Biodiversity and relationships of Urochloa grasses for application in sustainable tropical forage systems

世界上一半以上的农业用地是牧场，但热带饲料植物很少受到关注。人们对它们的关系和生物多样性知之甚少。尾草属（Brachiaria）非洲禾草群被作为饲料带到南美洲，现在驯化的饲料作物对小农的可持续动物生产很重要。在这个明确界定的博士项目中，我们可以回答有关野生非洲尾藻物种与栽培二倍体和多倍体的关系，驯化过程，其生物多样性，种质资源（饲料作物及其野生亲缘）以及物种形成过程中遗传瓶颈的发生等关键问题。先前的研究表明，毛斑尿藻（Urochloa brizantha）、U. decumbens、U. ruziziensis和U. humidicola形成了一个起源不确定的复杂多倍体系列。在全球挑战研究基金（GCRF NERC/BBSRC）项目中（涉及三名监督小组成员）的工作已经显示了多倍体的基因组构成，但我们需要将我们的工作扩展到未研究的相关野生物种，并确定哪些物种提供了二倍体基因组。目前还没有对尾藻进行系统发育重建的尝试，这项工作将建立一个基于DNA和形态学的框架，结合地理、生态和环境数据，允许在当前和气候变化、土地利用压力和生物多样性丧失的条件下利用遗传资源进行育种，以实现可持续性。在过去的200年里，邱园的草分类学家建立了非洲草的分类系统，邱园的植物标本馆是唯一一个全面的参考收藏。该项目将把这些物种置于进化的背景下，在植物多样性研究和作物科学之间建立一座桥梁，并为可持续农业开发更好的饲料作物做出贡献。它将利用莱斯特大学开发的遗传标记系统和基因组特异性序列，以及种质资源收集。研究结果将有助于测定该物种的生物多样性和基因组组成，以及确定该物种的系统发育和分类界限。

More than half of the world's agricultural land is grazing land, but tropical fodder plants receive little attention. Their relationships and biodiversity are poorly understood. The Urochloa (Brachiaria) group of African grasses were brought to South America as forages and the now domesticated forage crops are important for sustainable animal production by smallholders. Within this well-demarcated PhD project we can answer critical questions about the relationships of wild African Urochloa species to the cultivated diploids and polyploids, the processes of domestication, their biodiversity, germplasm resources (in forage crops and their wild relatives), and the occurrence of genetic bottlenecks during speciation. Previous work has shown that Urochloa brizantha, U. decumbens, U. ruziziensis and U. humidicola form a complex polyploid series of uncertain origins. Work within a Global Challenges Research Fund (GCRF NERC/BBSRC) project (involving the three supervisory team members) has shown genome constitutions of polyploids, but we need to expand our work to unstudied related wild species, and define which species have provided donor diploid genomes. No phylogenetic reconstruction of Urochloa has been attempted, and the work will build a framework based on DNA and morphology, integrated with geographical, ecological and environmental data, allowing exploitation of genetic resources in breeding for sustainability now and under conditions of climate change, land-use pressures and biodiversity loss. Over the last 200 years grass taxonomists at Kew have built the classification system for African grasses, and the Kew herbarium is the only comprehensive reference collection. This project will place these species in an evolutionary context, build a bridge between plant diversity research and crop science, and contribute towards developing better forage crops for sustainable agriculture. It will exploit genetic marker systems and genome-specific sequences developed at the University of Leicester, along with germplasm collections. The results will lead to measurement of biodiversity and genome compositions in the accessions, as well as defining phylogeny and taxonomic boundaries of the Urochloa species.