Collecting, conservation and utiklization of plant genetic resources and their global distribution are essential componentes of international crop improvement programmes. Inevitably, the movement of germplasm involves a risk of accidentally introducing plant quarantine pests*along with the host plant material; in particular, pathogens that are often symptomless, such as viruses, pose a special risk. In order to minimize this risk, effective testing (indexing) procedures are required toensure that distributed material is free of pests that are of quarantine concern. The ever-incrrrreasing volume of germplasm exchanged internationally, coupled with recent rapid advances in biotechnology, has created a pressing need for crop-specific overviews of the existing kno.