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Tracking Raspberry bushy dwarf virus from pollen to systemic infection reveals RNA1 replicates in a resistant cultivar in the absence of RNA2
K. K. LANNING (1), P. P. Moore (1), R. R. Martin (2). (1) Washington State Univ, Puyallup, WA, U.S.A.; (2) USDA-ARS Horticulture Crops Research Unit, Corvallis, OR, U.S.A.

<i>Raspberry bushy dwarf virus</i> (RBDV) is the most prevalent virus of <i>Rubus </i>species worldwide. It’s a pollen-borne virus that often causes drupelet abortion resulting in significant quality and yield reductions. Little has been done on the movement of RBDV from infected pollen to the stigma and subsequent systemic movement through the pollinated plant. To address this, a pollination experiment was designed in which ‘Willamette’ (R) and ‘Meeker’ (S) plants were placed between RBDV-infected plants in a screenhouse. Bumblebees were introduced at the time of bloom. Receptacle, pedicle, fruiting lateral and floricane tissue was destructively sampled and analyzed for RBDV using real-time RT-PCR with RBDV-RdRp specific primers and probe. RBDV was detected in all tissue types in both ‘Willamette’ and ‘Meeker’ plants three weeks post-bloom. Grafting from RBDV-positive ‘Willamette’ plants confirmed that the virus was graft transmissible. Further analysis using RBDV-CP specific primers in RT-PCR resulted in amplicons of the correct size amplified consistently from ‘Meeker’ samples, while only two ‘Willamette’ samples yielded weak bands. Previously reported to be resistant to RBDV based on repeated negative ELISA tests, these results suggests RBDV RNA1 is able to replicate and move systemically in ‘Willamette’. Further work is underway to determine if RBDV is present in pollen of ‘Willamette’, and if present does it transfer horizontally during pollination.

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