Curtoviruses, members of the Geminiviridae, have wide host ranges, including weeds and crops and are often found in mixed infections of different strains. While other members of the Geminiviridae have been demonstrated to interact through competition and synergism in mixed infections in plants, either type of interaction has not been reported in curtoviruses. This research used qPCR to study the interactions between Beet curly top virus, pepper curly top strain, isolate BV3 (BCTV-PeCT-BV3) and Beet curly top virus, beet severe curly top strain (BCTV-Svr) in three plant hosts. A significant decrease in virus titer in both BCTV-PeCTV and BCTV-Svr in co-infected sugar beets was observed when compared to beets infected with either virus, indicating competition. Chile pepper showed a significant increase in BCTV-PeCT titer in co-infected plants, compared to singly infected plants, indicating synergism. BCTV-PeCT caused severe symptoms and yielded high virus titer in chile, compared to the lack of symptoms and extremely low titer of BCTV-Svr in that plant host. These results indicate that curtovirus symptoms and infection can be host specific and such host may influence mixed infections of virus. Curtoviruses can interact through both competition and synergism and the response may be dependent on the type of host plant.
Key words: Beet curly top virus, interspecific competition, host specificity, mixed infections
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