马尾松育种进程中的遗传增益与遗传多样性变化

【目的】通过对广西马尾松3次改良过程中的遗传多样性及改良增益进行分析,总结育种进程中的遗传多样性变化动态。分析通过育种群体结构设计、选择方法提高改良效果的可行性,为制定马尾松长期育种策略及良种发展战略提供理论参考。【方法】以广西马尾松天然群体及第1代、第1.5代、第2代育种群体为材料,采用SSR标记分析其遗传多样性,根据遗传测定结果估算历次改良所得遗传增益。【结果】广西马尾松的第1次改良过程,获得约32%材积增益,损失约14%的低频等位基因,Shannon多样性指数(I)没有发生变化,观测杂合度(H_o)约上升27%。第2次改良过程获得19.34%的遗传增益,损失了约16%的低频等位基因,Shannon指数(I)约下降了6%,观测杂合度(H_o)没有变化,近交系数约下降了20%。第3次遗传改良过程获得23.68%的遗传增益,损失约12%的低频等位基因,Shannon指数(I)下降约25%,观测杂合度(H_o)下降约20%,近交系数下降约47%。【结论】广西马尾松 3次改良均获得了较高的遗传增益,并有效降低了群体的近交程度,遗传多样性损失相对较少。由此说明,所用的选择策略可以有效兼顾遗传增益与遗传多样性。

Changes of genetic gain & genetic diversity in the breeding process of Pinus massoniana

【Objective】 Provide theoretical support for the development of long-term breeding strategies and elite varieties for masson pine(Pinus massoniana). Additionally, the changes in genetic diversity and gain of Guangxi masson pine in the breeding process were analyzed, and the feasibility of obtaining improved effects by the design of breeding population structure and the selection method was discussed. 【Method】 The genetic diversities of the natural, first-generation, 1.5-generation and second-generation breeding populations were analyzed by the SSR molecular marker technique. The corresponding genetic gains were estimated basing on the genetic test results. 【Result】 In the first-generation of genetic improvement, the gain of wood volume and loss of low-frequency alleles for masson pine were approximately 32% and 14%, respectively. The Shannon diversity index(I)remained unchanged, but the observed heterozygosity(H_o)increased nearly 27%. In the 1.5-generation of genetic improvement, the gain of wood volume and loss of low-frequency alleles were 19.34% and 16%, respectively. The I and inbreeding coefficient decreased 6% and 20%, respectively, whereas H_o remained unchanged. In the second-generation of genetic improvement, the gain of wood volume and loss of low-frequency alleles were 23.68% and 12%, respectively. The I, H_o and inbreeding coefficient decreased approximately 25%, 20% and 47%, respectively. 【Conclusion】 During the three processes of genetic improvement of Masson pine in Guangxi, the genetic gain was high, and the loss of genetic diversity was relatively low. The degree of inbreeding was also effectively reduced. It is suggested that the selection strategy was effective in striking a balance between the genetic gain and genetic diversity.