Analysis of Cotton Leafroll Dwarf Virus P0 Gene Sequences from South Carolina Reveals Low Variability Among Isolates.

Cotton leafroll dwarf virus (CLRDV) is emerging across the major cotton-producing states of the southern United States. Because it was detected in nearly all cotton-producing states within a few years of its initial detection in the United States, the spread of the virus has apparently occurred rapidly. In this study spanning three growing seasons in South Carolina, we collected CLRDV isolates from symptomatic and asymptomatic cotton plants in 10 counties. The genomic region encoding P0, the viral suppressor of RNA silencing, was sequenced and compared among CLRDV isolates. Low variability among CLRDV P0 sequences from South Carolina isolates with similarities to other United States isolates was revealed by amino acid sequence alignment and phylogenetic analysis. Low variability among South Carolina isolates was also confirmed by sequencing a subset of eight near-complete genomes of CLRDV isolates. Although sequence variability was low among South Carolina isolates, this data should be taken in the context of all United States isolates, for which diversity may be higher than initially expected. Sequences gathered in this study add to the body of knowledge on CLRDV diversity in the United States.