9417791 Beagle-Ristaino Ancient potato tubers and sweetpotato storage roots unearthed form the middens of four archaeological sites located near the coastal desert city of Casma in the Department of Ancash, Central Peru have been collected and are housed in the herbarium at Southern Illinois University. These ancient tubers and storage roots represent some of the oldest known mummified specimens of potato ans sweetpotato in the world. The collections date from the Preceramic Period (2000 BC) to the Initial Period (1200 BC). The potato tubers have been identified and belong to the cultivated potato (Solanum tuberosum L., sensu lato) and the storage roots have been identified as sweetpotato (Ipomoea batatas Lam.) by their extant features and starch grains. The state of preservation of the specimens is excellent because the archaeological sites are in a dry subtropical coastal desert that receives less than 5 mm of rainfall per year. New techniques and approaches will be applied of these ancient plant specimens. These tolls will permit research questions never before possible with ancient plant material. The objectives of this study are to determine whether these ancient specimens contain morphological evidence of plant pathogenic fungi or actinomycets; DNA can be amplified from the organisms observed and the identity of the organisms be confirmed utilizing PCR technology; and the DNA sequences of the ancient plant pathogenic organisms compare to modern day plant pathogenic organisms that infect potatoes and sweetpotatoes. There are over 100 specimens in the collection. Some tubers have obvious symptoms of common scab caused by Streptomyces scabies. It is highly unlikely that the samples have been recently colonized by plant pathogens since the dessert archaeological sites would not be conducive for infection or survival of plant pathogens and specimens were excavated below 1 meter depths. In addition, cultivated and wild solanaceous species and sweetpotatoes are not currently grown i n the area. The research has potentially far reaching implications. First, the plant pathogenic fungus, Phytophtora infestans, cause of potato late blight and the Irish potato famine may be present in the ancient tubers. The disease is endemic in Peru but the supposed center of origin of the disease is in the Toluca Valley of Mexico, a secondary center of diversity of Solanaceous species. The presence of the late blight pathogen in ancient tubers would challenge the current dogma in the science and could shift current research studies on the population genetics of the fungus and the search for sources of resistance in wild species to Peru. Second, movement of tubers and storage roots and potential pathogens out of Peru after colonization by the Spaniards may have led to secondary centers of epidemic development in other areas of the world. Third, ancient DNA amplified, cloned and sequenced from both the plant hosts and pathogen species may be useful in more clearly elucidating the phylogenetic relationships between ancient and modern pathogens and domesticated species of potato and sweetpotato.
