (Northwestern Italy) with a 10-year-old poplar stand. There were no detectable effects of the antagonistic Fusarium strains on ammonifiers, ammonium oxidizers, nitrite oxidizers, nonsymbiotic anaerobic nitrogen fixers, nonsymbiotic aerobic nitrogen fixers and denitrifiers evaluated with the most probable number (MPN) method. Also, no effects were observed on amylolytic, proteolytic, cellulolyfc, pectolytic and total bacteria evaluated with the plate count (PC) method. Survival and population dynamics of the antagonistic Fusarium strains were monitored during the experiments, and a decline over time of the introduced microorganisms was assessed.