Modeling Pollen-Mediated Gene Flow in Rice: Implications for Assessing and Managing Transgene Escape

Rice and rice gene pool A cultivated rice (Oryza sativa L., referred to hereafter as rice) is an important world crop, providing staple foods for nearly one half of the global population. Achieving high productivity, including improved breeding methods, is always the challenge in meeting the demand for food security and nutritional sufficiency, particularly for the developing world. Apart from Asian rice, there is another cultivated rice species (O. glaberrima), domesticated in West Africa, that remains only locally important in some areas. In addition to the two cultivated species, there are more than 20 wild relative species in the genus Oryza and about 50 other wild species in the tribe Oryzeae of the grass family (Poaceae).1 All wild species in the tribe compose a valuable rice gene pool that is significant for providing germplasm for the genetic improvement of rice cultivars, in addition to other ecological functions. Species in the genus Oryza contain ten different genome types (i.e., AA, BB, CC, BBCC, CCDD, EE, FF, GG, JJHH, and JJKK genomes), reflecting their relatedness to each other in terms of evolution. Rice contains the AA genome, which is shared by a group of six wild (including weedy) Oryza species that have the closest evolutional relationships to the crop. Consequently, pollen-mediated gene flow or hybridization occurs naturally between rice and its close wild relatives to various extents.1