Ministry of Education, Key Laboratory for Biodiversity Science and Ecological Engineering, Department of Ecology and Evolutionary Biology, Fudan University, Shanghai, China.
PLoS One. 2011 Jan 13;6(1):e16189. doi: 10.1371/journal.pone.0016189.
Introgression plays an important role in evolution of plant species via its influences on genetic diversity and differentiation. Outcrossing determines the level of introgression but little is known about the relationships of outcrossing rates, genetic diversity, and differentiation particularly in a weedy taxon that coexists with its conspecific crop.
METHODOLOGY/PRINCIPAL FINDINGS: Eleven weedy rice (Oryza sativa f. spontanea) populations from China were analyzed using microsatellite (SSR) fingerprints to study outcrossing rate and its relationship with genetic variability and differentiation. To estimate outcrossing, six highly polymorphic SSR loci were used to analyze >5500 progeny from 216 weedy rice families, applying a mixed mating model; to estimate genetic diversity and differentiation, 22 SSR loci were analyzed based on 301 weedy individuals. Additionally, four weed-crop shared SSR loci were used to estimate the influence of introgression from rice cultivars on weedy rice differentiation. Outcrossing rates varied significantly (0.4~11.7%) among weedy rice populations showing relatively high overall Nei's genetic diversity (0.635). The observed heterozygosity was significantly correlated with outcrossing rates among populations (r² = 0.783; P<0.001) although no obvious correlation between outcrossing rates and genetic diversity parameters was observed. Allelic introgression from rice cultivars to their coexisting weedy rice was detected. Weedy rice populations demonstrated considerable genetic differentiation that was correlated with their spatial distribution (r² = 0.734; P<0.001), and possibly also influenced by the introgression from rice cultivars.
CONCLUSIONS/SIGNIFICANCE: Outcrossing rates can significantly affect heterozygosity of populations, which may shape the evolutionary potential of weedy rice. Introgression from the conspecific crop rice can influence the genetic differentiation and possibly evolution of its coexisting weedy rice populations.
通过影响遗传多样性和分化，基因渗入在植物物种的进化中起着重要作用。异交决定了基因渗入的程度，但对于异交率、遗传多样性和分化的关系知之甚少，特别是在与同种作物共存的杂草类群中。
方法/主要发现：利用微卫星（SSR）指纹图谱分析了来自中国的 11 个野生稻（Oryza sativa f. spontanea）种群，以研究异交率及其与遗传变异性和分化的关系。为了估计异交，使用 6 个高度多态性的 SSR 位点分析了来自 216 个野生稻家族的 >5500 个后代，应用混合交配模型；为了估计遗传多样性和分化，基于 301 个野生个体分析了 22 个 SSR 位点。此外，还使用了 4 个杂草-作物共享的 SSR 位点来估计来自水稻品种的基因渗入对野生稻分化的影响。野生稻种群的异交率差异显著（0.4~11.7%），总体 Nei 遗传多样性较高（0.635）。观察到的杂合度与种群间的异交率显著相关（r²=0.783；P<0.001），尽管没有观察到异交率与遗传多样性参数之间的明显相关性。从水稻品种到共存的野生稻的等位基因渗入被检测到。野生稻种群表现出相当大的遗传分化，与它们的空间分布相关（r²=0.734；P<0.001），可能也受到来自水稻品种的基因渗入的影响。
结论/意义：异交率可以显著影响种群的杂合度，这可能塑造了野生稻的进化潜力。同种作物水稻的基因渗入可以影响其共存的野生稻种群的遗传分化和可能的进化。
