A rapid technique for assessing the resistance of families of potato seedlings to potato leaf roll virus

A technique is described by which families of potato seedlings can be rapidly screened for resistance to potato leaf roll virus (PLRV) in the greenhouse with a minimum expenditure of labour and bench space. Seed of different families was sown in rows in four replicated blocks and the seedlings produced were exposed to viruliferous Myzus persicae when very young. Symptoms resembling those typical of secondary infection with PLRV developed within a few weks and families with few affected seedlings compared with the susceptible control were classed as resistant. Tests done at different times with similar sets of families gave similar results. Applying infective M. persicae by shaking heavily colonised potato shoots above the seedlings was more effective and far less time consuming than transferring them individually by hand using a fine paint brush.