Cisgenesis: a modern way of domesticating traits of the breeders' gene pool.

Plant breeding is a multidisciplinary scientific activity with tool development as driving force. It is clear from history that availability of genetic variation and selection methods are bottom lines for variety development. The genetic source of traditional plant breeding is restricted to domestication of traits from the so-called 'breeders' gene pool', consisting of crossable sources. Gene cloning and genetic transformation broaden the available genetic variation to genes from all living organisms. The so-called new genes in genetically modified organism (GMO) plants, consist of transgenes, with (chimaeric) genes from outside the 'breeder's gene pool'. Transgenic plants needed additional biosafety rules such as Directive 2001/18EC. However, these are not needed after transformation of the four rol-genes from wild-type Agrobacterium rhizogenes. In the meantime, cloned cisgenes, natural dominant genes from 'breeders' gene pool', are available, enabling cisgenic crops after marker-free transformation, which extends plant breeding with traditional traits. From long-term experience, it is clear that traditional breeding with the 'breeders' gene pool' has a history of safe use. Different scientific committees concluded that cisgenic crops are as safe as traditionally bred varieties. So, cisgenesis is a powerful new tool for plant breeding with traditional traits as indicated in the potential examples on: (1) breeding for durable resistance to potato late blight and apple scab by R-gene stacking; (2) the new possibility to come to stacking of monogenic resistance alleles in wheat; (3) engineering of restoration of cytoplasmic male sterility by cloned restorer genes and of altering gametophytic incompatibility by introducing additional S-alleles; (4) increasing phytase activity by gene dosage effect in barley; and (5) the possibility of changing hormone metabolism in (fruit) trees leading to important morphological alterations. In near future, because of availability of many more cisgenes, it is expected that the possibilities of cisgenesis will increase rapidly as the next step in plant breeding with traditional traits, if treatment as non-GMO is approved.