SGER: Tracking Ancient Epidemics: Survey of Plant Pathogens of Preceramic Peru

在秘鲁中部安卡什省沿海沙漠城市卡斯马附近的四个考古遗址中出土的古代马铃薯块茎和甘薯储存根被收集起来，存放在南伊利诺伊大学的植物标本馆里。这些古老的块茎和储存根代表了世界上已知最古老的马铃薯和甘薯木乃伊标本。这些藏品的年代从前陶瓷时期（公元前2000年）到初始时期（公元前1200年）。马铃薯块茎经鉴定属于栽培马铃薯（Solanum tuberosum L., sensu lato），贮藏根经鉴定为甘薯（Ipomoea batatas Lam.）。这些标本的保存状况非常好，因为考古遗址位于亚热带干燥的沿海沙漠中，年降雨量不到5毫米。这些古老的植物标本将应用新的技术和方法。这些通行费将允许对古代植物材料进行前所未有的研究。本研究的目的是确定这些古代标本是否含有植物病原真菌或放线菌的形态学证据；利用PCR技术可以从所观察的生物中扩增DNA并确认生物的身份；并将古代植物致病生物的DNA序列与感染土豆和甘薯的现代植物致病生物进行比较。收藏品中有100多个标本。有些块茎有明显的由疥疮链霉菌引起的常见结痂症状。由于沙漠考古遗址不利于植物病原体的感染或生存，而且标本挖掘深度低于1米，因此这些样本最近被植物病原体定植的可能性很小。此外，该地区目前还没有种植栽培和野生的茄类植物和甘薯。这项研究具有潜在的深远影响。首先，引起马铃薯晚疫病和爱尔兰马铃薯饥荒的植物病原真菌——植虫菌可能存在于古代块茎中。这种疾病是秘鲁的地方病，但假定的疾病起源中心是墨西哥的托卢卡山谷，这是茄科物种多样性的第二个中心。在古代块茎中发现晚疫病病原体将挑战目前的科学教条，并可能将目前对真菌种群遗传学的研究和对野生物种抗性来源的研究转移到秘鲁。其次，在西班牙人殖民之后，块茎、储存根和潜在病原体从秘鲁移出，可能导致世界其他地区成为流行病发展的次要中心。第三，对植物寄主和病原菌的古代DNA进行扩增、克隆和测序，可能有助于更清楚地阐明古代和现代病原菌与马铃薯和甘薯驯化种之间的系统发育关系。

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.