北京板栗种群的遗传多样性与进化历史研究

Genetic Diversity and Evolution History of Chinese Chestnut(Castanea mollissima)Populations in Beijing

野生种群是重要的种质资源,了解本地野生种群和栽培种群之间的遗传多样性和群体演化有助于野生种群的科学保护和可持续利用。本研究基于北京板栗自然与栽培分布区,采集5个栽培种群和1个野生种群共93份种质的叶片,并采集湖北宜昌1个种群(作为外群)共16份种质的叶片,筛选16对微卫星SSR引物分析板栗种群的遗传多样性和进化历史。结果表明北京板栗种群的遗传多样性相对较高,其中红螺寺野生板栗种群的遗传多样性高于其他种群。板栗各种群之间有明显的遗传分化(Fst=0.232),基因交流频率较低(Nm=0.547)。分子生物学方差分析(AMOVA)分析表明板栗种群内的遗传变异(57.70%)大于群体之间(42.30%)。群体遗传结构分析显示,宜昌板栗种群明显区别于北京板栗种群,北京板栗分为两组,红螺寺野生种群单独为一组,明代板栗园古树种群和其他栽培种群聚为一组,说明北京栽培板栗可能来自于明代板栗园古树种群。非加权组平均法聚类分析(UPGMA)、主坐标分析(PCoA)和主成分分析(PCA)结果均支持群体遗传结构结果。Treemix分析结果显示从宜昌种群到北京种群发生过历史基因交流,说明板栗从华中地区向北迁移的路线。种群历史结果表明,北京种群在大约8.3万年前从宜昌种群种分化出来,北京本地野生种和栽培种的分化时间大约在3.2万年前。本研究结果支持板栗由华中向北迁移的假说,栽培种的驯化降低了北京板栗种质资源的遗传多样性,北京板栗野生种和栽培古树保留了高的遗传多样性,应该优先得到保护。

Wild populations are important germplasm resources,and studying their genetic diversity and variation pattern of local wild and cultivated populations can facilitate their scientific protection and sustainable utilization.This study is based on the natural and cultivated distribution area of Chinese chestnut in Beijing,collecting leaves from a total of 93 germplasm of 5 cultivated populations and 1 wild population,and collecting leaves from a total of 16 germplasm of 1 population(as an outgroup)in Yichang(YC),Hubei.Sixteen pairs of microsatellite primers(SSR)were used to analyze the genetic diversity and genetic structure.The wild C.mollissima populations in Beijing was found with relatively high genetic diversity,and the genetic diversity of the wild Hongluosi population(HLS)was significantly higher than that of other populations.There was significant genetic differentiation between populations of C.mollissima(Fst=0.232),with low frequency of gene flow(Nm=0.547).AMOVA analysis showed that the intra-population genetic variation(57.70%)was greater than that among populations(42.30%).The genetic structure analysis showed that YC chestnut population was significantly different from Beijing chestnut populations.The HLS wild population was independent of Banliyuan population(BLY,an ancient tree population)and the other cultivated populations that were clustered into a group,indicating that cultivated chestnuts might come from the ancient tree population in Beijing.A coincidence was observed as well based on the UPGMA clustering,PCoA and PCA analysis.Treemix analysis showed that the chestnut populations in Beijing were likely from the YC population in southern China,indicating an evolutionary path for chestnut to migrate from central China to Beijing.The population history results indicate that the Beijing populations differentiated from the YC populations approximately 83,000 years ago,while the differentiation of local wild and cultivated species in Beijing occurred approximately 32,000 years ago.Our results support the hypothesis of chestnut migrating northward from central China.The domestication of cultivated species reduced the genetic diversity of chestnut germplasm resources in Beijing.The wild populations and cultivated ancient trees retain high genetic diversity,which should be protected preferentially.