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

小行星9417791 从位于中部秘鲁安卡什省沿海沙漠城市卡斯马附近的四个考古遗址的垃圾堆中出土的古代马铃薯块茎和甘薯贮藏根已被收集起来，并存放在南伊利诺伊大学的植物标本馆中。 这些古老的块茎和储藏根代表了世界上已知的最古老的马铃薯和甘薯木乃伊标本。 这些收藏品的年代从陶瓷时代前（公元前2000年）到最初时期（公元前1200年）。 马铃薯块茎已被鉴定并属于栽培马铃薯（Solanum tuberosum L.，广义上的甘薯（Ipomoea batatas Lam.）和淀粉粒所决定。 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，每年降雨量不到5毫米。 新的技术和方法将应用于这些古老的植物标本。 这些通行费将允许研究问题从来没有可能与古代植物材料。 本研究的目的是确定这些古老的标本是否包含植物病原真菌或放线菌的形态学证据;可以从观察到的生物体中扩增DNA，并利用PCR技术确认生物体的身份;将古代植物病原生物体的DNA序列与感染马铃薯和甘薯的现代植物病原生物体进行比较。 收藏了100多件标本。 有些块茎有明显的由疥疮链霉菌引起的普通疮痂病症状。 这些样本最近被植物病原体定殖的可能性很小，因为沙漠考古遗址不利于植物病原体的感染或存活，而且标本是在1米以下的深度挖掘的。 此外，该地区目前不种植栽培和野生茄科物种和甘薯。 这项研究具有潜在的深远影响。 首先，植物病原真菌，致病疫霉，马铃薯晚疫病和爱尔兰马铃薯饥荒的原因可能存在于古老的块茎。 该疾病是秘鲁的地方病，但假定的疾病起源中心是在墨西哥的托卢卡山谷，茄科物种多样性的次要中心。 在古老的块茎作物中发现晚疫病病原体，将对科学界目前的教条提出挑战，并可能将目前关于真菌群体遗传学的研究和在野生物种中寻找抗性来源的工作转移到秘鲁。 第二，块茎、贮藏根和潜在病原体在西班牙人殖民后移出秘鲁，可能导致世界其他地区的次级流行病发展中心。 第三，从植物宿主和病原物种中扩增、克隆和测序的古代DNA可能有助于更清楚地阐明马铃薯和甘薯的古代和现代病原体与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.