Abstract
By structuring farmers’ informal networks of seed exchange, kinship systems play a key role in the dynamics of crop genetic diversity in smallholder farming systems. However, because many crop diseases are propagated through infected germplasm, local seed systems can also facilitate the dissemination of seedborne pathogens. Here, we investigate how the interplay of kinship systems and local networks of germplasm exchange influences the metapopulation dynamics of viruses responsible for the cassava mosaic disease (CMD), a major threat to food security in Africa. Combining anthropological, genetic and plant epidemiological data, we analyzed the genetic structure of local populations of the African cassava mosaic virus (ACMV), one of the main causal agents of CMD. Results reveal contrasted patterns of viral diversity in patrilineal and matrilineal communities, consistent with local modes of seed exchange. Our results demonstrate that plant virus ecosystems have also a cultural component and that social factors that shape regional seed exchange networks influence the genetic structure of plant virus populations.
Highlights
By structuring farmers’ informal networks of seed exchange, kinship systems play a key role in the dynamics of crop genetic diversity in smallholder farming systems
Understanding how social networks of seed exchanges influence the population dynamics of plant diseases is key to designing effective disease management programs, which increasingly rely upon community-based approaches to curb the spread of crop diseases[6,7]
Cassava diversity in Gabon exhibits a strong phylogeographic structure, with high varietal diversity in the south and low diversity in the north, resulting from the strong matrilineal/ patrilineal geographic divide that has contributed to maintaining regional patterns of genetic diversity that mirror the geographic distribution of patrilineal and matrilineal societies[11]. We investigate whether this southern-matrilineal/northern-patrilineal contrast influences the spatial structure of viruses responsible for the cassava mosaic disease (CMD), a major pandemic that threatens regional food security in Africa
Summary
By structuring farmers’ informal networks of seed exchange, kinship systems play a key role in the dynamics of crop genetic diversity in smallholder farming systems. Understanding how social networks of seed exchanges influence the population dynamics of plant diseases is key to designing effective disease management programs, which increasingly rely upon community-based approaches to curb the spread of crop diseases[6,7]. In patrilineal societies in northern Gabon farmers rely mostly or sometimes exclusively on “heirloom” landraces that the bride receives from her mother-in-law when she moves in with her husband (affinal transmission); by discouraging seed exchanges between villages, affinal transmission keeps cassava genetic diversity within the boundaries of the community but can act as a barrier against the introduction of seedborne pathogens
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