【作者】 郑健；

【导师】 郑勇奇；

【作者基本信息】 中国林业科学研究院 ， 林木遗传育种， 2008， 博士

【摘要】 本研究对我国特有的乡土树种花楸树(Sorbus pohuashanensis (Hance) Hedl.)的天然资源,采用文献资料、标本整理以及实地调查的方法,研究了其地理分布、生境条件以及自然更新情况。在此基础上,对来自3个省区(山东省、山西省、河北省)7个群体(群体)171个家系花楸树一年生幼苗形态性状的地理变异进行了分析;采用水平切片淀粉凝胶同功酶电泳技术,对来自4个省区(山东省、山西省、河北省、辽宁省)8个天然群体的遗传多样性和遗传结构进行了研究;进而利用多位点异交率估测程序(MLT)对其中的6个群体的交配系统进行了估测。同时,开展花楸树引种栽培研究,在引种地对其物候表现、生长发育状况进行了观测;分别以露地成年母树和温室内一、二年生幼树萌生的当年生枝条为扦插材料,以不同浓度(500、1000、1500、2000、2500、3000 mg?kg-1)的IBA、NAA、IBA+NAA(10:1)、IBA+NAA(5:1)、IBA+NAA(2:1)、IBA+NAA(1:1)等为外源激素处理插穗,以泥炭+珍珠岩(3:1)、蛭石、河沙为扦插基质,研究花楸树嫩枝扦插繁殖技术。旨在为花楸树遗传资源的评价、保存以及开发利用等提供科学理论依据。通过以上研究,得出以下主要研究结果:1.花楸树在我国由主要分布在暖温带落叶阔叶混交林区域,有少部分分布在温带针阔叶混交林区域,属于湿润山地植被带类型。花楸树作为伴生树种散生分布在山地阔叶混交林、山地针阔叶混交林、山地落叶松纯林内或林缘以及山顶灌丛4种植被带(包括12种森林群落)类型中。花楸树垂直分布在海拔500-2200 m范围内,集中分布在海拔1200-2000 m间。除在雾灵山阳坡有分布外,花楸树大多生长在半阳坡、半阴坡、阴坡以及沟谷环境中,其分布区土壤类型以山地棕壤、暗棕壤为主。海拔、气温、空气湿度可能直接影响花楸树的自然分布。其自然更新方式有种子繁殖更新和萌蘖(包括根蘖和桩蘖)繁殖更新两种,以桩蘖为主要的的更新方式。2.花楸树各群体内家系子代幼苗的苗期性状变异十分丰富,种群性状间、群体内性状间变异系数的差异明显,花楸树表型10个性状在群体间、群体内家系间的差异均达到极显著水平。群体间平均表型分化系数为34.38%,群体内家系间的变异是花楸树表型变异的主要来源,群体内家系间的变异高于群体间的变异。根据表型多样性综合指标的聚类结果,将花楸树7个群体划分为两大类。群体苗木性状与产地地理气候因子的相关分析发现,苗高与纬度呈显著负相关,产地温度、降雨量则是造成这种负相关主要环境因子;地径则与经度呈正相关,因此初步判断花楸树为经纬向双重变异模式,其中纬度起主要作用。3. 4个酶系统10个位点的检测结果表明,参试的8个花楸树天然群体都存在稀有基因;花楸树群体水平上的遗传多样性较高,每位点平均等位基因数(Na)为2.2,多态位点百分率(P)为100%,期望杂合度(He)为0.4240;花楸树8个群体间的遗传多样性差异较小,以Ne、H、Shannon信息指数三个指标对8个群体遗传多样性从高到低次序为河北驼梁山(HBT)>河北雾灵山(HBW)>山西庞泉沟(SXP)>河北白石山(HBB)>山东崂山(SDL)>河北塞罕坝(HBS)>山东泰山(SDT)>辽宁老秃顶(LNL);花楸树群体间遗传分化系数(Fst)为0.0758,群体间总的基因流(Nm)较高,为3.0472,表明花楸树群体间遗传分化程度小,这与群体间较高的遗传一致度(I=0.8585-0.9872)的结果一致;在单个群体中,通过卡方(χ2)检验(P<0.05)显示,花楸树群体有73.62%的群体-位点组合显著偏离哈迪-温伯格平衡,总种群的Fit、Fis分别为-0.3105、-0.4180,表明无论在总体水平还是群体内个体间,花楸树种群表现为杂合体过量的现象。UPGMA聚类结果显示,8个群体的遗传距离与地理距离呈现弱相关性。4.花楸树各群体的花粉库与胚珠库中,各位点基因的配子比例不平衡,t检验结果显示,6个群体的雌雄配子比例差异均不显著。各群体多态位点异交率均很高,在0.981以上,多位点异交率与单位点异交率平均值的差值(tm-ts)显示出花楸树各群体都存在轻度的自交或近交。此外,驼梁山群体的子代内异交父本相关系数(rp=0.420)最高,各群体母本异交率(rt)为0.083-0.108。因此,花楸树属于混合交配类型,以杂交为主,表现为高度异交。根据电泳数据计算的近交衰退(δ=1),表明花楸树天然群体的近交衰退相当大。5.花楸树在引种地区,物候表现基本正常;在炎热夏季受高温影响,花楸树的叶片易发生日灼,主要发生在6-7月份,遮荫处理可以避免日灼发生;不经任何防寒措施,花楸树可以安全越冬。在大树遮荫条件下,其高生长在4月底出现生长高峰,属于春季生长类型;地径生长高峰出现在5月、6月和8月。花楸树叶片秋季变为红色、黄色,可进行苗期选择。在夏季采取保护措施的条件下,花楸引种平原地区有望成功。6.取自成年母树的插穗仅有愈伤组织没有不定根生成,取自一、二年生幼树的插穗平均生根率70.37%以上,不定根平均长度4.85cm以上,不定根数量19条以上;枝条的下部位生根效果明显优于上部位;采穗及扦插时间在春季萌芽后1.5-2个月时为宜;扦插基质选用蛭石或者泥炭土+珍珠岩(3:1) ;外源激素选用IBA+NAA(10:1)或者IBA+NAA(5:1),以1500 mg?kg-1为最佳浓度处理,生根率达90%以上,不定根平均长度在6.67cm以上,不定根数量在34条以上;花楸树嫩枝扦插以皮部生根为主,属于皮部生根类型。7.花楸树为高度异交物种,其遗传资源的保存应从源头开始,进行原地保存的同时,多地点或多群体收集种子(或其它繁殖材料),构建种质资源圃,建立种源/家系试验林,选择优良单株营造无性系收集圃,构建种子库开展设施保存,同时还可借助植物园的优势开展资源保存工作。更多还原

【Abstract】 The natural distribution, habitat conditions and natural regeneration of indigenous tree species, Sorbus pohuashanensis (Hance) Hedl. were studied based on literature, specimen and field investigations. 8 populations were sampled in Shandong, Shanxi, Hebei and Liaoning provinces. 7 populations (171 families in total) of them were used for analysis of geographical variation in 10 morphological and growth traits of 1-year-old seedlings. Genetic structure and diversity of all the 8 populations and mating system of 6 populations were aasayed using isozyme markers. A domestication trial was established in Changping Experiment Nursery of Beijing Municapl Forestry Bureau. Propagation by softwood cutting were also conducted to analyze effects of auxins (types and concentrations), position of cuttings on trees, and rooting conditions. This study is intended to provide guidelines for evaluation, domestication and conservation of the genetic resources of the species. Major results are described as follows:1. Most S. pohuashanensis naturally occur in mixed broad-leaved warm temperate forest, and some occur in mixed coniferous and broad-leaved temperate forest, belonging to humid mountain vegetation zone. The habitats can be grouped into 4 vegetation types (including 12 community types): mixed broad-leaved mountain forest, mixed coniferous and broad-leaved mountain forest, pure larch mountain forest and mountain top shrub forest. The altitudinal distribution of the species ranges from 500 to 2200 m with majority occuring between 1200 and 2000m. The species grows mostly in semi-sunny, semi-shade, shade slopes and gullies, however, it grows in sunny slopes in Wulingshan, Hebei province. The brown mountain soil and dark brown soil are the main soil types in the whole natural range of the species. Altitude, temperature and air humidity are likely the main factors affecting the distribution of the species. The species can naturally regenerate through seed and through sprout from roots and stumps. The stump-sprouting is the main pattern of natural regeneration.2. Analysis of variance showed that there are significant differences between population and between families within popuation for morphological and growth traits. The mean phenotypic differentiation coefficient for the 10 traits is 34.38%, indicating that the variance from families within population is the main part of the phenotypic variation. According to the result of cluster analysis based on several phenotypic diversity indices, the 7 populations can be divided into two groups. Correlation between the growth of seedlings and the geographical and climatic factors was calculated. A significant negative correlation was found between the height growth and the latitude. Temperature and mean annual rainfall are the main factors that affected the population variation. However, a significant positive correlation was found between the ground diameter and the longitude. A primary opinion is that the provenance variance of the species is influenced by both the latitude and the longitude, and the latitude plays the major role.3. Genetic structure and diversity of the 8 populations of the species were studied at 10 loci encoding 4 enzymes using horizontal starch gel electrophoresis, Rare alleles were found in each of the 8 populations sampled. The levels of genetic diversity were high at species level with the mean number of alleles per locus Na=2.2, the percentage of polymorphic loci P=100%, and the mean expected heterozygosity He=0.4240. The 8 populations were ranked as HBT>HBW>SXP>HBB>SDL>HBS>SDT>LNL according to He. And same order applies to Ne and Shannon′s information index. A low Level of genetic differentiation among populations was detected (Fst=0.0758) and a higher estimate of gene flow (Nm=3.0472) coincided with a high level of genetic identity (I) among the populations (from 0.8585 to 0.9872). Wright’s F-statistics analysis indicated an excessive of heterozygotes both at population level (Fis=﹣0.4180) and at total population level (Fit=﹣0.3105). The results ofχ2-test (P<0.05) indicated that 73.2% of population-loci departed the Hardy-Weinberg equilibrium. The UPGMA cluster analysis suggested that the genetic distances among population were weakly correlated with their geographic distances.4. The horizontal starch gel electrophoresis for polymorphic loci of isozymes was used to exame the genotypes in 6 populations, sampled in Laoshan and Taishan, in Shandong province, Pangquangou, in Shanxi province, Tuoliangshan and Baishishan, in Hebei province, Laotuding, in Liaoning province. Mating system was also analysed using MLT software. The 8 polymorphic loci selected for analysis were Pgm-1、Pgm-2、Pgm-3、Pgi-1、Pgi-2、Pgd-1、Pgd-2、Pgd-3. The results indicated that the gametes ratio of each locus in pollen and ovule pools was imbalance in the 6 populations. The male to female gametes ratio of the six populations was not significantly different shown t-test. The outcrossing rates of polymorphic loci were above 0.981. The margin of multi-locus and single-locus outcrossing rate (tm-ts) showed that slight inbreeding existed in the each population of the species. In addition, the correlation of outcrossed paternity within progeny arrays (rp=0.420) of the Tuoliangshan population was the highest and the outcrossing rate of female parents (rt) of all the 6 populations ranged from 0.083 to 0.108. Therefore, S. pohuashanensis, having a mixed mating model, is a highly outcrossing species. The inferred inbreeding depression (δ= 1) from the electrophoresis data indicated that the natural populations of the species suffered serious inbreeding depression.5. The phenology and growth pattern on 2-year-old seedlings of S. pohuashanensis were studied. The results showed that S. pohuashanensis could grow well in shaded conditions and its phenology was normal in the introductional experimental site during the 2 years of observation. In open field, the leaves of the seedlings are subject to sunburn in hot summer, mainly in 6-7 month, and shading can be used to avoid sunburn. Under the shade of big trees, the peak shoot growth was in late April. The diameter growth peaked in May, June and August respectively. The leaf color gradually turns into red or yellow in autumn, selection can be made to develop varibilities with different leaf colors. High temperature and sunborn are probably the main factors restraining the growth in summer in the low altitudes.6. Using different types of auxins (IBA, NAA, IBA+NAA (10:1), IBA+NAA (5:1), IBA+NAA (2:1) and IBA+NAA (1:1)), with different concentrations (500, 1000, 1500, 2000, 2500 and 3000 mg?kg-1), and different types of rooting media (vermiculite, peat+perlite (3:1) and sand), the rooting ability of cuttings collected from field-grown and greenhouse-grown S. pohuashanensis was studied. Rooting rate, length and number of adventitious roots were measured. Only callus but no adventitious roots were found for the cuttings collected from lateral branches at the top of adult tree. However, the adventitious roots were visible for the cuttings collected from 1-2-year-old saplings, with larger rooting rate (above 70.37%), length (above 4.85 cm) and number (above 19) of adventitious roots. The softwood cuttings collected from the lower part of stems was obvious better than that from the upper parts. Cuttings should be taken early in the season before they were not completedly lignified, about 1.5-2 months after bud shooting. The rooting of softwood cutting was improved by a basal dip in IBA+NAA (10:1) and IBA+NAA (5:1). The vermiculite or peat+perlite (3:1) was the appropriate rooting media. The best rooting rate (above 90%), the largest length (above 6.67cm) and numbers of adventious roots (above 34) were obtained following the 1500 mg?kg-1 treatments.7. The results indicate that S. pohuashanensis is a predominantly outcrossing species. For any genetic resource conservation programe, sampling of seeds (or propagation materials) from more populations with a smaller number of trees at each site is preferable except for in situ conservation. Conservation stands/gene banks, provenance/families trials, clone banks and seed banks shoud be established. While some botanical gardens and arboretums are also proposed to conserve the genetic resources of the species.更多还原