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

A field release of genetically engineered potato plants that produce bacter iophage T4-lysozyme for enhanced bacterial resistance was monitored for cha nges in plant-associated bacterial populations, in the functions of potenti ally beneficial bacteria and in the diversity of antagonistic bacterial spe cies. These parameters have been analyzed for two T4-lysozyme-expressing li nes, a transgenic control and a non-transgenic line, over a period of 2 yea rs at different stages of plant development and at two different locations. Two microenvironments, the rhizo- and geocaulosphere, were investigated, N o 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 a cid = IAA]-producing isolates) and antagonistic bacteria (antagonists to Er winia carotovora and Verticillium dahliae) were found. The diversity of ant agonistic species isolated from each plant line and microenvironment was in vestigated to determine if the diversity and composition of potentially ben eficial bacteria were influenced. Altogether, 28 different potato-associate d species with antagonistic effects to phytopathogens were detected. Antago nistic strains of seven species were found only on control plants. The obse rved effect was minor relative to the natural variability observed during t he monitoring period. This is the first study including plant-associated ba cteria responsible for plant growth and health and provides an example for performing risk assessment studies for transgenic plants under a variety of environmental conditions. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.