Relationship between Loci conferring downy mildew and powdery mildew resistance in melon assessed by quantitative trait Loci mapping

ABSTRACT Partial resistance to downy mildew (Pseudoperonospora cubensis) and complete resistance to powdery mildew (Podosphaera xanthii races 1, 2, 3, and 5 and Golovinomyces cichoracearum race 1) were studied using a recombinant inbred line population between 'PI 124112' (resistant to both diseases) and 'Védrantais' (susceptible line). A genetic map of melon was constructed to tag these resistances with DNA markers. Natural and artificial inoculations of Pseudoperonospora cubensis were performed and replicated in several locations. One major quantitative trait loci (QTL), pcXII.1, was consistently detected among the locations and explained between 12 to 38% of the phenotypic variation for Pseudoperonospora cubensis resistance. Eight other Pseudoperonospora cubensis resistance QTL were identified. Artificial inoculations were performed with several strains of four races of Podosphaera xanthii and one race of G. cichoracearum. Two independent major genes, PmV.1 and PmXII.1, were identified and shown to be involved in the simple resistance to powdery mildew. Three digenic epistatic interactions involving four loci were detected for two races of Podosphaera xanthii and one race of G. cichoracearum. Co-localization between PmV.1, resistance genes, and resistance genes homologues was observed. Linkage between the major resistance QTL to Pseudoperonospora cubensis, pcXII.1, and one of the two resistance genes to powdery mildew, PmXII.1, was demonstrated.     

Quantitative trait loci for adult-plant resistance to Mycosphaerella graminicola in two winter wheat populations

Septoria tritici blotch (STB) is one of the most important leaf spot diseases in wheat worldwide. The goal of this study was to detect chromosomal regions for adult-plant resistance in large winter wheat populations to STB. Inoculation by two isolates with virulence to Stb6 and Stb15, both present in the parents, was performed and STB severity was visually scored plotwise as percent coverage of flag leaves with pycnidia-bearing lesions. 'Florett'/'Biscay' and 'Tuareg'/'Biscay', each comprising a cross of a resistant and a susceptible cultivar, with population sizes of 316 and 269 F(7:8) recombinant inbred lines, respectively, were phenotyped across four and five environments and mapped with amplified fragment length polymorphism, diversity array technology, and simple sequence repeat markers covering polymorphic regions of ≈1,340 centimorgans. Phenotypic data revealed significant (P < 0.01) genotypic differentiation for STB, heading date, and plant height. Entry-mean heritabilities (h(2)) for STB were 0.73 for 'Florett'/'Biscay' and 0.38 for 'Tuareg'/'Biscay'. All correlations between STB and heading date as well as between STB and plant height were low (r = -0.13 to -0.20). In quantitative trait loci (QTL) analysis, nine and six QTL were found for STB ratings explaining, together, 55 and 51% of phenotypic variation in 'Florett'/'Biscay' and 'Tuareg'/'Biscay', respectively. Genotype-environment and QTL-environment interactions had a large impact. Two major QTL were detected consistently across environments on chromosomes 3B and 6D from 'Florett' and chromosomes 4B and 6B from 'Tuareg', each explaining 12 to 17% of normalized adjusted phenotypic variance. These results indicate that adult-plant resistance to STB in both mapping populations was of a quantitative nature.     

Quantitative trait Loci mapping of resistance to sugarcane mosaic virus in maize

ABSTRACT Sugarcane mosaic virus (SCMV) is an important virus disease of maize (Zea mays) in Europe. In this study, we mapped and characterized quantitative trait loci (QTL) affecting resistance to SCMV in a maize population consisting of 219 F(3) or immortalized F(2) families from the cross of two European maize inbreds, D32 (resistant) x D145 (susceptible). Resistance was evaluated in replicated field trials across two environments under artificial inoculation. The method of composite interval mapping was employed for QTL detection with a linkage map based on 87 restriction fragment length polymorphism and 7 mapped microsatellite markers. Genotypic and genotype x environment interaction variances for SCMV resistance were highly significant in the population. Heritabilities ranged from 0.77 to 0.94 for disease scores recorded on seven consecutive dates. Five QTL for SCMV resistance were identified on chromosomes 1, 3, 5, 6, and 10 in the joint analyses. Two major QTL on chromosomes 3 and 6 were detected consistently in both environments. Significant epistatic effects were found among some of these QTL. A simultaneous fit with all QTL in the joint analyses explained between 70 and 77% of the phenotypic variance observed at various stages of plant development. Resistance to SCMV was correlated with plant height and days to anthesis.     

Evaluation and QTL mapping of resistance to powdery mildew in lettuce

Lettuce (Lactuca sativa) is the major leafy vegetable that is susceptible to powdery mildew disease under greenhouse and field conditions. Quantitative trait loci (QTLs) for resistance to powdery mildew under greenhouse conditions were mapped in an interspecific population derived from a cross between susceptible L. sativa cultivar Salinas and the highly susceptible L. serriola accession UC96US23. Four significant QTLs were detected on linkage groups LG 1 (pm‐1.1), LG 2 (pm‐2.1 and pm‐2.2) and LG 7 (pm‐7.1), each explaining between 35 to 42% of the phenotypic variation. The four QTLs are not located in the documented hotspots of lettuce resistance genes. Alleles for the disease resistance at the four QTLs originated from both parents (two from each), demonstrating that even highly susceptible accessions may provide alleles for resistance to powdery mildew. These QTLs appeared to operate during limited periods of time. Results of the field trials with F_2:3 and F_3:4 families derived from a Soraya (moderately resistant) × Salinas cross demonstrated effective transfer of resistance to powdery mildew in this material. An integrated rating approach was used to estimate relative levels of resistance in 80 cultivars and accessions tested in a total of 23 field and greenhouse experiments. Generally, very low resistance was observed in crisphead‐type lettuces, while the highest relative resistance was recorded in leaf and butterhead types. Comparison of two disease assessment methods (percentage rating and the area under the disease progress steps, AUDPS) for detection of QTLs shows that the two approaches complement each other.     

Field assessment of resistance to powdery mildew in mature wheat plants

Rankit transformation of mildew scores was used in regression analyses to compare the times and methods of scoring resistance. This showed that time and method of assessment significantly altered the relative rank positions of different cultivars. Examination of 10 cultivars in detail showed that changes in rank were associated with differences in organ resistance.
Whole plot assessments based on a 0–9 scale provided a rapid and reliable means of ranking cultivars. Where possible, and particularly for breeders, at least two assessments are recommended, the first at or soon after flowering to estimate foliar infection, and the second 2 or 3 weeks later to estimate ear infection. For general comparisons of cultivars, sufficient information may be acquired from a single assessment when all plant organs are present and when the disease has had time to become well established.     

小麦新品系抗白粉病基因分析

 本文对6个小麦新品系所含的抗白粉病基因进行了遗传分析。将感病品种Liaochun10分别与SM 20121、SM 203390、SM 20125、SM 200332、SM 20126、SM 20005杂交和自交,并将这6个品系互配成半双列杂交组合。用小麦白粉菌15号小种的单孢堆菌系对各杂交组合的亲本、F₁、F₂代群体及F₃代家系进行了苗期抗病性鉴定。遗传分析表明,供试的6个品系对小麦白粉菌15号小种的抗性均由1对显性基因控制。等位性分析推断:SM 20121、SM 203390、SM 20125和SM 200332含有抗白粉病基因Pm12;SM 20126含有抗白粉病基因Pm21;SM 20005含有抗白粉病基因Pm16。建议将这6个品系作为优良抗病亲本利用。     

Quantitative trait loci for high-temperature adult-plant and slow-rusting resistance to Puccinia striiformis f. sp. tritici in wheat cultivars

Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most damaging diseases of wheat (Triticum aestivum) globally. High-temperature adult-plant resistance (HTAPR) and slow-rusting have great potential for sustainable management of the disease. The wheat cultivars Luke and Aquileja have been previously reported to possess HTAPR and slow-rusting to stripe rust, respectively. Aquileja displayed less number of stripes per unit leaf area than Luke, while Luke showed lower infection type than Aquileja at adult-plant stages of growth under high-temperature conditions. The objectives of this study were to confirm the resistances and to map the resistance genes in Luke and Aquileja. Luke was crossed with Aquileja, and 326 of the F(2) plants were genotyped using 282 microsatellite primer pairs. These F(2) plants and their derived F(3) families were evaluated for resistance to stripe rust by inoculation in the fields and greenhouses of high- and low-temperatures. Infection type was recorded for both seedlings and adult plants, and stripe number was recorded for adult plants only. Two quantitative trait loci (QTL) were identified, on the short arm of chromosome 2B, to be significantly associated with infection type at adult-plant stages in the fields and in the high-temperature greenhouse. The locus distal to centromere, referred to as QYrlu.cau-2BS1, and the locus proximal to centromere, referred to as QYrlu.cau-2BS2, were separated by a genetic distance of about 23 cM. QYrlu.cau-2BS1 was flanked by the microsatellite markers Xwmc154 and Xgwm148, and QYrlu.cau-2BS2 was flanked by Xgwm148 and Xabrc167. QYrlu.cau-2BS1 and QYrlu.cau-2BS2 explained up to 36.6 and 41.5% of the phenotypic variation of infection type, respectively, and up to 78.1% collectively. No significant interaction between the two loci was detected. Another QTL, referred to as QYraq.cau-2BL, was detected on the long arm of chromosome 2B to be significantly associated with stripe number. QYraq.cau-2BL was flanked by the microsatellite markers Xwmc175 and Xwmc332, and it explained up to 61.5% of the phenotypic variation of stripe number. It is possible that these three QTL are previously unmapped loci for resistance to stripe rust.     

A major gene for powdery mildew resistance transferred to common wheat from wild einkorn wheat

ABSTRACT A major gene for resistance to wheat powdery mildew (Blumeria graminis f. sp. tritici = Erysiphe graminis f. sp. tritici) has been successfully transferred into hexaploid common wheat (Triticum aestivum, 2n = 6x = 42, AABBDD) from wild einkorn wheat (Triticum monococcum subsp. aegilopoides, 2n = 2x = 14, AA). NC96BGTA5 is a germ plasm line with the pedigree Saluda x 3/PI427662. The response patterns for powdery mildew resistance in NC96BGTA5 were tested with 30 differential isolates of B. graminis f. sp. tritici, and the line was resistant to all tested isolates. The analyses of P(1), P(2), F(1), F(2), and BC(1)F(1) populations derived from NC96BGTA5 revealed two genes for wheat powdery mildew resistance in the NC96BGTA5 line. One gene, Pm3a, was from its recurrent parent Saluda, and the second was a new gene introgressed from wild einkorn wheat. The gene was determined to be different from Pm1 to Pm21 by gene-for-gene and pedigree analyses. The new gene was identified as linked to the Pm3a gene based on the F(2) and BC(1)F(1) populations derived from a cross between NC96BGTA5 and a susceptible cultivar NK-Coker 68-15, and the data indicated that the gene was located on chromosome 1A. It is proposed that this new gene be designated Pm25 for wheat powdery mildew resistance in NC96BGTA5. Three random amplified polymorphic DNA markers, OPX06(1050), OPAG04(950), and OPAI14(600), were found to be linked to this new gene.     

某些小麦品种抗白粉性遗传研究简报

 小麦白粉病近年在我省各地普遍发生,造成一定损失,研究明确主要品种抗白粉性的遗传行为,提高抗白粉小麦育种的效能,是一项急待开展的工作。本文简述了1983-1985年间我们对4个抗原品种在田间接种下进行抗白粉遗传研究的部分结果。     

三个小麦农家品种的苗期抗白粉病遗传分析

[目的]对3份小麦农家品种‘矮秆芒麦’、‘红头麦’和‘大红头’进行苗期抗性的遗传分析,研究它们的抗白粉病遗传特点,为其在抗病育种中的有效利用提供依据.[方法]将这3份小麦农家品种分别与感病品种‘铭贤169’正、反杂交,获得了F1和F2代.利用白粉菌E09菌株,分别对这3份农家品种、感病亲本‘铭贤169’以及各自的F1和F2代植株进行抗性鉴定.调查统计的数据经卡方测验分析其符合度.[结果]这3份农家品种对白粉菌E09菌株的抗性均由1对隐性核基因控制.[结论]3份农家品种对石家庄本地区的混合白粉病菌表现出良好的抗性,并且对E09的抗性均由1对隐性基因控制.可以进一步对它们进行分子标记及定位研究,为其作为抗源在小麦抗白粉病育种中的应用奠定基础.     

小麦慢白粉品种的抗性组分研究

 2003~2004年度和2004~2005年度在田间测定了16个小麦品种(系)对小麦白粉菌E20菌株的抗性组分,包括潜育期、侵染几率、产孢量、病斑扩展和传染期。结果表明,小麦慢白粉品种(系)与高感对照品种相比,表现为潜育期长、侵染几率低、产孢量低、病斑扩展慢的特点,且这4个抗性组分与对照的差异都达到了显著和极显著水平,但慢白粉品种的传染期变化无一定规律。参试慢白粉品种的抗性组分参数与病情曲线下面积(AUDPC)的相关分析表明,潜育期与AUDPC呈负相关,但相关性不显著;产孢量和病斑扩展与AUDPC呈正相关,两年数据相关性均达到显著水平;侵染几率与AUDPC呈正相关,但2003-2004年度相关性不显著,而2004~2005年度相关性显著;传染期与AUDPC相关关系不明显。由此可见,在慢白粉品种的病害流行中起主要作用的是产孢量、病斑扩展,而侵染几率、潜育期和传染期作用相对较小。     

山西小麦品种和育种材料抗锈病、白粉病鉴定

2011—2015年,采用人工接菌方法,对25个育种单位的601份小麦品种和育种材料进行了小麦条锈病、叶锈病和白粉病的抗病性鉴定,筛选出对小麦条锈病抗性表现良好的品种材料36份,对小麦叶锈病抗性表现良好的品种材料16份,对小麦白粉病抗性表现良好的品种材料12份。     

50个小麦生产及后备品种(系)的抗白粉病基因推导

为明确我国小麦品种(系)中抗白粉病基因的组成,利用25个不同毒性的小麦白粉菌菌株对50个小麦生产及后备品种(系)进行抗白粉病基因推导,结果表明,参试的50个小麦品种(系)中有8个小麦品种(系)对供试的25个菌株全部感病,5个品种含有抗病基因Pm8,2个品种含有Pm4a,9个品种含有Pm2+6,4个品种含有Pm2,22个品种(系)可能含有供试基因之外的其他抗性基因或新基因。此研究结果可为小麦抗病育种以及品种利用提供依据。     

Ontogenic resistance to powdery mildew in grape berries

ABSTRACT Berries of Vitis vinifera are reported to be susceptible to infection by Uncinula necator until soluble solids levels (brix) reach 8%, and established colonies are reported to sporulate until brix reach 15%. However, our analysis of disease progress on fruit of selected V. vinifera cultivars indicated that severity became asymptotic several weeks earlier in fruit development. When mildew-free fruit clusters of V. vinifera 'Chardonnay', 'Riesling', 'Gewürztraminer', and 'Pinot Noir' were inoculated at stages ranging from prebloom to 6 weeks postbloom, only fruit inoculated within 2 weeks of bloom developed severe powdery mildew. Substantial ontogenic resistance to infection was expressed in fruit nearly 6 weeks before fruit brix reached 8% and over 2 months before they reached 15%. Rachises of 'Chardonnay' and 'Riesling' fruit clusters developed severe powdery mildew when inoculated at bloom, and disease increased steadily over the next 60 days. The rachis of fruit clusters inoculated 31 days after bloom developed only trace levels of powdery mildew. Berry weight of all four cultivars at harvest was reduced when fruit clusters were inoculated at bloom or 16 days postbloom, primarily by splitting, rotting, and dehydration of mildewed berries, but the weight of later-inoculated berries was not reduced. Inoculation of berries just as ontogenic resistance increased markedly, approximately 3 to 4 weeks postbloom, resulted in the development of inconspicuous, diffuse, non-sporulating mildew colonies on berries, sometimes associated with a network of necrotic epidermal cells. Rather than a protracted and relatively static period of berry susceptibility lasting 3 months, fruit of V. vinifera appear to acquire ontogenic resistance rapidly after fruit set. A refocusing of disease management on this critical period of high fruit susceptibility should greatly improve the efficacy of fungicides directed against powdery mildew.     

天水市小麦品种系抗白粉病性鉴定

1999～2001年,在抗病性观察圃,利用常规的抗病性鉴定方法,对29份大田主栽冬小麦品种进行抗白粉性鉴定。结果表明,不同小麦品种系对白粉病抗、感性存在明显差异。高抗、中抗、中感及高感的品种系分别占参试材料的13.8%、58.6%、10.3%及17.2%。其中中88375、中85130、蓝天3号、清山895等4个品种系对小麦白粉病连续2a以上表现出稳定的抗性。     

普通小麦“兰考90(6)”品系对白粉病抗性的遗传研究

 普通小麦(Triticum aestivum L.)"兰考90(6)"系列品系是以六倍体小黑麦(X Triticosecale Wittmack;AABBRR)为白粉病抗源培育的新的小麦-黑麦1BL/1RS异易位系。这些品系高抗白粉病。小麦白粉病抗性基因推导试验证明,"豫麦66"携带的抗病基因与大多数已经报道的小麦抗白粉病基因不同。用白粉菌[Blumeria graminis (DC.) E. O. Speer f. sp. tritici]单孢堆分离物进行的遗传分析表明,"兰考90(6)"品系携带一个小种专化的隐性抗白粉病基因。对"中国春"和"兰考90(6)21-12"杂交F₂分离群体进行1RS染色体检测,结果证明该抗白粉病基因不在1RS染色体臂上。本研究为有效利用"兰考90(6)"系列品系中的抗白粉病基因提供了科学依据。     

Mining wild barley for powdery mildew resistance

Powdery mildew, caused by Blumeria graminis f. sp. hordei (Bgh), is a worldwide disease problem on barley (Hordeum vulgare) with potentially severe impact on yield. Historically, resistance genes have been identified chiefly from cultivated lines and landraces; however, wild barley (H. vulgare subsp. spontaneum) accessions have proven to be extraordinarily rich sources of powdery mildew resistance. This study describes the characterization of a collection of 316 wild barley accessions, known as the Wild Barley Diversity Collection (WBDC), for resistance to powdery mildew and the genetic location of powdery mildew resistance loci. The WBDC was phenotyped for reaction to 40 different Bgh isolates at the seedling stage and genotyped with 10 508 molecular markers. Accessions resistant to all 40 isolates of Bgh were not found; however, three accessions (WBDC 053, 085 and 089) exhibited resistance to 38 of the isolates. Gene postulation analyses revealed that many accessions, while resistant, contained none of the 12 genes present in the Pallas near‐isogenic lines Mla1, Mla3, Mla6, Mla7, Mla9, Mla12, Mla13, Mlk1, MlLa, Mlg, Mlat and Ml(Ru2), suggesting that the accessions carry novel genes or gene combinations. A genome‐wide association study of powdery mildew resistance in the WBDC identified 21 significant marker‐trait associations that resolved into 15 quantitative trait loci. Seven of these loci have not been previously associated with powdery mildew resistance. Taken together, these results demonstrate that the WBDC is a rich source of powdery mildew resistance, and provide genetic tools for incorporating the resistance into barley breeding programmes.     

61个小麦后备品种对白粉病的抗性分析及抗病基因推导

为明确中国61个小麦后备品种对白粉病的抗性水平及其抗病基因,将2016年从黄淮海冬麦区、长江中下游冬麦区及东北春麦区的9个市采集分离的269株单孢子堆白粉病菌,分别接种于61个小麦后备品种进行抗性测定;用NTSYSpc 2.10e软件对供试品种表型数据进行聚类分析;用35株鉴别菌株对29个含已知抗白粉病基因小麦材料和61个小麦后备品种进行鉴别,比较其抗谱并推导61个小麦后备品种所含抗白粉病基因。结果显示,61个小麦后备品种间的抗谱存在明显差异,国豪麦5号和7号、BL5008、绵麦系列、黔麦系列、楚麦16号、内麦101和366等18个品种抗谱较宽,抗性频率均大于97.0%;泰科麦5303、邯11-5272和临Y8222等10个品种的抗性频率在42.0%～56.1%之间;郑麦0943等33个品种的抗性频率小于37.9%。聚类分析可将61个小麦后备品种分成5大类,第I类有11个品种,其中8个品种的抗性频率在42.0%～56.1%之间;第II类和第III类共30个品种,抗性频率均小于32.7%;第IV类有2个品种,抗性频率分别为53.5%和53.2%,第V类有18个品种,抗性频率均大于97.0%;聚类显示来自于同一地区且抗性频率相近的品种具有相似或相近的抗性遗传背景。本研究推导出21个小麦后备品种含抗病Pm基因,其中,邯11-5272含有Pm30,安科1503含有Pm2、Pm5a、Pm6、Pm19和Pm30,临Y8222含有Pm5a、Pm6、Pm19和Pm30,云154-15含有Pm5a、Pm6、Pm7、Pm19和Pm2+ta,泰科麦5303等6个品种含有Pm2和Pm30,华麦7号等5个品种含有Pm5a、Pm6和Pm19,扬麦24号等6个品种含有Pm5a、Pm6、Pm19和Pm2+ta。研究表明,54.1%的小麦后备品种对白粉病菌群的抗性频率小于37.9%,存在适宜条件下小麦白粉病暴发流行的风险,因此这些小麦后备品种推广种植时需加强病害预警和监测。     

Quantitative trait Loci associated with resistance to gray leaf spot of corn

ABSTRACT The susceptible parent FR1141, the resistant parent 061, the F1 cross, and 301 families selfed once from backcrosses to the susceptible parent were evaluated for gray leaf spot (GLS) severity for two years in Urbana, IL, and one year in Andrews, NC. Linkage between ear height and GLS severity was suspected. Therefore, plant height characteristics were noted for two years in Urbana, IL. Eighty-six polymorphic probes were used to construct a random fragment length polymorphism linkage map, and the presence, locations, effects, and interactions of quantitative trait loci (QTL) associated with GLS, plant and ear height were determined. Five QTL were significantly associated with GLS resistance across all environments and rating periods. These five regions are associated with additive effects on phenotype and account for between 51.0 and 58.7% of the phenotypic variation associated with GLS severity. Additionally, six QTL were identified with maturity-dependent associations to GLS severity. Heritability of GLS resistance was estimated to be approximately 0.73. Four QTL were identified with associations to ear height relative to total plant height. One of the four was associated with higher ear height and GLS resistance.     

小麦抗白粉病基因Pm2的SSR标记筛选

为筛选与小麦抗白粉病基因Pm2紧密连锁的分子标记,将感病品种Chancellor与Pm2的近等基因系杂交,获得F1、F2分离群体,采用分离群体分组法对Pm2进行了微卫星(microsatellite,又称simple sequence repeats,SSR)标记分析.结果表明,定位于小麦5D染色体上的71对SSR引物中有12对引物能在Pm2的近等基因系、Chancellor间稳定地揭示出多态性差异,7对引物Xcfd189、Xcfd29、Xcfd8、Xcfd102、Xcfd7、Xcfd57和Xgwm190分别能在抗病、感病池间和F2分离群体的抗病、感病单株间稳定地扩增出特异性产物.7对引物所扩增的特异谱带分别为:Xcfd189360、Xcfd29190、Xcfd8160、Xcfd102250、Xcfd7200、Xcfd57245和Xgwm190210,它们与Pm2基因间的遗传距离分别为0、1.5、2.3、5.4、10.2、31.5和54.3 cM,其中标记Xcfd189360与Pm2共分离,标记Xcfd29190、Xcfd8160和Xcfd102250与Pm2紧密连锁,可用于Pm2的标记辅助选择.