A Distinct Subpopulation of Cauliflower mosaic virus (CaMV) in South Iran

Abstract

Cauliflower mosaic virus (CaMV) with a high incidence and widespread distribution on Brassica crops in Iran reduces the yield and quality of these crops. The complete sequences of three open reading frames (ORFs) 2, 4 and 6 coding for aphid transmission (AT), coat protein (CP) and inclusion body protein/translation transactivator (TAV) genes, respectively, were determined for two Iranian CaMV isolates from Kerman (south Iran). They induced latent or mild mottle (L/MMo) infection in Brassica oleracea var. capitata so are considered as the (L/MMo) biotype. Clear recombination breakpoints were detected between ORF2 and ORF6 in two Kerman isolates using concatenate fragments. Phylogenetic analysis revealed three Iranian CaMV subpopulations in which the two Kerman isolates in the new subgroup C were added to the two previously reported Iranian subpopulations A (central and west Iran) and B (north-east Iran). Also three regions of pairwise identity were detected which representing: 97.1-100, 93.8-97.1 and 90.6-93.8% for subgroups A, C and B, respectively. Our analysis showed the high variability of Iranian CaMV population and provided valuable new information for understanding the diversity and evolution of caulimoviruses. Furthermore, star phylogeny was found in the subgroup C with overall lack of nt diversity and high haplotype diversity as evidence of a recent population expansion after a genetic bottleneck although this may have been modified subsequently by clinal genetic drift. The appearance of new genetic types demonstrates a high potential of risks and should be considered in the planning of efficient control programmes.