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1.
John M. Warren 《Euphytica》1993,72(1-2):121-126
Summary Isozyme polymorphism in four enzyme systems was used to estimate the genetic diversity in nine populations of Theobroma cacao L. The distribution of allelic variation observed in this study was inconsistent with the currently held view that the Upper Amazon region of Peru is the centre of cacao genetic diversity. All the populations analysed from this area of Peru were genetically similar, and contained a low level of isozyme polymorphism. It is argued that this is a result of genuine low diversity in the region rather than a sampling artifact. If a centre of diversity of wild cacao truly exists, this work indicates that it lies further north in Ecuador and Colombia.Although they are morphologically highly variable, Trinitario cacao populations derived from cultivation are currently accorded low priority for conservation. This phenotypic variation was observed to be reflected in high levels of isozyme polymorphism. It is suggested that the present strategy for the conservation of cacao germplasm, which accords priority to the Upper Amazon region of Peru while neglecting the Carribbean should be reconsidered.  相似文献   

2.
As it is related to the variability in genome expression, variability in protein quantities revealed by two-dimensional electrophoresis was proposed for describing phenotypic diversity. The objective of this study was to compare the predictive power of different genetic distances derived from molecular markers and from protein quantitative variations in a diallel of 210 hybrids among 21 maize inbred lines (Zea mays L.) of various origin. The lines were characterized for: 1. 142 markers resulting from the analysis of enzyme, RFLP, and protein-structure polymorphism; and 2. The variation in relative quantities of 190 proteins. The hybrids were evaluated for six forage traits in four environments. Correlations between the genetic distances computed for 142 marker loci and hybrid performances were moderate to high in diallels using crosses between related lines. Genetic distances based on protein quantities showed, in most cases, similar or lower correlations. Distance measures were not useful as predictors of hybrid performance for crosses between unrelated lines. Protein quantities were better for revealing specific genotypes.  相似文献   

3.
The aim of this study was to determine the genetic components controlling yield in an F1 cacao cross between Catongo and Pound 12 clones. Genetic maps were constructed for the two parents using molecular markers which detected 158 polymorphic loci covering 772 cM for the heterozygous genotype Pound 12 and only 4 loci representing 16.9 cM of a linkage group which indicated a high level of homozygosity of Catongo. Yield was recorded twice a month during 15 years on 55 individuals from this segregating population. Ten yield QTL were detected on eight linkage groups. Some of these QTL were frequently detected over 15 years of production, while others were specific for a given year. Total yield genetic variance, on a yearly basis, ranged from 0 to 56%. Two major QTL (E and I) each explained approximately 20% of the total variance of the average yield over 15 years. The analysis of potential cacao yield components, such as pod index and trunk diameter, suggested that some regions of the genome exert effects on more than one trait, providing a possible genetic explanation for the correlations detected between some of title traits studied. Data showed that correlation between successive annual yield decreased when the lag between corresponding seasons increased. When separated by more than 10 years, annual yields were no longer correlated. The utilisation of molecular markers alone or in combination with phenotypic selection showed an advantage in the early selection of the best cacao producer trees. Further use of molecular markers in breeding programs is discussed with a view to reducing the generation time of a selection procedure. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

4.
C. Lanaud 《Euphytica》1988,38(3):221-228
Summary The origin of haploid plants of cacao was studied using morphological and enzyme markers. Analysis of 250 haploids arising either from controlled crosses or from open pollination in a biclonal seed-garden showed the existence of several types. They could be either or in origin, or chimaeric haploids or diploid/haploid chimaeras. In the majority of cases these chimaeras, visible at the cotyledon stage, were not maintained at the level of foliage, where only one genotype was observed. Studies of the haploid/diploid chimaeras show that the diploid part could be heterozygous and thus correspond to the fusion of the two parental gametes occurring after gametic cell divisions have produced haploid tissue. This phenomenon of semigamy could be facilitated in cacao by its particular system of self-incompatibility.  相似文献   

5.
C. Lanaud 《Plant Breeding》1987,99(3):196-202
The expression of monogenic and polygenic characters has been studied in families of spontaneous haploids of cocoa which nave been doubled with colchicine. Segregation of six enzyme markers, heterozygous in the various parent clones, has been analysed in the doubled haploids for alcohol dehydrogsnase (ADH), malate dehydrogenase locus B (MDH-B), isocitrate dehydrogenase (IDH), acid phosphatase (ACP), phosphoglucomutase (PGM) and phosphoglucose isomerase (PGI). Nine of the eleven families showed a Mendelian-type segregation, two presented distortions but all alleles were found in the haploid progenies. Polygenic characters were expressed with great variability: A few DHs showed similar or even higher values than their parents for individual characters, but the majority were lower, and large depressions could be seen for the group of characters studied. These results have consequences for the use of doubled haploids of cocoa which must both give a sure production of hybrid seeds and be good progenitors; no prediction of their value as progenitors seems possible after observation of their own characteristics and the only selection made from these plants will be a propos their characters directly involved in seed production. These selected doubled haploids will subsequently have to be tested as progenitors.  相似文献   

6.
Classically, selection for superior genotypes in cacao has been based on the successive harvest records across a number of years. Little information on the minimum duration of these harvest periods is available in the literature. The repeatability coefficient (ρ) was used to estimate this period. Twenty five cacao genotypes were assayed in a randomized block design with four replications and 16-plant plots. The following yield components were studied: number of healthy fruits per plant, number of collected fruits per plant, weight of humid seeds per plant and per fruit, and percentage of diseased fruits per plant, over 5 years (1986–90). Repeatability estimates were higher than 0.84 for all components, except percentage of diseased fruits per plant (^ρ - 0.41). With such estimates, it is possible to select genotypes on the basis of only two years of successive harvests, with a determination coefficient of 90%. The advantages of applying the repeatability coefficient to the cacao breeding program are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

7.
选用来源于中国黄淮和美国的熟期组II~IV的8个大豆品种, 按Griffing方法II设计, 配成28个双列杂交组合, 包括8个亲本共计36份材料。选用300个SSR标记, 对8个大豆亲本进行全基因组扫描, 利用基于回归的单标记分析法, 对大豆杂种产量和分子标记进行相关性分析, 估计等位变异的效应和位点的基因型值, 剖析杂种组合的等位变异。结果表明, 300个SSR标记中有38个与杂种产量显著相关, 分布于17个连锁群上, 其中D1a和M等连锁群上较多, 有8个位于连锁定位的QTL区段内(±5 cM)。单个位点可分别解释杂种产量表型变异的11.95%~30.20%。杂种的位点构成中包括有增效显性杂合位点、增效加性纯合位点、减效加性纯合位点和减效显性杂合位点4部分, 其相对重要性依次递减。从38个显著相关的SSR标记位点中, 遴选出Satt449、Satt233和Satt631等9个优异标记基因位点, Satt449~A311、Satt233~A217和Satt631~A152等9个优异等位变异, 以及Satt449~A291/311、Satt233~A202/207和Satt631~A152/180等9个优异杂合基因型位点。这些结果为理解杂种优势的遗传构成和大豆杂种产量聚合育种提供了依据。  相似文献   

8.
Indonesia is the third largest cocoa-producing country in the world. Knowledge of genetic diversity and parentage of farmer selections is important for effective selection and rational deployment of superior cacao clones in farmers’ fields. We assessed genetic diversity and parentage of 53 farmer selections of cacao in Sulawesi, Indonesia, using 152 international clones as references. Cluster analysis, based on 15 microsatellite markers, showed that these Sulawesi farmer selections are mainly comprised of hybrids derived from Trinitario and two Upper Amazon Forastero groups. Bayesian assignment and likelihood-based parentage analysis further demonstrated that only a small number of germplasm groups, dominantly Trinitario and Parinari, contributed to these farmer selections, in spite of diverse parental clones having been used in the breeding program and seed gardens in Indonesia since the 1950s. The narrow parentage predicts a less durable host resistance to cacao diseases. Limited access of the farmers to diverse planting materials or the strong preference for large pods and large bean size by local farmers, may have affected the selection outcome. Diverse sources of resistance, harbored in different cacao germplasm groups, need to be effectively incorporated to broaden the on-farm diversity and ensure sustainable cacao production in Sulawesi.  相似文献   

9.
Cocoa butter is the major commercial product from seeds of Theobroma cacao (cacao). However, most cacao breeding programs have only considered as selection criteria total seed yield per plant and disease resistance. Progress in cocoa butter yield might be possible if variability for fat content exists and its associations with the other production components are established. The average fat content in dry unfermented seeds for 490 accessions of the Centro de Pesquisa do Cacau germplasm collection in Ilhéus, Bahia, Brazil was 53.2%, ranging from 45.4% in CC 57 to 60.3% in NA 312. Fat content averaged over series indicated that genotypes originally collected in the Upper Amazonian region had higher fat levels, while the Trinitario-Criollo and Bahian genotypes tended to have lower fat content. When considering total fat yield plant-1 an opposite trend arose with the series with low fat content having the highest total fat yield. The correlation between fat content and fat yield plant-1 was not significant, while there was a significant negative correlation between dry seed yield plant-1 and fat content. Despite the significant negative association between fat content and dry seed yield plant-1, the correlation coefficient was rather low, and genotypes could be identified with both high fat content and dry seed yield. A significant pollen effect on fat content was observed based on a complete diallel crossing scheme between three genotypes with high and three with low levels. The average fat content values in progenies were similar to the average of the parents, and the segregation range transgressed the distribution of the parents. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

10.
The cacao tree (Theobroma cacao L.) is a species of great importance because cacao beans are the raw material used in the production of chocolate. However, the economic success of cacao is largely limited by important diseases such as black pod, which is responsible for losses of up to 30–40% of the global cacao harvest. The discovery of resistance genes could extensively reduce these losses. Therefore, the aims of this study were to construct an integrated multipoint genetic map, align polymorphisms against the available cacao genome, and identify quantitative trait loci (QTLs) associated with resistance to black pod disease in cacao. The genetic map had a total length of 956.41 cM and included 186 simple sequence repeat (SSR) markers distributed among 10 linkage groups. The physical “in silico” map covered more than 200 Mb of the cacao genome. Based on the mixed model predicted means of Phytophthora evaluation, a total of 6 QTLs were detected for Phytophthora palmivora (1 QTL), Phytophthora citrophthora (1 QTL), and Phytophthora capsici (4 QTLs). Approximately 1.77–3.29% of the phenotypic variation could be explained by the mapped QTLs. Several SSR marker-flanking regions containing mapped QTLs were located in proximity to disease regions. The greatest number of resistance genes was detected in linkage group 6, which provides strong evidence for a QTL. This joint analysis involving multipoint and mixed-model approaches may provide a potentially promising technique for detecting genes resistant to black pod and could be very useful for future studies in cacao breeding.  相似文献   

11.
A. Bellamy    F. Vedel  H. Bannerot 《Plant Breeding》1996,115(2):128-132
Random amplified polymorphic DNA (RAPD) markers were used to distinguish between several Cichorium intybus genotypes, comprising four white witloof inbred lines, three red witloof experimental inbred lines and a number of F1 hybrids derived from two white parents. Amplification conditions and reproducibility of RAPD patterns were examined. Comparison of polymerase chain reaction (PCR) products obtained by using 100 10-mer arbitrary primers allowed identification of all the lines analysed. With several primers, we defined line-specific RAPD markers, while with others polymorphism was more extensive, revealing several RAPD markers for several lines. All the differences were confirmed both on individual heads and young seedlings for each genotype. Because of the Mendelian segregation of these molecular markers, this method was applied to evaluate the genetic purity of F1 hybrid seed samples.  相似文献   

12.
J.R. Witcombe  C.T. Hash 《Euphytica》2000,112(2):175-186
Marker-assisted selection (MAS) for resistance genes (R-genes), identified using molecular markers and quantitative trait loci (QTL) analysis, is now possible in many crops. MAS can be used to pyramid several R-genes into a single host genotype. However, this may not provide durable genetic resistance because the pathogen is exposed to a full homozygous pyramid during hybrid seed production and to a full heterozygous pyramid in the resultant hybrid. Alternative gene deployment strategies that generate genetic variability were analysed, for hybrid cereal cultivars of pearl millet, maize, sorghum and rice, using maintainer lines (B-lines) with two smaller complementary pyramids. An F1 seed parent, produced on two such B-lines, can be used to produce a three-way hybrid. All target loci are heterozygous for resistance alleles in the F1 seed parent, and the pathogen is exposed in the hybrid to a host population that is heterogeneous and heterozygous for alleles at the resistance loci targeted by MAS. Alternatively, single-cross hybrids can be made on seed parents that are maintained by two B-lines that differ for the complementary resistance gene pyramids. In a cross-pollinated crop, the B-lines are allowed to intermate to produce a synthetic B-line. In an inbreeding crop, the B-lines are equivalent to a two-component multiline variety. In inbreeding crops, because there is no intermating between the B-line components, the resultant synthetic seed parents have a higher frequency of genotypes with resistance alleles (R-alleles) at several resistance loci. However, in both cross-pollinated and inbreeding crops the genotypic structure in the hybrids is almost the same. All alternatives to a single-cross hybrid having a full pyramid produce hybrid cultivars having lower frequencies of resistance alleles. The frequency of genotypes having R-alleles at several loci increases greatly in both seed parent and hybrid when the overall frequency of R-alleles in the maintainer lines increases. This is simply done by adding a maintainer line that has a full pyramid or by the component lines having overlapping pyramids. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

13.
为了将分子标记技术更好的应用到家畜育种工作中。本文详细总结了分子标记技术在家畜遗传多样性分析、亲缘关系分析、遗传图谱构建、基因定位、杂种优势预测、性别鉴定和抗病育种等诸多方面的应用研究。提出应将表型性状、系谱和分子标记三者结合应用于家畜遗传育种等方面的工作。  相似文献   

14.
Sweet potato virus disease (SPVD), a result of the co-infection of whitefly transmitted Sweet potato chlorotic stunt virus (genus Crinivirus, family Closteroviridae) and the aphid transmitted Sweet potato feathery mottle virus (genus Potyvirus, family Potyviridae), is the most destructive disease of sweet potato in East Africa. A study was conducted to establish if genotypes identified as resistant or susceptible to SPVD in Kenya could be distinguished using molecular markers. A total of 47 unrelated sweet potato genotypes were selected from germplasm collections and classified into two phenotypic groups as resistant or susceptible to SPVD. Genotype selection was based on disease severity or days to symptom development in plants following graft inoculation. Amplified fragment length polymorphism (AFLP) marker profiles were generated for each individual and used in association studies to identify markers suitable for classifying the two pre-defined phenotypic groups. Analysis of molecular variance showed significant (P < 0.002) variation between the two groups using 206 polymorphic AFLP markers. Discriminant analysis and logistic regression statistical methods were used to select informative markers, and to develop models that would classify the two phenotypic groups. A training set of 30 genotypes consisting of 15 resistant and 15 susceptible were used to develop classification models. The remaining 17 genotypes were used as a test set. Four markers, which gave 100% correct classification of the training set and 94% correct classification of the test set, were selected by both statistical methods.  相似文献   

15.
This study describes the identification of a quantitative trait locus (QTL) in the recombinant inbred line population of ILL2024 × ILL6788 and subsequent validation of associated molecular markers. A high‐quality genetic linkage map was constructed with 758 markers that cover 1,057 cM, with an average intermarker distance of 2 cM. QTL analysis revealed a single genomic region on Lc2 to be associated with B tolerance and accounted for up to 76% of phenotypic variation (Vp). The best markers for B tolerance were assessed for their utility in routine breeding applications using validation panels of diverse lentil germplasm and breeding material derived from ILL2024. A marker generated from the dense genetic map of this study was found to be the most accurate of all markers available for B tolerance in lentil, with a success rate of 93% within a large breeding pool derived from ILL2024. However, given the number of the unrelated lines for which the marker–trait association was not conserved, B tolerance screening is still required at later stages to confirm predicted phenotypes.  相似文献   

16.
This research was conducted to study the genetic diversity in safflower (Carthamus tinctorius L.) using agro-morphological traits and RAPD markers. Sixteen selected lines derived from landraces growing in various agro-climatic regions of Iran along with four exotic genotypes were evaluated in a randomized complete block design with three replications under field conditions. Days to emergence, days to initial flowering, days to flowering, days to maturity, plant height, branches per plant, capitula per plant, seeds per capitulum, 1,000-seed weight, seed yield per plant, seed yield, and reaction to powdery mildew (Leveillula taurica Arnaud) were evaluated in this study. Genetic diversity of the genotypes was assessed by RAPD markers. The results indicated significant differences among genotypes for the agro-morphological traits and clustering based on these traits classified the genotypes into five groups. Analysis of the RAPD markers revealed 15 polymorphic primers out of 50 used primers. Based on RAPD data, the highest genetic similarity was observed between the cultivars of “AC Sunset,” “AC Sterling” from Canada and the lowest relatedness observed between a local breeding line “E2428” and genotype “GE62923” from Germany. Cluster analysis based on RAPD markers and 54% coefficient of similarity divided the genotypes into five distinct groups. Comparing the clusters based on agro-morphological traits with those from molecular markers showed slight similarities. The finding of high genetic variation for agro-morphological traits and polymorphism at DNA level reveal that agronomic traits can be improved by selection programs.  相似文献   

17.
旨在探索黄瓜种质资源的遗传多样性,为今后黄瓜选育优良品种提供可靠依据。以48份黄瓜种质资源为材料,用DPS软件对各品种的13个表型性状进行聚类分析,同时利用SRAP分子标记对其进行遗传多样性研究。结果表明:根据果实性状等形态学标记聚类分析得出,在阈值75.0处,可以将48份黄瓜种质资源分成5大类群。利用UPGMA法对SRAP分子标记结果聚类分析发现,黄瓜种质间的遗传相似系数在0.52~0.93之间,在遗传相似系数为0.64处,可以将其分成5大类群,形态学标记和SRAP分子标记的聚类结果存在较大差异。由此可见,SRAP分子标记较形态学标记能更好地分析品种间亲缘关系的远近,对黄瓜遗传多样性研究更具指导意义。  相似文献   

18.
The resistance of cacao (Theobroma cacao. L)leaves to 10 isolates of Phytophthora palmivora(Butler) Butler was investigated in 18 genotypes of cacao in three experiments. Tissue-paper-mount and punch-inoculation methods were used to distinguish between resistance at the penetration and post-penetration levels based on lesion frequency and size, respectively. There was a 5–6 fold difference in aggressiveness among isolates collected from different locations in the islands of Trinidad and Tobago for both types of resistance. However, host genotype ×isolate interaction effects were not significant for resistance at both the penetration and post-penetration levels. A strong positive relationship (r = 0.8) was observed in the abilities of isolates to effectively breach the two types of resistance. This suggests that the same isolate can be used in screening for both types of resistance. No significant relationship was found between resistance at the penetration and post-penetration levels suggesting that the resistance mechanisms were different. Subsequent experiments using a wider range of cacao genotypes from the International Germplasm Collection, Trinidad, confirmed the initial results. These experiments indicate that resistance found using one isolate would be equally valid using other isolates of Phytophthora palmivora. The implications of the findings are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

19.
Microsatellite polymorphism in Pisum sativum   总被引：8，自引：0，他引：8  
J. Burstin    G. Deniot    J. Potier    C. Weinachter    G. Aubert  A. Barranger   《Plant Breeding》2001,120(4):311-317
Pisum sativum sequences were retrieved from Genbank/EMBL databases and searched for all possible dinucleotide and trinucleotide tandem repeats. One‐hundred and seventy‐one simple sequence repeats (SSRs) were found among 663 sequences. The different dinucleotide or trinucleotide motifs occurred at varying frequencies. CT/AG was the most frequent dinucleotide, and TCT/AGA the most frequent trinucleotide. Forty‐three microsatellite markers were generated from these sequences and used to assess the genetic variability among 12 pea genotypes. Thirty‐one were polymorphic among the genotypes and the average number of variants per marker was 3.6 when considering only polymorphic markers. Overall, the number of variants for a given SSR marker was correlated with the length of the SSR but some 12‐bp long SSRs showed the same degree of polymorphism as longer ones. The groupings resulting from the SSR genotyping among the 12 genotypes gave an interesting insight into the possible origin of one recent cultivar. Database‐derived SSR markers are highly variable. They can provide useful information on the genetic diversity among P. sativum cultivated types.  相似文献   

20.
利用RAPD标记研究燕麦属不同种的遗传差异   总被引：12，自引：1，他引：12  
利用RAPD标记对我国8个燕麦种共21份材料的遗传差异及类群划分进行了研究。22个多态性引物在21个基因型间共扩增出114条带，其中97条带具有多态性，占85．1％。用这些条带计算了不同基因型间的遗传距离，发现各种间的遗传距离(0．053～0．510)普遍大于不同种内的遗传距离(0．022～0．087)。聚类结果显示，21份材料可划归为5大类群8个亚群，并与传统的分类结果基本一致。由此表明，用RAPD标记对燕麦进行遗传关系和分类研究是可行的。  相似文献   

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