High-density genetic linkage maps with over 2,400 sequence-anchored DArT markers for genetic dissection in an F2 pseudo-backcross of Eucalyptus grandis × E. urophylla

Traits that differentiate cross-fertile plant species can be dissected by genetic linkage analysis in interspecific hybrids. Such studies have been greatly facilitated in Eucalyptus tree species by the recent development of Diversity Arrays Technology (DArT) markers. DArT is an affordable, high-throughput marker technology for the construction of high-density genetic linkage maps. Eucalyptus grandis and Eucalyptus urophylla are commonly used to produce fast-growing, disease tolerant hybrids for clonal eucalypt plantations in tropical and subtropical regions. We analysed 7,680 DArT markers in an F2 pseudo-backcross mapping pedigree based on an F1 hybrid clone of E. grandis and E. urophylla. A total of 2,440 markers (31.7%) were polymorphic and could be placed in linkage maps of the F1 hybrid and two pure-species backcross parents. An integrated genetic linkage map was constructed for the pedigree resulting in 11 linkage groups (n = 11) with 2,290 high-confidence (LOD ≥ 3.0) markers and a total map length of 1,107.6 cM. DNA sequence analysis of the mapped DArT marker fragments revealed that 43% were located in protein coding regions and 90% could be placed in the recently completed draft genome assembly of E. grandis. Together with the anchored genomic sequence information, this linkage map will allow detailed genetic dissection of quantitative traits and hybrid fitness characters segregating in the F2 progeny and will facilitate the development of markers for molecular breeding in Eucalyptus.     

Comparative genetic linkage maps of <Emphasis Type="Italic">Eucalyptus grandis</Emphasis>, <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> and their F<Subscript>1</Subscript> hybrid based on a double pseudo-backcross mapping approach

Comparative genetic mapping in interspecific pedigrees presents a powerful approach to study genetic differentiation, genome evolution and reproductive isolation in diverging species. We used this approach for genetic analysis of an F₁ hybrid of two Eucalyptus tree species, Eucalyptus grandis (W. Hill ex Maiden.) and Eucalyptus globulus (Labill.). This wide interspecific cross is characterized by hybrid inviability and hybrid abnormality. Approximately 20% of loci in the genome of the F₁ hybrid are expected to be hemizygous due to a difference in genome size between E. grandis (640 Mbp) and E. globulus (530 Mbp). We investigated the extent of colinearity between the two genomes and the distribution of hemizygous loci in the F₁ hybrid using high-throughput, semi-automated AFLP marker analysis. Two pseudo-backcross families (backcrosses of an F₁ individual to non-parental individuals of the parental species) were each genotyped with more than 800 AFLP markers. This allowed construction of de novo comparative genetic linkage maps of the F₁ hybrid and the two backcross parents. All shared AFLP marker loci in the three single-tree parental maps were found to be colinear and little evidence was found for gross chromosomal rearrangements. Our results suggest that hemizygous AFLP loci are dispersed throughout the E. grandis chromosomes of the F₁ hybrid.Communicated by O. Savolainen     

Discovery, validation, and in silico functional characterization of EST-SSR markers in Eucalyptus globulus

Eucalyptus globulus is the most commonly planted hardwood species for pulpwood in temperate regions. We aimed to develop and characterize functional molecular markers for population genetic analyses and molecular breeding in this model tree species. Public expressed sequence tag (EST) databases were screened for nonredundant sequences to predict putative gene functions and to discover simple sequence repeats (EST-SSRs), which were then validated in E. globulus and six other Eucalyptus species. A total of 4,924 nonredundant sequences were identified from 12,690 updated E. globulus ESTs. Approximately 19.3% (952) were unigenes and contained 1,140 EST-SSR markers, which were mainly trimeric (58.6%). A set of 979 primers for putative SSR markers was designed after bioinformatic analysis. The predicted functions of these ESTs containing SSR were classified according to their gene ontology (GO) categories (biological process, molecular function, and cellular component). GO categories were assigned to 226 ESTs (30.2%). Most ESTs containing SSR (78.7%) had significant matches (E ≤ 10⁻⁵) with the nonredundant protein database using BLASTX. From a set of 56 random primer pairs, 37 could be validated in eight E. globulus genotypes and were also tested for cross-transferability to other six Eucalyptus species (Eucalyptus grandis, Eucalyptus saligna, Eucalyptus dunnii, Eucalyptus viminalis, Eucalyptus camaldulensis, Eucalyptus tereticornis). Seventeen polymorphic EST-SSR markers for E. globulus were evaluated in 60 unrelated trees, being representative of the species’ natural distribution. As a result, six highly informative markers were proposed for genetic diversity analyses, fingerprinting, and comparative population studies, between different species of E. globulus.     

Genotyping systems for Eucalyptus based on tetra-, penta-, and hexanucleotide repeat EST microsatellites and their use for individual fingerprinting and assignment tests

Eucalypts are keystone species in their natural ranges and are extensively planted worldwide for high-quality woody biomass. A novel set of 21 polymorphic and interspecifically transferable microsatellite markers based on tetra-, penta- and hexanucleotide repeats were developed and tested for high-precision genotyping of species of Eucalyptus. These microsatellites were characterized in population samples of four species, Eucalyptus grandis, Eucalyptus globulus, Eucalyptus urophylla, and Eucalyptus camaldulensis, representing three phylogenetic sections of subgenus Symphyomyrtus. These markers provide a clear advantage for accurate allele calling due to their larger allele size difference. Two multiplexed microsatellite combinations, a 14-locus/four-dye and an 18-locus/five-dye set, analyzable in single lanes were designed, providing resolution and throughput analogous to those routinely used in human DNA profiling. This set of microsatellites was shown to have high resolution for clone fingerprinting, inter-individual genetic distance estimation, species distinction, and assignment of hybrid individuals to their most likely ancestral species. These systems will be particularly useful for comparative population genetics and molecular breeding applications that require consistent allele calling across different points in time or laboratories.     

Development, characterization and mapping of microsatellite markers in Eucalyptus grandis and E. urophylla

 We report on the development, genetic characterization and linkage mapping of a battery of SSR (simple sequence repeat) loci in Eucalyptus grandis and E. urophylla. This study reveals the abundance of SSRs in Eucalyptus, the very high information content of these markers for mapping and individual identification, and demonstrates the feasibility of constructing a comprehensive microsatellite-based linkage map for Eucalyptus. Primer sequence for a set of 20 highly informative EMBRA (Eucalyptus microsatellites from Brazil) loci are made available together with their map position and estimates of the expected heterozygosity and allele size range in these two species. Using genomic library enrichment and anchored-PCR screening prior to sequencing, the efficiency of SSR marker locus development was 63% from sequencing data to operationally useful SSR loci. Absolute transportability between the two species and very high levels of allelic variability and expected heterozygosity (H) were seen at all SSR loci surveyed. The number of alleles per locus ranged from 9 to 26 with an average of 16.3±4.8. The average H of 15 loci was 0.86±0.04, 0.83±0.08 and 0.89±0.04, respectively, for E. urophylla, E. grandis and the combined two-species estimate. In the mapping analysis 16 out of 20 marker loci segregated in a fully informative configuration, allowing the determination of synteny of six homologous linkage groups between the two species. The availability of transportable, multiallelic, PCR-based co-dominant SSR loci represents a dramatic improvement in our ability to carry out detailed population genetic analysis and to search, understand, and manipulate allelic variation at QTLs (quantitative trait loci) in species of Eucalyptus. Received: 16 March 1998 / Accepted: 22 March 1998     

Moderate-density molecular maps of Eucalyptus urophylla S. T. Blake and E. tereticornis Smith genomes based on RAPD markers

Moderate-density molecular maps were constructed for the genomes of Eucalyptus urophylla S. T. Blake and E. tereticornis Smith using RAPD markers and an interspecific cross between the two species. One hundred and eighty-three primers were employed to generate 245 and 264 parent-specific markers in E. urophylla and E. tereticornis, respectively, as well as 49 parent-shared markers. The normally segregating markers, including 208 (84.9%) specific to maternal E. urophylla, 175 (66.3%) to paternal E. tereticornis, and 48 shared by both parents, were used for framework map construction for each parental species. For maternal E. urophylla, the linkage map consisted of 23 linkage groups, 160 framework markers, and 60 accessory markers, defining a total map distance of 1504.6 cM and an average interval of 11.0 ± 8.07 cM. For paternal E. tereticornis, the linkage map contained 23 linkage groups, 126 framework markers, and 92 accessory markers, defining a total map distance of 1035.7 cM and an average interval of 10.1 ± 7.23 cM. Genome length was estimated at 1585.7 and 1507.5 cM for E. urophylla and E. tereticornis, respectively, indicating map coverage of 94.9 and 68.7% of the corresponding genomes. Construction of such maps will be valuable for quantitative trait loci (QTLs) detection, marker-assisted selection (MAS), comparative mapping, and whole genome based fingerprint characterization in Eucalyptus breeding programs.     

A novel set of EST-InDel markers in <Emphasis Type="Italic">Eucalyptus</Emphasis> L’Hérit.: polymorphisms,cross-species amplification,physical positions and genetic mapping

Insertion/deletion (InDel) markers are valuable for genetic applications in plant species, and the public databases of expressed sequence tags (ESTs) have facilitated the development of genic InDel markers. In this study, we developed a novel set of 144 InDel markers in an important tree genus Eucalyptus L’Hérit. using the ESTs of GenBank. Amplicon sequencing against two parents of a mapping population (Eucalyptus urophylla S. T. Blake × E. tereticornis Smith) revealed that the InDel size ranged from 2 to 44 bases, and the dinucleotide type was the most abundant (37.3 %). The cross-species/subgenus amplification rate ranged from 62.5 % in E. tessellaris F. Muell. (subgenus Blakella) to 99.3 % in E. grandis Hill ex Maiden (subgenus Symphyomyrtus) with an average of 85.4 %. There were 121 EST-InDels (84.0 %) polymorphic among 12 individuals of E. grandis, and the mean number of alleles per polymorphic locus (N _a), observed heterozygosity (H _o), expected heterozygosity (H _e) and polymorphic information content (PIC) were 4.0, 0.278, 0.538 and 0.465, respectively. Physical positions of 143 EST-InDels were predicted on the E. grandis genome sequence. A total of 81 EST-InDels were incorporated into prior dense genetic maps of E. urophylla and E. tereticonis, and extensive synteny and colinearity were observed between E. grandis genome sequence and the mapped EST-InDel markers. These EST-InDels will provide a valuable resource of functional markers for genetic diversity evaluation, genome comparison, QTL mapping and marker-assisted breeding in Eucalyptus.     

5种相思树和尾巨桉人工林土壤养分和酶活性特征

为揭示固氮树种土壤养分转化的酶学机制,对固氮树种[厚荚相思(Acacia crassicarpa)、黑木相思(A. melanoxylon)、卷荚相思(A.cincinnata)、大叶相思(A.auriculiformis)和马占相思(A.mangium)]及非固氮树种尾巨桉(Eucalyptusurophylla×E.grandis)人工林的土壤养分含量、酶活性及其相关性进行研究。结果表明,相思林40～60cm土层的pH均高于尾巨桉林;5种相思林土壤各土层的TP、TK含量均低于尾巨桉林,而20～40 cm土层的TC、TN含量均高于尾巨桉林,黑木相思林和马占相思林各土层的有效养分均显著高于尾巨桉林(P0.05)。0～10 cm土层中,相思林的土壤酸性磷酸酶和纤维素酶活性均高于尾巨桉林,大叶相思林的土壤脲酶、蔗糖酶、纤维素酶和芳基硫酸酯酶活性显著高于尾巨桉林(P0.05),卷荚相思林的土壤脲酶、纤维素酶、几丁质酶和淀粉酶活性显著高于尾巨桉林(P0.05)。相关分析结果表明,土壤脲酶、蔗糖酶和几丁质酶活性与AP显著负相关(P0.05),蔗糖酶和纤维素酶活性与NH4+-N显著负相关(P 0.05),脲酶、纤维素酶、芳基硫酸酯酶与土壤TK显著负相关(P0.05),几丁质酶活性与TN含量呈显著正相关(P0.05),土壤淀粉酶活性与NH4+-N呈显著正相关(P 0.05),过氧化氢酶活性与土壤TK含量呈显著正相关。可见,与尾巨桉人工林相比,在我国南方退化山地引种相思树可提高土壤关键酶的活性,对土壤有效养分具有明显改良作用,有利于退化地土壤的生态修复及人工林长期生产力的维持。     

AFLP genetic maps of Eucalyptus globulus and E. tereticornis

 Amplified fragment length polymorphism (AFLP) analysis is a rapid and efficient technique for detecting large numbers of DNA markers in eucalypts. We have used AFLP markers in a two-way pseudo-testcross strategy to generate genetic maps of two clones of different Eucalyptus species (E. tereticornis and E. globulus). Of 606 polymorphic fragments scored, 487 segregated in a 1 : 1 ratio, corresponding to DNA polymorphisms heterozygous in one parent and null in the other. In the maternal E. tereticornis map, 268 markers were ordered in 14 linkage groups (919 cM); the paternal E. globulus map had 200 markers in 16 linkage groups (967 cM). Results from PGRI software were compared with MAPMAKER. The average density of markers was approximately 1 per 3.9 cM. Framework markers were ordered with an average confidence level of 90%, covering 80–100% of the estimated Eucalyptus genome size. In order to investigate the homologies between the E. tereticornis and the E. globulus genetic linkage maps, we included 19 markers segregating 3 : 1 in the analysis. Some homeologous linkage groups were recognized. The linkage data developed in these maps will be used to detect loci controlling commercially important traits. Received: 17 July 1997 / Accepted: 13 October 1997     

速生树种尾巨桉和竹柳幼苗耗水特性和水分利用效率

速生树种尾巨桉和竹柳因其水分消耗和利用问题引起了一些争议,因而受到了广泛的关注,由于尚缺乏科学的观测数据,而其中许多指责或支持也尚无定论,因此必须深入研究此2种树种耗水性能和水分利用效率,以期科学评价其水分消耗和利用性能。采用盆栽苗木称重法和Li-6400光合系统测定方法分别测定尾巨桉(Eucalyptus urophylla×Eucalyptus grandis)和竹柳(Salix sp.)苗木在不同土壤水分条件下耗水量、耗水速率和苗木不同生长期叶片净光合速率(Pn)、蒸腾速率(Tr)和水分利用效率(WUE),研究表明:(1)正常水分条件下,尾巨桉和竹柳日总耗水量和最大耗水速率分别为(182.05±12.74)g/d、(100.48±10.95)g/d和(66.31±9.91)g·m-2·h-1、(89.50±13.54)g·m-2·h-1,土壤水分条件下降时,2种苗木耗水量和耗水速率均呈显著下降趋势,严重干旱胁迫时尾巨桉降幅更大。(2)正常水分条件和轻度水分胁迫下2种苗木耗水速率日变化趋势均为明显"单峰"曲线,且峰值均出现在12:00—14:00,中度干旱胁迫时则其变化趋势呈"双峰"曲线,峰值分别在10:00—12:00和14:00—16:00出现,严重干旱胁迫时日变化规律不明显。(3)正常水分条件和轻度水分胁迫下2种苗木耗水速率与环境温度显著正相关,与相对湿度显著负相关,随着干旱胁迫的发展,环境因子对耗水速率的影响有所减弱。(4)叶片水平来看,与尾巨桉相比,竹柳具有高光合、低蒸腾、高水分利用效率的特点,2种苗木由生长初期进入生长旺期时,净光合速率和蒸腾速率均发生相同幅度增加,而水分利用效率基本保持不变。(5)从单株耗水量和耗水速率以及叶片水分利用效率综合来看,竹柳属节水性能较好速生树种,而尾巨桉虽然存在叶片水平高蒸腾和低水分利用效率的情况,但从单株苗木水平上来讲,其耗水速率甚至低于竹柳,特别在土壤水分严重亏缺情况下其白天平均耗水速率仅为(4.02±0.60)g·m-2·h-1,也表现出了一定的抗旱节水能力。     

Effects of nitrogen supply rate on photosynthesis,nitrogen uptake and growth of seedlings in a Eucalyptus/Dalbergia odorifera intercropping system

• The introduction of N₂-fixing species into a Eucalyptus plantation resulted in a successful planting system. It is essential to understand the contribution of nitrogen (N) competition and photosynthetic efficiency to plant dry matter yield to shed more light on the growth mechanism of the Eucalyptus/legume system.
• We compared N competition, photosynthesis and dry matter yield of Eucalyptus urophylla × E. grandis and the N₂-fixing tree species Dalbergia odorifera in intercropping and monoculture systems under different N levels.
• The photosynthesis of E. urophylla × E. grandis was improved, while that of D. odorifera was inhibited in the intercropping system. Intercropped E. urophylla × E. grandis increased the N utilization and the dry matter yield by 6.57–48.46% and 7.59–97.26%, and decreased those of D. odorifera by 10.21–30.33% and 0.48–13.19%, respectively. Furthermore, N application enhanced the competitive ability of E. urophylla × E. grandis relative to D. odorifera and changed the N contents and chlorophyll synthesis to optimize the photosynthetic structure of both species.
• Our results reveal Eucalyptus for photosynthesis, N absorption and increasing the growth benefit from the introduction of N₂-fixing species, which hence can be considered to be an effective sustainable management option of Eucalyptus plantations.

     

Microsatellite diversity and genetic structure of the commercially important tropical tree species <Emphasis Type="Italic">Eucalyptus urophylla</Emphasis>, endemic to seven islands in eastern Indonesia

Eucalyptus urophylla (Timor mountain gum) is an economically important plantation species that occurs naturally in a series of disjunct populations on the volcanic slopes of seven islands in eastern Indonesia. Twelve microsatellite markers were used to investigate the distribution of nuclear genetic diversity among 19 geographically defined E. urophylla populations. High levels of gene diversity were observed throughout the geographic range (H _E = 0.703 to 0.776). The level of genetic differentiation among populations was low (F _ST = 0.031), but the amount of differentiation increased with geographic distance. A phenogram produced by a neighbor-joining analysis illustrated that populations clustered according to islands. However, a Bayesian clustering approach revealed a more cryptic population structure comprising two genetically homogeneous groups. Gene flow among the populations is likely responsible for the apparent weak influence of geographic insularity on the genetic diversity and structure of the island species. These findings provide direction for conservation and breeding strategies in E. urophylla. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

QTL mapping for resistance to Ceratocystis wilt in <Emphasis Type="Italic">Eucalyptus</Emphasis>

Ceratocystis wilt caused by the fungus Ceratocystis fimbriata, is currently one of the major diseases in commercial plantations of Eucalyptus trees in Brazil. Deployment of resistant genotypes has been the main strategy for effective disease management. The present study aimed at identifying genomic regions underlying the genetic control of resistance to Ceratocystis wilt in Eucalyptus by quantitative trait loci (QTL) mapping in an outbred hybrid progeny derived from a cross between (Eucalyptus dunnii × Eucalyptus grandis) × (Eucalyptus urophylla × Eucalyptus globulus). A segregating population of 127 individuals was phenotyped for resistance to Ceratocystis wilt using controlled inoculation under a completely randomized design with five clonal replicates per individual plant. The phenotypic resistance response followed a continuous variation, enabling us to analyze the trait in a quantitative manner. The population was genotyped with 114 microsatellite markers and 110 were mapped with an average interval of 12.3 cM. Using a sib-pair interval-mapping approach five QTLs were identified for disease resistance, located on linkage groups 1, 3, 5, 8, and 10, and their estimated individual heritability ranged from 0.096 to 0.342. The QTL on linkage group 3 overlaps with other fungal disease-resistance QTLs mapped earlier and is consistent with the annotation of several disease-resistance genes on this chromosome in the E. grandis genome. This is the first study to identify and attempt to quantify the effects of QTLs associated with resistance to Ceratocystis wilt in Eucalyptus.     

Quantitative trait dissection analysis in Eucalyptus using RAPD markers: 1. Detection of QTL in interspecific hybrid progeny, stability of QTL expression across different ages

 The objective of this study was to use random amplified polymorphic DNA (RAPD) to determine the genetic location and effects of genomic regions controlling wood density, stem growth and stem form in two species of Eucalyptus. Two hundred F₁ trees generated from an interspecific cross E. urophylla×E. grandis between two elite trees were used. Genetic maps were constructed for each parent with markers segregating in the 1:1 ratio in FS progeny. A total of 86 and 92 markers distributed among 11 linkage groups covered 1295 cM and 1312 cM for the E. urophylla and E. grandis parent, respectively. Traits were measured three times up to selection age (38 months). The magnitude of the phenotypic variation explained by the joint action of the segregating quantitative trait alleles indicated that genetic factors of large effect were involved in the control of the studied characters. Several regions controlling part of the variation for the studied traits were identified by interval mapping. Some regions of the genome exerted effects on more than one trait, providing a genetic explanation for at least some of the correlation between the traits. On the basis of an age-by-age analysis, a partial stability of QTL expression was observed with 68% of the QTL being expressed at two ages and 32% being age-specific. No QTL were significant for all three ages. Taking advantage of repeated measurements on the same material across different ages, we investigated with a maximum statistical power, the effect of marker genotype on traits, with age and QTL×age interaction effects being removed. A two-way analysis of variance made it possible to detect significant marker-trait associations over the period studied. Most of them had already been detected in the annual analysis. This result is very encouraging for the application of marker information to the early selection of hybrid trees to be vegetatively propagated for the production of clonal varieties. Received: 2 December 1996/Accepted: 4 April 1997     

尾叶桉与窿缘组树种间杂交种的生长特征

选定组配树种对桉树杂交种的特性起决定作用,但不同种间杂交种的生长表现常常不容易预测。为掌握华南地区桉树重要树种间杂交种的生长特征,促进桉树杂交育种的精准化,该文以父本为混合花粉的人工杂交种为遗传材料,以尾叶桉×巨桉为对照,进行了尾叶桉与桉树窿缘组树种(布拉斯桉、细叶桉、钝盖赤桉、昆北赤桉)的4种组配杂交种的生长特征研究。结果表明:在材积生长量上,尾叶桉与窿缘组树种杂交种低于尾叶桉×巨桉,但其内部树种间差异显著(P0.05),其中尾叶桉×昆北赤桉具有显著优势;尾叶桉与窿缘组树种杂交种的树高、胸径均显著小于尾叶桉×巨桉,但其高径比显著大于尾叶桉×巨桉(P0.05);尾叶桉与窿缘组树种杂交种具有高的和一致的保存率,且在不同组配间、家系间(组配内)均无显著差异,5年生值为84.4%～89.6%;尾叶桉与窿缘组树种杂交种的5年生材积的平均变异系数约为64%,组配间、家系间差异大,都大于尾叶桉×巨桉。尾叶桉与窿缘组树种杂交种的速生性、树形等与尾叶桉×巨桉间存在显著差异,尾叶桉与窿缘组树种杂交种的组配、家系间具有显著的生长差异,可为桉树遗传改良提供丰富的多样性。     

Verification of QTL linked markers for propagation traits in <Emphasis Type="Italic">Eucalyptus</Emphasis>

In a previous study, several quantitative trait loci (QTLs) affecting vegetative propagation traits were detected in a hybrid cross between Eucalyptus tereticornis and Eucalyptus globulus. The objective of this work was to confirm stable QTL linked markers (detected in different years) for propagation traits in an independent set of the same segregating population and in two related crosses involving the original E. globulus parent. Phenotypic averages of groups of individuals carrying alternative allelic forms of the stable QTL linked markers were statistically tested for significant differences. Adventitious rooting and petrification marker–trait associations, detected previously in the E. tereticornis parent, were verified in an independent sample of the original progeny. In the E. globulus parent, the QTL linked marker was only verified in one related genetic background. Verification was possible only for high-effect QTL linked markers. This study highlights the importance of sample size in QTL detection for low-heritability traits.     

华南地区尾巨桉和马占相思人工林地表温室气体通量

为探索华南地区尾巨桉人工林和马占相思人工林地表温室气体的季节排放规律、排放通量和主控因子,采用静态箱-气相色谱法,对两种林型地表3种温室气体(CO_2、CH_4、N_2O)通量进行为期1年的逐月测定。结果表明:(1)尾巨桉人工林和马占相思人工林均为CO_2和N_2O的排放源,CH_4的吸收汇。马占相思林地表N_2O通量显著(P0.01)高于尾巨桉林,CO_2通量和CH_4通量无明显差异。(2)两种林型3种温室气体通量有着相似季节变化规律,地表CO_2通量均呈现雨季高旱季低的单峰规律;地表CH_4吸收通量表现为旱季高雨季低的单峰趋势;地表N_2O通量呈现雨季高旱季低且雨季内有两个峰值的排放规律。(3)地表CO_2、N_2O通量和土壤5 cm温度呈极显著(P0.01)正相关,3种温室气体地表通量同土壤含水量呈极显著(P0.01)或显著相关(P0.05)。(4)尾巨桉林和马占相思林温室气体年温室气体排放总量为31.014 t/hm~2和28.782 t/hm~2,均以CO_2排放占绝对优势(98.46%—99.15%),CH_4和N_2O处于次要地位。     

A comparative analysis of population structure of a forest tree, Eucalyptus globulus (Myrtaceae), using microsatellite markers and quantitative traits

Eucalyptus globulus (Myrtaceae) is a forest tree native to southeastern Australia, but is grown globally for pulpwood and timber. Eight microsatellite loci were used to determine the degree of selectively neutral differentiation between native populations of the geographic races of E. globulus that are used in a national breeding programme. Spatial differentiation was detected among 340 samples from across the species range (F _ST=0.09±0.02). Analysis of molecular variance showed that there was significant variation between the races, and an unweighted pair group method with arithmetic mean analysis of Nei’s genetic distance between races showed that geographically proximal races tended to be more closely related than geographically distant races. This contrasted markedly with analyses based on quantitative genetic data, where some races appeared to be highly divergent from their geographically closest neighbours. Comparison of racial differentiation based on quantitative (Q _ST) and molecular (F _ST) data suggested that at least five of the quantitative traits used for defining races of E. globulus have been influenced by natural selection, resulting in cases of both phenotypic divergence of parapatric races and phenotypic convergence of allopatric races. We conclude that selectively neutral molecular markers are more useful than quantitative genetic data for identifying the evolutionary affinities and lineages within E. globulus. However, both sources of information should be used in defining evolutionarily important units for conservation. The population structure observed in E. globulus has important consequences for future association studies and may also affect breeding strategies if significant genome co-adaptation has occurred.     

尾巨桉胚状体诱导及愈伤组织差异研究

以尾巨桉优良无性系无菌苗茎段为外植体,通过对多种不同浓度生长调节剂组合的优化,进行胚状体诱导研究;并对胚性与非胚性愈伤组织进行形态解剖学观察、相关生理指标检测以及相关基因荧光定量PCR分析,以揭示尾巨桉胚性愈伤组织非胚性化发生的机理,为建立尾巨桉体细胞胚胎再生体系提供参考。结果表明:(1)胚性愈伤组织在MS+0.1mg/L NAA+0.01mg/L TDZ培养基中诱导得到胚状体,外植体经过0.5mol/L蔗糖处理12h有助于胚性愈伤组织产生胚状体,胚状体最高发生率为16.7%。(2)尾巨桉胚性与非胚性愈伤组织石蜡切片观察发现,两者的细胞形态特征存在明显的差异,胚性愈伤组织细胞体积小,排列紧密,表现出典型的胚性细胞特征,而非胚性细胞比较大,排列疏松,细胞呈不规则形状。(3)生理生化指标检测结果表明,非胚性愈伤组织中蛋白质含量、SOD、PPO及CAT活性均显著低于胚性愈伤组织,非胚性愈伤组织中木质素、可溶性糖含量以及PAL和POD活性要高于胚性愈伤组织,二者的反肉桂酸4-单加氧酶基因、淀粉磷酸化酶基因、谷胱甘肽硫转移酶基因、葡萄糖-1-磷酸腺苷酸转移酶基因、葡萄糖六磷酸异构酶基因、分支酸合酶基因以及苯丙氨酸解氨酶基因表达差异也达到显著水平。     

Molecular relatedness of the polygalacturonase-inhibiting protein genes in Eucalyptus species

Plants produce polygalacturonase-inhibiting proteins (PGIPs) as part of their defense against disease. PGIPs have leucine-rich motifs, a characteristic shared by many proteins involved in plant resistance against pathogens. The objective of this study was to clone and analyse the partial sequences of the pgip genes from five selected commercially important Eucalyptus species. Genomic DNA from E. grandis, E. urophylla, E. camaldulensis, E. nitens and E. saligna was isolated from young leaves and used as the template in PCR reactions. Primers PC1, previously described, and Per3, developed in this study, were used in a degenerate PCR reaction to amplify a pgip fragment. A PCR fragment of 909 bp was amplified from each Eucalyptus spp., cloned and sequenced. The Eucalyptus pgip genes were highly conserved (98–100% identity). Analysis of the deduced amino-acid sequences revealed high similarities (44–94%) with other known PGIPs. In general, PGIPs have high homologies within genera as is the case in the genus Citrus. These observations strengthen the belief that PGIP plays an important role in plants. Received: 19 June 2000 / Accepted: 31 August 2000