普通野生稻小种群的交配系统与遗传多样性

小种群的遗传动态是保育遗传学关注的核心问题之一,而种群遗传动态又与交配系统密切相关.普通野生稻(Oryza rufipogon Griff.)是具有重要经济价值的濒危物种,目前其种群规模都较小,研究其小种群交配系统与遗传变异性对普通野生稻的保护具有重要意义.运用7对SSR引物,对采自江西东乡普通野生稻小种群的36份种茎和其中20个家系共计601份子代进行了分析.结果显示:该种群的表观异交率为0.318,多位点法估计(MLTR)的多位点异交率为0.481;50%以上的子代共享亲本,非随机交配明显;东乡普通野生稻种群交配系统属于混合交配类型.比较亲本和子代种群的遗传变异性显示:子代种群比亲本种群遗传变异性更丰富;子代种群的杂合子不足与种群变小自交比例上升有关;而亲本种群杂合子过剩可能与杂合基因型的选择优势有关.这些结果说明创造条件扩大种群规模对普通野生稻的原生境保护显得尤为重要.

Mating system and genetic diversity in a small population of perennial wild rice Oryza rufipogon

Genetic changes of populations that experience drastic size decline is a central issue in conservation genetics. The genetic changes of small populations are tightly associated with their mating pattern, because small populations generally have increased selfing and local inbreeding rates, leading to the effect of genetic drift and loss of genetic variability. Oryza rufipogon Griff. is agriculturally the most important but seriously endangered wild rice species due to rapid decline of population size. To better understand how mating system can be used for species conservation, outcrossing rate, genetic variability at maternal and seedling phases in a small population were examined at seven polymorphic microsatellite DNA loci. Thirty six reproductive individuals and 601 progenies from 20 open-pollinated seed families were measured. The family outcrossing rates varied among plants with an average of 0.318. A high correlation of matings was revealed and about 50% offspring shared the same paternal and maternal genitors, indicating a mixed mating system in the Oryza population. The level of genetic diversity in progeny population was higher than that in maternal population. The maternal population showed significant heterozygote excess, suggesting the selection advantage of heterozygotes. In contrast, significant heterozygote deficit occurred in progeny population, which might have been caused by the increasing of inbreeding in declining population. These results suggest that expanding population size is of significance for in-situ conservation of Oryza rufipogon.