Detection and integration of gene mapping of downy mildew resistance in maize inbred lines though linkage and association

Association mapping relies on the variation and extent of linkage disequilibrium within a species to identify genes of interest; this is an alternative to linkage mapping in traditional biparental population, which exploits only the variation in the two parents of the mapping population. This study was designed to identify association between 48 SSR markers and downy mildew (DM) resistance using a set of 60 public and private maize inbred lines in Thailand. Genetic diversity and population structure in the set were calculated. A total of 489 alleles with an average gene diversity of 0.70 revealed two subpopulations among the 60 maize inbred lines. Analysis of variance resulted in significant effects of phenotypic values of tested entries, with significant effects of inbred lines, locations, and their interaction. In addition, the analysis of variance for broad sense heritability also indicated high heritability (0.97), and association analysis revealed three significant SSR-trait associations (P < 0.05). These three significant SSR loci have not been reported in previous linkage mapping studies. Our results suggest that new allelic variants associated with DM resistance in these germplasm collections should be useful to help identify new lines carrying alleles for DM resistance in breeding marker-assisted selection programs.     

不同供水条件下玉米耐旱生理特性比较

【研究目的】本试验研究玉米耐旱生理特性,为玉米耐旱品种选育提供依据。【方法】试验以玉米品种正大619、农大108为材料,分别在间隔4天、8天、12天、16天灌一次水的不同水分处理条件下,分析玉米叶片叶绿素、脯氨酸（Pro）、丙二醛（MDA）的含量及超氧化物歧化酶（SOD）和过氧化物酶（POD）的活性。【结果】结果表明：随着水分胁迫程度加大,玉米叶片脯氨酸的含量、MDA含量和POD活性呈现不同程度的增加,而叶绿素含量和SOD活性则随着水分胁迫程度加大而降低。且敏感型品种农大108的变化明显强于抗旱型的正大619。【结论】脯氨酸（Pro）、丙二醛（MDA）的含量及超氧化物歧化酶（SOD）和过氧化物酶（POD）的活性可以作为玉米耐旱品种选育参考。     

玉米霜霉病的分子遗传学研究进展

玉米霜霉病是一种重要病害,特别是在热带、亚热带地区,常常造成玉米生产的重大损失。笔者从玉米霜霉病抗性的遗传表现、抗性基因的QTL定位、QTL效应及QTL与环境的互作、抗性的分子标记及抗性遗传多态性变异等方面对其分子遗传研究进展情况进行了概述。并就加强玉米霜霉病抗性基因克隆、近等基因系构建及分子标记辅助育种体系建立等研究工作进行了展望     

Genetic variability for resistance to sorghum downy mildew (Peronosclerospora sorghi) and Rajasthan downy mildew (P. heteropogoni) in the tropical/sub-tropical Asian maize germplasm

Downy mildews cause considerable damage to maize (Zea mays L.) worldwide, particularly in the tropical Asia. We have evaluated a set of 42 tropical/sub-tropical maize inbred lines developed in different countries in Asia (India, Thailand and Philippines), and Mexico, for analysing the genetic variability for resistance to sorghum downy mildew [Peronosclerospora sorghi; SDM] and Rajasthan downy mildew [P. heteropogoni; RDM]. Experiments were carried out in replicated trials under artificial infection in field conditions against SDM and RDM at Mandya in Karnataka, India, and Udaipur in Rajasthan, India, respectively, during 1999 and 2000. The study resulted in identification of five inbred lines offering consistent and strong resistance to both SDM and RDM, while several inbred lines revealed resistance only to RDM. It was also revealed that the SDM-resistant inbreds are invariably resistant to RDM, while the RDM-resistant inbreds might show differential responses to the SDM. The maize inbred lines identified in this study with broad-spectrum resistance to downy mildews could be potentially useful for basic and applied research work on downy mildews in tropical Asia. This revised version was published online in August 2006 with corrections to the Cover Date.     

SSR荧光检测解析224份山西玉米自交系的遗传结构与遗传关系

为利用杂种优势,对玉米自交系的遗传结构及遗传关系进行解析非常必要.本研究基于40个SSR位点的分析,对山西224份玉米自交系的遗传结构与遗传关系进行了解析.共检测出171个等位变异,平均每个位点4.28个;平均每个位点多态性信息量PIC、标记索引指数、基因多样性指数分别为0.44、2.02和0.50;有9份种质存在特异...     

Methods for screening maize against downy mildew Peronosclerospora sorghi

Methods of inoculum delivery and timing of test-row planting were assessed for efficacy in promoting development of downy mildew (Peronosclerospora sorghi) in susceptible maize, and for cost of implementation in terms of personnel and labour. Direct inoculation of pre-germinated seed of spreader rows resulted in consistent and high incidence of downy mildew infected plants and required substantially less labour and inoculum than the spray inoculation of spreader rows. The optimum time to plant test rows was around 15 days after inoculation of spreader rows. Eight breeding lines were screened for resistance to downy mildew using the revised inoculation method. After one cycle of screening with the new method, resistance levels improved by a range of 0–44% over the previous cycle.     

Identification of quantitative trait loci for downy mildew resistance in cucumber (Cucumis sativus L.)

Downy mildew, caused by Pseudoperonospora cubensis (Berk. & Curt.) Rostov, is one of the most economically important foliar diseases in cucumber (Cucumis sativus L.). Cucumber line CS-PMR1, derived from self-pollination of USDA Plant Introduction 197088, has a high level of resistance to downy mildew and is considered to be promising breeding material. In this study, we performed quantitative trait locus (QTL) analysis for downy mildew resistance using 111 recombinant inbred lines (RILs) derived from a cross between CS-PMR1 and the old Japanese cultivar Santou, which exhibits moderate resistance. The resistance of the RILs and their parents was evaluated by diverse methods using different plant organs (cotyledons, true leaves), stages (seedlings and adult plants), and evaluation criteria (lesion expansion and extent of sporulation). The high resistance of CS-PMR1 was associated with many QTLs with relatively small effects, whereas the moderate resistance of Santou was associated with one major QTL and possibly two others with relatively small effects. In all assays, the major QTL at which the Santou allele was associated with increased resistance had the largest effect. This QTL allele from Santou and several of the most effective QTL alleles identified in CS-PMR1 should be highest priority for selection to efficiently breed new cultivars that carry adequate levels of downy mildew resistance.     

Detection of downy and powdery mildew resistance QTL in a ‘Regent’ × ‘RedGlobe’ population

One hundred and eighty six F₁ plants from a ‘Regent’ × ‘RedGlobe’ cross were used to generate a partial linkage map with 139 microsatellite markers spanning all 19 chromosomes. Phenotypic scores for downy mildew, taken over two years, confirmed a major resistance QTL (Rpv3) against downy mildew in the interval VVIN16-cjvh to UDV108 on chromosome 18 of ‘Regent’. This locus explained up to 62 % of the phenotypic variance observed. Additionally a putative minor downy mildew resistance locus was observed on chromosome 1 in one season. A major resistance locus against powdery mildew (Ren3) was also identified on chromosome 15 of ‘Regent’ in the interval UDV116 to VChr15CenGen06. This study established the efficacy of and validated the ‘Regent’-derived downy and powdery mildew major resistance genes/QTL under South African conditions. Closely linked SSR markers for marker-assisted selection and gene pyramiding strategies were identified.     

甘肃部分玉米自交系SSR遗传多样性分析

分析甘肃省部分骨干玉米自交系的遗传多样性并划分群体结构。利用全自动DNA分析仪荧光SSR-PCR技术和66 对核心SSR引物研究了148 份玉米(Zea mays L.)自交系的遗传多样性,并分别使用模型结构聚类和遗传距离聚类法进行群体结构分析。在148 份自交系中,66 对SSR标记共检出279 个等位变异,每对引物检测到等位基因2~8 个,平均4.2273 个。多态性信息量(PIC)和标记指数(MI)的平均值分别为0.4879 和2.1808。模型结构聚类将148 份自交系分为SS 群和NSS群;遗传距离聚类分为5 个类群,根据常规测验种自交系可将5 个类群归并为SS 群和NSS群。2 种聚类方法所得结果与材料的系谱信息基本一致。甘肃省部分玉米自交系在育种实践中正在向2 个相对独立的优势类群转化,2 个类群之间的遗传多样性水平存在一定的差异。     

基于SSR分子标记的玉米自交系遗传多样性分析

了解新选育自交系遗传背景,确定其所属的杂种优势群,是组配杂交组合,选育新的杂交种的关键措施。此研究利用SSR标记技术分析了46份玉米自交系的遗传多样性,结果表明：12对稳定的SSR引物共检测出45个等位基因变异,每个SSR的多态性信息量（PIC）的变幅为0.31~0.76,平均为0.57,显示了较高的多态性。聚类分析显示46个玉米自交系可划分为5个类群,每一类群内所包含的自交系与系谱分析的结果基本一致。研究结果还表明,快捷、准确鉴定种质资源亲缘关系的SSR分子标记技术可以广泛应用于育种实践,提高玉米优势组合选配的效率。     

应用SSR分子标记分析国外种质对我国小麦品种的遗传贡献

利用363对SSR标记分析了在我国小麦生产和育种中发挥了重要作用的11份国外引进品种和33份选育品种的遗传组成,旨在揭示国外种质对我国小麦品种改良的遗传贡献,指导种质资源引进和利用。国外种质包含了选育品种所发现等位变异的76.3%。与不同时期小麦品种等位基因多样性比较发现,国外种质的平均等位变异数最多(3.92),20世纪60年代(2.86)和70年代(3.01)基本一致,80年代有所升高(3.46)。品种间遗传距离比较与品种等位基因多样性结果相吻合。比较引进和选育品种在SSR位点的等位变异频率变化,发现至少在33个SSR位点,国外种质等位变异在我国小麦育种中被优先选择(该等位变异在引进和选育品种的分布频率均高于70%),其中一些位点已知与产量、生育期和抗病等性状密切相关。表明引进品种在以上基因组区域对我国小麦品种具有非常高的遗传贡献。     

应用SSR分子标记分析国外种质对我国小麦品种的遗传贡献

利用363对SSR标记分析了在我国小麦生产和育种中发挥了重要作用的11份国外引进品种和33份选育品种的遗传组成,旨在揭示国外种质对我国小麦品种改良的遗传贡献,指导种质资源引进和利用。国外种质包含了选育品种所发现等位变异的76.3%。与不同时期小麦品种等位基因多样性比较发现,国外种质的平均等位变异数最多(3.92),20世纪60年代(2.86)和70年代(3.01)基本一致,80年代有所升高(3.46)。品种间遗传距离比较与品种等位基因多样性结果相吻合。比较引进和选育品种在SSR位点的等位变异频率变化,发现至少在33个SSR位点,国外种质等位变异在我国小麦育种中被优先选择(该等位变异在引进和选育品种的分布频率均高于70%),其中一些位点已知与产量、生育期和抗病等性状密切相关。表明引进品种在以上基因组区域对我国小麦品种具有非常高的遗传贡献。     

糯玉米自交系SSR标记遗传多样性及群体遗传结构分析

为了解糯玉米种质的遗传基础,利用29对SSR标记对87份糯玉米自交系进行遗传多样性分析,共检测出180个等位变异,平均每个位点6个等位变异,多态性信息含量变幅为0.308～0.915,平均为0.572。材料间遗传相似系数为0.49～0.93,平均为0.66。通过聚类分析UPGMA (unweighted pair-group method with arithmetic means)方法在遗传相似系数0.64处将87份糯玉米自交系划分为4个类群,分别包含9、66、10和2份材料。此外,利用Structure群体遗传结构分析也将87份糯玉米自交系分为4个类群,分别包含24、25、19和19份材料;进一步分析表明,供试群体中大部分糯玉米自交系的遗传变异较单一。本研究为糯玉米新品种选育和遗传进化分析提供了种质基础和理论依据。     

Genetical Studies of Resistance of Powdery Mildew in Barley Lines Derived from Hordeum spontaneum Collected from Israel

Genetical studies on mildew resistance were carried out with Hordem spontaneum derived lines. A total of 28 lines (66 %) showed monofactorial segregation for mildew resistance, For 14 lines, a bifactorial mode of inheritance was found. In total fifty six mildew resistance genes take part in the inheritance of mildew resistance of the H. spontaneum derived lines, while the presence of known genes for mildew resistance (i.e, Ml-a.9 and Ml-p) was established only in two cases. Independent segregation from the Ml-a locus was found in 10 mbnofaetorial segregating lines, The genes conditioning mildew resistance in barley lines derived from the accessions 1B-54B, RS 170-47, RS 20-1. 1B-86B, RS 145-39 and 1B–152B of H. spontaneum were closely linked or alleles to the Ml-a locus, but shown to be different from 15 previously identified Ml-a alleles. It is suggested that these genes should be designated Ml-a16, Ml-18, Ml-19 Ml-20 and Ml-a21 respectively. No recombinants were found in test crosses when both parents carried genes/alleles of the Ml-a locus. In addition, polymorphism has been observed also for the Ml-a locus. In 4 lines mildew resistance was conditioned by two dominant complementary genes. For one of the 2 genes, conditioning mildew resistance of line RS 42-8 × OrioL a new locus was found located near the centromere of the long arm of chromosome 5, and should be designated Ml-i The potential use of H. spontaneum genes for mildew resistance in barley breeding is discussed.     

Genetic diversity and relatedness of selected Iranian rice cultivars and disease resistance donors assayed by simple sequence repeats and candidate defense gene markers

As a prerequisite to improving diseaseresistance and grain quality in Iranianrice cultivars, we determined the geneticrelatedness of popular local cultivars andblast-resistance donor germplasm usingfingerprints derived from simple sequencerepeat (SSR) and plant defense genemarkers. Fifty SSR markers and 28 defensecandidate genes were used to assess thegenetic diversity among popular ricecultivars from Iran and donors of blastresistance from breeding programs in Asia.Gene diversity estimate of the 16 corebreeding lines was 0.440 ± 0.028 basedon SSR markers. Genetic relationships amongthe cultivars were determined by clusteranalysis using SSR and candidate genedatasets. DNA fingerprints derived fromSSR and defense gene markers gave similargroupings of cultivars consistent withtheir genetic background: a) Iranian localvarieties, b) improved varieties in Iranplus donor indica germplasm from Asia, andc) japonica germplasm. Within-groupsimilarities for the traditional andimproved cultivars were greater than 80%and 75%, respectively. The traditional andimproved cultivars showed differentialreaction to blast pathogen isolates; alltraditional varieties were susceptible toblast pathogen isolates in Iran butresistant to isolates in the Philippines,whereas the improved varieties showedopposite reaction to pathogen isolates inIran and the Philippines. Both molecularand phenotypic data suggest a narrowgenetic basis in local and improvedcultivars in Iran and the need forincluding more diversity for the breedingprogram. The high degree of polymorphismobserved between local cultivars and donorsof blast resistance provide the neededinformation to follow the transmission ofresistance alleles from the donors inadvancing breeding lines.     

利用SSR分子标记划分杂交籼稻亲本群的研究

杂种优势群和杂种优势利用模式可以为植物的杂种优势利用提供重要信息。与玉米相比,水稻杂种优势群的研究相对薄弱。本研究利用72对SSR引物对我国47个杂交籼稻骨干亲本进行了类群划分。共检测出328个等位基因变异,每对引物检测等位基因2~13个,平均4.56个;引物的多态性信息量（PIC）范围为0.120~0.878,平均值为0.567。材料之间的遗传相似系数(GS)范围在0.633~0.928,平均为0.741。用类平均法（un-weighted pair-group method using an arithmetic average）将亲本材料划分为保持系群、温敏核雄性不育系群、恢复系群,其中保持系群和恢复系群又各分为3个亚群,分群结果基本符合系谱信息。并结合杂交水稻生产实践提出了7种杂种优势组合配组模式。分子标记是一种划分杂交籼稻亲本群的有效途径,本研究结果对杂交籼稻的亲本选配具有一定指导意义。     

The long and winding road leading to the successful introgression of downy mildew resistance into onion

Downy mildew resistance originating from Allium roylei Stearn provides a complete resistance to onions and is based on one, dominant gene. Since A. roylei can successfully be hybridized with onion (A. cepa L.), a breeding scheme aimed at the introgression of this gene was initiated ca. 20 years ago. Several setbacks in this programme were encountered, firstly the identified molecular marker linked to the downy mildew resistance locus became increasingly difficult to use and finally lost its discriminating power and secondly the final step, making homozygous introgression lines (ILs), turned out to be more difficult then was hoped. GISH analysis showed that the chromosomal region harbouring the resistance locus was the only remaining piece of A. roylei in the nuclear background of onion and it also confirmed that this region was located on the distal end of chromosome 3. It was hypothesized that some factor present in the remaining A. roylei region was lethal when homozygously present in an onion genetic background. The identification of an individual with a smaller and more distally located introgression fragment and homozygous ILs in its progeny validated this hypothesis. With the help of these nearly isogenic lines four AFLP^® markers closely linked to the resistance gene were identified, which can be used for marker-aided selection. The introduction of downy mildew resistance caused by Peronospora destructor into onion is a significant step forward in the development of environmentally-friendly onion cultivars.     

利用SNP芯片和BSA分析规模化定位小麦抗白粉病基因

规模化定位小麦品种携带的抗白粉病基因对于抗病性种质创新和新品种选育具有重要的意义。本研究采用Illumina Infinium iSelect 90k SNP芯片结合集群分离分析法(bulked segregate analysis,BSA)对36个河南省小麦新品系携带的抗白粉病基因进行了定位。SNP芯片检测表明,在24个小麦品系构建的抗、感池DNA间可检测到一个明显富集的SNP峰,表明其可能携带单一主效抗白粉病基因;在其他12个小麦品系构建的抗、感池DNA间可检测到多个SNP峰,推测其可能含多个抗白粉病基因。有26个小麦品系在2AL染色体上检测到的SNP数目最多,推测其携带位于2AL染色体上的Pm4b抗白粉病基因。开发出与2AL染色体上抗白粉病基因紧密连锁的分子标记Xwggc116,可用于这些小麦品系中抗白粉病基因的分子检测。研究结果表明高通量SNP分析技术平台可以用来规模化定位小麦品种中的抗白粉病基因,明确了河南省抗白粉病小麦品系中携带Pm2、Pm4b、Pm21和新1BL/1RS易位等有限的抗白粉病基因,抗病基因资源非常狭窄,亟需引进新的多样化抗病基因资源,拓宽遗传基础,培育抗病小麦新品种。     

黔东南地方玉米品种SSR分子标记指纹图谱构建

利用SSR分子标记技术研究了黔东南地方玉米品种,筛选出48对引物,共检测出309个等位基因变异,每对引物检测出3～12个,平均为6.44个。每个位点的SSR多态信息量(PIC)变化为0.37～0.88,平均为0.70,标记索引系数平均为4.68。21个材料间的遗传相似性系数变化为0.57～0.90,平均为0.68。利用4对多态信息量高的引物建立了21个地方品种的DNA指纹图谱。     

Inheritance of quantitative resistance to downy mildew (Plasmopara halstedii) in sunflower (Helianthus annuus L.)

Quantitative resistance to sunflower downy mildew was studied on inbred lines and hybrids not carrying efficient major gene resistance, in field trials in one to four sites over 3 years. Hybrids from factorial crosses showed that inheritance is under additive control and comparison with reactions of parental inbred lines gave narrow sense heritabilities of 27–57%. Analysis of a polymorphic recombinant inbred line population without efficient major gene resistance indicated that two highly significant Quantitative Trait Loci (QTL) explained 42% of variation in field reaction to downy mildew. These QTL were mapped on linkage groups 8 and 10, and do not appear related to any of the known major resistance gene clusters. Possible bases of this type of resistance and its use in breeding are discussed.