The functional and structural microbial diversity of soil under potato (baseline)

PhD ceremony: Ms. Ö. Inceoglu, 11.00 uur, Aula Academiegebouw, Broerstraat 5, Groningen

Dissertation: The functional and structural microbial diversity of soil under potato (baseline)

Promotor(s): prof. J.D. van Elsas

Faculty: Mathematics and Natural Sciences

The main ideas behind the research of Özgül Inceoglu were to (1) determine the variation among soil microbiological parameters as a result of cropping of a series of different potato cultivars, and (2) weigh the putative effects of GM potato plants to those of the selected cultivars. This way, as a first outcome, an assessment of the normal operating range (NOR) of potato cropping would become tangible. In addition, the question whether the putative effects of the GM plant remained within or reached outside the NOR would receive an answer. Inceoglu placed an emphasis on the assessment of the overall bacterial community composition as well as on that of individual microbial populations as these are affected by plants.

Soil-borne microbial communities are influenced by plant roots due to, among other factors, the excretion of organic compounds in the exudates. Plants thus selectively attract microorganisms in their rhizospheres which then consume particular excreted compounds. It clearly follows that microbial communities in the rhizosphere may be differentially influenced by plant genotype as well as developmental stage if these incur different patterns of root exudation. However, there is a paucity of knowledge on the extent to which such community shifts may occur, on the dynamics of the changes and on the putative effects regarding the functioning of the system.

Depending on the objective of the modification, genetically modified (GM) plants can have great potential to advance agriculture. On the other hand, there are concerns about the potential ecological effects of GM plants intended for routine cropping. For instance, GM plants might exert undesirable effects on soil organisms, in comparison to the parent plant. In order to weigh effects of transgenic plants, it is important to first assess the overall community composition as well as individual microbial populations as these are affected by plants, and study fluctuations therein.

Furthermore, the use of agricultural practices such as fertilization and tillage played an important role on the bacterial community. In conclusion, based on the modification or crop type, indicator organism must be predetermined and tracked. In the case of Inceoglus research, genetic modification for increasing the starch content, betaproteobacterial community changes was a sensitive indicator for the assessment of side effects.