RNA interference (RNAi) is being developed and exploited to improve plants by modifying endogenous gene expression as well as to target pest and pathogen genes both within plants (i.e. host-induced gene silencing) and/or as topical applications (e.g. spray-induced gene silencing). RNAi is a natural mechanism which can be exploited to make a major contribution towards integrated pest management and sustainable agricultural strategies needed worldwide to secure current and future food production. RNAi plants are being assessed and regulated using existing regulatory frameworks for GMO. However, there is an urgent need to develop appropriate science-based risk assessment procedures for topical RNAi applications within existing plant protection products legislation.

Out-crossing between genetically modified herbicide-tolerant (GMHT) and non-GM rape cultivars was studied using GMHT source field plots of approximately 0.8 ha. Levels of cross-pollination between adjacent fully fertile rape varieties declined rapidly with increasing distance from the interface between plots. A varietal association with low levels of male sterility showed higher levels of out-crossing than other varieties. Out-crossing data were used to compare negative exponential and inverse power-law models for their fit to describe the observed relationship between cross-pollination and distance from source. Results showed that the inverse power-law model provided a better fit of the data.

There are concerns that the cultivation of genetically modified herbicide tolerant (GMHT) crops treated with broad spectrum herbicides will cause declines in botanical diversity and hence loss of biodiversity. Cultivation systems of these have different levels of inputs and management interventions and some incorporate the use of minimal/no tillage. Research results show a range of effects and the priority is to determine whether research studies show shifts in botanical diversity and/or declines in plant populations in GMHT compared with conventionally managed crops.