THE STUDY OF DELAMINATION IN THE STRUCTURAL STEELS

The influence of temperature and stress state on delamination in the pipe-line steel has been studied by tensile tests at different temperature and stress states. It is found that the' delamination always takes place along the centerline segregation band in pipe-line steel produced by continuous casting and then controlled rolling. At room temperature, the delamination appears to be caused by micrbvoid nucleation and coalecence. And the delamination appears to be caused by the cleavage cracking along (100) plane at low temperatur.e. The best way to eliminate the delamination is to reduce the degree of centerline segregation.     

QTL Mapping of Important Agronomic Traits on Chromosomes Showing Marker Segregation Distortion in Interspecific Backcross Cotton Populations

[Objective] The purpose of this study was to map QTLs for yield, maturity, and fiber quality traits of cotton interspecific hybrid populations and to mine favorable alleles from the cotton genome for QTL fine mapping, gene cloning, and molecular marker-assisted selection. [Method] Four BC₁F₁ populations, E(E3), E(3E), (E3)E, and (3E)E, were developed by crossing sea island cotton 3-79 ("3") and upland cotton 'Emian 22' ("E"), and with "Emian 22" as the recurrent parent. BC1F2 populations derived from BC1F1 populations were phenotyped to allow mapping of QTLs for yield-, maturity-, and fiber quality-related traits on chromosomes showing segregation distortion. [Result] A normal distribution test indicated that six fiber quality-related traits, except for the micronaire value in E (E3) and the short fiber ratio in all populations, followed a normal distribution pattern; in contrast, earliness-related traits were not normally distributed in all populations, which suggests that genotype-environment interactions have strong effects on maturity-related traits. Using composite interval mapping, 47 QTLs were detected on three chromosomes (2, 16, and 18): 15 in (E3)E, 13 in (3E)E, 12 in E(E3), and 7 in E(3E), with the phenotypic variation explained (PVE) ranging from 8.8%–30.9%. A total of 27 fiber-related QTLs were discovered, with the PVE ranging from 9.0%–30.9%. Five yield-related QTLs (PVE = 8.8%–17.4%) and 13 maturity-related QTLs (PVE = 9.4%–19.4%) were also identified. [Conclusion] Comparison analysis showed that most QTLs in our study were consistent with the MetaQTL, including QTLs for boll weight, fiber length, fiber length uniformity, lint percentage, and micronaire value on chromosome 2; QTLs for fiber length, fiber strength, and fiber length uniformity on chromosome 16; and QTLs for boll weight, date of boll opening, fiber length, fiber strength, fiber length uniformity, and micronaire value on chromosome 18. Several detected QTLs in our study were not found in the MetaQTL, such as QTLs for date of boll opening and lint percentage on chromosome 16 and a QTL for the date from seedling to flowering stages on chromosome 18. These newly identified QTLs may provide novel insights for cotton QTL analysis.     

基于玉米单倍体性状表现的轮回选择试验研究

单倍体水平的选择可以提高轮回选择程序的效率。经过4个周期的单倍体轮回选择之后,一个综合群体SPC4的产量达到了当前商业杂交种的产量水平。SPC4群体与27个来自于爱荷华州立大学的综合群体相比较具有更好的群体表现。两个单交种在单倍体水平上表现出株高和穗长的超亲分离,表明利用单倍体植株来鉴定、创造和改良优良的育种材料是非常有效的方法。     

偏凸-柱穗山羊草双二倍体与普通小麦不同杂种世代的染色体及性状分离特点

为探讨偏凸山羊草－柱穗山羊草双二倍体SDAU18在小麦遗传改良中的利用价值,以SDAU18和普通小麦品种烟农15及其9个杂种世代为材料,分析不同自交和回交世代染色体和性状分离的特点。结果表明,随自交和以烟农15为轮回亲本回交世代的增加,染色体数目逐渐减少,回交比自交能使后代的染色体数目更快趋近普通小麦的42条,至F₅和BC₃F₁代,染色体数目为42的植株已分别达93.9%和92.0%。与自交世代相比,回交后代减数第一分裂中期的花粉母细胞的染色体构型较为简单,回交次数过多不利于外源染色体与普通小麦染色体发生重组,一般应以回交2~3次为宜;随自交和回交世代的增进,杂种的育性提高,至F₃和BC₂F₁代育性基本稳定。在不同杂种世代可分离出具有矮秆、大穗、大粒、对白粉病、条锈病免疫或高抗及外观品质优良的变异类型,以F₃和BC₁F₁代的变异类型最丰富。     

竹类植物种质资源栽植隔离方法研究

从国内竹类园或种质资源保存库所采用的栽植隔离方法着手,对不同的隔离方法的优缺点进行比较和评述,综合竹类隔离经验,旨在为其他竹园的建设提供借鉴。     

A SSR Linkage Map of Maize×Teosinte F2 Population and Analysis of Segregation Distortion

In this study,a linkage genetic map was constructed using a F2 population derived from a cross between a elite maize inbred,B73,and its progenitor,Teosinte(Z. mays ssp.mexicana),through 205 simple sequence repeat(SSR)markers and one morphological marker.By Mapmaker 3.0,polymorphic markers were clustered into 1 0 groups,covering 10 chromosomes of maizexteosinte,with a total length of 2002.4 cM and an average interval of 9.7 cM.Genotyping errors were detected using R/QTL(LOD=2.0)in 109 markers referring to 176 individuals,distributed across all 10 chromosomes with a ratio 1.2%.Projected error loci were re-run and 304 out of the 460 were confirmed as errors and replaced.A new linkage map was constructed,in which markers maintained the same order but the total map length decreased to 1947.8 cM,with an average interval of 9.4 cM between markers.In total,25.2%(P<0.05)markers were identified to have segregation distortion,in which 34.6%deviated towards the pollination parent(B73),30.8%deviated towards Teosinte,32.7%deviated towards heterozygote and 1.9%deviated towards both parents,This map was also compared with published nlaizexteosinte and maize IBM map.     

栽培大豆耐盐性的主基因+多基因混合遗传分析

选用栽培大豆南农1138-2(耐盐)、南农88-31(较耐盐)和Jackson(盐敏感)配制的南农1138-2×南农88-31和南农88-31×Jackson等2套组合,通过P1、P2、F1、F2和F2:3苗期植株耐盐性调查,利用主基因 多基因混合遗传模型联合分离分析了栽培大豆耐盐性的遗传规律.结果表明南农88-31×Jackson和南农1138-2×南农88-31耐盐性遗传均符合加性-显性-上位性多基因遗传模式.在高世代选择耐盐性植株的效率较高,从F2:3估计,南农88-31×Jackson组合的NaCl耐性微效基因遗传率为82.13%;南农1138-2×南农88-31组合的耐盐性微效基因遗传率为67.47%.     

蕈菌交配型因子偏分离现象的研究进展

简要综述了近年来蕈菌交配型因子偏分离的研究概况。四极性蕈菌交配型A、B因子是非连锁的,双核菌丝体经原生质体单核化后2种交配型和担孢子4种交配型的比例应分别为1：1和1：1：1：1。但在实际的遗传分析中,许多蕈菌这2类交配型的比例并非总以1：1和1：1：1：1的形式出现。菌丝体经原生质体单核化后只找到1种交配型和担孢子只找到2种或3种交配型的现象并不罕见。香菇担孢子的4种交配型中,偏离孟德尔分离的担孢子以与亲本双核菌丝体相同的那2种交配型为多。对蕈菌交配型因子偏分离现象的系统研究报道极少,现有的一些试验结果认为：蕈菌交配型因子偏分离现象与单核体的再生能力和生长速度差异,与A、B交配型因子连锁的具致死效应的生育抑制因子的存在以及B交配型基因对自异核体分离的核存活的影响力不同有关。此外,可能导致交配型因子偏分离的因素还有交配型因子位点间或位点内重组,亲本交配型因子的异质状态以及细胞质基因组对核选择的细微影响等。