Fénart Stéphane, Austerlitz Frédéric, Cuguen Joël, Arnaud Jean-François
Laboratoire de Génétique et Evolution des Populations Végétales, UMR CNRS 8016, FR CNRS 1818, Bâtiment SN2, Université des Sciences et Technologies de Lille - Lille 1, F-59655 Villeneuve d'Ascq cedex, France.
Mol Ecol. 2007 Sep;16(18):3801-13. doi: 10.1111/j.1365-294X.2007.03448.x.
Gene flow is a crucial parameter that can affect the organization of genetic diversity in plant species. It has important implications in terms of conservation of genetic resources and of gene exchanges between crop to wild relatives and within crop species complex. In the Beta vulgaris complex, hybridization between crop and wild beets in seed production areas is well documented and the role of the ensuing hybrids, weed beets, as bridges towards wild forms in sugar beet production areas have been shown. Indeed, in contrast to cultivated beets that are bi-annual, weed beets can bolt, flower and reproduce in the same crop season. Nonetheless, the extent of pollen gene dispersal through weedy lineages remains unknown. In this study, the focus is directed towards weed-to-weed gene flow, and we report the results of a pollen-dispersal analysis within an agricultural landscape composed of five sugar beet fields with different levels of infestation by weed beets. Our results, based on paternity analysis of 3240 progenies from 135 maternal plants using 10 microsatellite loci, clearly demonstrate that even if weedy plants are mostly pollinated by individuals from the same field, some mating events occur between weed beets situated several kilometres apart (up to 9.6 km), with rates of interfield-detected paternities ranging from 11.3% to 17.5%. Moreover, we show that pollen flow appears to be more restricted when individuals are aggregated as most mating events occurred only for short-distance classes. The best-fit dispersal curves were fat-tailed geometric functions for populations exhibiting low densities of weed beets and thin-tailed Weibull function for fields with weed beet high densities. Thus, weed beet populations characterized by low density with geographically isolated individuals may be difficult to detect but are likely to act as pollen traps for pollen emitted by close and remote fields. Hence, it appears evident that interfield pollen-mediated gene flow between weed beets is almost unavoidable and could contribute to the diffusion of (trans)genes in the agricultural landscape.
基因流是一个关键参数，它会影响植物物种遗传多样性的组织形式。在遗传资源保护以及作物与其野生近缘种之间和作物物种复合体内部的基因交流方面，基因流具有重要意义。在甜菜复合体中，种子生产区作物甜菜与野生甜菜之间的杂交已有充分记载，并且已经证明了由此产生的杂种——杂草甜菜，在甜菜生产区作为通向野生类型的桥梁所起的作用。的确，与两年生的栽培甜菜不同，杂草甜菜可以在同一个作物季节抽薹、开花并繁殖。然而，通过杂草谱系进行的花粉基因扩散程度仍然未知。在本研究中，重点是杂草间的基因流，我们报告了在一个由五个杂草甜菜侵染程度不同的甜菜田组成的农业景观中进行的花粉扩散分析结果。我们的结果基于对135株母本植物的3240个后代使用10个微卫星位点进行的父本分析，清楚地表明，即使杂草植物大多由同一块田中的个体授粉，但相距数公里（最远达9.6公里）的杂草甜菜之间也会发生一些交配事件，检测到的田间父本率在11.3%至17.5%之间。此外，我们表明，当个体聚集时，花粉流似乎受到更多限制，因为大多数交配事件仅发生在短距离类别中。对于杂草甜菜低密度种群，最佳拟合扩散曲线是肥尾几何函数，而对于杂草甜菜高密度田块，最佳拟合扩散曲线是瘦尾威布尔函数。因此，以低密度且地理隔离个体为特征的杂草甜菜种群可能难以检测，但可能会成为近距离和远距离田块释放花粉的花粉陷阱。因此，很明显，杂草甜菜之间通过花粉介导的田间基因流几乎是不可避免的，并且可能有助于（转基因）基因在农业景观中的扩散。
