Monitoring the persistence of a genetically modified strain of the diazotroph Azorhizobium caulinodans in the rhizosphere of wheat (Triticum aestivum L.)

Abstract

A protocol was developed to monitor persistence and spread of a genetically modified strain of the growth
promoting diazotroph Azorhizobium caulinodans used to inoculate field grown wheat. The protocol was used to
identify an endogluconase(egl) overproducing strain of A. caulinodansre-isolated from inoculated soils. A
detection limit of 2500 cfu/g and 108
–1010CFU/g of soil was determined using the BIOLOG®
fingerprinting
method and PCR technique, respectively. Since none of the tested samples were positive for the bacteria or the
Egl 1 gene construct, it was concluded that A. caulinodans ORS 571 pGV910-C1 did not persist or spread in any
of the tested field locations. This result may be due to low soil temperatures and competition of indigenous
microorganisms: environmental factors that were not favorable for the diazotroph to thrive in the test locations.
The application of different inoculation methodologies, as well as the study of other rhizobial genera for the
inoculation of wheat in further experiments, is strongly recommended.