Bryan Harrison has made many original observations in plant virology whilst leading a very successful group of virologists. Bryan discovered the soil transmission and nematode vectors of several nepoviruses and tobraviruses and provided evidence for the importance of virus coat proteins in nematode transmissibility. He established many salient features of the ecology of these viruses and methods for their control. He showed nepoviruses to have a bipartite RNA genome; that the larger part can replicate independently; and discovered a genome-linked protein important for infectivity. Bryan showed that larger particles of tobraviruses are infective and mostly accumulate earlier in infection than the shorter ones. He discovered potato mop-top virus and its transmission by Spongospora subterranea. He also discovered circular single-stranded DNA genomes in two plant viruses. He applied modern taxonomic methods (with Adrian Gibbs) for the delineation of groups of plant viruses.