Summary

Apomixis (asexual reproduction through seeds) has been proposed as a possible method by which to contain transgenes in genetically modified (GM) crops. While over 400 apomictic plant species are known, apomixis is very rare among crop plants and the transfer of functional apomixis to crop varieties by conventional breeding has been largely unsuccessful. As an alternative de novo engineering of apomixis in sexually reproducing crops has been proposed, which takes advantage of the close developmental relationship between apomixis and sexuality. Although the use of engineered apomictic crops lies in the distant future, enormous benefits to agriculture could result from harnessing apomixis in crop plants. However, constitutively expressed dominant apomixis might result in the invasive spread of ‘infectious ’ apomixis as most natural apomicts produce viable pollen. Therefore, the containment of transgenes would require the engineering of autonomous apomixis, where both the embryo and endosperm develop in the absence of fertilization. Only autonomous apomixis could be combined with male sterility, which would prevent geneflow via pollen. It may, however, be difficult to engineer autonomous apomixis in the cereals since most, if not all, apomictic grasses require fertilization to induce endosperm development (pseudogamy), which is essential to seed formation. As an alternative, conditional apomixis technology allowing the trai