Abstract
Many of the major forage species used in agriculture are outcrossing and rely on the exchange of pollen between individuals for reproduction; this includes the major species used for dairy production in grazing systems: perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.). Cultivars of these species have been co-existing since contrasting cultivars were developed using plant breeding, but the consequences and need for strategies to manage co-existence have been made more prominent with the advent of genetic modification. Recent technological developments have seen the experimental evaluation of genetically modified (GM) white clover and perennial ryegrass, although there is no current commercial growing of GM cultivars of these species. Co-existence frameworks already exist for two major cross-pollinated grain crops (canola and maize) in Europe, and for alfalfa (Medicago sativa L.) in the US, so many of the principles that the industry has developed for co-existence in these crops such as detection techniques, segregation, and agronomic management provide lessons and guidelines for outcrossing forage species, that are discussed in this paper.
Highlights
Many of the major forage species used in agriculture are outcrossing and rely on the exchange of pollen between individuals for reproduction
We have shown gene flow in field grown wind pollinated, perennial ryegrass [37], and insect pollinated, white clover [38]
A review of co-existence strategies for maize grain crops in the European Union (EU) found that a reliance merely on isolation distances often led to legislation of isolation distances that were not based on scientific principles [6], and that management and biological issues such as pollen barriers flowering coincidence crop rotation regional strategies biological confinement should all be considered when developing co-existence frameworks
Summary
Many of the major forage species used in agriculture are outcrossing and rely on the exchange of pollen between individuals for reproduction. Co-existence frameworks already exist for two major cross-pollinated grain crops (canola and maize) and alfalfa for seed and hay production, so many of the principles that the industry has developed for co-existence in these crops such as detection techniques, segregation, and agronomic management provide lessons and guidelines for outcrossing forage species. The segregation of products during marketing and supply An example of these co-existence frameworks for grain crops are those developed within the European Union (EU) [5] which allow “the ability of farmers to make a practical choice between conventional, organic, and GM crop production” considering issues such as the segregation of GM and non-GM crops and the cost of this segregation. We will summarise the literature on aspects of functional equivalence and co-existence in perennial outcrossing forage species with a particular emphasis on those used in dairy production systems drawing on examples using both GM and non-GM plants
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