BeschreibungBlackleg disease of potatoes (Solanum tuberosum L.), caused by bacterial soft rot pathogens, e.g. Erwinia carotovora ssp. atrospetica (Eca), leads to enormous yield and quality losses worldwide. However, genetically modified (GM) potatoes producing antimicrobial substances (phage T4 lysozyme; lytic peptides attacin and cecropin) may offer useful strategies for future pathogen control. Regarding the ecological compatibility of GM crops, it appears very important to estimate them carefully for possible harmful effects on the environment, where the soil biota is integrally involved in biogeochemical cycles and their activities are crucial to the productivity of terrestrial ecosystems. The objective of the present study is to investigate possible side-effects of GM potatoes on the activity and structural composition of the rhizosphere microbial populations. Furthermore, the impact of individual parameters such as soil type, vegetation stage, as well as pathogen exposure (Eca) on functional activity and community structures of the rhizosphere microbial populations are discussed.A greenhouse experiment was performed in which four potato lines, Desirée, its transgenic, T4-lysozyme expressing derivative, Merkur and Merkur expressing attacin and cecropin were cultivated in two contrasting soil substrates (luvisol, chernozem). Rhizosphere samples were obtained at two vegetation stages (stem elongation and early flowering). Activities of seven rhizosphere soil enzymes which are involved in the C-, N- and P-nutrient cycles were measured as fluorescence using substrates containing the fluorescent compounds 4-MUF, and 7-AMC. Structural diversity of the rhizosphere bacterial communities was assessed by 16S rRNA-based T-RFLP analysis. Individual parameters had a distinct influence on the microbial activity and structure of bacterial populations in the rhizospheres. The degree of impact tended from soil > line > vegetation stage > Eca infection. The comparison of transgenic vs. conventional revealed a greater effect of T4 lysozyme as compared to the lytic peptides attacin and cecropin. T-RFLP showed clearer differences as the rhizosphere soil enzymes. Both analytical approaches proved to be sensitive tools for analyzing the activity and structure of microbial populations in the rhizospheres of tested potato lines. We can conclude from our results that soil type, plant variety, genetic modification, vegetation stage, as well as pathogen exposure, are factors influencing the soil microbial community structure and activity. Our results indicated unintended effects of the genetic modification on the activity and structure of bacterial rhizosphere populations, however, these differences were minor than or comparable to the variations caused by natural factors including soil type, plant genotype or vegetation stage.
|17 Nov. 2004
|Annual Meeting of Ph.D. and diploma students of ARC, Biogenetics and Natural Resources, and Boku, Institute for Soil Science
- Nicht definiert