马尾松桐棉种源天然群体遗传结构研究

广西桐棉是我国重要的马尾松优良种源区，该种源分布面积达1.56万hm2，马尾松遗传资源优质且丰富，但近30年来该地区的马尾松天然资源受到较为严重的破坏。为了解该地马尾松天然种质资源的遗传多样性现状，该研究利用SSR分子标记分析了桐棉马尾松的群体遗传结构。结果表明：16对 SSR 引物在285个样本中共检测到53个等位基因，多态位点百分率为100％。桐棉群体的平均等位基因数( N a )、平均有效等位基因数(Ne)、Shannon 多样性指数(I)、观测杂合度(Ho)、期望杂合度(He)分别为3.31、1.68、0.64、0.35和0.36，可见桐棉群体现今仍具有较高的遗传多样性。群体的遗传分化系数(GST)为0.049，固定指数(FST)为0.072，基因流(Nm)为3.21。这说明桐棉群体内基因型分布接近于平衡状态，未出现明显的杂合子过剩或不足，遗传变异主要存在于林分内，林分间不存在明显的遗传分化，群体内基因交流顺畅。同时，处于桐棉种源核心区域的4个林分遗传多样性水平显著低于核心区外围的3个林分，说明桐棉种源核心区域遭到更为严重的人为破坏。为了保障该处马尾松天然群体的正常更新及自然遗传改良能力应重视对马尾松天然林的科学管护。一方面通过遗传资源选择收集，建立大规模种质资源库；另一方面，对于桐棉种源这类分布面积大、利用价值高、目前所受破坏尚不严重的天然群体，应建立专门的自然保护区，严禁盗伐、主伐、非法采割松脂及过度采种。该研究结果对于马尾松天然种质资源的研究与保护具有重要参考价值。

Genetic structure of Pinnus massoniana on Tongmian natural populations in Guangxi

Guangxi Tongmian is an important superior provenance region of masson pine in China. The distribution area of this provenance had reached 15 600 hm². It had a high-quality and rich genetic resources of masson pine, and made a great contribution to the genetic improvement of masson pine. Over the last 30 years, natural resources of masson pine in this region have suffered serious damage. To understand the genetic diversity of natural germplasm resources of masson pine in this area, SSR molecular markers were used to analyze the population genetic structure of masson pine in Tongmian region. The results showed that 53 alleles were identified by 16 pairs of SSR primers in 285 samples, and the polymorphism rate was 100%. The mean number of alleles(N_a), the mean number of effective alleles(N_e), Shannon''s information index(I), observed heterozygosity(H_o), expected heterozygosity(H_e)were 3.31, 1.68, 0.64, 0.35 and 0.36. This showed that the Tongmian population still maintained high level of genetic diversity. Analysis on genetic structure of each stand in Tongmian population showed that coefficient of genetic differentiation(G_ST), fixation index(F_ST)and gene flow(N_m)were 0.049, 0.072 and 3.21. The genotype distribution was closer to Hardy-Weinberg equilibrium, and had no significant heterozygote excess or shortage. In Tongmian population, most genetic variation mainly existed within the stand, and no significant genetic differentiation existed among stands. The gene flow in it was smooth. Meanwhile, the genetic diversity of the four stands in the core region was lower than genetic diversity of three stands outside the core region. This indicated that the core region of Tongmian provenance suffered more serious man-made damage. In order to protect the natural updating and natural genetic improvement ability of the natural populations of masson pine in this area, we should pay attention to the scientific management of natural forest. On the one hand, genetic resources should be collected and large-scale germplasm resources should be established. On the other hand, we should establish special nature reserve and prohibit illegal felling, final felling, illegal resin tapping and excessive seeding for the natural population like Tongmian which has large distribution area, high utilization value and no serious damage at present. The results of this study have important reference value for the research and protection of the natural germplasm resources of masson pine.