毛红椿根蘖性状发生的生理和遗传机制

Toona ciliata var. pubescens is a kind of rare and endangered tree, although the sexual and asexual two reproductive modes coexist. Its sexual reproduction is usually blocked in the process of natural regeneration, replaced by a wide range of clonal integration to produce offsprings through root suckers. In this subject, two forest dominant communities of T. ciliata var. pubescens in Guanshan National Nature Reserve and Jiulianshan National Nature Reserve in Jiangxi province are took as the research objects. Taking the root suckers as the center, the trees and its root system as a whole, soil properties as the focus, root distribution and architecture as well as the variety of internal hormone and gene frequency of the creeping-rooted system will be studied. Combined with the analysis of symbiotic microorganisms (AM fungi) species and functional diversity, the physiological and genetic mechanism on sucker character in T. ciliata var.pubescens will be revealed, meanwhile its asexual reproduction theory will be improved. This study will provide technical support for T. ciliata var. pubescens natural forest protection and provide theoretical guidance for the rare and endangered tree species recovery.

珍稀濒危树种毛红椿虽以有性和无性两种繁殖方式并存，但天然更新过程中有性生殖通常受阻，而以广泛的克隆整合作用通过根蘖苗繁衍后代。本项目以江西九连山国家级自然保护区和江西官山国家级自然保护区毛红椿天然群落为研究对象，以根蘖苗为中心将毛红椿母树及其根系统作为一个整体，着重从土壤性状对毛红椿根蘖苗发生的影响进行分析，研究毛红椿根蘖型根系分布状况、根系构型及根蘖性状发生时内源激素和基因变化，并结合毛红椿共生微生物（AM真菌）群落多样性及功能多样性分析，揭示毛红椿根蘖性状发生的生理遗传机制，完善毛红椿无性繁殖理论，为毛红椿天然林保护提供技术支撑，为珍稀濒危树种种群恢复提供理论指导。

本研究在江西九连山国家级自然保护区和官山国家级自然保护区开展毛红椿群落调查、根系构型与根蘖控制原位试验，并开展接种丛枝菌根真菌（Arbuscular mycorrhizal fungi，AMF）的苗期盆栽试验，解析毛红椿根系分布、根蘖起源及根萌发生的生理机制，分析毛红椿天然林群落根际土壤AMF群落特征以及AMF与毛红椿共生关系，探讨AMF影响毛红椿根系构型的分子机制，揭示毛红椿根系适应环境的机制，为毛红椿天然种群的维持及稳定提供指导。.1.通过连续三年毛红椿天然林实地监测发现，96.44% 根萌芽点发生于裸露地表、土壤较湿润的侧根上，土壤内的根几乎没有根萌芽点；87%根萌芽以单芽形式出现在直径2mm - 6mm 的二级、三级侧根（占77%）上。解剖学发现根萌芽始于木栓形成层。从内源激素水平上来看，IAA、ZR、ABA和GA3含量在根不定芽发生过程中起到积极作用。.2.利用10对SSR分子标记分析表明九连山毛红椿4个居群有297个基株，克隆多样性较高，属于多克隆居群，居群间存在中等程度的遗传分化。.3.采用Illumina PE250高通量测序研究毛红椿天然群落3个优势树种和不同坡向植物根际土壤和根系中AMF群落特征。结果发现，球囊霉科（Glomeraceae）是根际土壤和根系中最丰富的AM真菌科，其相对丰度在毛红椿根际土中达到58.75%，聚集程度相对较高的AMF主要存在于根系中。北坡和南坡均不影响AM真菌多样性，但显著影响AM真菌群落结构和组成。.4.接种控制试验的结果表明，虽然毛红椿幼苗菌根侵染率较低，但AM真菌能显著促进毛红椿生长、影响非结构性碳水化合物、叶绿素含量和各器官N、P、K吸收量并调控根系构型；RNA-sep转录组技术研究表明，接种毛红椿根系显著上调差异基因占比多，且上调基因的差异倍数显著大于下调基因的差异倍数，说明接种土著AM真菌后促进了毛红椿根系基因的表达。