Population Dynamics of Triticum Mosaic Virus in Various Host Species

A series of serial passages of Triticum mosaic virus (TriMV) was performed in winter wheat under greenhouse conditions to examine the dynamics of sequence variation in the TriMV population. The variation within the protein 1 (P1) and the coat protein (CP) of TriMV was assessed by single-strand conformational polymorphism (SSCP) assay, followed by nucleotide sequencing. Three lineages were established to compare diversity between and within each TriMV population. Different SSCP patterns among clones were associated with single-nucleotide substitutions. The new haplotypes detected within the P1 and CP cistrons were mostly random, with little correlation between lineages or passages. These results are consistent with stochastic changes due to genetic drift which have been reported to occur in population structures after repetitive and severe bottlenecks. TriMV mutations observed in the populations after serial passages were dominated by singletons within the P1 and CP cistrons, with no obvious bias to particular regions. Examination of non-consensus variation revealed the number of unique substitutions remained constant in frequency during passaging. These results suggest that stochastic processes such as bottlenecking are impacting the population. The mutation frequency per nucleotide was discovered to be 2.231 x 10 -4 /nt at passage 9 within the CP cistron. The mutation frequency of the P1 cistron was determined to be 0.580 x 10 -4 /nt. The mutation frequencies determined were low, not only compared to other Potyviridae family members, but also compared to other (+)-sense, single stranded plant RNA viruses in general. It was concluded that negative selection and genetic drift must be evolutionary processes influencing TriMV populations.