基于混池测序的抗玉米灰斑病QTL定位

玉米灰斑病是由玉米尾孢菌(Cercospora zeine)和玉蜀黍尾孢菌(Cercospora zeae-maydis)引起的真菌性病害,是世界范围内重要的玉米叶部病害之一。以玉米灰斑病抗病自交系Suwan1和感病自交系HM01构建的BC1F1群体为研究材料,在自然发病条件下通过对BC1F1群体中玉米灰斑病的抗性鉴定,选择30株抗病材料和30株感病材料分别构建DNA抗、感混池。在对两个混池进行高通量测序后,通过质量控制和数据分析得到两个极端混池中的变异信息。利用高质量SNP标记对应的两个混池中测序深度差异进行统计检验,成功鉴定了29个玉米灰斑病抗性QTL (quantitative trait loci)。利用MaizeGDB网站在29个抗病QTL内共搜索到2 768个基因,通过Phytozome网站与拟南芥和水稻基因组进行同源比对,在1号、5号和10号染色体上分别确定了1个基因作为抗玉米灰斑病的候选基因。     

大豆灰斑病菌毒素产生条件的研究

大豆灰斑病作为一种世界性的真菌病害,受到国内外植物病理学家与遗传育种界的普遍关注并开展了大量的研究（李海英等,１９９８;杨庆凯等,１９８８）,而有关大豆灰斑病菌毒素的研究国内外报道极少。我所曾利用固体培养基提取毒素（陈绍江等,１９９８）,但由于固体培养基的成分、ＰＨ值、菌丝生长量等难以控制和测定,增加了毒素提纯过程的难度。本试验对大豆灰斑病在液体培养基中毒素产生条件进行了研究,旨在为进一步深人研究该毒素理化特性、致病组分,揭示大豆灰斑病菌的致病机理并利用毒素进行抗原筛选等打下基础。１材料与方法１…     

玉米种质资源抗灰斑病鉴定与评价

2001-2004年,于田间应用人工注射接种的方法对413份玉米自交系和59份玉米杂交种进行抗灰斑病(Gray leaf spot)鉴定,筛选出病级1级高抗(HR)自交系6份、3级抗病(R)自交系28份和杂交种7份.鉴定结果表明,在供试的不同玉米自交系及杂交种间的抗病性存在明显差异,而表现高抗的玉米自交系较少,没有发现高抗杂交种.加强玉米抗灰斑病种质资源的收集和评价,对玉米抗病育种非常必要.     

防治苹果树早期落叶病新菌株筛选

防治苹果树早期落叶病新菌株筛选胡永兰,董德鑫,宗玉丽,张爱玲,邢歧,王志（辽宁省微生物研究所,朝阳１２２０００）苹果树的早期落叶病也称苹果叶斑病,主要包括褐斑病、灰斑病和轮斑病,均属真菌性病害,其危害最严重的是斑。Ｉｓ落叶病,病原菌Ａｆｔ。ｍａｒｉａ...     

大豆的农艺性状与大豆灰斑病抗性关系的初步分析

对大豆灰斑病抗性水平不同的品种资源的农艺性状,包括结荚习性、株型、叶形、花色、茸毛色进行调查分析,结果表明,在灰斑病抗性较好的品种中,分枝型、圆叶、紫花、棕色茸毛的品种所占比率较大,这种现象可供今后灰斑病抗源筛选及抗灰斑病育种参考.     

大豆的农艺性状与大豆灰斑病抗性关系的初步分析

对大豆灰斑病抗性水平不同的品种资源的农艺性状,包括结荚习性、株型、叶形、花色、茸毛色进行调查分析,结果表明,在灰斑病抗性较好的品种中,分枝型、圆叶、紫花、棕色茸毛的品种所占比率较大,这种现象可供今后灰斑病抗源筛选及抗灰斑病育种参考。     

玉米RFLP连锁图谱构建及大斑病QTL定位

玉米大斑病菌存在有生理小种分化的现象,目前5个已定名的生理小种在我国均已发现,还有一些尚未定位名的新类群也出出现,提高玉米对大斑病的抗性,只有提高数量抗性才能达到目的,为了弄清楚玉米对大斑病数量抗性的基因数目及效效应,利用抗病自交5系P138和感病自交系缩3为亲本构建了F2：3家系群体,采用RFLP标记构建了包含了124个标记的玉米RFLP连锁图,覆盖玉米基因组1999．8cM,标记间平均距离为16．5cM,定位了玉米大斑病的病斑长,病斑宽和病斑面积的QTL分别为3、3、2个,其联合贡献率分别为58．1％、71．5％和27．5％,没有检测到病斑数／叶的QTL,其表现为单基因或者寡基因控制的性状,研究结果增加了对玉米大斑病的认识,对玉米抗大斑病育种具有重要的指导意义。     

本期重点推介

正灰飞虱Laodelphax striatellus是亚洲地区重要的农业害虫,除以刺吸危害水稻、大麦、小麦、玉米等多种经济作物外,还能传播水稻黑条矮缩病、水稻条纹叶枯病、小麦丛矮病及玉米粗缩病等多种病毒病害,造成作物产量的巨大损失。昆虫体内具有复杂的微生物群落,在昆虫生长发育及繁殖过程中发挥重要的作用,是害虫防治中可开发利用的一类重要资源。为了掌握灰飞虱体内细菌型微生物的资源状况,为后续     

扬彩防治玉米大、小斑病和灰斑病示范报告

扬彩200SE+福戈WG70ml+8g/亩对玉米螟的防控效果可达90%以上,在玉米大斑病、灰斑病和玉米螟发生较重的地块,推荐施用扬彩200SE+福戈WG70ml+8g/亩,有明显的防病防虫增产效果。     

两种葡萄孢属真菌对不同品种百合花瓣和叶片的侵染能力比较

为明确两种葡萄孢属真菌对不同百合品种叶片和花瓣的侵染能力,采用离体叶片接种法测定灰葡萄孢Botrytis cinerea和椭圆葡萄孢Botrytis elliptica对4个百合品种叶片和花瓣的侵染时间和病斑扩展速度。结果表明,供试百合花瓣接种灰葡萄孢病斑出现时间明显早于叶片,而不同品种花瓣接种椭圆葡萄孢病斑出现时间差异显著。此外,百合品种‘木门’叶片接种椭圆葡萄孢96 h后仍没有病斑出现,而花瓣接种后48 h病斑出现,说明‘木门’叶片对椭圆葡萄孢抗性较强,而花瓣较易感病。     

High-density mapping for gray leaf spot resistance using two related tropical maize recombinant inbred line populations

Molecular Biology Reports - Gray leaf spot (GLS) caused by Cercospora zeae-maydis or Cercospora zeina is one of the devastating maize foliar diseases worldwide. Identification of GLS-resistant...     

Bayesian inference to study genetic control of resistance to gray leaf spot in maize

Gray leaf spot (GLS) is a major maize disease in Brazil that significantly affects grain production. We used Bayesian inference to investigate the nature and magnitude of gene effects related to GLS resistance by evaluation of contrasting lines and segregating populations. The experiment was arranged in a randomized block design with three replications and the mean values were analyzed using a Bayesian shrinkage approach. Additive-dominant and epistatic effects and their variances were adjusted in an over-parametrized model. Bayesian shrinkage analysis showed to be an excellent approach to handle complex models in the study of genetic control in GLS, since this approach allows to handle overparametrized models (main and epistatic effects) without using model-selection methods. Genetic control of GLS resistance was predominantly additive, with insignificant influence of dominance and epistasis effects.     

Targeted discovery of quantitative trait loci for resistance to northern leaf blight and other diseases of maize

To capture diverse alleles at a set of loci associated with disease resistance in maize, heterogeneous inbred family (HIF) analysis was applied for targeted QTL mapping and near-isogenic line (NIL) development. Tropical maize lines CML52 and DK888 were chosen as donors of alleles based on their known resistance to multiple diseases. Chromosomal regions (“bins”; n = 39) associated with multiple disease resistance (MDR) were targeted based on a consensus map of disease QTLs in maize. We generated HIFs segregating for the targeted loci but isogenic at ~97% of the genome. To test the hypothesis that CML52 and DK888 alleles at MDR hotspots condition broad-spectrum resistance, HIFs and derived NILs were tested for resistance to northern leaf blight (NLB), southern leaf blight (SLB), gray leaf spot (GLS), anthracnose leaf blight (ALB), anthracnose stalk rot (ASR), common rust, common smut, and Stewart’s wilt. Four NLB QTLs, two ASR QTLs, and one Stewart’s wilt QTL were identified. In parallel, a population of 196 recombinant inbred lines (RILs) derived from B73 × CML52 was evaluated for resistance to NLB, GLS, SLB, and ASR. The QTLs mapped (four for NLB, five for SLB, two for GLS, and two for ASR) mostly corresponded to those found using the NILs. Combining HIF- and RIL-based analyses, we discovered two disease QTLs at which CML52 alleles were favorable for more than one disease. A QTL in bin 1.06–1.07 conferred resistance to NLB and Stewart’s wilt, and a QTL in 6.05 conferred resistance to NLB and ASR.     

Resistance to Gray Leaf Spot of Maize: Genetic Architecture and Mechanisms Elucidated through Nested Association Mapping and Near-Isogenic Line Analysis

Gray leaf spot (GLS), caused by Cercospora zeae-maydis and Cercospora zeina, is one of the most important diseases of maize worldwide. The pathogen has a necrotrophic lifestyle and no major genes are known for GLS. Quantitative resistance, although poorly understood, is important for GLS management. We used genetic mapping to refine understanding of the genetic architecture of GLS resistance and to develop hypotheses regarding the mechanisms underlying quantitative disease resistance (QDR) loci. Nested association mapping (NAM) was used to identify 16 quantitative trait loci (QTL) for QDR to GLS, including seven novel QTL, each of which demonstrated allelic series with significant effects above and below the magnitude of the B73 reference allele. Alleles at three QTL, qGLS1.04, qGLS2.09, and qGLS4.05, conferred disease reductions of greater than 10%. Interactions between loci were detected for three pairs of loci, including an interaction between iqGLS4.05 and qGLS7.03. Near-isogenic lines (NILs) were developed to confirm and fine-map three of the 16 QTL, and to develop hypotheses regarding mechanisms of resistance. qGLS1.04 was fine-mapped from an interval of 27.0 Mb to two intervals of 6.5 Mb and 5.2 Mb, consistent with the hypothesis that multiple genes underlie highly significant QTL identified by NAM. qGLS2.09, which was also associated with maturity (days to anthesis) and with resistance to southern leaf blight, was narrowed to a 4-Mb interval. The distance between major leaf veins was strongly associated with resistance to GLS at qGLS4.05. NILs for qGLS1.04 were treated with the C. zeae-maydis toxin cercosporin to test the role of host-specific toxin in QDR. Cercosporin exposure increased expression of a putative flavin-monooxygenase (FMO) gene, a candidate detoxification-related gene underlying qGLS1.04. This integrated approach to confirming QTL and characterizing the potential underlying mechanisms advances the understanding of QDR and will facilitate the development of resistant varieties.     

QTL mapping of resistance to gray leaf spot in ryegrass

Gray leaf spot (GLS) is a serious fungal disease caused by Magnaporthe grisea, recently reported on perennial ryegrass (Lolium perenne L.), an important turfgrass and forage species. This fungus also causes rice blast and many other grass diseases. Rice blast is usually controlled by host resistance, but durability of resistance is a problem. Little GLS resistance has been reported in perennial ryegrass. However, greenhouse inoculations in our lab using one ryegrass isolate and one rice-infecting lab strain suggest presence of partial resistance. A high density linkage map of a three generation Italian × perennial ryegrass mapping population was used to identify quantitative trait loci (QTL) for GLS resistance. Potential QTL of varying effect were detected on four linkage groups, and resistance to the ryegrass isolate and the lab strain appeared to be controlled by different QTL. Of three potential QTL detected using the ryegrass isolate, the one with strongest effect for resistance was located on linkage group 3 of the MFB parent, explaining between 20% and 37% of the phenotypic variance depending on experiment. Another QTL was detected on linkage group 6 of the MFA parent, explaining between 5% and 10% of the phenotypic variance. The two QTL with strongest effect for resistance to the lab strain were located on linkage groups MFA 2 and MFB 4, each explaining about 10% of the phenotypic variance. Further, the QTL on linkage groups 3 and 4 appear syntenic to blast resistance loci in rice. This work will likely benefit users and growers of perennial ryegrass, by setting the stage for improvement of GLS resistance in perennial ryegrass through marker-assisted selection.     

Fine mapping of a quantitative resistance gene for gray leaf spot of maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) derived from teosinte (<Emphasis Type="Italic">Z. mays</Emphasis> ssp. <Emphasis Type="Italic">parviglumis</Emphasis>)

Key message

In this study we mapped the QTL Qgls8 for gray leaf spot (GLS) resistance in maize to a ~130 kb region on chromosome 8 including five predicted genes.

Abstract

In previous work, using near isogenic line (NIL) populations in which segments of the teosinte (Zea mays ssp. parviglumis) genome had been introgressed into the background of the maize line B73, we had identified a QTL on chromosome 8, here called Qgls8, for gray leaf spot (GLS) resistance. We identified alternate teosinte alleles at this QTL, one conferring increased GLS resistance and one increased susceptibility relative to the B73 allele. Using segregating populations derived from NIL parents carrying these contrasting alleles, we were able to delimit the QTL region to a ~130 kb (based on the B73 genome) which encompassed five predicted genes.

     

QTL mapping for resistance of maize to grey leaf spot

Grey leaf spot (GLS) is a global maize leaf disease that seriously endangers maize production. Discovering and utilizing genetic loci for GLS resistance would be useful for breeding new varieties with improved resistance. In this study, 233 F_2:3 families (produced from the susceptible inbred line 08‐641 × the resistant inbred line 446) were used for quantitative trait locus (QTL) mapping of resistance to GLS. Five GLS resistance QTLs were detected on chromosomes 1, 2, 3, 4, and 6, which explained 6.7%‐21.3% of the phenotypic variation. The QTLs, qRgls.CH‐4, qRgls.CH‐1, qRgls.CH‐2, and qRgls.CH‐6, were stably expressed in the four environments, and all loci for GLS resistance were derived from the resistant parent, 446. The additive effects of qRgls.CH‐4, qRgls.CH‐1, and qRgls.CH‐6 were significantly greater than their single dominant effects, which may be beneficial for GLS resistance breeding. The QTL qRgls.CH‐6, located in bins 6.02–6.05, did not overlap with any previously reported resistance QTL and thus was identified here for the first time. QTL analysis of PI (leaf performance index) detected three leaf function QTLs on chromosomes 4, 8, and 9 were related to GLS resistance and explained 4.8%‐6.2% of the phenotypic variation. Among them, qPI.CH‐4 was significantly stronger expressed in several environments; this allele associated with increased leaf function came from the resistant parent, 446, and its interval overlapped with that of qRgls.CH‐4. Furthermore, both qRgls.CH‐4 and qPI.CH‐4 were located in a hotspot area for GLS resistance in bins 4.05‐4.06, indicating that GLS resistance was significantly related to leaf performance and that GLS significantly reduced leaf photosynthetic performance.     

Genetic gain and cost efficiency of marker-assisted selection of maize for improved resistance to multiple foliar pathogens

Northern corn leaf blight (NCLB) caused by Exserohilum turcicum, gray leaf spot (GLS) caused by Cercospora zeae-maydis and maize streak caused by maize streak Mastrevirus (MSV) are the most destructive foliar diseases limiting maize production in sub-Saharan Africa. Most foliar diseases of maize are managed using quantitative (partial) resistance, and previous studies have reported quantitative trait loci associated with host resistance (rQTL). Our objective was to compare the genetic gain and costs resulting from phenotypic, genotypic, and marker-assisted selection of partially inbred lines derived from many families for resistance to infection by three foliar pathogens. We developed a population of 410 F2:3 families by crossing inbred line CML202 with a breeding line designated VP31. These families were planted in nurseries inoculated separately with each pathogen. We conducted one cycle of early generation pedigree selection using three different procedures, phenotypic, genotypic, and marker/phenotypic index, for improvement of resistance to each pathogen. We used simple sequence repeat (SSR) markers flanking six target rQTL associated with partial resistance. Broad- and narrow-sense heritability estimates were also obtained for the F2:3 families, and selected and non-selected F2:4 families. Genetic gains resulting from the selection procedures were determined. Gene action of the candidate rQTL was determined using orthogonal contrasts. Estimates of costs based on lower boundary values indicated that the cost of marker-based selection was lower than that of phenotypic selection. Our results indicate that molecular markers linked to target rQTL can facilitate pyramiding resistance to multiple diseases during early generation pedigree selection.