A recent study shows how awesome genetic engineering methods are and how they can be used to the trace the evolution of something like the sweet potato.
In a blog post of the Proceedings of the National Academy of Sciences, Charles Choi writes of the findings of a couple of researchers looking at viral elements (leftover bits of virus genes or immunological responses to viral infection) in the sweet potato genome.
What they found was genetic inserts from Agrobacterium, a bacteria that is attracted to damaged plant tissue and causes crown gall tumours. The tumours result from the insertion of the piece of DNA from the bacteria into the plant cells which increase hormones, and therefore growth, of the cells, in turn forming the tumours.
Agrobacterium tumefaciens is used in biotechnology as one method of inserting DNA into plants.
Finding such inserts in the sweet potato genome, particularly if they managed to effect root growth genes, could be the cause of the significant growth in their tubers compared to related plants.
The evolution of our food is amazing and one can only guess at what can be established, what good can come to people, if we can use genetics to assist our future food production.