海南两个自然保护区野生荔枝遗传多样性研究

采用常规聚丙烯酰胺凝胶电泳技术,对海南吊罗山和霸王岭两个国家级自然保护区野生荔枝等位酶遗传多样性进行了研究。13个酶系统、18个酶位点的检测结果表明,两个自然保护区野生荔枝具有较低的居群间遗传变异水平和较高的居群内遗传变异。吊罗山保护区野生荔枝的遗传多样性参数为:P=61.1%,A=2.05,He=0.27。霸王岭居群野生荔枝的遗传多样性参数为:P=61.1%,A=2.05,He=0.28。两个群体的遗传分化极小,GST=0.047.居群间遗传一致度较高I=0.977。共检测到7个稀有等位基因。两个自然保护区的野生荔枝均有各自特有的稀有等位基因,都应采取措施予以保护。     

Changes in genetic diversity during seven cycles of recurrent selection for grainyield in oat, Avena sativa L.

Variability for desirable alleles within elite breeding populations is a requirement for long-term genetic improvement. Changes in genetic diversity were evaluated in a recurrent selection programme for enhanced grain yield in oat, Avena sativa L., using coefficient of parentage (r_p) and restriction fragment length polymorphism (RFLP) based genetic similarity (S) estimates. Both r_p and s increased during seven cycles of recurrent selection, indicating a reduction in the level of genetic diversity within the population. The relationship between genetic diversity and agronomic performance was also examined. Genetic similarity measures were poor predictors of the near-homozygous progeny performance and general and specific combining ability effects for three agronomic traits in the recurrent selection programme. In addition, there was no apparent trend for preferential selection of progeny from either more similar or more diverse parents within a given cycle of selection. The overall reduction in genetic diversity in this population has not affected selection response for grain yield. Variability remaining at important loci or de novo variation are possible explanations for the continued selection progress.     

Recurrent selection of cocoa populations in Côte d'Ivoire: comparative genetic diversity between the first and second cycles

In Côte d'Ivoire, the cocoa breeding programme has been based on the creation of hybrids between different genetic groups. From 1990 onward, a reciprocal recurrent selection programme has been set up with the purpose of improving simultaneously the characteristics of the two main genetic groups: Upper Amazon Forastero (UA) and a mixture of Lower Amazon Forastero (LA) and Trinitario (T). Based on data obtained from 12 microsatellite primers, the genetic diversity and genetic distances of the parental populations used in the first and second selection cycles are presented. The results revealed that the diversity of populations UA0 and UA1 on the one hand and (LA+T)0 and (LA+T)1 on the other is similar. The genetic distances were small between the parental populations used for the first and second cycles. Genetic diversity was greater in the UA group than in the LA+T group. The number of rare and of private alleles was reduced for both genetic groups, as well as the number of the frequent alleles in the LA+T group.     

不同轮回选择方法对玉米窄基群体的改良效果

利用轮回选择进行群体改良,是玉米种质扩增与改良的有效方法,能为选育优良自交系提供基本素材,进而提高选育自交系及杂交种的效率。本研究以玉米窄基群体P4C0及其经过不同轮回选择方法改良的10个群体为材料,通过多点田间表型鉴定和配合力测定,研究不同轮回选择方法对玉米窄基群体的改良效果,利用SSR分子标记分析不同轮回选择方法对群体遗传多样性的影响。结果表明,几种轮回选择方法都能有效改良群体的主要性状及其一般配合力(GCA)。以时间计算,控制双亲混合选择(MS)对群体P4C0主要性状及其GCA改良效果优于半同胞-S2:3(HS-S2:3)轮回选择,但在株高和穗位高的改良上,HS-S2:3选择效果较好。以轮次计算,开放改良对群体P4HSC1主要性状及其GCA的改良效果优于MS,但开放改良后,群体株高和穗位高有较大幅度的增加。不同轮回选择方法对群体遗传多样性和遗传结构的影响不尽一致。P4C0经过5轮MS后,在群体改良的低代,群体遗传多样性得到了较好的保持,而多代的改良导致群体遗传多样性下降;P4C0经过1轮HS-S2:3选择后,遗传多样性比P4C0有较大幅度的下降。P4HSC1经过1轮开放改良后,遗传多样性有较大幅度的增加。P4HSC1经过3轮MS改良后,群体遗传多样性呈增大的趋势,但每轮增加的幅度均较小。     

Originality of M3S maize population and changes in allele frequencies revealed by SSR markers after two cycles of selfed progeny recurrent selection

Maksimir 3 Synthetic (M3S) maize population was developed at the Faculty of Agriculture University of Zagreb by intercrossing inbred lines, whose origins trace back to several open-pollinated varieties and local populations from different regions of the former Yugoslavia. The population was subjected to two cycles of selfed progeny recurrent selection for grain yield. The objectives of this study were: (i) to determine genetic distances among the parental inbred lines of the M3S population (M3S progenitors), the M3S population before and after two cycles of recurrent selection, and elite inbred lines representing the BSSS and Lancaster heterotic group; and (ii) to examine the effect of two cycles of recurrent selection on allele frequency changes in the population. Nine M3S progenitors, three BSSS lines, and three Lancaster lines were genotyped at 24 SSR loci, out of which nine randomly chosen loci were used for genotyping 96 individuals from both C0 (the M3S population before selection) and from C2 (M3S population after two cycles of selection). A total of 101 alleles were detected across 24 loci in the 15 lines, whereas 83 alleles were found in the nine M3S progenitors. Among the latter 83 alleles 31 were unique, i.e. found only in one of the progenitors. Mean genetic distance among nine M3S progenitors was 0.61 indicating a broad genetic base of the M3S population. High mean genetic distance was found between M3S progenitors and BSSS lines (0.69) and M3S progenitors and Lancaster lines (0.71). This indicates that the M3S population represents a germplasm source unrelated to both the BSSS and Lancaster germplasm. Mean genetic distance between the M3S population and BSSS as well as Lancaster lines decreased slightly after two cycles of recurrent selection suggesting the need to introduce testers from both groups in future selection in the M3S population in order to maintain heterotic complementarity of the M3S population to these groups. A test of selective neutrality identified several non-neutral loci in the population whose allele frequency changes from the C0 to the C2 cannot be explained by genetic drift. The majority of non-neutral alleles, whose frequency increased after two cycles of selection, were present in at least one line from the BSSS or Lancaster heterotic group.     

陕西省野生大豆种质资源的SSR遗传多样性研究

为了研究陕西地区野生大豆的遗传多样性特点,利用SSR分子标记分析了陕西省6个野生大豆(Glycine soja)天然种群和1个栽培大豆(Glycine max)种群的遗传结构与遗传多样性。结果显示：13个位点共检测出113个等位基因,平均每个位点的等位基因数(A)为8.69个,等位基因数目范围为4~13个,有效等位基因数(N_e)范围为2.135(Satt590)~9.385 (Satt487),平均有效等因基因数为5.623;观察杂合度(H_o)变化范围为0.033~0.121,平均为0.080;预期杂合度(H_e)的变化范围为0.312~0.658,平均为0.482;种群平均Shannon遗传多样性指数(I)为0.657;野生大豆种群基因多样度比率(F_ST)为0.465。该研究显示,陕西省野生大豆具有较高水平的遗传多样性,野生大豆的遗传多样性普遍高于栽培大豆;随着海拔的不断升高,野生大豆遗传多样性变低;陕西中部、南部的野生大豆种质资源丰富、种群具有较高的遗传多样性,推测该区域为陕西省野生大豆的遗传多样性中心。     

Genetic diversity of feral alfalfa (<Emphasis Type="Italic">Medicago</Emphasis> <Emphasis Type="Italic">sativa</Emphasis> L.) populations occurring in Manitoba,Canada and comparison with alfalfa cultivars: an analysis using SSR markers and phenotypic traits

Feral populations of cultivated crops may act as reservoirs for novel traits and aid in trait movement across the landscape. Knowledge on the genetic diversity of feral populations may provide new insights into their origin and evolution and may help in the design of efficient novel trait confinement protocols. In this study, the genetic diversity of 12 feral alfalfa (Medicago sativa) populations originating from southern Manitoba (Canada) and 10 alfalfa cultivars and a M. falcata germplasm were investigated using eight SSR markers (i.e., microsatellites) and 14 phenotypic traits. We found that the genetic diversity observed in feral populations was similar to the diversity detected among the 10 cultivars. Analysis of molecular variance revealed that there was great genetic variation within (99.8%) rather than between different feral populations. Cluster analysis (unweighted pair-group method using arithmetic average) revealed no differentiation between feral populations and cultivars for neutral loci. High levels of population differentiation for phenotypic traits (and not for neutral markers) suggest the occurrence of heterogeneous selection for adaptive traits. The phenotypic traits we studied did not distinctly separate feral populations from cultivars but there was evidence of natural selection in feral populations for traits including winter survivability, rhizome production, and prostrate growth habit. Our results suggest that feral alfalfa populations need to be considered in the risk assessment of alfalfa containing novel genetically modified (GM) traits. Further, feral alfalfa populations may be regarded as a source of new germplasm for plant improvement.     

控制双亲混合选择对不同玉米合成群体的改良效应

基于田间试验的统计分析和SSR分子标记的遗传参数评估,分析了3个玉米人工合成群体GP3、GP4和GP5经4轮控制双亲混合选择的改良效应。结果表明,多数性状在不同群体及不同轮回间存在真实的遗传差异,粒深遗传增益以GP4＞GP5＞GP3,穗行遗传增益以GP3＞GP5＞GP4,各个群体C4的粒深、穗行均值都显著或极显著大于C0,直接选择效应显著;株高和穗位高随选择周期增加呈明显增加趋势,且GP4的增幅显著大于GP3和GP5,单株产量及穗粗的遗传增益以GP4大于GP3和GP5,各群体多数产量性状的均值以C4显著大于C0,相关选择效应显著;除株高、穗位高外,其他性状GCA变异群体间差异达显著或极显著水平,GP5多数产量性状的GCA优于GP3和GP4,各群体多数产量性状的GCA效应值随改良进展呈增加趋势,对照优势大于8%的大部分测交组合均为各群体C4所配组合,间接选择效应显著;随改良世代进行,群体部分性状的表型变异系数虽有所减小,但变化幅度不大;基于SSR分子标记估算的群体内遗传相似系数,GP3和GP4改良后代呈略增趋势,GP5变化不大,对于群体基因型数,GP3和GP4随改良代数增加呈略减趋势,GP5呈略增趋势。上述结果说明,适度控制双亲混合选择在有效改良群体的同时,还能较好地保持群体的遗传多样性,但不同基础群体及不同性状间,其改良效应存在一定的差异。     

Inbreeding Depression and Other Genetic Effects in Populations of Maize Containing Highland Tropical Germplasm

A variety cross diallel of five populations of maize (Zea mays L.) was evaluated in a cool, temperate environment. Two of the parental populations were Corn Belt Dent synthetics (AS3 and BS22), one was developed from selected lines from a CIMMYT population developed for highland regions of the tropics and four Corn Belt Dent inbred lines (NZS3), and the other two had the pedigrees ‘Criollo de Toluca’× AS3² (NZS1) and ‘San Gerónimo’× BS222 (NZS2). ‘Criollo de Toluca’ is from the highlands of Mexico and ‘San Gerönimo’ is from the highlands of Peru. The objective was to study the influence of introgressing highland tropical germplasm into elite Corn Belt Dent synthetics on genetic effects, especially inbreeding depression, and to develop recommendations for the utilization of the introgressed populations. Inbreeding depression explained the greatest proportion of the variation among entries for grain yield, days to silking and plant height, but not for grain moisture at harvest and root lodging. For grain yield, NZS1, NZS2, and NZS3 had high levels of inbreeding depression and the difference between NZS1 and AS3 was statistically significant. High levels of root lodging were associated with NZS1 and high grain moisture at harvest with NZS2. These results indicate that a recurrent selection method, such as S₁ selection, which effectively reduces inbreeding depression, should be used in early cycles of selection with introgressed populations containing highland tropical germplasm.     

用多态位点率和香农指数分析的 飞蝗地理种群遗传多样性

研究多态位点率和香农指数两种多样性参数所展示的飞蝗不同地理种群的遗传多样性。采用多态位点率和香农指数对飞蝗不同地理种群的RAPD数据进行了遗传多样性分析。飞蝗各种群平均多态位点率为59.17%-77.38%,平均香农指数为4.95-6.09。尽管两参数在不同引物之间存在极显著差异,但各种群的两参数之间的差异都不显著（p<0.05）。将香农指数分解为种群内和种群间两种水平的多样性,种群内多样性都比种群间的要大,平均所占比率分别为66.85%和23.15%,与用其他方法得到的结果类似。多态位点率和香农指数展示出中国飞蝗不同地理种群具较高的遗传多样性。两种多样性性参数分析RAPD数据来展示昆虫遗传多样性是可行的。     

鱼腥草种质资源群体表型遗传多样性研究

本试验通过观测湖南怀化市不同地域鱼腥草居群,以揭示其变异规律和检测种质资源的遗传多样性状况,为其保护和利用提供依据.以湖南省怀化市的16份鱼腥草种质资源为材料,观测了其群体表型性状特征,并分析了这些表型性状的变异系数、遗传参数和遗传多样性.结果表明,鱼腥草种质资源的不同表型质量性状的频率不同,以绿色地上茎、白色地下茎和心形叶最具代表性.居群问各表型数量性状以地上茎的分枝数和鲜质量、地下茎的节间数、4-甲基-1-异丙基-3-环己烯-1-醇和2,4-甲基-3-环己烯基异丙醇变异较大,根的直径变异最小;而居群内以地上茎分枝数的变异系数最大(39.8%),甲基正壬酮含量最低(13.4%).居群内各表型数量性状多样性指数为0.182～0.710,而居群间为0.213～0.804;不同地域类群间表型多样性指数存在一定差异,黄岩地区最高(1.024),鸡公界地区最低(0.574).群体问的平均表型变异约占总变异的1/2而群体内的约占1/3,说明群体问变异是表型变异的主要来源;群体间表型分化最大的是地上茎的分枝数(77.04%),最小的是根的直径(51.88%).在5%的选择强度下数量性状的绝对遗传进度都较小(RGS%<40%)但遗传力均较大(h~2>50%).当遗传距离分别为2.0和1.5时,材料被聚为2类和3类,而且聚类首先是按地上部分的茎色,其次是按叶型,再次是以海拔高度,最后是以地域而划分的.群体表型变异丰富而且具有遗传分化程度较高.     

Genetic diversity among populations and breeding lines from recurrent selection in Brassica napus as revealed by RAPD markers

Recurrent selection facilitated by dominant male sterility has been conducted to broaden the genetic basis for cultivar development in Brassica napus. This study aimed to evaluate the genetic variation in four base populations (C0‐C3) and breeding lines from two of the populations produced during recurrent selection by random amplified polymorphic DNA (Rapd) markers. Genetic variation in four populations declined gradually with the advance of selection cycles as measured by expected genetic heterozygosity (from 0.2058 in C0 to 0.1536 in C3) but the decline was not statistically significant. When compared with the average genetic distances for 21 germplasm collections with wide geographical and genetic origins (0.4712) and seven breeding lines from pedigree selection (0.2059), seven breeding lines selected from the C1 population and 11 from the C3 population had a larger average genetic distance (0.5339 and 0.5486, respectively). Clustering analysis indicated that the lines from recurrent selection had a much lower genetic similarity than lines from pedigree selection. Our results suggest that base populations derived from recurrent selection could provide a wider genetic variation for selection of breeding lines with more broad genetic bases.     

Genetic diversity of natural populations of Atriplex halimus L. in Morocco: An isoenzyme-based overview

Based on polyacrylamide gel electrophoresis, nine natural populations of Atriplex halimus L., a perennial shrub, collected in different regions of Morocco, were studied for their genetic variation using isoenzyme polymorphism of the highly active enzyme systems: esterases (EST), acid phosphatases (ACP) and glutamate oxaloacetate transaminase (GOT). Different allozyme frequencies from 7 different loci were obtained for all populations of this halophyte species. High levels of genetic diversity were revealed. The mean number of alleles per locus (A = 1.9–2.0), the percentage of polymorphic loci (p = 71.4–85.7) and the mean expected heterozygosity (H_e = 0.339–0.385) showed an important variability in all populations. Gene diversity was essentially explained by the within population component. The between populations differentiation accounted for 8% of the whole diversity (F_ST, averaged over all loci, is 0.08). The relationships among the 9 populations were inferred from the Nei’s genetic distances. Four major groups were formed. The northern population ‘Tanger’, forming a unique group, was highly divergent from the other groups. It appeared that the genetic distance between all groups was related to the geographic distance that separates them. This revised version was published online in August 2006 with corrections to the Cover Date.     

Relationship of intra- and interpopulation tropical maize single cross hybrid performance and genetic distances computed from AFLP and SSR markers

Two sets of tropical maize inbred lines, one derived from the BR-105 population and another derived from the BR-106 population, were assayed for Amplified Fragment Length Polymorphism's (AFLP) and for Simple Sequence Repeat (SSR), in order to investigate genetic distances among lines and their relationship to heterotic group assignment and single cross yield performance. Genetic distances were on average greater for interpopulation than intrapopulation crosses for both AFLP and SSR. Cluster analysis was in agreement with the original assignment for heterotic groups. Inbred line 16, derived from BR-106, was assigned to the BR-105 set, in agreement with single cross yield performance from intra- and interpopulation crosses. However, the same pattern was not observed for SSR where another two lines from BR-106 were also assigned to the BR-105 set. Correlation coefficients of genetic distances (GD) with F₁ grain yield and heterosis were high for BR-106 ×BR-106 crosses (0.91^** and 0.82^** for AFLP and SSR, respectively), moderate for BR-105 × BR-105 crosses (0.52^* for AFLP and SSR) and low for BR-105 × BR-106 crosses (0.29 and 0.16 for AFLP and SSR, respectively). The lower correlation at interpopulation level was due to the smaller range of GD caused probably by a previous selection for combining ability. General results showed that the AFLP molecular marker is efficient in assigning maize lines to heterotic groups and that AFLP-based GD is suitable for predicting the maize single cross performance for intrapopulation crosses of broad-based populations. The efficiency of SSR in assigning lines to heterotic groups and for predicting single cross performance was smaller than AFLP. This revised version was published online in July 2006 with corrections to the Cover Date.     

改良S1选择法对12个玉米群体改良效果的比较分析

为了对玉米群体进行合理有效的改良利用,通过改良S1选择法对12个玉米群体改良一轮后进行效果比较分析。结果表明,穗行数、行粒数和百粒重是构成产量的三因素,遗传增益最大的群体为蒙群2,其他依次为蒙群4、蒙群1等7个群体,蒙群3及3个国外引进群体遗传增益为负值;玉米群体在穗部、植株性状以及遗传变异中均存在一定的变化。试验研究得出,蒙群2、蒙群4、中综7号、蒙C群、蒙A群产量遗传增益均较大,并在其他农艺性状中改良效果显著,可直接选择优株自交进行选系,而其余7个群体遗传增益小,改良利用潜力不大。     

MS1与MS1-HS两种选择方法的比较研究Ⅱ.遗传方差、配合力及杂种优势

对ZZ4完成了4轮MS1-HS和MS1选择.结果表明,经4轮选择的群体,两种方法均有效地保留了各主要性状的遗传方差.MS1-HS选择的群体遗传方差下降速率更慢,C4群体的单株籽粒产量的遗传方差仅减少3.7%.穗长、穗粗、粒行数、行粒数、出籽率、百粒重的遗传方差的变化与单株籽粒产量一致,MS1C4的遗传方差减少了8%～15%,MS1-HSC4的遗传方差仅减少了4%～15%.株高、穗位高、抽丝期、植株保绿度、抗倒性等相关选择性状的遗传方差的变化与产量性状基本一致.MS1-HS法对改良玉米群体籽粒产量与测验种间的特殊配合力十分有效,呈逐轮上升的趋势;改良群体与测验种综系140间的杂交后代产量平均每轮提高6%,杂种优势平均每轮提高6.9%.两种方法在改良群体产量性状一般配合力方面,均得到了良好的效果.同时,穗部性状及株高、穗位、抽丝期、散粉期、抗性等田间农艺性状的一般配合力也获得了同步改良.通过ZZ4改良群体与6个测验种间杂交组合产量及杂种优势的比较研究,得出ZZ4与黄早四类种质为杂种优势模式对.     

Genetic divergence in two tropical maize composites after four cycles of reciprocal recurrent selection

Two tropical maize composites were subjected to four cycles of reciprocal recurrent selection to develop divergent inbred lines with good combining ability. This study was conducted to examine the extent of genetic diversity, changes in allele composition and genetic structure, of 100 randomly selected S₁ lines each from the original (C₀) and advanced (C₄) selection cycles of TZL COMP3 and TZL COMP4, genotyped using single nucleotide polymorphism (SNP) markers. Results revealed that the proportion of alleles at both low and high frequencies decreased from C₀ to C₄, whereas those at intermediate frequencies increased at C₄ in the two composites. More unique and other alleles were lost at C₄ in TZL COMP3 relative to those in TZL COMP4. The changes in different measures of genetic diversity were either small or negligible with selection in the two composites. The proportion of markers departing from Hardy–Weinberg equilibrium (HWE) decreased with selection, whereas the total number of pairs of markers in linkage disequilibrium increased with selection in the two composites. Examination of changes in population structures using a model‐based approach as well as cluster and multivariate analyses found a high degree of concordance in stratifying the 400 S₁ lines into four non‐overlapping groups corresponding to the two selection cycles each within the reciprocal composites. The observed molecular‐based divergence between cycles within the same composite and the clear differentiation between the complementary composites highlight the importance of reciprocal recurrent selection for preserving genetic diversity for long‐term selection. This increases the potential of the advanced selection cycles to sustain genetic gain in productivity of hybrids adapted to the savannas in West and Central Africa.     

Allozyme variation and conservation genetics of common wild rice (Oryza rufipogon Griff.) in Yunnan, China

In order to reveal levels and distribution of genetic variation within Oryza rufipogon Griff. of Yunnan, China, where one of the centers of genetic diversity for Asian cultivated rice O. sativa L. is located, allozyme variation encoded by 22 loci was electrophoretically analyzed in 149 individuals of all three existing populations as well as five from other regions (Guangxi, Hainan and Jiangxi provinces) of China. As compared to the level of genetic diversity (the mean A = 1.2, P = 24.1%, Ho = 0.045 and He = 0.079) for the populations from other regions, a rather low genetic diversity (the mean A = 1.1, P = 7.6%, Ho = 0.007 and He = 0.011) was found in Yunnan, which may originate from marginal nature of these populations, recent reduction of populations and consequent drift. The result suggests that the current center of genetic diversity for O. rufipogon fail to agree with that for cultivated rice in China. The genetic differentiation for all the eight populations(F_ST = 0.254) was slightly lower than that for three populations from Yunnan (F_ST = 0.302), indicating a fairly high genetic differentiation in the region. Finally, a conservation plan for sampling/preserving fewer populations but more individuals from each population for the species was given, and an appropriate strategy for conserving the three surviving populations from Yunnan was proposed. This revised version was published online in August 2006 with corrections to the Cover Date.     

中国与东南亚三国（越、老、柬）普通野生稻遗传多样性的比较研究

利用24对SSR引物,对来自中国10个代表性居群和越南、老挝、柬埔寨的5个居群共计282份普通野生稻材料进行遗传多样性比较研究。结果表明,(1)24个微卫星位点共检测到等位基因289个,平均等位基因数(A)为12,有效等位基因数(Ae)为7;期望杂合度(He)平均为0.812,观察杂合度(Ho)平均为0.543,香农指数(I)平均为1.99;(2)4个国家中,中国普通野生稻的遗传多样性最丰富,老挝次之,越南和柬埔寨最低,香农指数(I)分别为1.92、1.69、1.47和1.45;(3)采用UPGMA方法对供试15个居群进行聚类分析。老挝和柬埔寨2个居群的亲缘关系最近,二者与越南居群有着较近的亲缘关系;(4)在中国所有参试居群中,广西武宣和贺州居群与东南亚3国亲缘关系最近。     

高坡红米的SSR遗传多样性分析

利用145对SSR引物,对22份高坡红米材料及典型的籼粳稻品种93-11和日本晴进行遗传多样性分析,发现有13个标记具有多态性,共检测出57个等位基因变异,每对引物可检测2～10个等位变异,平均为4.3846个,平均Nei基因多样性指数(He)为0.521,范围为0.285 4(RM 18)～0.7674(RM 5414).用UPCMA聚类进行分析,在相似系数为0.52处可将高坡红米品种分为两大类,即籼稻和粳稻;PCO三维空间图揭示,所有供试材料在图中的分布与UPGMA聚类结果完全吻合,两种分析方法相互得到了印证.