乐昌油杉遗传资源评价及重要性状的SRAP关联分析

Chinese fir "Lechan" is one of the superior provenance in Cunninghamia lanceolata（Lamb.）Hook (Chinese fir) due to its desirable attributes of fast growth, good quality timber, high heartwood ratio (red heartwood) and well adaptability.In the present study, a large-scale system investigation on the genetic resources of Chinese fir "Lechan" was conducted in Lechan area of guangdong, and the superior plus genetic resources (the plus trees) were therefore positioned and grafting saved in a resources gene bank.Based on that, a series of important traits including height,DBH (diameter at breast height),volume,and BR (bark ratio),shape,DEN (wood basic density),HR （heartwood ratio）,and WS (wood shrinkage),WH (wood hygroscopicity),tracheid morphological characteristics were analyzed for the plus trees or their grafted clones. Furthermore, a sequence-related amplified polymorphismon (SRAP)system was employed to determine the molecular polymorphism of the superior plus genetic resources in Chinese fir "Lechan". It was higly expected that the present genetic resources could be effectively evaluated on both the phenotypical and molecular levels. It was also thought that a clustal of genomic loci for some important economical traits could be exploited following an assosiation analysis on the informatic phenotype and SRAP data,and finally some real superior genotypes could be discovered. Briefly, the present study will provide a scientific basis for protection and further exploitation of the genetic resources of Chinese fir "Lechan" in the near future.

乐昌油杉为我国杉木[Cunninghamia lanceolata（Lamb.）Hook.]优良种源之一，具有速生、优质、心材（红心材）比率高、适应性强等特点。本研究通过对广东省乐昌地区杉木林分进行大规模、系统调查的基础上，采集优异遗传资源（优树）穗条并嫁接保存，同时对优树树高、胸径、单株材积、树皮比率、形质、木材基本密度、心材比、木材干缩性与吸水性、管胞形态等重要经济性状及嫁接无性系的生长开花结实特性进行测定与性状变异模式分析；另外，通过建立稳定、高效的SRAP分子标记体系，在分子水平上对乐昌油杉遗传资源进行多态性遗传变异检测。项目从表型水平与分子水平两个层次对乐昌油杉遗传资源进行综合评价，同时耦合表型分析数据与SRAP多态性标记信息，检测到与重要经济性状显著连锁的SRAP标记位点，最终发掘携带优良基因的杉木资源。研究结果将为我国杉木优良种源乐昌油杉遗传资源的保护与开发利用提供科学依据。

乐昌油杉是我国杉木最为优良的地方类型之一，具有速生、适应性较强，木材色红且坚实等特点，但近年来随着林地更新利用速度的加快与单一种系（杉木）经营策略的实施，现存乐昌油杉资源面积逐年递减，其遗传多样性及优异的基因资源随之逐步丧失。本项目通过对广东省乐昌地区杉木林分进行系统调查，综合选出104份乐昌油杉优树资源，入选优树树高、胸径、单株材积现实增益分别为0.4%~97.1%、32.3%~131.8%、82.6%~712.5%；高径比、冠径比、木材基本密度、红心材比率、木材干缩性、木材吸水性总体变幅则分别为38.9~76.5、8.7~21.9、0.2511~0.3931g/cm3、29.2%~72.3%、0.8%~32.4%、189.0%~332.9%；木材干缩性变异程度最大，CV值达100%，而木材基本密度变异程度较低，CV值仅为11%。项目组随后对乐昌油杉优树资源进行了有效保存，并建立适于杉木分子多态性检测的SRAP标记体系。对异地嫁接保存的103份乐昌油杉遗传资源及其对照试样进行分子多态性检测发现，乐昌油杉遗传资源多样性达中等水平以上，PPB、PIC、H和I值分别为92.83%、0.1805、0.1911及0.3080。UPGMA聚类结果显示，试样间遗传相关系数变幅在0.46～0.81间，总体可分为3大类即A类、B类及复合类。A类聚合了乐昌油杉遗传资源中87.4%的样品，表明乐昌油杉遗传资源具有一定程度的地理特异性。研究还发现，乐昌油杉遗传资源遗传相似性属中等水平以上（0.40～0.81），多数资源相似性介于0.50～0.59间，LH06和LH10间相似性最高（0.81），LM18与其它资源间遗传距离最远，其遗传相关关系为从分子水平上判别其亲缘关系提供了依据。上述优树资源极大拓宽了现有乐昌油杉育种资源的遗传基础，为杉木新种质创制提供了宝贵的资源，同时也为重要性状基因资源的挖掘提供了一个有价值的基因池。另外，为解析乐昌油杉生长和材质性状与SRAP标记的相关性，项目组还对杉木基因库中24年生乐昌油杉无性系及其对照株系生长材质性状进行测定，率先检测到一批（77个）与杉木生长和材质性状紧密关联的SRAP位点，其表型变异解释率（R2）均较高（8.3%26.4%），当中18个位点序列已测序完成，这些位点将为杉木分子标记辅助育种策略的实施提供重要的支撑。