DISSERTATION RESEARCH: Evolution of polyploidy and storage roots in sweet potato and its wild relatives

甘薯富含碳水化合物和维生素，是许多国家人民的重要营养来源。目前提高甘薯产量的努力主要集中在少数几个育种品系上。作物物种的野生近缘种也可能是作物改良遗传物质的重要来源，但甘薯与其野生近缘种之间的进化关系目前尚不清楚。该项目将利用基因组数据重建甘薯及其野生近缘种之间的进化关系，并阐明对栽培甘薯富含碳水化合物和维生素的储存根进化做出贡献的遗传变化。甘薯野生近缘品种的根系特征和遗传变异尚不清楚，该项目将大大提高对甘薯野生近缘品种育种潜力的了解。该项目将训练一名研究生和几名本科生掌握实验室技术。研究结果将整合到初中、高中和本科学生的新教材中，这些教材强调驯化过程和作物育种计划中多样性的重要性。本研究将表征甘薯（Ipomoea batatas）及其近缘种全基因组重复事件的时间，并测试这些事件是否与该群体储存根的进化有关。许多研究表明，多倍体是复杂表型进化的主要驱动因素；然而，很少有研究将全基因组复制事件与新根系性状的进化联系起来。本研究将应用现代系统基因组学方法来估计Ipomoea batatas复合体内部的关系，并重建该群体的多倍体化和储存根发育历史。本研究通过基因捕获和限制性内切位点相关DNA测序（RADSeq）技术开发的遗传标记将有助于种质资源中心对甘薯和整个甘薯复合体的多样性进行表征和保护。这些发现将推动红薯育种工作，包括最近为非洲开发高产和健壮的红薯品种的工作。

Sweet potato, with its carbohydrate- and vitamin-rich storage roots, is a vital source of nutrition for people in many countries. Current efforts to improve crop yield in sweet potato are focused on a small number of breeding lines. Wild relatives of crop species can also be an important source of genetic material for crop improvement, but the evolutionary relationships between sweet potato and its wild relatives are currently unknown. This project will use genomic data to reconstruct evolutionary relationships between sweet potato and its wild relatives, and shed light on the genetic changes that have contributed to the evolution of the carbohydrate- and vitamin-rich storage root in cultivated sweet potato. Root characteristics and genetic variation are poorly known for wild relatives of sweet potato and this project will provide a greatly improved understanding of the potential of wild relatives for sweet potato breeding programs. The project will train one graduate student and several undergraduates in laboratory techniques. Results from the research will be integrated within new teaching materials for middle school, high school and undergraduate students that emphasize the domestication process and importance of diversity in crop breeding programs.This research will characterize the timing of whole genome duplication events within sweet potato (Ipomoea batatas) and closely related species, and test whether these events are linked to the evolution of storage roots in the group. Numerous studies have implicated polyploidy as a major driving factor in the evolution of complex phenotypes; however, few studies have linked whole genome duplication events with the evolution of novel root traits. This study will apply modern phylogenomic methods to estimate relationships within the Ipomoea batatas complex and reconstruct the history of polyploidization and storage root development in the group. Genetic markers developed through gene capture and Restriction site Associated DNA Sequencing (RADSeq) technologies through this research will be useful for germplasm stock centers characterizing and preserving diversity within sweet potato and across the Ipomoea batatas complex. These findings will advance sweet potato breeding efforts, including recent work to develop productive and robust cultivars for Africa.