【作者】 姚俊修；

【导师】 李火根；

【作者基本信息】 南京林业大学 ， 遗传学， 2010， 硕士

【摘要】 异交物种易发生近交衰退。鹅掌楸为濒危树种,现存种群规模小,其天然种群更新可能受到近交衰退的影响,因此,开展鹅掌楸近交子代遗传分析对于了解鹅掌楸濒危机制有重要意义,同时,对于鹅掌楸杂交育种及种子园管理也具有实践价值。本文以鹅掌楸属树种不同交配类型子代为材料,从种子饱满度、出苗率、苗期生长量、遗传多样性、纯合位点百分率等方面进行比较分析,估算鹅掌楸近交衰退程度。主要结论如下:种子饱满度及出苗率在不同母本间、交配类型间、交配类型内组合间差异均达到了极显著水平。种内交配子代种子饱满度与出苗率均最高,种内交配子代饱满度平均高出种间杂交、回交交配、自交组合的33.30%、89.02%、612%;出苗率平均高出90.56%、119%、362%,不同交配类型子代饱满度、出苗率有相同的变异趋势:种内>种间>回交>自交。在苗高和地径性状上,交配类型间、交配类型内组合间差异均达极显著水平。种间交配子代在两性状上均最高,种间交配子代地径平均高出自交组合、回交交配、种内组合分别为7.98%、19.73%、91.30%;苗高平均高出9.59%、36.70%、47.45%,不同交配类型子代地径与苗高变异趋势为:种间>自交>回交>种内。12对SSR引物对27个交配组合进行遗传多样性分析,以观测杂合度和shannon多样性指数为指标,种间群体均最高,Ho平均高出回交群体、种内群体、自交群体的17.99%、27.75%、269%;shannon多样性指数平均高出5.22%、13.34%、19.77%;遗传多样性变异趋势:种间>回交>种内>自交。自交子代的纯合位点百分率最高为76.82%,分别高出种内群体、回交群体,种间群体的1.04倍、1.37倍、2.73倍;由此推算出鹅掌楸、北美鹅掌楸亲本的平均基因杂合度分别为42.72%、47.62%。综上所述,与种内及种间交配子代相比较,鹅掌楸近交子代在种子饱满度、出苗率、遗传多样性、纯合位点百分率等方面均存在不同程度的衰退,但对于苗期生长量,近交衰退不明显。更多还原

【Abstract】 Outcrossing species is prone to inbreeding depression. Liriodendron is endangered species and the existing population size is small, the ability to reproduce of natural populations of Liriodendron may be affected by inbreeding depression, it is significant to understand endangered mechanism ,hybrid breeding, management of seed orchard of Liriodendron which developed genetic studies of inbred offspring.In this paper, plumpness and germination rate of seed,seedling growth ,the genetic diversity, percentage of homozygous loci of different mating types in Liriodendron were studied and compared which is to analysis the extent of recession of Inbred offspring , the main results were as follows:Significant variations of plumpness and germination rate of seeds existed among different female parents, mating types, mating combinations within types. Plumpness and germination rate of seeds are all maximum in intra-species progenies , Plumpness of seeds exceeded plumpness of inter- species progenies,backcross progenies,self-cross progenies 33.30%、89.02%、612%. Emergence of seeds exceeded plumpness of inter- species progenies,backcross progenies,self-cross progenies 90.56%、119%、362%. Variation trend of plumpness and emergence is consistent: intra-species progenies> inter- species progenies > backcross progenies >self-cross progenies.In height and GLD traits, significant variations of growth at seedling stage existed among mating types, mating combinations within types, the two traits are all maximum in inter-species progenies , GLD exceeded GLD of self-cross progenies,backcross progenies, intra- species progenies 7.98%、19.73%、91.30%. height exceeded height of self-cross progenies ,backcross progenies, intra- species progenies 9.59%、36.70%、47.45%. Variation trend of height and GLD traits is consistent: inter- species progenies > self-cross progenies > backcross progenies > intra-species progenies.The progenies of 27 mating combinations in Liriodendron were analyzed by using 12 polymorphic primers. Observed heterozygosity and shannon index are all maximum in inter- species progenies,Observed heterozygosity exceeded Observed heterozygosity of backcross progenies, intra-species progenies ,self-cross progenies 17.99%、27.75%、269%; shannon index exceeded shannon index of backcross progenies, intra-species progenies ,self-cross progenies 5.22%、13.34%、19.77%, Variation trend of genetic diversity: inter- species progenies > backcross progenies > intra-species progenies >self-cross progenies.Percentage of homozygous loci is maximum in self-cross progenies ,it exceeded percentage of homozygous loci of intra-species progenies,backcross progenies,inter- species progenies 104%、137%、273%,Variation trend of percentage of homozygous loci : self-cross progenies > intra-species progenies >backcross progenies >inter- species progenies. Gene heterozygosity of Liriodendron and Liriodendron tulipifera parents is respectively 42.72%、47.62%.To conclude,the plumpness and germination rate of seeds、genetic diversity、percentage of homozygous loci are all lower than intra-species and inter- species progenies in varying degrees, but recession of seedling growth is not significant.更多还原