The purpose of the project was to develop RYMV resistant rice suitable for cultivation in West Africa. In the first phase, susceptible cultivated rice varieties were transformed with cDNA constructs based on fragments from the RYMV genome. The aim was to produce an RNA-based resistance called homology dependant resistance. Transgenic cultivated rice varieties have successfully been produced which resist RYMV through a mechanism of homology dependant resistance. In addition a strain survey has been initiated and those isolates which have been tested on the transgenic plants are resisted through the same mechanism. Since the mechanism of resistance does not rely on the production of functional viral proteins the resistance would be likely to have fewer risks for the environment. Since the resistance trait has been found to be stable over several generations they may be suitable for introduction into field agriculture over a 3-10 year time frame (Starting from 1995). These cultivated varieties will then improve the efficiency of sustainable rice production in West Africa through the production of rice lines that are resistant to rice yellow mottle virus.