Apr 29, 2011

Research Projects

Send

What impact does genetically modified wheat have on beneficial soil-dwelling organisms?

(2007 – 2011) Institute of Ecology and Evolution, University of Bern

Topic

Genetically modified (GM) wheat, into which a gene has been inserted that confers resistance to wheat powdery mildew could potentially have damaging effects on non-target organisms. Important non-target organisms living in the soil include worms or the larvae of flying insects, since they feed on dead plant material. This project therefore investigated the effect that transgenic wheat leaf material has on these soil-dwelling organisms. Feeding experiments were conducted with GM wheat, the isogenic parent variety and various conventional wheat lines. The reproductive behaviour, mortality and development characteristics of the soil-dwelling organisms were studied.

Experiment description

The test organisms used were annelid worms (Enchytraeus Albidus) and two species of fly (Drosophila melanogaster and Megaselia scalaris).

Feed material used

The parent variety for the GM feed was a wheat variety that is susceptible to powdery mildew (Bobwhite SH 98 26). It was transformed with an allele of a resistance gene taken from wheat (Pm3b). This allele confers a specific resistance to powdery mildew. In addition, transgenic lines were produced that contain two enzyme-producing genes taken from barley. These enzymes, chitinase and glucanase, confer a non-specific fungal resistance on the wheat plants by dissolving fungal hyphal walls. In order to measure the impacts of a natural range of varieties, five conventional lines were also included in the trial plan. The feeding trial with annelids used material from a field trial conducted by the Agroscope Reckenholz-Tänikon research institute (ART) in Switzerland. The food plants for the flies and their larvae were grown in climate chambers at the institute.

Feeding experiment with annelids

Feeding cycles lasted six weeks. Before the start of a cycle, a plastic container was filled with 20 g of earth per wheat variety and water was added. The feed consisted of pulverised leaves from one wheat variety (67 %) and organic wholemeal oatmeal (33 %), which were mixed with water. Ten adult annelid worms were placed in each container along with enough food for three days. After three weeks the first part of the experiment was complete and the living adult worms were counted and removed. The developing young worms were fed for a further three weeks and then counted. This cycle was repeated ten times. Throughout the experiment, leftover food was removed every three days and new food was added to prevent fungus formation.

Feeding experiment with flies and their larvae

The feeding experiments were conducted under controlled conditions in climate chambers. In each trial, the food consisted of leaves from the wheat varieties in the experiment, which were pulverised together with ready-made fly food. This was mixed with water to form a nutrient medium. One male and one female of each species of fly were placed for 48 hours in a glass container with the nutrient medium to mate and lay eggs, and were then removed. Checks for larvae were carried out every 24 hours. At the end of the experiment, the progeny were fed on fly food for two to five days before being used for breeding again. Various fitness parameters, including number of progeny, the ratio of male to female flies, and the time taken for the progeny to develop, were measured over four generations.

Results

Feeding experiment with annelids

After three weeks an average of 85 % of the original worms had survived. This meant that the minimum of 80 % required by the ISO standard was met. After a further three weeks, an average of 50 young worms were found. The GM wheat containing the Pm3b allele was not found to have any significant impacts on the survival rate of the adult worms or on the number of young worms. Food with a non-specific resistance (from chitinase or glucanase) did affect the survival rate of the adult worms. However, these effects fell within the range of varietal effects for the conventional plants.

Feeding experiment with fly larvae

Occasional differences in development time or number of progeny were identified for both species of fly depending on the feed composition. However, the GM food was not found to have any impact on the various fitness parameters.