【作者】 杨青；

【导师】 周志春；

【作者基本信息】 中国林业科学研究院 ， 林木遗传育种， 2012， 博士

【摘要】 马尾松是我国分布面积最广的树种之一，适应性广泛、速生丰产性强、材性优良、非木质产品丰富，支撑着我国造纸、木材加工、林产化工等产业发展。然而我国南方森林酸性红壤中有效磷匮乏严重，磷素贫瘠和地力衰退已严重影响了该区域的马尾松人工林的持续高产经营。虽然目前已开展了马尾松等树种的磷效率遗传改良，然而相关研究几乎都以土壤养分呈均质分布为前提开展，却忽视了森林土壤养分呈高度异质性分布的普遍现状；同时，有关氮素养分信号、光照、种间竞争等环境因子对林木根构型及磷素营养效率的影响，研究报道较少。本论文分别选取马尾松一代种子园优良自由授粉家系、马尾松三代控制授粉家系、马尾松不同种源、以及马尾松高磷效率种源内的不同家系为实验材料，设置同质低磷胁迫、异质低磷胁迫等不同类型低磷胁迫的模拟盆栽实验，揭示不同马尾松基因型和生态型分别适应不同类型低磷胁迫、促进根系磷素吸收和生物量积累的生物学机制，明确氮素养分信号、种间竞争及光照对磷效率变异的影响模式，以期为选育和推广马尾松磷高效优良基因型提供重要理论依据和指导。主要研究结果如下：1.不同类型低磷胁迫下马尾松家系的根构型和磷效率变异在同质低磷胁迫和异质低磷胁迫下，主要磷效率指标表现出显著的家系变异，且家系遗传力均较高，证实开展马尾松磷效率的遗传改良具有极大潜力和必要性。在同质低磷和异质低磷胁迫下，磷高效家系分别为‘3201’、‘1217’和‘5910’、‘1217’。在同质低磷胁迫下，高磷效率马尾松可通过整体根系的增生发育产生较为发达的根系，促进植株的P营养吸收和干物质生产能力。在异质低磷胁迫下，根构型的适应性变化是决定马尾松磷效率家系变异的重要生物学基础，磷高效家系将通过根系空间构型变浅使根系在表层富磷介质显著增生，从而增加其磷素吸收效率和干物质生产能力，形成较高的磷效率。相反，低磷效率的家系，其根系空间构型的适应性变化能力较低，根系在富磷表层介质适应性增生发育较少，导致磷素吸收效率较小，磷效率和干物质积累量也较低。与磷利用效率相比，磷素吸收效率对于马尾松家系磷效率的贡献较大。不同类型的低磷胁迫环境和马尾松家系磷效率之间存在显著的互作效应，因而在开展磷效率遗传改良时，应充分考虑并利用这种互作效应，有针对性地为不同磷营养特性的马尾松主产区选育和推广理想的磷高效马尾松优良种质。2.低磷胁迫下马尾松不同种源的根构型和磷效率研究无论是在异质低磷还是同质低磷下，不同种源的性状和磷效率指标均存在这极显著的种源间变异，其中，广东信宜和福建武平为磷高效种源，广西岑溪和浙江淳安为磷低效种源。与磷效率的家系变异的生物学基础类似，根构型的适应性变化是异质低磷胁迫下决定马尾松磷效率种源变异的重要生物学基础，磷高效种源将通过根系空间构型变浅使根系在表层富磷介质显著增生，从而增加其磷素吸收效率和干物质生产能力，形成较高的磷效率。在异质和同质低磷胁迫下，磷效率最高种源（广东信宜）的干物质积累量分别是最低种源（浙江淳安）的2.1倍和2.0倍。与家系水平的变异相比，马尾松在种源水平的营养性状变异更大，因此在种源上进行磷效率改良的潜力较大。3.磷高效马尾松种源内磷效率的家系变异及苗期-大田回溯相关分析进一步研究揭示，在磷高效的广东信宜马尾松种源内部，各家系之间也存在显著的磷效率遗传差异，其苗高、地茎、干物质积累量等主要磷效率指标在家系间的变异均达到显著或极显著水平，且家系遗传力达到0.70以上。这一结果揭示，在马尾松高磷效率优良种源内部进一步发掘并充分利用磷效率的家系变异，选育磷高效优良家系具有较大的潜力和可行性。低磷胁迫下，参试的9个马尾松家系中185，337，33和67家系表现较好，其苗高、地径和干物质积累量，以及根系参数和主要磷效率指标都明显优于其他家系。通过对各家系根系参数的分析认为，整体根系参数的适应性变化是磷效率和生物量形成的决定性因素。通过苗期-大田生长回溯相关分析发现，通过马尾松家系的苗期磷效率指标，能较好地预测大田生长条件下马尾松的树高等生长性状。不过，苗期生物量与材积性状仅达到0.10水平相关（p<0.1），表明苗期盆栽试验-大田生长回溯相关的程度尚有进一步提高的必要。4.低磷胁迫下根际氮素信号对马尾松磷效率和根构型的调控以马尾松三代控制授粉家系子代为试验材料，研究根际氮素养分信号对低磷下根系发育及磷效率的影响和调控，并揭示马尾松根系分泌酸性磷酸酶活性与磷效率的关系。在施加外源氮素养分时，氮素和磷素存在显著的交互作用：在磷素极度匮乏的异质低磷胁迫下，马尾松根系对根际氮素不敏感，氮素对马尾松生长的影响较小。而在异质低磷胁迫和高磷环境下，马尾松根系发育对氮素较为敏感，根际氮素可作为信号因子调节和促进部分马尾松基因型的根系形态的发育，并改善和提升马尾松磷素营养效率。根据这一研究结论，结合当前大气氮沉降日益加重的现状，应加强选育对氮素养分信号敏感的马尾松磷高效基因型，以提高氮沉降背景下马尾松的磷效率和低磷贫瘠立地上的生产力。研究揭示无论同质低磷还是异质低磷胁迫，都对马尾松根系分泌APase活性产生诱导作用。随着低磷胁迫程度的加剧，各家系APase活性呈逐渐升高的趋势，揭示低磷胁迫下马尾松APase活性的适应性增加，是其适应同质和异质低磷胁迫，高效获取磷素并提高磷效率的重要机制。比较分析发现，无论在同质还是异质低磷胁迫下，马尾松三代控制授粉家系与一代自由授粉家系相比，其磷效率指标和干物质积累量都得到较大提升，说明经过三代遗传改良后，马尾松对同质低磷胁迫和异质低磷胁迫的适应能力得到了显著地提高。在同质和异质低磷胁迫下，三代控制授粉家系的磷效率存在显著的家系变异，揭示在马尾松三代子代内开展磷效率遗传改良的必要和潜力。5.重要环境因子（竞争、光照）对马尾松根构型及磷效率的影响与重要阔叶树种木荷相比，马尾松对异质低磷胁迫的适应能力更强、磷效率更高。进一步分析表明，异质低磷胁迫下马尾松在富磷表层介质的根系分布比例较高，这导致了马尾松具有较高磷素吸收效率和磷效率。种间竞争对马尾松和木荷的影响模式，与其所处的磷素养分环境有关，在异质养分环境下，马尾松根系保持了在富磷表层介质的较高分配比例，因而保持了较高竞争优势。在同质低磷胁迫下，马尾松磷效率较低，而木荷的种间竞争进一步降低了马尾松的主要生长性状与磷效率。与马尾松相反，木荷适应同质低磷胁迫的能力较强，在同质低磷胁迫下根系发育和磷素吸收利用具有显著优势，种间竞争将增加木荷对同质低磷胁迫的适应能力与磷效率。根据这一结果，在马尾松-木荷混交人工林中施肥时，应针对马尾松和木荷采用不同施肥策略：针对马尾松应集中施肥以促成异质养分环境、促进马尾松根系发育和生长。而针对木荷，则应均匀施肥以获得最佳的促进生长效果。遮阳将显著降低马尾松苗高、地径和干物质量，证实了马尾松是喜阳树种。进一步研究揭示，马尾松对光照条件的依赖与磷素养分环境有关，在低磷胁迫下马尾松对光照的依赖程度更高，遮阳对马尾松磷效率的降低幅度更大。根据这一结论，在磷素匮乏的立地上尤其应注意对马尾松人工林保持充分的光照，以提高马尾松磷素养分吸收和利用效率。无论在高磷还是低磷环境下，遮阳对木荷生长的影响不显著，证实木荷属于耐阴性植物，具有较好的耐荫蔽能力。更多还原

【Abstract】 Masson pine (Pinus massoniana) is a native evergreen conifer with high timber yield andexcellent timber quality. It is widely distributed in the southern part of China, and the area ofmasson pine plantations has expanded rapidly with an estimated area of5.7million hectares.Masson pine plantations are distributed mainly in the tropical and subtropical area in China,where the red soils is widely distributed and the available P can easily be bound by Ca, Al, andFe through chemical precipitation or physical adsorption. The limited availability of P in forestsoils is thus one of the most important factors causing a decline in productivity of masson pineplantations. Genetic improvement on phosphorus efficiency of masson pine has been focused.However, most of reported researches were conducted on the assumption that verticallydistribution of P is homogeneous. The adaptive mechanism in response to verticallyheterogeneous low P condition has not been regarded. Moreover, the influence of environmentfactors such as light conditions and interspecific competition on phosphorus efficiency ofmasson pine has not been studied. Therefore, we design pot experiments to disclose theadaptive mechanisms and P efficiency of masson pine in response to different types of low Pconditions. The objectives of this study were to provide insight for selecting and breeding offavorite genotypes with higher P efficiency. Through our researches, we have demonstratedthat:1. Large genotypic variations in P efficiency were observed under different types oflow-P conditions. The adaptive mechanism for P deficiency was different under heterogeneousand homogeneous low-P conditions. Under homogeneous low-P conditions, adaptive responsesof root growth parameters were present in genotypes with high-P efficiency such as ‘3201’ and‘1217’, while it was not observed in genotypes with low-P efficiency. Under heterogeneouslow-P conditions, root architecture was found to closely related to P efficiency. Genotypes withshallow root architecture had optimal root parameters including root length, surface area andbiomass in the top layer of soil, thus having the greater ability for P absorption and having higher P efficiency and biomass. The heritability for the root biomass and the proportion ofroot in the top soil layer was0.88and0.72, respectively. A significant interac-tive effectbetween patterns of low-P conditions and P efficiency was observed. Given that P. massonianahas great genetic potential for adaptation to low-P soils, the selection of high-P efficiencygenotypes with optimal root architecture may significantly increase wood production of P.massoniana under low-P conditions.2. Four provenances of Pinus massoniana were used to investigate the genotypicvariations and adaptive mechanism in response to heterogeneous and homogeneous lowphosphorus (P) depress. Large variations in seedling height，ground diameter and dry matteraccumulation among provenances of Pinus massoniana were demonstrated in both types oflow P depress (p<0.01). Guangdong Xinyi and Fujian Wuping provenances exhibited higher Pefficiency and dry matter accumulation in heterogeneous low phosphorus treatment. The higheradaptable ability of root architecture and increased root parameters in the top layer of soil,which leading to higher phosphorus absorption efficiency, should be responsible for higher Pefficiency and larger dry matter accumulation. Under heterogeneous low P depress, significantpositive correlation between root architecture and dry matter accumulation were detected withcorrelation coefficient>0.95. Under homogeneous low P deress, there were no significantcorrelation between root parametres and P efficiency，whereas in common or in top layer.Difference in the adaptive mechanism for heteroneneous and homogeneous low P efficiencywere demonstrated, implying different strategies should be considered in the slection ofhigh-P-efficiency varieties for different forest stands.3. Pot experiment comprising treatments of high level and low level of phosphorus wasconducted using9open-pollinated families randomly selected from Guangdong provenece.Most of the tested families exhibit relatively high PE and better growth performance incomparison with open-pollinated families that are randomly selected from the first-generationseed orchard. Moreover, significant genetic variations in growth traits and PE are detectedamong the nine tested families, indicating the potential for selecting families with better growth performance and higher PE from provenance with high PE. Familiesof‘185,’‘337’,‘33’and‘67’exhibit better growth performances and higher PEs than those ofother families under the low P condition. Families with higher PE have greater root parametersthan those of the families with lower PE, and significant correlations with correlationcoefficients of0.700-0.999are found between PE and root parameters. These results indicatethat the genetic variations in root parameters should responsible for the family variations in PEand biomass accumulation. The results of the retrospective analysis indicate that there arepositive correlations between growth traits in1-year pot experiment and growth traits in5-year-age progeny trials. Based on the above results, the pot experiment can be used as aneffective approach for early selection for genotypes with high phosphorus efficiency andfavorite growth performance.4. Large genotypic variations in P efficiency were observed among differentthird-generation full-sib families under different types of low-P conditions. The adaptiveexudation of APase activity in response to P deficiency was observed under both heterogeneousand homogeneous low-P conditions. Under homogeneous low-P conditions, larger degree ofAPase activity was detected as compared with heterogeneous low P conditions, indicating largecontribution of root APase activity to P efficiency. There were significant interaction effect ofN*P treatment. Under homogeneous low-P conditions, root growth traits were not sensitive toN supply. In comparison, under heterogeneous low-P conditions, sensitive growth response ofroot to N supply was observed, as major root parameters were enhanced with N supply. As aresult, major growth traits as well as P efficiency components were elevated by N treatment.Given that N concentration would be largely increased by nitrogen deposition from air, theselection of high-P efficiency genotypes with large sensitivity to rhizosphere N maysignificantly increase wood production of P. massoniana under low-P conditions. Most of thetested third-generation full-sib families exhibit relatively high PE and better growthperformance in comparison with the first-generation of open-pollinated families, indicating thegrowth potential and productivity of improved genetic materials of masson pine was large. 5. Under heterogeneous low P conditions, P.massoniana exhibited larger P efficiencyand better growth performance as compared with S superb. Further analysis revealed that thelarger proportion of root allocated in the top soil layer with high P availability should beresponsible for the larger P efficiency of P.massoniana. The influence of interspecificcompetition on growth traits and P efficiency of P.massoniana was related to P level. Underheterogeneous low P conditions, P.massoniana exhibited large competition ability, as it havelarger P efficiency and better growth performance as compared with S superb. The largerproportion of root in the top soil layer and greater P acquisition ability should be responsiblefor the larger competition ability of P.massoniana. In contrast, under homogeneous low Pconditions, S superb exhibited larger competition ability and larger P efficiency thanP.massoniana, owing to its larger degree of root proliferation under homogeneous low Pconditions. Light conditions had significant effect on growth and development of P.massoniana,whereas the influence on S superb was relatively small. Under shading conditions, growthtraits, dry matter accumulation, phosphorus uptake efficiency and root parameters ofP.massoniana was significantly decreased. In contrastion, the influence of light contions ongrowth traits and P efficiency of S superb was not large.更多还原