培育边际土地上高产芒草的遗传基础

Miscanthus is a C4 perennial grass capable of producing high biomass and resisting environmental stresses. With the development of biorefinery and the needs for high quality ecological conditions, Miscanthus, as a potential new crop that provides feedstock for biorefinery and plants for ecological restoration, has attracted a growing attention of research. Given the rich resources of Miscanthus germplasm and its utilization potential in China, Yi Zili and his team collected and evaluated all the species of Miscanthus across the distributional range of China. They also developed cultivation and breeding techniques and obtained the F2 population resulting from a cross between M. lutarioriparius and M. sacchariflorus. Sang Tao and his team collected and planted the core germplasm of Miscanthus on the marginal land of drought, cold, infertile, and salinity soil for screening and domesticating valuable cultivars. They also obtained the reference transcriptome of Miscanthus and established analytical methods for candidate genes beneficial to adaptation and yield. In this proposal, the progenies resulting from a cross between M. lutarioriparius and M. sacchariflorus were planted on mine recovery area in the Loess Plateau. We will sequence the transcriptome of the population and construct a high-density genetic map. A QTL analysis will be conducted on the yield and growth traits and gene expression will be associated with physiological traits to identify candidate genes related to adaptation. The results of the proposed study should address the key question of how to effectively and accurately identify QTL and candidate genes for important traits in order to assist further molecular breeding of Miscanthus. It will also serve as an example for the similar work on non-major crops and the development of new cultivars under various stressful growing conditions.

芒草是抗逆性强、生物量大的多年生C4草本植物。随着生物炼制技术的发展和生态文明建设的需要，芒草作为提供生物炼制原料及生态修复功能的新型作物更是备受关注。针对我国芒草资源开发与生态利用需求，易自力团队收集评价了中国所有种和分布区的芒草种质资源，建立了芒草栽培和育种技术并创制了南荻×荻的杂交群体。桑涛团队收集了芒草核心种质，进行了干旱、寒冷、瘠薄和盐碱边际土地上的筛选驯化，并构建了芒草参考转录组序列和候选基因分析技术。本项目拟将上述杂交群体在黄土高原矿山恢复区进行实地筛选，进一步开展其转录组测序、高密度遗传图谱构建、产量和生长性状关键QTL分析，并通过表达量与生理性状关联分析鉴定适应性候选基因。通过这些遗传基础研究，来探索如何高效准确地鉴定重要性状QTL和候选基因的关键科学问题，为芒草分子育种研究奠定遗传基础，并为进行其它非主要农作物同类研究和培育适应胁迫环境的新品种提供参考模式。

芒草(Miscanthus Andersson)是一类生态适应性强、生长速度快、生物量高的多年生C4草本植物。近年来，因其生态修复功能、生物炼制原料特性和生物质能源潜力而受到学界广泛关注。由于芒草是天然异交作物，且属于古异源多倍体，其基因组融合了二倍体高粱和多倍体甘蔗，因此有着十分复杂的遗传机制。针对芒草遗传基础不清晰、遗传背景复杂的现状，本项目以南荻（M. lutarioriparus）与荻（M. sacchariflorus）的种间杂交F1群体为研究对象，开展黄土高原环境下芒草田间表型性状分析、群体转录组测序、多态性SNP标记鉴定、遗传连锁图谱构建、抗逆性状QTLs分析、生态适应性相关候选基因鉴定以及优良种质筛选等系列研究。结果表明：（1）F1杂交种平均越冬率为97%，平均建植率为95%，平均存活率为66%，极显著高于亲本，表明杂交种在黄土高原具有更好的适应性；（2）通过转录组测序，共获得多态性SNP标记8830个，排除偏分离比例的标记，最终获得461个有效SNP分子标记，标记有效率为5.33%，并利用joinmap软件，构建了一个具有19个连锁群的遗传连锁图谱，总长度为3215.53cM，每个连锁群的长度范围为95.03cM(LG3) -228.63cM(LG9)；（3）通过生物量、株高、分蘖数等重要表型性状及光合速率等重要生理性状与SNP标记的分析，定位了64个与黄土高原生态适应性相关的 QTLs，QTL的LOD阈值在2.510到4.935之间，9号连锁群QTL数目最多，为11个，包括了茎秆重量、整株重量、光合效率、胞间二氧化碳浓度、气孔导度和水分利用效率等6个性状；（4）筛选到MluLR3275、K41_C314568、MluLR866等基因同时对脂肪酸代谢、脂肪酸延长、淀粉与蔗糖的代谢、次生代谢产物的生物合成等代谢通路进行调控并呈现上调或者下调趋势，这暗示着上述候选基因经过对代谢通路的协作调控，使F1相对于父（母）本具备了更好地适应黄土高原环境；（5）利用隶属函数法在F1群体中筛选出34个具有环境适应性强，生物量高的优质基因型个体，为后期创制南荻×荻F2群体奠定了材料基础。以上研究结果为揭示芒草的遗传背景和遗传机制提供了参考，同时为培育能适应黄土高原气候的芒草新品种提供了途径。