Nov 2, 2004

Research Projects

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Transgenic fructan potatoes – possible ecological effects on bacteria and fungi

(2001 – 2004) Centre for Agricultural Landscape Research (ZALF) e. V., Institute for Primary production and Microbiological Ecology, Müncheberg

Topic

Fructan potatoes have an altered carbohydrate metabolism. They produce a novel type of sugar, inulin, and contain a higher level of soluble sugars.

All substances produced in plants can make their way into the soil, and the fructan produced by transgenic fructan potatoes is no exception. Secreted fructan could affect the nutrition of bacteria and fungi that live in association with potatoes. This could potentially modify soil and foliar surface microecology.

The research project was initiated to find out if fructan potatoes could have a lasting effect on plant-associated bacteria and fungi.

Summary

This project investigated the effects of transgenic fructan potatoes on plant-associated bacteria and fungi. The population densities of cultivable microbes varied without relation to whether the plants were transgenic or conventional. Even the composition of microbial communities as determined by genetic fingerprinting showed no variation with respect to the different lines, suggesting fructan potatoes have no effect on plant-associated microbial communities. Therefore, the study’s findings do not substantiate any ecological risks to microorganisms. Through the process of determining the insertion sites for the foreign DNA in the transgenic potato lines, the company ConGen GmbH developed methods of identifying specific transgenic lines, which they have validated and now use routinely.

Experiment description

Analysis of the microflora

To determine possible effects of fructan potatoes on root and leaf associated microorganisms, tests were carried out on roots/soil and leaves collected from the field grown fructan potato plants. The composition and population densities of fungi and bacteria were determined.

The data collected from the fructan potatoes were compared with data taken from conventional varieties. The goal of these investigations was to determine if the differences between the transgenic and conventional lines exceeded the inherent variation observed with conventional varieties.

Identification of transgenic lines

Potential effects of transgenic plants could be specific to a particular transformation event. Therefore, details on the integration sites of the foreign genes in the plant genome were collected for each individual transgenic line under investigation. Based on this data, simple PCR tests can differentiate between different transgenic events derived from the same foreign DNA. These testing protocols could be useful for enforcing GMO regulations, because GMO authorisations are always specific to a particular event.

Results

Analysis of the microflora

Analysis of cultivable microorganisms showed only slight variations in microbial populations between transgenic lines and conventional varieties. Although statistically significant differences were observed in isolated instances, no consistent trends were observed during the duration of the experiment.

Fungal and bacterial populations were profiled using genetic fingerprinting. Statistical methods were used to compare the soil zone fingerprints of various lines, and only slight differences were observed. The transgenic lines fell within the range of variation observed among conventional varieties.

Differences in soil conditions within the test plots, on the other hand, did have a significant effect on the observed microbial populations. As confirmed in other studies, the plants’ local environment has a much greater effect on plant associated microorganisms than the variety of potato. On the leaf surface, some double transformants showed differences, but these differences were smaller than year to year fluctuations and were obscured by environmental variability.Overall there is no reason to expect an increased risk to microflora.

Identification of transgenic lines

Individual transgenic lines were identified by locating the integration site of the foreign DNA. Every transgenic line has one more unique integration sites, which enables scientists to differentiate between different transgenic lines carrying the same foreign gene. A simple analytical PCR test was developed for each line by taking the foreign DNA sequence and the sequence of the adjacent plant DNA.

Line specific identification was used by the research group to identify the offspring of the transgenic lines. In addition, ConGen used collected data to develop a quantitative PCR based detection method.