School of Plant Science and Cooperative Research Centre for Forestry, University of Tasmania, Private Bag 55, Hobart, Tasmania, 7001, Australia.
Ann Bot. 2010 May;105(5):737-45. doi: 10.1093/aob/mcq036. Epub 2010 Mar 12.
One of the major factors affecting the outcrossing rate in Eucalyptus globulus is thought to be the inherent self-incompatibility (SI) level of the female tree. SI in this species is mainly due to late-acting pre- and post-zygotic mechanisms operating in the ovary, and not S alleles. This study aimed to assess the phenotypic variation in SI levels within E. globulus and determine its genetic control and stability across pollination techniques, sites and seasons.
SI levels were estimated for 105 genotypes originating from across the geographical range of E. globulus over multiple years of crossing. Separate grafted trees of some genotypes growing at the same and different sites allowed the genetic basis of the variation in SI to be tested and its stability across sites and seasons to be determined. The SI level of a tree was measured as the relative reduction in seeds obtained per flower pollinated following selfing compared with outcross pollinations. Thus, if seed set is the same, SI is 0 %, and if no self seed is set, SI is 100 %.
The average SI in E. globulus was 91 % and genotypes ranged from 8 to 100 % SI. Most genotypes (>75 %) had SI levels >90 %. There were highly significant differences between genotypes and the within-site broad-sense heritability of percentage SI was high (H(2) = 0.80 +/- 0.13). However, there was evidence that growing site, and to a lesser extent season, can affect the expression of SI levels. Trees with low reproductive loads produced relatively more seed from selfed flowers.
There is a strong genetic basis to the phenotypic variation in SI in E. globulus within a site. However, the level of SI was affected, but to a lesser extent, by the environment, which in part may reflect the higher probability of selfed zygotes surviving on sites or in seasons where competition for resources is less.
影响蓝花楹杂交率的主要因素之一被认为是母树固有的自交不亲和性（SI）水平。该物种的 SI 主要是由于卵巢中晚期发挥作用的合子前和合子后机制，而不是 S 等位基因。本研究旨在评估蓝花楹内在 SI 水平的表型变异，并确定其在不同授粉技术、地点和季节的遗传控制和稳定性。
对来自蓝花楹地理分布范围的 105 个基因型进行了多年杂交的 SI 水平估计。一些基因型的单独嫁接树在同一和不同地点生长，允许测试 SI 变异的遗传基础及其在地点和季节之间的稳定性。一棵树的 SI 水平是通过自花授粉与异花授粉相比每朵花授粉获得的种子相对减少来衡量的。因此，如果种子设定相同，则 SI 为 0%，如果没有自花种子设定，则 SI 为 100%。
蓝花楹的平均 SI 为 91%，基因型范围为 8%至 100% SI。大多数基因型（>75%）的 SI 水平>90%。基因型之间存在显著差异，位点内的广义 SI 遗传力很高（H(2)=0.80 +/- 0.13）。然而，有证据表明生长地点，在较小程度上，季节可以影响 SI 水平的表达。生殖负荷较低的树木从自花授粉的花朵中产生相对更多的种子。
在一个位点内，蓝花楹的 SI 表型变异具有很强的遗传基础。然而，SI 水平受到环境的影响，但程度较小，部分原因可能反映了在资源竞争较少的地点或季节中，自交合子存活的可能性更高。
