【作者】 李朴芳；

【导师】 熊友才；

【作者基本信息】 兰州大学 ， 生态学， 2014， 博士

【摘要】 早地麦类作物的株型演变及其对逆境的适应策略一直是最重要的基础科学问题之一。以人工选择为主导的麦类作物驯化主要包括长期驯化和相对短暂驯化两种类型,其中小麦和大麦经历了长期驯化历史,燕麦和小黑麦经历了相对短暂人工驯化历史。本文以达尔文进化论、瓦维洛夫同源变异法则和生物代谢理论为基础,以进化上有亲缘关系、不同驯化程度的小麦和燕麦品种为试验材料,实验验证与Meta分析相结合,测定干旱、高温弱光和密度等胁迫条件下株型变化、水分利用、产量形成、渗透调节和气体交换参数等指标,揭示人工选择压力下麦类作物的株型演变特征、株型塑造方向及对逆境的适应策略,为旱地麦类作物的栽培管理和育种实践提供新的理论潜力。主要得出如下结果：1.田间试验结果表明,旱地小麦叶型经历了从二倍体紧凑型的空间姿态到四倍体松散型、再到六倍体紧凑型的方向演变,且单叶形态逐渐变短变宽。田间试验观测了二倍体MO1和M04、四倍体DM22和DM31、古老六倍体和尚头和现代六倍体陇春8275的上三叶型态变化,结果发现三个不同倍体的叶夹角、叶开角和叶弯曲度分别介于22.1°-34.6°、30.0°-66.0°和19.0°-36.4°之间,其中四倍体最高,六倍体的叶开角大于二倍体,但其叶夹角和弯曲度小于二倍体。另外,叶长宽比介于13.7-26.5之间,并随着倍体增高呈现逐渐降低趋势。2.田间试验进一步表明,长期人工选择压力下,旱地小麦上三叶叶重、各节节重、总叶重、叶鞘重、茎重等从二倍体到四倍体均显著升高,但从四倍体到六倍体变化不显著,穗重随着染色体倍数的增加呈显著增加趋势,粒叶比从二倍体到四倍体未发生变化,但是从四倍体到六倍体显著增加。上述结果揭示出旱地小麦源库关系演化经历了“先增源、后扩库”的过程。随着倍体增加,根生物量逐渐减小,总生物量、籽粒产量和收获指数逐渐增加,但净光合速率并未改善。从二倍体到四倍体光合速率显著减少,从四倍体到六倍体光合速率显著增加。3.盆栽控水试验表明,随着倍体增加,生物量分配呈现从根到穗的“由下向上”迁移特征,总分蘖减少但有效分蘖比例增大,水分利用效率显著提升。在盆栽控制50%田间持水量的干旱胁迫条件下,三个不同倍体总生物量仍呈显著性增加趋势,根、茎、叶和穗所占总生物量百分比分别为43.2%、19.2%、12.4%和26.7%(二倍体)、21%、33.9%、16.2%和28.7%(四倍体)和14%、33.6%、14.5%和37.8%(六倍体),呈现明显的自下而上转移的分配格局,根冠比显著下降且粒叶比显著增加；籽粒产量从二倍体的0.48g/株上升到0.96g/株再上升到1.34g/株,千粒重显著增加。随着倍体增加,各器官生物量与总生物量的异速生长指数呈降低趋势,表明在不同倍体小麦的漫长演化过程中这种异速生长关系被人工驯化削弱,人工种群的性质得到强化。4. Meta分析结果表明,旱地小麦株型向“高产节水”演变的同时,干旱适应策略表现为耐旱能力增强,避旱能力削弱。研究中搜集了国内外与旱地小麦干旱适应性研究相关的800篇文献,其中包含300个野生品种、古老品种和现代品种。对株型、生理指标对比表明,干旱胁迫下不同年代早地小麦地上生物量、株高、分蘖数和叶面积等生长指标保持率显著降低,但现代小麦品种降低最少,古老小麦品种次之,野生品种最多。叶片渗透势差异性明显,现代品种最低,野生品种最高；水分利用效率则表现为现代品种中最高,野生品种最低。这些变化表明,随着人工驯化程度提高,旱地小麦耐旱能力显著提升。然而,干旱胁迫下野生品种和古老品种根系生物量均显著增加,现代品种则显著减少,表明人工选择使避旱能力一定程度上被忽略。5.盆栽试验验证了Meta分析结果。同时采用盆栽控水的试验方法,研究了6个不同倍体小麦品种干旱适应机制。结果发现,二倍体和四倍体小麦品种在干旱胁迫下根冠比显著增加,叶面积、分蘖数以及株高显著减少,叶角度显著增加；六倍体小麦中脯氨酸和可溶性糖含量显著增加,渗透调节能力在三个倍体中最强。试验结果与Meta分析结果相互印证,一定程度上印证了小麦在长期驯化过程中,野生品种和古老品种采取避旱和耐旱协同进化策略,而现代品种侧重强化耐旱策略。人工选择压力下强化了旱地小麦的耐旱能力,从而提高产量和水分利用效率,并忽略了对避旱能力的协同管理。6.人工选择压力下早地麦类作物株型对高温弱光胁迫耐逆性具有增强趋势,驯化强度越大,耐逆性越强,但避逆性有弱化趋势。选择不同驯化程度的近10年育成的2个燕麦品种和6个不同倍体小麦品种在高温弱光胁迫条件下进行管栽试验。结果发现,单株籽粒产量为二倍体小麦为零,四倍体小麦DM22和DM31分别为0.09和0.04g/株,六倍体燕麦品种OA1256和OA128分别为0.12和0.14g/株,六倍体小麦品种和尚头和陇春8275最高,分别为0.21和0.28g/株；高温弱光胁迫下籽粒产量保持率与产量呈现同样趋势。另外,驯化程度高的品种叶片具有较高的脯氨酸和可溶性糖含量、相对含水量和绿叶面积；高温弱光胁迫下二倍体和四倍体小麦通过叶片大面积卷曲和起白霜等避逆方式来适应高温逆境环境,表明耐逆能力随着驯化程度提高有增强趋势,而避逆性状有弱化趋势。7.两种株型燕麦密度梯度对照试验结果表明,燕麦松散型株型品种Oa1316-1密度胁迫下适应性较好,表现出相对互利的株型特征,具有较高的产量、叶面积和有效分蘖率。两个燕麦品种的产量、地上生物量、叶面积、叶绿素含量、株高和茎粗随着密度的增加均显著性降低,但根系生物量分配比例均增加。两个燕麦品种采取不同的适应策略。直立叶型品种Manotick在高密度种植环境下叶面积显著减少,叶绿素含量降低,根比重增加3-10%,同时产生50%的无效分蘖来提高自身的竞争力维持自身的生存；松散叶型品种Oa1316-1减少了对根系的分配和无效分蘖数的形成,分配到繁殖器官的生物量增加,这种策略有利于产量的维持,更适宜高密度种植环境。总之,人工选择压力下旱地麦类作物的株型演变朝向“高产高效、耐逆性不断增强但避逆性趋弱、且适合密植”的方向演变,将来的努力可放在对叶型的塑造、提高光合效率、不断减少生长冗余、同时考虑提高避逆能力和强化株型的互利性特征,从而达到“开源节流、群体产量最优”的目标。本研究旨在揭示主要麦类作物的株型进化及对典型逆境因子的适应机制,为达尔文进化论在栽培作物育种和栽培管理上的应用和创新认识起到抛砖引玉的作用,在材料选择和逆境因子的全面性等方面尚存不足,有待将来更进一步努力。更多还原

【Abstract】 Evolvement of plant type in dryland Triticeae crops and its adaptation to adversity is one of the most important fundamental scientific issues. Domestication of Triticeae crops is mostly due to the result of artificial selection, and it is briefly categorized into two types including strong domestication type (mainly refers to as wheat and barley) and weak domestication type (mainly refers to as oat and triticale). In this paper, a group of studies were conducted on the basis of Darwin’s theory of evolution, Vavilov’s homologous variation law and biological metabolism theory using wheats and oats as representative crops. The test materials were chosen from Triticeae crops with genetically evolutionary relationship and various domestication gradients in the combination of experimental verification and meta-analysis methods. A series of eco-physiological and agronomic data were measured and recorded including the parameters of the variation in plant type, water use, yield formation, osmotic adjustment and gas exchange and so on, under adverse stresses including drought, high temperature&low light and high population density. The objectives of this study are to reveal the evolutionary characteristics of crop plant type, reconstruction direction of plant architecture, and the strategies of adaptation to adversity under the pressure of artificial selection. The results would provide new theoretical potential for cultivation management and breeding practice of dryland Triticeae crops. Major results were achieved as follows:1. The results from field experiments showed that plant architecture was evolved towards the tendency from a compact type in diploid wheats to an incompact type in tetraploid wheats, and further to more compact type in hexaploid wheats. Leaf morphological traits tend to become wider and shorter. Field experiment was designed to determine morphological changes in the upper three leaves in three different ploidy wheat species (two diploid MO1and MO4, two tetraploid DM22and DM31, and two hexaploid L8275and Monkhead). The results showed that basal angle, opening angle and cambering angle of three ploidy wheats ranged from22.1°to34.6°,30.0°to66.0°and19.0°to36.4°, respectively. In three ploidy wheats, tetraploid wheats had the highest values among these parameters. The opening angles of hexaploid wheats are greater than diploid wheats, but their basal angles and the cambering angles are lower than those of diploid wheats. Moreover, leaf length-width ratios of leaf, ranged from13.7to26.5, and they increased along with the rise in chromosome sets.2. Field experiments further suggested that source-sink relationship in the evolvement of dryland wheats from wild to modern varieties has undergone two important phases. The first phase was to enhance source dimension, and the second one was to strengthen sink dimension. Yet, leaf net photosynthetic rate has not been improved. With the similarity as the above results, the biomass of leaf, stem, sheath and aboveground biomass all increased significantly from diploid to tetraploid, but there were not significant difference in the transition from tetraploid to hexaploid. From diploid to tetraploid and hexaploid, population yield and harvest index increased, although root biomass decreased gradually. In addition, diploid wheats had the largest net photosynthetic rate, tetraploid wheat was at second place, and hexaploid had the lowest net photosynthetic rate.3. Pot-culture experiment illustrated that biomass allocation pattern experienced an upward shift "from down to up". Upward shift of biomass allocation was observed in three wheat species, in which the dry weight percentages of root, stem, leaf and ear in total biomass were43%,20%,10%and27%in diploid species,21%,34%,16%and29%in tetraploid species and14%,34%,14%and38%in hexaploid species respectively. The number of tiller was significantly greater in diploid species than that of either tetraploid or hexaploid species. Yield was increased from diploid to hexaploid (0.48to0.96g/plant); thousand seed weight was also increased from diploid to hexaploid. Allometric analysis of biomass allocation and water use with other parameters indicated that body-size scaling exponents of total biomass vs ear weight, stem weight, leaf weight, sheath weight and root weight were generally greater in wild relatives than those of hexaploidy wheats. The results verified that this allometry was weakened by artificial selection while characteristics of artificial populations had been enhanced.4. Results of meta-analysis indicated that plant type evolvement of dryland wheats was endowed with high-yield and water-saving characteristics, in which drought tolerance strategy was enhanced during the process of domestication of dryland wheat. A meta-analysis was made through collecting about800papers of drought adaptability in wheats which had been published over past decades. In meta-analysis, indexes of plant type including leaf area, plant height, tiller number and root length, decreased significantly for wild, old, and modern wheat genotypes under drought stress. In comparison with wild and old cultivars, modern wheat cultivars had the lowest reduction. Root biomass of modern wheats decreased under drought stress, but increased in wild and old wheats. Root to shoot ratio increased for all three species, and the old cultivars showed the highest value. Osmotic potential decreased significantly in three species, with the largest decline in modern wheats. WUE were both decreased for wild and old genotypes. In contrast, WUE for modern wheat cultivars increased under drought stress. Results illustrated that drought avoidance strategy become weakened during the process of domestication.5. Pot-culture experiment using different ploidy wheats was conducted to verify the results of meta-analysis. The results indicated that diploid and tetraploid wheats tended to take an adaptive strategy to avoid drought using increasing their root to shoot ratio (RSR), changing their leaf orientation (leaf angle) and decreasing leaf area. In contrast, modern hexaploid cultivars tended to improve their drought tolerance mainly through increasing osmotic adjustments and maintaining higher WUE and lower RSR, as well as higher photosynthetic capacity. Grain yield of modern cultivars has been improved remarkably during the domestication of dryland wheat. Under the pressure of artificial selection, the character of drought avoidance was gradually weakened, while drought tolerance ability was strengthened considerably.6. Tolerance ability was gradually enhanced during the process of artificial selection. In this study, we selected eight Triticeae varieties of different evolutionary gradients, and the plant material was imposed by high temperature and low light intensity. The results suggested that diploid and tetraploid crops had worse adaptability for abiotic stresses and also lower final yield. Yields of two diploid wheats MO1and MO4were0g/plant, and tetraploid wheats DM22and DM31were0.09and0.04g/plant respectively. Diploid and tetraploid cultivars were observed to reduce tiller number, and allocate more biomass to vegetative organs, so maintained individual survival through leaf rolling and leaf glaucous to avoid high temperature and low light intensity stresses. As a result of artificial selection, modern hexaploid crops and oats acquired better tolerance abilities to adapt high temperature and low intensity and keep higher maintenance ratio of final yield. Proline and soluble sugar contents of leaf were greater in these cultivars than those of other cultivars under stress conditions. Overall, highly-domesticated Triticeae cultivars displayed better adaptability to high temperature and low light conditions and maintained larger green leaf area and better water conservation status.7. Oats cultivars with different plant type responded to density stress in different adaptive mechanism. Two oat genotypes, Manotick with erect leaf type and Oa1316-1with prostrate leaf, were applied in four planting densities in a factorial experimental design with4replicates. Our data showed that yield, leaf area, chlorophyll content, plant height and stem diameter of both genotypes decreased significantly with increasing plant density. Biomass allocated to aboveground organs decreased while the biomass allocated to roots increased at higher density. Under high density stress (8and16plants per pots) conditions, compared to solid treatment, Manotick allocated 3-10%more biomass to the root system, produced50%more tillers, leading to higher number of non-productive tillers, and resulted in lower harvest index under the alternative arrangement. In contrast, the prostrate type Oa1316-1allocated proportionally more biomass to the panicles and stems, and less to roots. Consequently, fewer tillers produced in Oa1361-1. Our data indicates that yield differences between the two types of oats resulted from diverse life history strategies. With increasing plant density and strengthening plant-to-plant competition, Manotick reduced aboveground biomass allocation, which led to lower yield, while Oa1316-1decreased biomass allocation to the root, but increased biomass allocation to the stems and panicles under increasingly competitive environment. These adjustments in prostrate type genotypes maintained high and strong stems, ensured biomass allocation to reproductive components and achieved high final yield.To sum up, plant type domestication of Triticeae crop is evolved towards the high-yielding and high-efficiency direction with enhancing stress tolerance ability but weakening stress avoidance ability, and being apt to close planting circumstances. Future efforts would be focused on spatial reconstruction of leaf type, exertion of leaf photosynthetic rate and reducing growth redundancy. Due to high complexity of plant type evolvement and its adaptive mechanism for Triticeae crop, further work will be needed to improve stress avoidance ability and strengthen mutual advantages of plant type, finally to satisfy the pursuit of high yield and high population superiority in the future.更多还原