Field releses of genetically modified Pseudomonas fluorescens and Azospirillum brasilense ,

From 1994 to 1999 several strains of genetically modified Pseudomonas fluorescens and Azospirillum brasilense were constructed, evaluated for their performance as biological control agents and phytostimulators, respectively, and finally released in the field, taking advantage of concomitant field releases of GM rhizobia. In 1994, 1995 and 1998 the strains to be released were modified by the insertion of suitable marker genes, other than antibiotic resistance. This was performed in order to evaluate possible ecological effect of the genetic modification per se, along with the effect of the strains on the target crops. In 1999 the modifications involved also functional genes. A gusA tagged P. fluorescens F113R pCUGP, modified for improved production of DAPG (a natural metabolite with antifungal activity), and luc tagged A. brasilense strains modified for altered production of indole-3-acetic acid, have been released as biocontrol agent against rhizomania in sugar beet and phytostimulator for sorghum, respectively. A total of 15 field releases were performed in 6 years. The agronomic performances as well as ecological effects on resident culturable microbial populations, were evaluated.