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Mixed viral infections are common in plants, and the evolutionary dynamics of viral populations may differ depending on whether the infection is caused by single or multiple viral strains. However, comparative studies of single and mixed infections using viral populations in comparable agricultural and geographical locations are lacking. Here, we monitored the occurrence of pepino mosaic virus (PepMV) in tomato crops in two major tomato-producing areas in Murcia (southeastern Spain), supporting the evidence that the PepMV disease-affected plants had single infections of the Chilean 2 (CH2) strain in one area, while the other area exhibited the long-term coexistence of the CH2 and European (EU) strains. We hypothesize that circulating strains of PepMV might be modulating the differentiation between them and shaping the evolutionary dynamics of PepMV populations. Our phylogenetic analysis of 106 CH2 isolates randomly selected from both areas showed a remarkable divergence between the CH2 isolates, with an increased nucleotide variability in the geographical area where both strains co-circulate. Furthermore, the potential virus-virus interaction was studied further by constructing six full-length infectious CH2 clones from both areas, and assessing their viral fitness in the presence and absence of an EU type isolate. All CH2 clones showed decreased fitness in mixed infections, and although complete genome sequencing indicated a nucleotide divergence of those CH2 clones by area, the magnitude of the fitness response was irrespective of the CH2 origin. Overall, these results suggest that the co-circulation of both strains may have implications on the genetic variability of PepMV populations.
PMID: 31524081 [PubMed - as supplied by publisher]