Studies on the sampling strategy for collecting plant germplasms as genetic resources

1. 遗传优势效应即使在同质环境中也可能发生，当植物自交花粉的比率与来自其他植物的花粉的相对数量成正比时。边缘效应的发生方式是，外围地区的植物比中心地区的植物具有更高的纯合性和遗传分化程度。在植物密度稳定的情况下，交配系统的遗传分化得以发展。这种分化的程度和模式受组成种群的植物数量的影响。在基因流距离的标准差小于环境斜纹或袋纹宽度的条件下，形成了一种追踪环境斜纹或袋纹的遗传模式。这种遗传模式在背斜环境中比在口袋环境中更容易发育。亚洲野生稻居群异交率范围广，为5 ~ 60%。异交率与生活史性状密切相关；异交率低的群体往往是一年生的，具有较高的繁殖努力（总种子重量/株重）和较低的授粉努力（花药重量/粒重），而高异交率的群体往往是多年生的，具有较低的繁殖努力和较高的授粉努力。在异交率高的群体中，异交率存在遗传分化；生长在外围地区的植株异交率较低。

1. Genetic edge effect may occur even with homogeneous environment, when plants operate selfing with a rate proportional to the relative amount of pollen of their own to that coming from other plants. The edge effect occurs in such a way that plants in peripheral region take a higher degree of homozygosity and genetic differentiation than those in central region. Genetic differentiation in mating system may develop in the presence of a stable pattern in plant density. The degree and pattern of this differentiation is influenced by the number of plants composing the population.2. A genetic pattern tracing the pattern of environmental cline or pocket develops under the condition that the standard deviation of gene flow distance is smaller than the width of the environmental cline or pocket. The genetic pattern develops more easily in the cline environment than in the pocket.3. Asian wild rice populations showed a wide range of outcrossing rate, 5-60%. The outcrossing rate is highly associated with life history characters ; populations with low outcrossing rates tended to be annual and have a high reproductive effort (total seed weight/plant weight) and a low pollination effort (anther weight/grain weight), while populations with high outcrossing rates tended to be perennial and have a low reproductive effort and high pollination effort. Genetic differentiation in outcrossing rate was recognized within populations with high outcrossing rates ; plants growing in peripheral region tended to have lower outcrossing rates.