【作者】 杜克兵；

【导师】 涂炳坤； 沈宝仙；

【作者基本信息】 华中农业大学 ， 园林植物与观赏园艺， 2008， 博士

【摘要】 杨树（Populus L）是世界范围内广泛种植的速生用材树种。杨树的遗传改良和推广对于解决木材产品需求不断扩大与木材供应不足之间的矛盾具有重要作用和意义。在我国,杨树已成为最主要的工业用材林和生态防护林树种之一。本研究以杨属资源中经济价值最大的黑杨派杨树为主要试材,以培育速生、高抗性杨树新品种为目标,围绕杨树的杂交育种和抗涝性开展试验。主要结果如下:1.利用离体培养基法研究了不同温度贮藏条件下杨树花粉生活力随时间变化的规律,以及贮藏1～2 a后用于杂交育种的可行性。结果表明:当培养基固定成分包括0.7%琼脂+300 mg/L CACl₂+200 mg/L MgSO₄+100 mg/L KNO₃时,1-63杨、辽宁杨花粉萌发的最佳蔗糖、硼酸浓度分别为20%、100 mg/L和15%、100 mg/L。1-63杨和辽宁杨花粉于-20℃贮藏1 a后生活力分别为23.77%和34.19%,与新鲜花粉相比,其生活力分别降低48.51%和62.23%,花粉管长度分别减少48.9%和48.45%。用4℃条件贮藏1 a或-20℃条件贮藏2 a的花粉授粉后仍可以得到正常发芽的种子,尤以-20℃下贮藏的效果为好。2.通过室内发芽试验研究了杨树种子的耐贮性。结果表明:干燥方法、种子含水量、贮藏温度和贮藏时间均对辽宁杨和I-72杨种子的发芽率、成苗率、苗高、胚根长度等活力指标有极显著影响。对于杨树种子贮藏,室内阴干等缓慢脱水的干燥方法较硅胶干燥等快速脱水的方法好,尤以室内阴干1 d为最好,此时辽宁杨种子的含水量为10.16%。低温条件可提高种子的耐贮性,辽宁杨种子贮藏温度越低效果越好,其中以-70℃最好,贮藏110 d后种子的生活力比新鲜种子下降19.73%;I-72杨种子以4℃的低温贮藏效果最好,贮藏110 d后种子的生活力比新鲜种子下降65.02%。在各种贮藏温度条件下,随着贮藏时间的延长,种子的各项活力指标均明显降低。对于杨树种子贮藏而言,贮藏温度比干燥方法和种子含水量更重要。3.选取湖北省广泛栽培的黑杨优良品种（辽宁杨、I-63杨、I-69杨、I-72杨）为亲本进行室内切枝水培杂交育种,以期选育适宜于湖北地区栽培的杨树优良新品种。结果表明:杂交子代遗传变异丰富,杂种优势显著。苗高、地径生长均属于高遗传力性状。一年根一年杆苗木的苗高、地径的广义遗传力分别为76.74%、85.22%;苗高的一般配合力变量、特殊配合力变量分别为21.56%、78.44%,地径的分别为61.39%、38.61%。二年根一年杆苗木的生长表现与一年根一年杆苗木一致。杨树对锈病、溃疡病、天牛的抗性均受多基因控制,子代遗传变异丰富。子代的锈病抗性与亲本关系显著,而溃疡病和天牛抗性与亲本无显著相关性。以现有主栽杨树品种的苗高生长为标准进行苗期选择后,杂交子代可获得显著的超亲优势和遗传增益。部分杂交子代的生长量比当前主栽品种有较大提高,其中最高杂种子代的一年根一年杆苗木的苗高、地径比南林895杨分别提高14.98%和18.86%;二年根一年杆苗木的苗高、地径比南林895杨分别提高13.87%和41.38%,并具有优良的病虫害抗性。4.采用盆栽淹水试验研究了20个杂交子代和亲本的抗涝性,以估算杨树抗涝性的遗传参数,并初步选择抗涝杨树新品种。结果表明:淹水胁迫显著抑制了杨树的苗高、地径、叶面积、根系的生长,从而导致生物量显著下降。20个无性系均在淹水6～14 d后形成了膨大皮孔和不定根。与正常条件相比,淹水植株的净光合速率、气孔导度、蒸腾速率等气体交换参数和叶绿素荧光显著降低。淹水结束后,所有植株均快速恢复。即使在淹水胁迫下,杂交子代仍然具有显著的杂种优势,但小于正常条件下的杂种优势。淹水胁迫下,子代的苗高和地径均具有丰富的遗传变异,其最大超亲优势分别为68.63%和20.83%。以提高抗涝性为目标的杂交育种中,亲本的选择标准与正常条件下有所不同。亲本的特殊配合力效应值和一般配合力效应值比其自身的耐涝性更重要。以耐涝性较差的无性系做杂交亲本,仍然可以得到高抗涝性的子代。就育种目标而言,淹水胁迫下,苗高生长性状最重要,地径生长性状次之。依据试验结果,利用聚类分析法可以将20个无性系明显分为3类:无性系Lu、E4、E9、E29、A2、A8、A9、B1、B3、B4和D8聚为一类,耐涝性最强:无性系Lf、Ha、Lm、D1、D7、F9和F21聚为一类,耐涝性次强;无性系Sm和F13聚为一类,耐涝性最差。5.采用盆栽淹水试验研究了2个耐涝性具有显著差异的杨树无性系对淹水胁迫的响应,以探索杨树的耐涝机理。结果表明:I-69杨的抗涝性强,而小叶杨对淹水胁迫敏感,两者抗涝性的差异体现在形态、解剖、生理等多方面。I-69杨与小叶杨抗涝能力的差异主要体现在淹水后期（8～22 d）,而后期差异的形成与前期（1～8 d）两者对淹水胁迫响应的不同密切相关。生理方面,I-69杨在淹水前期即大幅度降低叶片水势,诱导气孔快速关闭,以减少水分散失,并保持较高的自由水含量和水分利用率,从而维持较高的光合速率。同时,I-69杨还通过迅速、大量分解叶绿素以减少对光能的吸收,降低光能过剩和光氧化对光合系统的破坏作用,并分解蛋白质以合成其它抗逆物质,提高植株抗性。小叶杨则缺乏相应机制,在淹水胁迫前期,叶片水势降低缓慢,气孔关闭迟缓,水分大量散失,导致植株水分平衡破坏,且大量自由水转变为束缚水,水分利用效率降低。同时,小叶杨叶绿素分解缓慢,造成光能过剩和光氧化作用严重,导致PSⅡ的光合性能受损,光合速率大幅降低。形态方面,I-69杨膨大的皮孔在淹水胁迫过程中一直保持正常,而小叶杨膨大的皮孔在淹水后期易受细菌感染,大量腐烂。I-69杨的根系可忍受长期淹水胁迫,能够形成并保持较大的孔隙度,而小叶杨的根系虽然可形成较大孔隙度,但淹水后期大量腐烂,孔隙度迅速变小。淹没处理下,I-69杨的叶片可保持完整结构,而小叶杨的叶片则表皮破裂,结构严重受损。解剖方面,I-69杨的叶片能够在长期淹水胁迫下保持较完整的超微结构,而小叶杨叶片的超微结构在淹水后期损伤严重,细胞器大量解体。作者认为,耐涝杨树品种兼具避缺氧性与耐缺氧性机制,而敏感品种则缺乏相应机制。淹水胁迫下,迅速皮孔膨大并保持正常活性、快速降低水势并关闭气孔、保持高光合速率和水分利用效率、快速分解叶片叶绿素和蛋白质、增大并保持根系孔隙度、提高叶片超微结构稳定性等响应对杨树的存活与生长具有十分重要的作用,可作为耐涝杨树品种选择的参考和指标。更多还原

【Abstract】 Poplar, a widely cultivated tree species in the world, was of significance for meeting the inconsistency between increase of woody products requirement and scarce of provision. In china, poplar was one of the most important tree species for afforestation in woody production forests and ecology protection forests.In the present study, we adopted Aigerious section poplar clones as our research materials for their maximum economic values. The study was focused on cross breeding and flood tolerance of poplar to breed some new clones with characteris of fast-growing and strong tolerance.The major results are as follows:1. Cultured in vitro, time courses of viabilities of poplar pollens stored in different temperatures were studied, as well as the feasibilities of the stored pollens used for cross breeding. Results showed that the optimum concentrations of sucrose and boric acid for germination of I-63 and Liaoning poplar pollens were, respectively, 20%, 100 mg/L and 15%, 100 mg/L when medium containing 0.7% agar+300 mg/L CaCl₂+200 mg/L MgSO₄+100 mg/L KNO₃ The viabilities of I-63 and Liaoning poplar pollens after one-year storage in -20℃were 23.77% and 34.19%, respectively, decreasing 48.51% and 62.23% compared with fresh pollens. The length of pollen tube decreased 48.90% and 48.45%, respectively. It was feasible to obtain vigorous seeds using the pollens for pollination in cross breeding, which were stored in 4℃for one year or in - 20℃for two years. The optimum storage temperature was - 20℃.2. Storage capacities of poplar seeds were studied using germination method indoor. Results showed that drying method, moisture content, storage temperature and time all significantly affected viabilities of I-72 and Liaoning poplar seeds, including germination rate, seedling rate, seedling height and radicle length. In terms of storage, poplar seeds were suitable to be slowly dehydrated indoor naturally, but not be rapidly dehydrated by silica dehydration, and the optimum duration was one day. In this way, 10.16% of moisture content could be obtained for Liaoning poplar seeds. Storage capacities of Sect. Aigeiros poplar seeds could be enhanced in low temperature. Seeds of Liaoning poplar preferred cryopereservation below 0℃and -70℃was the best. However, I-72 could get better effect if it was stored at 4℃. After stored for 110 days, viability index would respectively decrease 19.73% and 65.02% compared to fresh seeds for Liaoning poplar seeds in -70℃and I-72 seeds in 4℃. With storage time prolonging, all items related to seed viabilities were declined significantly. For storage of poplar seed, storage temperature was more important than drying method and moisture content of seed.3. Cross breeding was performed using superior poplar clones of Aigeiros Section （Liaoning poplar, I-63,I-69 and I-72） widely cultivated in Hubei Province to breed new poplar clones. The progenies showed abundant genetic variation and obvious heterosis. Seedling growth of height and root-collar diameter both were characters with high heritabilities. Heritabilities in the broad sense of one-year old seedlings with one-year old roots in height and root-collar diameter were respectively 76.74 % and 5.22 %. The general combining ability variable and specific combining ability variable of height were 21.56 % and 78.44 %, respectively, as well as 61.39 % and 38.61 % in root-collar diameter. All of them were consistent with the one-year old seedlings with two-year old roots. Resistance of poplar to rust disease, canker and longicom beetles were controlled by multiple genes. The resistance of progenies to rust disease was obviously relative with their parents, but this kind relativity have not occurred in resistance of canker and longicom beetles. According to height growth of widely cultivated clones, obvious heterosis of higher-parent and genetic gain could be obtained after primary selection. Some progenies had much higher growth than the widely cultivated clones. Compared with Nanlin 895 poplar, the highest progenies increased 14.98% and 18.86%, respectively, in growth of height and root-collar diameter of one-year old seedlings with one-year old roots, as well as 13.87 % and 41.38 % in growth of height and root-collar diameter of one-year old seedlings with two-year old roots, and possessed characters of superior resistance to disease and insects.4. Flood tolerance of 20 clones, including progenies and their parents, were studied to select flood-tolerant clones primarily, as well as to estimate genetic variances in flood tolerance of poplar. Results showed that all the flooded cuttings showed significant reduction in growth of height, root-collar diameter, leaf, and root, as well as total biomass yield. All 20 clones formed hypertrophied lenticels and adventitious roots by Day 6 to 14 of flooding. And for flooded cuttings, net photosynthesis, stomatal conductance, transpiration, and chlorophyll fluorescence decreased significantly compared with the control. After flooding ended, all plants recovered rapidly. Heterosis existed in F1 generations, regardless of flooding condition. Whereas heterosis in flooding condition was lower than that of in watered condition. Under flooding, the maximum heterosis of higher-parent in height and root-collar diameter was 68.63% and 20.83%, respectively. Besides, variance of flood tolerance among progenies was obvious in growth of height and root-collar diameter. Selection criterions of parents in cross breeding were different between watered and flooding. Relative effect values of the specific combining ability （SCA） and relative effect values of the general combining ability （GCA） of parents were more important than their flood tolerance. Progenies with higher level of flood tolerance also could be obtained, although their parents were intolerant. In terms of breeding, height growth would be most important in flooding condition, and root-collar diameter growth was also very useful. Based on data of all measured values, the tested 20 clones were classified into three groups using hierarchical cluster analysis. Clones Lu, E4, E9, E29, A2, A8, A9, B1, B3, B4, and D8, were flood-tolerant. Clones Lf, Ha, Lm, D1, D7, F9, and F21 were moderately flood-tolerant. Clones Sm and F13 were flood-susceptible.5. Responses to soil flooding of two poplar clones with significantly different flood tolerance were studied to illuminate mechanism of poplar flood-tolerance. Results showed that P. deltoides cv.Lux ex. I-69/55 （Lu） was flood-tolerant, whereas P. simonii （Si） was flood-susceptible. They differed in morphological, ecophysiological, and anatomical characteristics when subjected to flooding. The difference between Lu and Si visualized in latter flooding period （8～22 d）, but it was closely related to their responses to flooding in former flooding period （1～8 d）. In terms of ecophysiology, in former flooding period, Lu could keep a high level of photosynthesis, as well as high free water content and water use efficiency, through inducing pore closure and reducing water lost due to decrease water potential of leaves rapidly. Meantime, chlorophyll of Lu was decomposed quickly to reduce sunlight absorbation and to avoid destruction to photosynthesis system by photooxidation due to light energy overplus. Protein of Lu was also rapidly decomposed to synthesize other substances to enforce its flood tolerance. Reversely, for Si, much water was evaported due to slow water potential decrease of leaves and pore closure in former flooding period, leading disorder of water system directly, as well as much free water transformed into bound water and lowered water use efficiency. Meanwhile, slow decompose of chlorophyll of Si lead light energy overplus and photosynthesis systemⅡ（PSⅡ） destruction occurred seriously. Therefore, photosynthesis rate of Si seriously decreased under flooding. As for morphology, all hypertrophied lenticels of Lu were fine during flooding, whereas many hypertrophied lenticels of Si were easy to be infected by bacteria and rot. Furthermore, Lu could form and maintain large root porosities during flooding period. However, Si could form large root porosities, but its roots easily rot to decrease the aerenchyma in latter flooding period. Under submergency, Lu could keep intact leaves structure. Nevertheless, leaf epidermis and structure of Si were destroyed seriously. In terms of anatomy, ultrastructure of leaves of Lu were still intact at the end of flooding, whereas ultrastructure of leaves of Si were destroyed seriously, and many organelles were decomposed. Therefore, the authors thought that flood-tolerant poplar clones were both with mechanisms of avoidng oxygen scarcity and tolerating oxygen scarcity. Whereas, flood-susceptible poplar clones lacked these mechanisms. Under soil flooding, responses of rapidly forming and maintaining hypertrophied lenticels, quickly decreasing water potential and closing pores, keeping high level of photosynthesis and water use efficiency, rapidly decomposing chlorophyll and protein of leaves, enlarging and maintaining root porosities, maintaining intact ultrastructure of leaves etc. were very important to survive and growth of poplar, which could be adopted as references and indexes for selecting flood-tolerant poplar chones.更多还原