Researchers at Penn State reported a few months ago that they have isolated a 1000-year-old plant virus - a chrysovirus - from corncobs recovered from the Antelope House Ruin in Canyon de Chelly National Monument, Arizona. This chrysovirus is not just the first chrysovirus found in corn, but it is the oldest plant virus scientists have found to date. [Antelope House image via americansouthwest.net; virus image via alchetron.com]
From the article in Science Daily, "...chrysoviruses are persistent plant viruses that are transmitted from generation to generation through seeds and can remain in their hosts for very long time periods. Persistent viruses typically do not cause disease and rarely are detected...."
More interestingly, unlike many other viruses this chrysovirus has changed very little since Ancestral Puebloans cultivated corn in the US Southwest 1000 years ago, and it has persisted in corn up to present day. This suggests to scientists that the virus may have some benefit to the corn that they have yet to puzzle out.