Influence of transgenic T4-lysozyme-producing potato plants on potentially beneficial plant-associated bacteria

Abstract

A field release of genetically engineered potato plants that produce bacteriophage T4‐lysozyme for enhanced bacterial resistance was monitored for changes in plant‐associated bacterial populations, in the functions of potentially beneficial bacteria and in the diversity of antagonistic bacterial species. These parameters have been analyzed for two T4‐lysozyme‐expressing lines, a transgenic control and a non‐transgenic line, over a period of 2 years at different stages of plant development and at two different locations. Two microenvironments, the rhizo‐ and geocaulosphere, were investigated. No significant differences in aerobic plate counts were observed between the four plant lines. In addition, no significant differences in the functions of potentially beneficial bacteria (percentage of auxin [indole‐3‐acetic acid=IAA]‐producing isolates) and antagonistic bacteria (antagonists to Erwinia carotovora and Verticillium dahliae) were found. The diversity of antagonistic species isolated from each plant line and microenvironment was investigated to determine if the diversity and composition of potentially beneficial bacteria were influenced. Altogether, 28 different potato‐associated species with antagonistic effects to phytopathogens were detected. Antagonistic strains of seven species were found only on control plants. The observed effect was minor relative to the natural variability observed during the monitoring period. This is the first study including plant‐associated bacteria responsible for plant growth and health and provides an example for performing risk assessment studies for transgenic plants under a variety of environmental conditions.

Plant-driven selection of microbes

“…However, in both microenvironments (rhizosphere and geocaulosphere) no statistically significant Fig. 2 Selective enrichments of antagonistic populations in the rhizosphere according to results obtained in a six-year field trial with Verticillium host plants (Berg et al , 2005 differences between transgenic and non transgenic plants were found in the following parameters: (i) the abundances of bacteria, (ii) the percentage of auxinproducing bacteria, (iii) the percentage of antagonistic bacteria, and (iv) on the diversity of bacterial antagonists on genotypic and phenotypic level (Lottmann and Berg 2001;Lottmann et al 1999;Lottmann et al 2000). In an additional approach, rifampicin resistant mutants of two antagonistic plant-associated bacteria were used for seed tuber inoculation of transgenic and nontransgenic potato lines.…”

Risikofolgeabschätzung für den Einsatz mikrobieller Antagonisten: Gibt es Effekte auf Nichtzielorganismen?

“…Die Applikation Rifampicin-resistenter Spontanmutanten der Biokontrollstämme zählt zu den gän-gigsten Methoden, um die Populationsdynamik inokulierter Stämme zu beobachten (Lottmann et al 1999;Viebahn et al 2005). Durch die Entwicklung einer entsprechend spezifischen Realtime-PCR kann die Populationsdynamik der applizierten BCA-Stämme noch exakter und auch unabhängig von der Verfügbarkeit Antibiotika-resistenter Mutanten untersucht werden.…”

Transgenic tobacco revealing altered bacterial diversity in the rhizosphere during early plant development

“…These interactions may be very sensitive to fluctuations in environmental factors, like the presence of specific microorganisms (Andreote et al 2004) or the cultivation of different species of plants (Salles et al 2004). In this scenario, the possibility that genetic modification of plants causes shifts in the microbial communities should be considered (Lottmann et al 1999;Heuer and Smalla 1999;Schmalenberger and Tebbe 2002;Gyamfi et al 2002;Baumgarte and Tebbe 2005). Hence, microbial communities could be used as indicators of environmental impact caused by the transgenic plants cultivation.…”