在长期进化过程中,植物形成了一系列防御机制,抵抗各类病原物入侵,抗病R基因在其中发挥着关键作用.R基因的研究,在农作物中取得很大进展,已成为植物病理学的研究热点.相比之下,树木抗病基因研究较为落后,虽从苹果、杨树和柚子中已分离了几个与已知R基因具有类似结构与功能的基因,但还没有真正的树木抗病R基因被克隆出来;目前,大部分研究主要集中在利用分子标记构建连锁图谱,寻找抗病数量性状位点(Q uan titativetra it loc i,QTL)和与R基因紧密连锁或共分离的质量性状标记;其中一些标记已经应用在分子辅助选育中,并显示了诱人的应用前景.另外,利用已知抗病R基因的保守区域,从多种植物中已扩增出许多抗病基因类似序列,它们大多被转化为与R基因紧密连锁的标记或被当作抗病候选基因.
This study uses two different mathematical models and gets two dimensional graphs of longitudinal and tangential section wood density at the same time by the radial wood density data measured by X_ray. The graph is direct and clear. It can be used to analyze the distribution and difference of wood density. It can also be done various kinds of transformation, including different angle, different colors, space and plane, part and entirety. This develops the visible analysis of wood density. Next the distribution of wood density of veneer will be simulated by new mathematical model and radial wood density data.
25 clones(6 trees from each clone) were sampled (aged 15 years) from clone test stand of Populus tomentosa. The fiber forms (fiber length, fiber width, ratio of fiber length and fiber width, fiber wall thinckness, fiber lumen diameter, ratio of 2 fiber wall thinckness and fiber lumen diameter, ratio of fiber lumen diameter and cell diameter) were analysed. Variance analysis showed that these 7 traits were significantly different among clones at 0.05 level. 2 characters, Fiber width and fiber lumen diameter, were strongly inherited, and others 5 traits were under moderate genetic control. The selection could be conducted effectively among clones. The variation analysis of microfibrillar angles showed that there was significantly difference among clones at 0.05 level. The clones repeatability (0.961) and single repeatability (0.651) of microfibrillar angles indicated that the character was under genetic control. And selection could be conducted effectively among clones and within clones. The variance analysis of transverse section tissue percentage include vessel percentage, fiber percentage and wood ray percentage of Populus tomentosa were perfected. All traits except vessel percentage were observed significant clonal differences at 0.05 level. The values of clone repeatability of vessel percentage and fiber percentage were 0.437 and 0.336 separately, and the values of clone repeatability of wood ray percentage was 0.711. This showed that genetic control for wood ray percentage is feasible.
