An ecotype (S023) of Beta vulgaris subsp. maritima was identified which was highly resistant to beet necrotic yellow vein virus (BNYVV) but susceptible to its fungal vector, Polymyxa betae. A comparative study of viral development in the roots showed that the resistance was effective from the early stages of infection. Mechanical inoculation experiments suggested that the resistance was not due to a lack of transmission of BNYVV by its fungal vector. Immunogold‐silver labelling of the viral coat protein in root sections confirmed the existence of BNYVV transmission in the resistant ecotype. Virus replicated in isolated root protoplasts of both susceptible and resistant genotypes. Viral particles localized by immunogold‐silver labelling diffused over short distances from the primary infected root cells in both resistant and susceptible plants. Evidence for inhibition of long‐distance movement in the resistant ecotype requires further investigation.