Molecular genetic analysis of virus isolates from wild and cultivated plants demonstrates that East Africa is a hotspot for the evolution and diversification of Sweet potato feathery mottle virus
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Date
2010
Journal Title
Journal ISSN
Volume Title
Publisher
Molecular ecology
Abstract
Sweet potato feathery mottle virus (SPFMV, genus Potyvirus) is globally the most
common pathogen of cultivated sweet potatoes (Ipomoea batatas; Convolvulaceae).
Although more than 150 SPFMV isolates have been sequence-characterized from
cultivated sweet potatos across the world, little is known about SPFMV isolates from
wild hosts and the evolutionary forces shaping SPFMV population structures. In this
study, 46 SPFMV isolates from 14 wild species of genera Ipomoea, Hewittia and
Lepistemon (barcoded for the matK gene in this study) and 13 isolates from cultivated
sweet potatoes were partially sequenced. Wild plants were infected with the EA, C or O
strain, or co-infected with the EA and C strains of SPFMV. In East Africa, SPFMV
populations in wild species and sweet potato were genetically undifferentiated,
suggesting inter-host transmission of SPFMV. Globally, spatial diversification of the
178 isolates analysed was observed, strain EA being largely geographically restricted to
East Africa. Recombination was frequently detected in the 6K2-VPg-NIaPro region of the
EA strain, demonstrating a recombination ‘hotspot’. Recombination between strains EA
and C was rare, despite their frequent co-infections in wild plants, suggesting purifying
selection against strain EA⁄C recombinants. Positive selection was predicted on 17 amino
acids distributed over the entire coat protein in the globally distributed strain C, as
compared to only four amino acids in the coat protein N-terminus of the EA strain. This
selection implies a more recent introduction of the C strain and a higher adaptation of the
EA strain to the local ecosystem. Thus, East Africa appears as a hotspot for evolution and
diversification of SPFMV.
Description
Keywords
East Africa, Ipomoea, Potyvirus, Recombination, Selection pressure, Wild plant species
Citation
Tugume, A. K., Cuellar, W. J., Mukasa, S. B., & Valkonen, J. P. (2010). Molecular genetic analysis of virus isolates from wild and cultivated plants demonstrates that East Africa is a hotspot for the evolution and diversification of Sweet potato feathery mottle virus. Molecular ecology, 19(15), 3139-3156. doi: 10.1111/j.1365-294X.2010.04682.x