DISSERTATION RESEARCH: Genome Evolution of a Polyploid Complex in Sorghum (Poaceae)

当今系统学中最具挑战性的问题之一是理解密切相关物种之间的关系，特别是那些受到杂交和多倍体（生物体基因组加倍）等过程影响的物种。本研究探讨了这些过程对高粱科植物种间亲缘关系的影响。高粱科。高粱包括栽培高粱[双色高粱（L.）]Moench]和强生草[高粱（L.）]珀耳斯。是世界上最有害的杂草之一。halepense是一种多倍体，被认为是由双色葡萄衍生而来。双色S. bicolise和halepense不是遗传分离的，可能会杂交，形成复杂的关系模式。来自该物种复合体个体的植物核和叶绿体基因组的多个部分的DNA序列数据将用于重建进化关系。这些关系可以检查模式的存在，这可能与地理、植物外观、入侵性或其他因素相关。鉴于这种物种复合体在高粱中的经济重要性，更好地了解它们的关系是必不可少的。栽培高粱是世界上第五大谷类作物，也是半干旱热带地区的主要粮食作物。与玉米相比，它具有较小的基因组大小，使其成为禾本科比较基因组学研究的理想模式生物。halepense是世界上十大最有害的杂草之一。入侵物种是全球生物多样性的第二大威胁，仅次于栖息地破坏，每年造成数十亿美元的作物减产。本研究也将有助于更好地了解多倍体的发生过程及其对植物进化的影响。多倍体的过程与广泛的基因组变化有关。目前的估计表明，至少50-70%的被子植物在其进化过程中经历了基因组复制，使多倍体成为植物进化的一个重要因素。多倍体还塑造了许多其他生物的基因组，比如脊椎动物，包括人类，并在某些癌症中发挥作用。多倍体和杂交都有可能增加物种内的遗传变异，并可能增加入侵能力。更好地了解这些过程及其对这些重要经济物种进化的影响可能对许多领域有益，包括植物育种和杂草控制工作。

NSF DDIG Non-technical AbstractOne of the most challenging problems in systematics today is understanding the relationships between closely related species, especially those that have been subject to processes such as hybridization and polyploidy, the doubling of an organism's genome. This research investigates the effects of these processes on the relationships among species of Sorghum sect. Sorghum (Poaceae). Sorghum sect. Sorghum includes cultivated sorghum [Sorghum bicolor (L.) Moench] and johnsongrass [Sorghum halepense (L.) Pers.], one of the world's most noxious weeds. S. halepense is a polyploid, thought to be derived from S. bicolor. S. bicolor and S. halepense are not genetically isolated and may hybridize, creating complex patterns of relationship. DNA sequence data for multiple sections of the plants' nuclear and chloroplast genomes from individuals of this species complex will be used to reconstruct evolutionary relationships. These relationships can be examined for the presence of patterns, which may be correlated with geography, plant appearance, invasiveness, or other factors.In light of the economic importance of this species complex in Sorghum, a better understanding of their relationships is essential. Cultivated sorghum is the fifth most important cereal crop in the world and a staple grain in the semi-arid tropics. It has a small genome size relative to that of maize, making it an ideal model organism for comparative genomics studies in the grasses. S. halepense is one of the ten most noxious weeds worldwide. Invasive species rank second behind only habitat destruction as the largest threat to biodiversity worldwide and cost billions of dollars each year in reductions in crop yields. This research also will contribute to a greater understanding of the process of polyploidy and its impact on plant evolution. The process of polyploidy has been linked to extensive genomic changes. Current estimates suggest that at least 50-70% of angiosperms have undergone genome duplication at some point in their evolutionary past, making polyploidy a significant factor in plant evolution. Polyploidy has also shaped the genomes of many other organisms, such as vertebrates, including humans, and plays a role in some cancers. Polyploidy and hybridization both have the potential to increase genetic variability within a species, and possibly invasive ability. A greater understanding of these processes and their effects on the evolution of these economically important species may be beneficial to a variety of fields, including plant breeding and weed control efforts.