Pollen barrier
Encyclopedia
A physical obstacle that hinders the movement of pollen
from a field of genetically modified
(GM) crops to neighbouring non-GM crops is called a pollen barrier. Such barriers are erected with the aim of reducing the out-crossing of GM plants. In the European Union they may, for example, help keep the GM content of neighbouring non-GM fields below the threshold of 0.9 percent - allowing conventional farmers to sell their harvest as non-GM products.
. A few rows of non-GM crops are equivalent to several metres of isolation distance. Detailed recommendations, however, exist only for maize at this time. Since co-existence has become a major topic in European agriculture, several research programmes – including Co-Extra
and SIGMEA - have emerged to investigate pollen barriers as a tool for the co-existence
of GM and non-GM crops.
In other regions, where GM crops have been planted for years without co-existence regulations, individual research projects are analysing the effective degree of mixing between GM and non-GM crops. However, most countries where GM plants have already been grown on a large scale are home to fields with large average sizes. Due partly to the longer average distances required for pollen travel, no specific co-existence measures or isolation distances may be needed to maintain admixture below the threshold. However, in regions such as Western and Southern Europe, average field sizes are much smaller and result in a higher admixture of GM and non-GM crops through pollen movement. Due to the limited space available on small fields, isolation distances may be inapplicable for co-existence. Pollen barriers, such as buffer strips, may be an appropriate alternative.
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
from a field of genetically modified
Genetic engineering
Genetic engineering, also called genetic modification, is the direct human manipulation of an organism's genome using modern DNA technology. It involves the introduction of foreign DNA or synthetic genes into the organism of interest...
(GM) crops to neighbouring non-GM crops is called a pollen barrier. Such barriers are erected with the aim of reducing the out-crossing of GM plants. In the European Union they may, for example, help keep the GM content of neighbouring non-GM fields below the threshold of 0.9 percent - allowing conventional farmers to sell their harvest as non-GM products.
Design of pollen barriers
Pollen barriers can be made of any species of hedge, tree or tall plantings which physically limit pollen movement. However, the most efficient pollen barriers are made of non-GM crops of the same species as the GM cultivation. This kind of pollen barrier is often called a "buffer strip" or "buffer zone", and is not only a physical hurdle but also obstructs GM pollen by producing its own competitive, GM-free pollen which also may fertilise the neighbouring GM-free fields. Consequently, however, crops in the buffer zone, although originally non-GM plants, also catch a lot of GM pollen, produce a lot of GM fruit and are considered a GM crop when harvested.Pollen barriers versus isolation distances
According to recent research, a buffer zone is more efficient than isolation distancesIsolation distance for genetically modified plants
Isolation distances are used in regions where genetically modified and conventional or organic crops are grown in co-existence. When different cropping systems are grown in proximity to each other, the "isolation distance" between fields refers to the area separating them, on which genetically...
. A few rows of non-GM crops are equivalent to several metres of isolation distance. Detailed recommendations, however, exist only for maize at this time. Since co-existence has become a major topic in European agriculture, several research programmes – including Co-Extra
Co-Extra
Co-Extra is an EU-funded research programme on co-existence and traceability of genetically modified crops and their edible derivatives. It has been granted €13.5 million under the Sixth Framework Programme of the European Union, and is conducted by more than 200 scientists in 52 organisations in...
and SIGMEA - have emerged to investigate pollen barriers as a tool for the co-existence
Co-existence of genetically modified and conventional crops and derived food and feed
In the context of agriculture and food and feed production, co-existence means using cropping systems with and without genetically modified organisms in parallel. For co-existence to be assured, the separation and the identity of the respective food and feed products must be maintained at all...
of GM and non-GM crops.
In other regions, where GM crops have been planted for years without co-existence regulations, individual research projects are analysing the effective degree of mixing between GM and non-GM crops. However, most countries where GM plants have already been grown on a large scale are home to fields with large average sizes. Due partly to the longer average distances required for pollen travel, no specific co-existence measures or isolation distances may be needed to maintain admixture below the threshold. However, in regions such as Western and Southern Europe, average field sizes are much smaller and result in a higher admixture of GM and non-GM crops through pollen movement. Due to the limited space available on small fields, isolation distances may be inapplicable for co-existence. Pollen barriers, such as buffer strips, may be an appropriate alternative.