Modeling avocado genetic diversity on farms

A major transition in agriculture over the last half century has been the shift from using many crop varieties to only a few select cultivars. While millions of dollars are spent annually on seed banks and other repositories to conserve traditional crop varieties, recent research has shown that many farmers continue to cultivate diverse traditional varieties alongside monocultures, arguing for on-farm conservation. Monocultures can interbreed with traditional varieties and swamp the genetic diversity of the crop population and an understanding of the importance of this process and cultural influences on genetic diversity is needed. I show here, using kinship analysis with molecular genetic markers, ethnobotanical techniques, and computer simulations in a study of avocado (Persea americana Mill.), that introgression rates are low and the projected loss of neutral allelic diversity on farms is minimal despite the dominance of monocultures. My data strongly suggest that farming practices can promote crop genetic conservation and provides evidence on a population genetic level that on-farm conservation of crop diversity is a viable alternative to costly seed banks. In addition, I present a methodology to assess some important elements in the dynamics between biological and cultural forces for crop genetic diversity on firms. Finally, a detailed study of cultural practices associated with cultivating avocado in Costa Rica is presented and their impact on genetic diversity is assessed.