Biological characterization and sequence analysis of Cucumber mosaic virus isolated from Capsicum annuum

Whereas most of isolates of Cucumber mosaic virus (CMV) can induce green mosaic systemic symptoms on zucchini squash, foliar symptoms of a pepper isolate of CMV (Pf-CMV)-infected zucchini squash revealed systemic chlorotic spots. To assess this biological property, infectious full-length cDNA clones of Pf-CMV were constructed using long-template RT-PCR. The complete nucleotide sequences of RNA2 and RNA3 of Pf-CMV were determined from the infectious full-length cDNA clones, respectively. RNA 2 and RNA3 of Pf-CMV contain 3,070 nucleotides and 2,213 nucleotides, respectively. Overall sequence homology of two RNAs revealed high similarity (90%) between CMV strains, and 60% similarity to those of Tomato aspermy virus and Peanut stunt virus strains. By sequence analysis with known representative strains of CMV, Pf-CMV belongs to a typical member of CMV subgroup IA. The virus has high evolutionary relationship with Fny-CMV, but the pathology of Pf-CMV in zucchini squash was quite different from that of Fny-CMV. The pesudorecombinant virus, F1P2P3, induced chlorotic spot leaf symptom and timing of systemic symptom in squash plants, similar to the plants infected by Pf-CMV. No systemic symptoms were observed when Pf-CMV-inoculated cotyledons were removed at 5 days postinoculation (dpi) while Fny-CMV showed systemic symptom at 2 dpi. These results suggest that the pepper isolate of CMV possesses unique pathological properties distinguishable to other isolates of CMVs in zucchini squash.