Doubled Haploids for Studying the Inheritance of Quantitative Characters

By using a doubled-haploid population derived from F₂ plants, additive and additive x additive genetic variances, as well as the number of segregating genes, can be estimated. An F₂-derived doubled-haploid population may contain almost 50% more of the best recombinant than an F₁-derived population. However, the best recombinant occurs in the same frequency in the two populations when there is no linkage between genes. The difference in the frequency of the best recombinant between F₂- and F₃-derived populations is small. This implies that the doubled-haploid method using F₂ plants provides only slightly less opportunity for recombination than the conventional breeding methods of self-pollinating crops. In the absence of additive epistasis, a weighted mean of recombination values can be estimated using an F₂-derived population and its parental lines. When additive epistasis is present, it can be estimated from doubled-haploid populations derived from two backcrosses. Studies on the linkage of quantitative characters are needed for determining whether doubled haploids should be produced from F₂ or from F₁ plants in a breeding program.     

Analysis of Genetic Diversity in the North Eastern Himalayan Maize Landraces using Microsatellite Markers

Population DNA fingerprinting of 48 selected North Eastern Himalayan (NEH) landrace accessions was undertaken using 41 polymorphic fluorescent dye-labelled microsatellite/Simple Sequence Repeat (SSR) markers, using a DNA Sequencer. The analysis revealed a large number of SSR alleles (576), with high mean number of alleles per locus (13.8), and Polymorphism Information Content (PIC) of 0.63, reflecting the level of diversity in the NEH accessions and the informativeness of the SSR markers. The study also led to identification of 135 unique alleles, differentiating 44 out of the 48 accessions. Five highly frequent (major) SSR alleles (umc1545 _80bp, phi062 _162bp, umc1367 _159bp, umc2250 _152bp and phi112 _152bp) were detected indicating that chromosomal regions harbouring these S SR alleles might not be selectively neutral. Analysis of population genetic parameters, including Wright’s F statistics, revealed high level of genetic differentiation, very low levels of inbreeding, and restricted gene flow between the NEH landraces. AMOVA (Analysis of Molecular Variance) showed that 67 per cent of the total variation in the accessions could be attributed to within-population diversity, and the rest between the accessions. Cluster analysis of SSR data using Rogers’ genetic distance and UPGMA, showed significant genetic diversity among the landraces from Sikkim. This is the first detailed study of SSR allele frequency-based analysis of genetic diversity in the NEH maize landraces of India.     

Doubled Haploids for Estimating Mean and Variance of Recombination Values

In a diallel cross analysis using doubled haploids, both additive and additive x additive genetic variances can be estimated. In addition, mean and variance of recombination values can also be estimated. Linkage affects the covariance between half-sibs the most, the covariance between grandparent and grand offspring to an intermediate degree and the covariance between full sibs the least. The covariance of parent and offspring is not affected by linkage.     

中国花生地方品种与育成品种的遗传多样性

以中国花生小核心种质中涉及来源于中国本土的145份地方品种和67份育成品种为材料,应用SSR技术从206对SSR引物中筛选出25对扩增效果好的多态性引物进行检测,并对其进行遗传多样性分析比较.结果表明:(1)地方品种与育成品种各具有特殊带型及各自独特的遗传特性.相似系数和多态性信息量均表明,地方品种的多样性比育成品种丰富,其中:地方品种之间的相似系数为0.57～0.99,平均0.795,多态性信息量0.530 0;育成品种之间的相似系数0.63～0.99,平均0.810,多态性信息量0.463 3.地方品种与育成品种之间的平均相似系数为0.794,变异范围0.56～0.99.(2)对不同生态区来源的分析表明,除黄河流域外其他各生态区地方品种的观测等位基因数和遗传多样性指数(分别为2.740 7～3.518 5和0.816 4～0.879 4)均比育成品种的对应值(分别为1.7012～2.145 6和0.4829～0.802 2)大,并以长江流域生态区地方品种的观测等位基因数和遗传多样性指数最大,分别为3.518 5和0.879 4.(3)聚类分析结果表明,花生核心种质中,中国本土资源分为3个品种群,即地方品种密枝亚种群、地方品种疏枝亚种群和育成品种群,与花生的亚种分类一致.(4)通过遗传多样性分析,鉴定出一批遗传差异较大的材料,其中zhh1398与zhh0041的遗传差异最大,相似系数为0.56,为花生品种的遗传改良及作图群体的构建奠定了基础.     

Diversity Assessment of Turkish Maize Landraces Based on Fluorescent Labelled SSR Markers

Landraces of maize represent a valuable genetic resource for breeding and genetic studies. Since 1970, landraces have been collected from all over Turkey, but the genetic diversity represented in this collection is still largely unknown. In this study, a sample of 98 landraces sampled from 45 provinces of Turkey was assessed genotypically at 28 simple sequence repeat (SSR) loci and phenotypically for 19 morphological traits. The landraces varied significantly for all the latter traits. A total of 172 SSR alleles were detected, giving a mean of 6.21 alleles per locus. The genetic distance between pairs of landraces ranged from 0.18 to 0.63, with a mean of 0.35. Positive and negative correlation exists among different morphological and agronomic traits. Positive association among different traits showed that improvement of one character may simultaneously improve the other desired trait. Based on UPGMA dendrogram and Neighbor-Net (NNET) analyses from both morphological traits and SSR data, respectively, it is obvious that maize landraces from the same geographical region were often placed in different clusters, indicating that grouping based on genetic parameters was not closely related to the geographic origin. The wide diversity present in Turkish maize landraces could be used as genetic resource in designing maize breeding program for developing new cultivars adapted to different geographic and climatic conditions, and may also contribute to worldwide breeding programs.     

The Use of Matroclinous Maize Haploids for Recurrent Selection

Two cycles of recurrent selection were performed in maize with the use of matroclinous haploids. Two synthetic populations, SP and SA, were improved. Each cycle consisted of two stages: (1) isolation of haploids from the synthetic populations and (2) growth of the haploids, pollination with pollen from diploid plants, and selection. The selection was performed for ear size in haploid plants. The mean gain in productivity in the synthetic populations SP and SA the per cycle was 16.48 and 20.98%, respectively. It is suggested that the high value of this index is related to the fact that haploid plants reveal useful genes with additive and epistatic effects. Natural selection may have played a part, too. The combination of artificial and natural selection in haploids resulted in a considerable gain in productivity in the synthetic populations to be improved.     

中国地方黄牛的Y染色体遗传多样性及其进化起源

中国黄牛的进化起源与遗传多样性一直是国内外动物遗传学家感兴趣的课题之一.本文主要从Y染色体的形态多样性和Y染色体特异性微卫星标记遗传多态性两个方面对中国地方黄牛的遗传多样性和进化起源进行了综述.中国地方黄牛Y染色体具有中着丝粒、亚中着丝粒和近端着丝粒3种类型,这说明中国地方黄牛起源于普通牛和瘤牛.利用Y染色体特异性微卫星标记对中国地方黄牛Y染色体单倍型分布特征及Y染色体基因流模式的分析表明,北方种群中普通牛单倍型频率最高,瘤牛单倍型在南方种群中占优势;在中国不同地域,瘤牛Y染色体单倍型频率呈现自南而北、自东而西逐渐降低的趋势,这再次证实了中国黄牛主要来源于普通牛和瘤牛,这可能是这两类牛群在长期的历史进化过程中,分别从东南方向和西北方向进入我国,并在中原地区汇合的结果.本文为中国地方黄牛品种资源保护和杂交育种工作提供了参考依据.     

转基因技术在玉米遗传育种中的应用

玉米转基因育种是通过基因转移方法创造玉米新种质或新品种。将转基因技术与玉米常规育种技术相结合,能尽快地培育出符合育种目标的新品种,带来了育种水平的提高、创新和突破,加快了玉米育种进程。论述了转基因技术在玉米育种中的主要应用方法、研究进展及应用现状。随着转基因技术的飞速发展及其研究的日趋成熟,转基因技术在拓宽玉米种质资源、提高杂交种的抗逆性、抗病虫性、提高产量和品质等方面将发挥更大的作用,应用前景广阔。     

新疆冬春麦区小麦地方品种贮藏蛋白遗传多样性研究

采用SDS-聚丙烯酰胺凝胶电泳（SDS-PAGE）对236份新疆小麦地方品种的高分子量麦谷蛋白亚基（HMW-GS）的组成进行了分析。结果表明：Glu-Ⅰ位点共有19种等位基因,其中Glu-Al位点3种,Glu-Bl位点7种,Glu—D1住点9种;亚基null、7＋8、2＋12在各自的位点上出现频率最高,分别达到91．95％、85．17％、80．93％;亚基组成类型共有21种,主要为null／7＋8／2＋12,频率达70．34％;同时筛选出33份含有1、2^＊、13＋16、14＋15、5＋10、1．5＋10、174-18等优质亚基的材料,可作为优质基因源。利用酸性聚丙烯酰胺凝胶电泳（A-PAGE）对其中的65份地方品种进行醇溶蛋白多样性分析。结果表明：电泳出现64条迁移率不同的谱带,构成65种组合,其中ω区出现的谱带最多,达17条;其次是β和γ区各16条,α区出现的谱带数最少,为15条。从每条谱带在65份材料中出现的频率看,总的变异范围为1．54％～93．85％;α、β、γ和ω4个分区多样性指数（H1）分别为0．498、0．386、0．523和0．348,表明新疆麦区小麦地方品种贮藏蛋白位点存在丰富的遗传多样性。     

长喙毛茛泽泻遗传多样性及其与繁育系统的关系

利用聚丙烯酰胺凝胶电泳技术测定了濒危植物长喙毛茛泽泻（ＲａｎａｌｉｓｍａｒｏｓｔｒａｔｕｍＳｔａｐｆ）及３个对照种冠果草［Ｓａｇｉｔａｒｉａｇｕａｙａｎｅｎｓｉｓｓｓｐｌａｐｐｕｌａ（ＤＤｏｎ）Ｂｏｇｉｎ］、武夷慈姑（ＳｗｕｙｉｅｎｓｉｓＪＫＣｈｅｎｅｔａｌ）、矮慈姑（ＳｐｙｇｍａｅａＭｉｑ）共６个自然居群的遗传多样性。自花受精和以营养繁殖为主的长喙毛茛泽泻维持较低的遗传多样性,预期杂合度和观察杂合度分别为００６４和０１０４。以自花受精为主的冠果草遗传多样性更低,预期杂合度和观察杂合度分别为００３９和００６７。异体繁育但以营养繁殖为主的武夷慈姑遗传多样性比长喙毛茛泽泻的高,预期杂合度和观察杂合度分别为０１１１和０１８３。以异体繁育为主和营养繁殖的矮慈姑遗传多样性在这４个种中最高,其预期杂合度和观察杂合度分别是０１５５和０２６９。４个种的内繁育系数Ｆ值全为负值。冠果草、长喙毛茛泽泻、武夷慈姑直至矮慈姑,其异交程度从几乎为零逐渐递增,而其遗传多样性指标也相应地增高。长喙毛茛泽泻的遗传多样性程度高于冠果草但冠果草并不濒危,因此遗传多样性较低并不是濒危的直接原因     

Farmers Drive Genetic Diversity of Thai Purple Rice (Oryza sativa L.) Landraces

Purple or black rice (Oryza sativa L.) is a culturally important germplasm in Asia with a long history of cultivation in northern Thailand. Purple rice is identified by the color of the rice pericarp, which varies from purple to black with the accumulation of phenolic acids, flavonoids, and anthocyanins. In the present study, we assessed molecular variation within and between wetland purple rice landraces germplasm from northern and northeastern Thailand using 12 microsatellite loci. All purple rice varieties surveyed showed high levels of homozygosity within varieties and strong genetic differentiation among varieties, indicating the fixation of genetic differences among them. This pattern is consistent with purple rice farming practices in northern Thailand, where a small portion of harvested seed is selected and replanted based on farmers’ preferences. The reduced genetic diversity and high homozygosity observed for purple rice is also consistent with patterns expected for this inbreeding crop. Genetic differentiation among the varieties showed some degree of structuring based on their geographical origin. Taken together, these data highlight that the genetic diversity and structure of wetland purple rice landraces is shaped by farmer utilization and cultivation through local cultural practices, and that conservation should focus on ex situ conservation across its cultivation range, along with on-farm, in situ conservation based on farmers’ seed-saving practices. In situ conservation may prove especially valuable for preserving the genetic identity of local varieties and promote adaptation to local environments.

     

Genetic Diversity and Molecular Evolution of Chinese Waxy Maize Germplasm

Waxy maize (Zea mays L. var. certaina Kulesh), with many excellent characters in terms of starch composition and economic value, has grown in China for a long history and its production has increased dramatically in recent decades. However, the evolution and origin of waxy maize still remains unclear. We studied the genetic diversity of Chinese waxy maize including typical landraces and inbred lines by SSR analysis and the results showed a wide genetic diversity in the Chinese waxy maize germplasm. We analyzed the origin and evolution of waxy maize by sequencing 108 samples, and downloading 52 sequences from GenBank for the waxy locus in a number of accessions from genus Zea. A sharp reduction of nucleotide diversity and significant neutrality tests (Tajima’s D and Fu and Li’s F*) were observed at the waxy locus in Chinese waxy maize but not in nonglutinous maize. Phylogenetic analysis indicated that Chinese waxy maize originated from the cultivated flint maize and most of the modern waxy maize inbred lines showed a distinct independent origin and evolution process compared with the germplasm from Southwest China. The results indicated that an agronomic trait can be quickly improved to meet production demand by selection.     

四川小麦地方品种Gli-1、Gli-2和Glu-1位点的遗传多样性(英文)

运用APAGE和SDS_PAGE方法 ,研究了 89个四川小麦 (TriticumaestivumL .)地方品种Gli_1、Gli_2和Glu_1位点的遗传多样性。在这些地方品种中 ,总共发现 32种醇溶蛋白带型和 3种高分子谷蛋白带型。在Gli_1、Gli_2和Glu_1位点上 ,分别检测出 14、15和 5个等位基因。在每一个位点上 ,出现频率最高的等位基因分别为Gli_A1a(89% ) ,Gli_B1h (46 % ) ,Gli_D1a (6 5 % ) ,Gli_A2a (6 4% ) ,Gli_B2j (45 % ) ,Gli_D2a (48% ) ,Glu_A1c (99% ) ,Glu_B1b (99% )和Glu_D1a (10 0 % )。四川小麦地方品种的Nei’s遗传变异系数平均为 0 .370 6 ,变幅为 0到 0 .70 87;其中Gli_B2位点的遗传多样性最高 ,而Glu_D1位点最低。同时 ,Gli位点的遗传多样性高于Glu_1位点的遗传多样性 ,但又低于现代品种Gli位点的遗传多样性。这些结果说明四川地方小麦品种的遗传基础狭窄。在研究中 ,“成都光头”与“中国春”的醇溶蛋白和高分子谷蛋白的带型完全一致 ,进一步证实“中国春”是“成都光头”的一个选系。     

老芒麦遗传多样性及育种研究进展

老芒麦（Elymus sibiricus）的研究对我国北方草原及青藏高原高寒草甸的退化草地改良、发展草地畜牧业具有重要意义。本文综述了老芒麦在形态学、细胞学、蛋白质和DNA分子水平上的遗传多样性研究概况,并总结了国内老芒麦的育种研究进展。目前国内外专门针对不同老芒麦种质材料（accession）或居群（populations）遗传多样性的研究鲜见报道,相关研究主要集中在与披碱草属（Elymus）及其近缘小麦族物种的系统进化研究方面;其次,我国仅有6个老芒麦国家审定品种,且育种手段较单一、落后,育成品种优势集中在产量和适应性上,缺乏对抗逆性种质的筛选培育。     

308个糯玉米审定品种SSR标记遗传多样性分析

随着中国糯玉米产业的蓬勃发展,每年通过审定的糯玉米品种逐渐增多,为了解其育成品种的遗传多样性和亲缘关系,本研究以308个糯玉米审定品种为材料,利用SSR标记从审定年份和适宜种植区2个角度分析近年来糯玉米审定品种遗传多样性特点和发展趋势.结果 表明,308份糯玉米审定品种在40个SSR标记上共检测出529个等位基因、14...     

利用SSR标记分析玉米轮回选择群体的遗传多样性

利用SSR标记技术分析了玉米基础群体DC0及其选择两轮后的群体HSC2和MSC2以及基础群体XFC0和其选择一轮后的群体XFC1的遗传多样性。结果表明：49对引物在5个玉米群体中共扩增出185个等位位点,每个SSR座位的等位基因数目为1～7个,平均为3．8个;基础群体多态性位点总数和多态性位点比例比其改良群体的略高;DC0、HSC2和MSC2 3个群体的基因平均杂合度相似,XFC0与XFC1的基因平均杂合度相似;基础群体与改良群体的平均遗传距离也相似;累加各引物扩增的基因型种类,改良群体的基因型种类偏少,但这些差异均不显著。以上结果说明轮回选择的基础群体与其改良后群体的遗传变异相似,轮回选择可以保持群体的遗传变异范围,改变群体的遗传组成,增加群体内个体间的异质性。     

Resistance of Maize Landraces to the Maize Weevil Sitophilus zeamais Motsch. (Coleoptera: Curculionidae)

The maize weevil Sitophilus zeamais Motsch. is an important pest of maize that attacks the grain both in the field and during storage. The damage caused by the maize weevil S. zeamais on maize landraces, Amarelo Antigo, Asteca, Caiano, Carioca, and Ferrinho, was evaluated by no-choice tests under laboratory conditions. The commercial varieties Sol da Manh?, BR 106, BR 451, and the synthetics PC 0203 and PC 9903 were evaluated for comparisons with the maize landraces. The parameters evaluated were susceptibility index, number of weevil progeny, development time, weevil progeny dry weight, and grain dry weight loss. The landraces were more susceptible to the maize weevil as compared to the commercial varieties. Based on the cluster analysis, two groups of susceptibility to the maize weevil were observed: one of more susceptible populations formed by local landraces and BR 451, and another less susceptible, with commercial varieties, synthetics, and the landrace Amarelo.     

Evaluation of Genetic Diversity of Chilli Landraces from North Eastern India Based on Morphology, SSR Markers and the Pun1 Locus

The chilli (Capsicum sp.) germplasm found throughout North Eastern (NE) India exhibits wide variability in fruit morphology, pungency, bearing habit and crop duration. As the genetic resources of chilli landraces from this region are not well documented, it is likely that they have hitherto unknown alleles and/or genes for economically important traits. In this study, 53 chilli accessions from different areas of this NE region were evaluated for genetic diversity using various morphological characters and 50 simple sequence repeat markers. It was found that erect and campanulate fruit types are grouped in separate clusters. The number of alleles per locus ranged from 3 to 9 with an average of 5.36. The average polymorphic information content value was 0.52. Percentage variation among populations, within individuals of population and within individuals was found to be 34, 57.9 and 8.05 %, respectively, indicating diversity in the landraces sampled. Allele mining across acyltransferase 3 (AT3) gene in a set of landraces led to identification of new single nucleotide polymorphisms (SNPs). Sequence analysis of the 2,349 bp AT3 region revealed the presence of a total of 79 SNPs and 3 indels. This overview of diversity of chilli landraces from NE India paves the way for conservation and utilisation of germplasm and contributes to the development of systematic breeding strategies.     

Genetic Diversity and Population Structure in a Legacy Collection of Spring Barley Landraces Adapted to a Wide Range of Climates

Global environmental change and increasing human population emphasize the urgent need for higher yielding and better adapted crop plants. One strategy to achieve this aim is to exploit the wealth of so called landraces of crop species, representing diverse traditional domesticated populations of locally adapted genotypes. In this study, we investigated a comprehensive set of 1485 spring barley landraces (Lrc1485) adapted to a wide range of climates, which were selected from one of the largest genebanks worldwide. The landraces originated from 5° to 62.5° N and 16° to 71° E. The whole collection was genotyped using 42 SSR markers to assess the genetic diversity and population structure. With an average allelic richness of 5.74 and 372 alleles, Lrc1485 harbours considerably more genetic diversity than the most polymorphic current GWAS panel for barley. Ten major clusters defined most of the population structure based on geographical origin, row type of the ear and caryopsis type – and were assigned to specific climate zones. The legacy core reference set Lrc648 established in this study will provide a long-lasting resource and a very valuable tool for the scientific community. Lrc648 is best suited for multi-environmental field testing to identify candidate genes underlying quantitative traits but also for allele mining approaches.