Epigenetics: Diversity and domestication

By Claire Agius, Epigenetics, Department of Plant Sciences, University of Cambridge

Many modern consumers would struggle to recognise the wild relatives of today’s staple crops. Striking differences are the result of thousands of years of crop domestication.
The first agriculturalists influenced crop development by selecting the tastiest, largest and most fruitful varieties then available. Modern landholders together with crop scientists continue this tradition, seeking out those same traits as well as a greater tolerance of environmental stresses such as drought and salinity, and greater resistance to plant diseases.
Our increased understanding of the molecular basis of crop traits facilitates a sophisticated approach to crop breeding. Ongoing research is uncovering the complex web of interactions that leads to desirable traits. If the presence of a particular gene – strings of DNA, which code for a protein – results in a desired trait, plants with that gene can be selected and preferentially grown.
Yet selective breeding over thousands of years has come at a cost – agricultural improvement has been characterised by a loss of diversity. Where once there might have been thousands of varieties of a single crop, now there may only be hundreds. At the molecular level, this means that there is less diversity of genes available for crop breeders as they look to develop new varieties that are able to cope with the demands of a changing climate and a growing global population. Efforts are underway to preserve the remaining diversity through such routes as establishing seed banks.
The gene pool is not the only potential source of diversity. Studies of large natural populations of plants have shown that there is considerable epigenetic variation between plants of the same species. From the Greek ‘epi’ meaning ‘above’ or ‘in addition’, epigenetics describes changes to DNA that do not affect the underlying four letter code of DNA. Some describe epigenetics as the punctuation marks of genetic material – epigenetic marks tell a plant how to read genes, influencing whether or not a plant expresses a certain trait from an ‘active’ gene or does not express the trait because the gene has been ‘turned off’, or silenced. 
As more is understood about the circumstances in which a gene is activated or silenced, and whether this can be done on a stable and heritable basis, crop scientists will come to understand the potential of epigenetics to be incorporated into crop breeding programmes, whether through conventional breeding approaches or through more directed modifications.
There is room to explore to what extent the loss of diversity is the result of smallholder choices, consumer demands, or corporate interests in seed stock and, more generally, in the food chain. What is clear, however, is that the critical importance of biodiversity is not just limited to natural environments but also extends to cultivated landscapes. Combining efforts to safeguard existing genetic diversity while exploring the potential to capitalise on natural epigenetic diversity will maximise the potential for improved crop productivity.
Photo credit: John Doebley, via Wikimedia Commons

Photos of Student Fieldwork