Occurrence and distribution of <Emphasis Type="Italic">Phytophthora</Emphasis> species in European chestnut stands,and their association with Ink Disease and crown decline

The Phytophthora complex associated with Castanea sativa Mill. was investigated in five European countries in 35 regions and with respect to various domestication levels. Annual precipitation and length of drought season were the main parameters that regulated the presence of Phytophthora species in the chestnut stands. Seven species of Phytophthora were detected; three of these, P. megasperma, P. cryptogea and P. syringae had not been previously reported on sweet chestnut. P. cinnamomi. P. cambivora and P. citricola were most frequently isolated. P. cinnamomi and P. cambivora were the species significantly associated with declining trees with symptoms of Ink Disease. P. cinnamomirequired distinct ecological conditions compared to the other species. P. cinnamomi was never detected in sites characterized by minimum temperatures below 1.4 °C, maximum temperature above 28 °C, or soil pH below 5.4. The results obtained provide useful information for modeling the probability of Ink Disease, crown decline and associated Phytophthora species in chestnut groves in global climatic change scenarios.     

Dynamic Finite Element Model Updating of Prestressed Concrete Continuous Girder Bridge Based on Real-Coded Accelerating Genetic Algorithm

The dynamic finite element model (FEM) of a prestressed concrete continuous girder bridge (PCCGB), named Zhangjiagang river main bridge, was established and updated based on the results of field ambient modal testing using real-coded accelerating genetic algorithm (RAGA), which objective function was defined based on frequency index and correlation coefficient index for evaluating the updated FEM. The dynamic FEM of the bridge was updated based on seven experimental modal parameters. The prediction ability of the updated FEM were evaluated based on three experimental modal parameters. The updated results and prediction ability of updated FEMs indicated that they can reflect adequately the dynamic characteristics of actual PCCGB by using the above objective function and RAGA.     

瓜类遗传连锁图谱构建的研究现状及比较分析

 截至目前,西瓜、黄瓜及甜瓜的全基因组测序工作已经基本完成,利用高密度饱和遗传连锁图谱将基因组序列锚定到染色体的具体位置并确定其在染色体上的方向,这为进一步开展基因组分析研究奠定了基础。本文中综述了瓜类遗传连锁图谱构建的研究现状并对遗传连锁图谱进行了比较分析。     

Converting restriction fragment length polymorphism to single‐strand conformation polymorphism markers and its application in the fine mapping of a trichome gene in cotton

A well‐characterized and systematically organized collection of genetic markers is crucial in the study of any crop species. It is the basis of map‐based gene cloning and crop improvements through marker‐assisted selections. Single‐strand conformation polymorphism (SSCP) has been a robust way of discovering new polymorphisms in marker development without the requirement of sequencing. Here, we report the first approach of applying SSCP marker discovery methods in the genetic map construction and gene mapping of cotton species. A total of 80 restriction fragment length polymorphism (RFLP) markers were selected from a region on published cotton genetic maps around the T1 gene related to cotton trichome. Among the 80 RFLPs, 28 showed polymorphisms through SSCP, showing a polymorphic rate of approximately 35%, which is much higher than that of simple sequence repeat (SSR) markers in the same region (7.8%). By integrating these newly generated SSCP markers, a detailed genetic map was reconstructed around this region using an F₂ population derived from a cross between Gossypium arboreum and G. herboceum. The reconstructed region comprises 22 SSCP markers, eight SSR markers and the T1 gene, spanning 21.6 cM. The marker order of the new map agrees well with published reference RFLP maps. The above results suggest that SSCP method can be applied very efficiently and reliably to the marker development of cotton genomes. It will prove to be even more valuable and robust after the public release of cotton whole‐genome sequences.     

Genetic linkage map of Chinese native variety faba bean (Vicia faba L.) based on simple sequence repeat markers

Simple sequence repeat (SSR) marker is a powerful tool for construction of genetic linkage map which can be applied for quantitative trait loci (QTL) and marker‐assisted selection (MAS). In this study, a genetic map of faba bean was constructed with SSR markers using a 129 F₂ individuals population derived from the cross of Chinese native variety 91825 (large seed) and K1563 (small seed). By screening 11 551 SSR primers between two parents, 149 primer pairs were detected polymorphic and used for F₂ population analysis. This SSR‐based genetic linkage map consisted of 15 linkage groups with 128 SSR. The map encompassed 1587 cM with an average genetic distance of 12.4 cM. The genetic map generated in this study will be beneficial for genetic studies of faba bean for identification of marker‐locus‐trait associations as well as comparative mapping among faba bean, pea and grasspea.     

Deformation behavior of alloy AZ31-0.5Sr-1.5Y at elevated temperature

The uniaxial hot compression test with Gleeble-1500D thermal simulator is performed on AZ31-0.5Sr-1.5Y alloy in the temperature range of 250-450 ℃ and stain rates of 0.01-1 s -1 with the maximum deformation degree of 0.85. The hot deformation behavior and hot workability of the alloy are studied. The constitutive equation and processing map of the alloy are established and studied by optical microstructure observation. The results show that the steady flow stress of AZ31-0.5Sr-1.5Y deforms at elevated temperatures can be described by the hyperbolic sine constitutive equation, and the activation energy is about 186.83 kJ/mol. After analyzing the hot processing map, at the true strain of 0.6, there is one unsafe deformation zone in the deformation temperature range of 250-300 ℃ and the strain rate range of 0.3-1 s -1. The optimal processing parameters obtained in the present work are the temperature range of 300-400 ℃ and strain rates of 0.01-1 s -1.     

基于绿视率的城市绿化评估——以武汉江汉区为例

目前我国仍以3大传统绿化指标评估城市绿化的二维情况,缺乏三维空间绿化效果评估。文章以武汉市江汉区为例,采用系统抽样法,将江汉区划分为472个250m×250m网格,基于腾讯地图的街景图像计算绿视率,从江汉区绿视率整体空间格局、不同用地类型绿视率差异性以及绿化覆盖率对绿视率的影响等方面评估该片区的三维绿化,结果显示:1)江汉区不同区域绿视率差异较大,平均值为16.26%;2)公园绿地、居住用地、商业用地的绿视率依次递减;3)绿视率随绿化覆盖率的增加而增加,但其增长趋势逐渐趋缓。     

基于科学知识图谱谈土壤有机碳研究进展

以"土壤有机碳"为主题词,从ISI Web of Science数据库核心集中检索出1975—2018年文献2 258篇,运用CiteSpace知识图谱分析工具,对合著国家、作者、机构、学科领域、文献共被引网络以及关键词共现网络等进行可视化分析,对土壤有机碳的研究进展及演变趋势进行了图谱解读和追踪分析。结果表明:(1)土壤有机碳研究经历了起步、发展、稳定三个阶段;(2)土壤有机碳研究具有很强的学科交叉性,涉及环境生态学、环境科学、农业综合、农艺学、化学、农学及生态学等众多学科领域;(3)当前的研究方向主要为土壤有机碳储量与稳定土分离;(4)研究趋势已转为碳储量与耕地管理研究;(5)中国土壤有机碳研究起步较晚但发展迅速,在国际上处于重要地位。     

林地“一张图”与林业“二类调查”成果对比分析研究

为进一步做好林地变更调查,通过对比森林资源规划设计调查成果与林地"一张图"数据,对两套成果数据的林地、森林、林分起源、生态公益林面积进行分析,初步总结归纳差异产生的原因,为今后的林地变更调查工作提供参考。