<p><i>Rubus</i> species, including raspberry and blackberry, are affected by over 40 known viruses that can impact fruit yield, plant vigor, and germplasm movement. These species differ markedly in their response to viral infection, yet the factors that contribute to susceptibility are unknown. We hypothesize this is due to differences in virus accumulation dynamics. We utilized an infectious clone of blackberry chlorotic ringspot virus to assess replication efficiency in ‘Munger’ black raspberry (<i>Rubus occidentalis,</i> L.), a virus indicator for <i>Rubus</i> viruses, and ‘Natchez’ blackberry (<i>Rubus L.&#xa0;subgenus Rubus</i> Watson), a cultivar that typically is asymptomatic to single virus infections. This study demonstrated that virus accumulation in ‘Munger’ is over 4.4 × 10⁵-fold higher than in ‘Natchez,’ based on a model-derived estimate averaged across sampling time points, providing evidence that the host genotype plays a key role in supporting virus replication. These findings deepen our understanding of virus-host interactions and further validate the use of ‘Munger’ as a virus indicator for <i>Rubus</i>.</p>