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

从位于秘鲁中部安卡姆省沿海沙漠城市卡斯马附近的四个考古遗址的中间地带出土的9417791块Beagle-Ristaino古马铃薯块茎和甘薯存储根已被收集并保存在南伊利诺伊大学的标本馆中。这些古老的块茎和存储根代表了世界上已知的一些最古老的土豆和红薯木乃伊标本。这些藏品的年代从史前时期(公元前2000年)到最初时期(公元前1200年)。经鉴定，马铃薯块茎属于栽培马铃薯(Solanum tuberosum L.，Sensu Lato)，其贮藏根被鉴定为甘薯(Ipomoea batatas Lam.)根据它们现存的特征和淀粉粒。这些标本的保存状况非常好，因为考古遗址位于干燥的亚热带沿海沙漠，每年的降雨量不到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。这项研究的目的是确定这些古代标本是否包含植物病原真菌或放线菌的形态证据；可以从观察到的生物中扩增DNA，并利用PCR技术确认生物的身份；以及古代植物病原生物的DNA序列与感染马铃薯和甘薯的现代植物病原生物的DNA序列进行比较。藏品中有100多个标本。一些块茎有明显的由链霉菌结痂引起的常见结痂症状。由于甜点考古地点不利于植物病原体的感染或存活，而样本是在一米深以下挖掘出来的，因此这些样本最近被植物病原体侵占的可能性极低。此外，该地区目前还没有种植栽培和野生茄科植物和红薯。这项研究具有潜在的深远影响。首先，古老的块茎中可能存在植物病原真菌--马铃薯晚疫病菌、马铃薯晚疫病菌和爱尔兰马铃薯饥荒。这种疾病在秘鲁是地方病，但据推测，这种疾病的起源中心在墨西哥的托卢卡山谷，那里是茄科物种多样性的二级中心。古块茎中晚疫病病原菌的存在将挑战科学中目前的教条，并可能将目前对该真菌种群遗传学的研究以及在野生物种中寻找抗性来源的研究转移到秘鲁。其次，在西班牙人殖民后，块茎和贮藏根茎以及潜在的病原体迁出秘鲁，可能导致了世界其他地区的次要疫情发展中心。第三，从植物寄主和病原菌物种中扩增、克隆和测序的古代DNA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物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.