基于亲缘关系的梨种质群系统构建及遗传结构分析

China is the origin center of genus Pyrus (Rosaceae) and one of the three centers of diversity for cultivated pears. There are 13 Pyrus species originated in China.Pear trees dispersed widely in China which can be found from frigid zone to tropical zone, from western highland region to eastern seaboard of China.There are more than 3000 varieties in China.The production and acreage of pear cultivation in China occupied more than two thirds of the world. Most of the pear germplasm accessions are wild accessions or traditional cultivars on the basis of biological status of origin.They arise from natural seedlings.Their genetic backgrounds are complicated due to no reproductive isolation in terms of interspecific hybridization.It is still unclear to us about the genetic relationship between Pyrus accessions.This restricts the germplasm enhancement and hybridization utilization. The concept and ideas of crop core collection can give us good references on pear germplasm research, which are beneficial for improving the effective sharing and utilization of pear germplasm.This research puts the genetic relationship analysis between Pyrus accessions as the starting point. Based on ecotope, the main phenotypes, SSR genotypes, chloroplast gene haplotype, and ecotype of pear accessions are going to be analyzed to reveal the genetic relationship of Pyrus accessions using the theories and methods of morphology, molecular phylogeny, and phytogeography. Most of the materials used in this study will be wild pear accessions or traditional cultivars. The purpose of our study is to systematically reveal the genetic relationship between pear accessions, build Pear Germplasm Group System based on genetic relationship, analyze the genetic structure and diversity level of main pear ecological zone, probe into the forming mechanisms of biogeographic pattern of Pyrus, and promote the sustainable development of pear industry.

中国是梨属植物起源中心和栽培梨的多样性中心之一，起源于中国的梨属植物有13个种，栽培品种3000个以上。梨树在中国栽培范围广泛，从寒带到热带，从西部高原到东部沿海均有分布，产量和面积占世界2/3以上。梨种质绝大多数为地方品种或野生资源，主要由实生繁殖而来，由于梨属种间杂交无生殖隔离，遗传背景复杂，种质之间亲缘关系不明确，制约种质创新和育种利用。为提高梨种质共享利用水平，参考农作物核心种质的概念和思路，以生态区为单元，以亲缘关系研究为切入点，以我国原产梨野生资源和地方品种为研究对象，综合运用形态学、分子系统学、谱系地理学的理论和方法，通过梨种质基于表型、SSR基因型、叶绿体基因单倍型、生态型的综合分析，系统研究梨种质的亲缘关系，构建基于亲缘关系的梨种质群系统，分析梨种质群遗传结构特点及多样性水平，探讨梨属植物地理格局形成机制，为梨种质保护和共享利用提供理论依据，促进梨产业可持续发展。

以梨属植物为研究对象，基于梨种质资源花表型、SSR基因型、叶绿体基因单倍型、多酚物质含量及组成、光合特性的综合分析，研究了梨种质的亲缘关系，构建种质群。结果表明：（1）13个种625份资源的花器官11个表型性状中，以白色花蕾、紫红色花药、柱头高于花药和花柱基部无茸毛等类型居多，分别占相对应描述符分布频率的50.56%、47.52%、63.20%和80.96%，花药颜色的Simpson指数和Shannon-weaver指数较高，分别为0.719和2.351，多样性最为丰富，基于花表型性状将脆肉资源聚为5大群体，将软肉资源聚为4大群体；（2）基于SSR分子标记，对171个脆肉型梨品种和75个软肉型梨品种进行亲缘关系分析，扩增出等位基因267个，期望杂合度分别为0.76和0.78，观测杂合度分别为0.59和0.60，构建12个脆肉型梨品种群和7个软肉型梨品种群；（3）基于叶绿体DNA多样性分析，评价了中国326份种质资源的叶绿体DNA多样性，获得变异位点48个，单一突变位点8个，简约信息性位点40个，插入/缺失片段 35个，单倍型34个，探索了基于cpDNA单倍型的梨属植物的演化路线，并确认了10个中国梨属品种群；（4）对梨品种叶片酚类物质的组成和含量进行了研究，共检测出17种酚类物质，9种准确定性，明确熊果苷是梨叶片中最主要的酚；（5）对我国原产山梨叶片形态及光合特性研究表明，野生山梨叶片比叶面积、叶干物质含量、胞间二氧化碳浓度的变异系数较低，光合速率、胞间二氧化碳浓度等8 项指标变异系数0.12～0.41，均表现出较高的多样性水平。本研究通过多种方法系统研究了梨种质资源的亲缘关系，为梨育种核心亲本选择、种质资源保护与利用提供了理论依据。