Effects of environment, disease progress, plant height and heading date on the detection of QTLs for resistance to Fusarium head blight in an European winter wheat cross

In order to characterise quantitative trait loci (QTLs) for Type I and Type II resistance against Fusarium head blight (FHB) in wheat, a population of recombinant inbred lines derived from the cross Cansas (moderately resistant)/Ritmo (susceptible) was evaluated in spray-inoculated field trials over three seasons. Map-based QTL analysis across environments revealed seven QTLs on chromosomes 1BS, 1DS, 3B, 3DL, 5BL, 7BS and 7AL (QFhs.whs-1B, QFhs.whs-1D, QFhs.whs-3B, QFhs.whs-3D, QFhs.whs-5B, QFhs.whs-7A, QFhs.whs-7B) associated with FHB resistance. They accounted for 56% of the phenotypic variance. QFhs.whs-1D primarily appeared to be involved in resistance to fungal penetration, whereas the other QTLs mainly contributed to resistance to fungal spread. FHB resistance was significantly correlated with plant height (PH) and heading date (HD). Including all single environments, corresponding overlaps of QTLs for FHB resistance and QTLs for PH/HD occurred at six loci, among them two consistently detected QTLs, QFhs.whs-5B and QFhs.whs-7A. When significant effects of PH and HD on FHB resistance were eliminated by covariance analysis, a second QTL analysis revealed possible escape mechanisms for the majority of the coincidental loci.     

Gene-for-gene relationship for resistance in wheat to isolates of Karnal bunt, Neovossia indica

Reactions to eight isolates of Karnal bunt, Neovossia indica, collected from seven different locations in northern India were studied on 13 host lines, including cultivars and breeding lines of Triticum aestivum, Triticum durum and Triticosecale in all possible combinations. The incidence of Karnal bunt varied from zero in PBW 34 and PBW 248 with isolates Ni8 and Ni2, respectively, to as high as 66.8% in a highly susceptible cultivar WL 711 with isolate Ni5. The differences in disease incidence among cultivars and isolates were highly significant. All the isolates could be distinguished on the basis of differential reactions on one or more of the host lines. Even the most resistant lines of durum (PDW 215), triticale (TL 1210) and wheat (HD 29) could be distinguished by the differential disease reaction with one or more of the eight isolates. The cultivar-isolate interaction for disease score was highly significant, indicating the probable existence of a gene-for-gene relationship in this host-pathogen system.     

QTL mapping of sheath blight resistance in a deep-water rice cultivar

Sheath blight, caused by the pathogen Rhizoctonia solani Kühn, is one of the most serious diseases of rice and leads to severe yield loss worldwide. A recombinant inbred line (RIL) population consisting of 121 lines was constructed from a cross between HH1B and RSB03, the latter of which is a deep-water rice variety. Five traits were used to evaluate sheath blight resistance, namely disease rating (DR), lesion length (LL), lesion height (LH), relative lesion length [RLL, the ratio of LL to plant height (PH)], and relative LH (RLH, the ratio of LH to PH). Using the RIL population and 123 molecular markers, we identified 28 quantitative trait loci (QTLs) for the five traits in two environments. These QTLs are located on nine chromosomes and most of them are environment specific. A major QTL for DR (qSBR1) on chromosome 1 was identified with contributions of 12.7% at Shanghai and 42.6% at Hainan, and it collocated with a QTL for PH. The allele at this locus from RSB03 enhances sheath blight resistance and increases PH. Another QTL for DR on chromosome 7 was adjacent to QTLs for heading date (HD) and four other disease traits. RSB03 also carries the resistant allele at this locus and shortens HD. The susceptible parent, HH1B, provides the resistance allele at the locus qSBR8, where QTLs for four other disease traits were identified. QTL mapping results showed that most QTLs for LL, LH, RLL, and RLH are collocated with QTLs for DR. Three QTLs for DR are independent from HD, PH, and four other disease traits, while four QTLs are closely related to HD and PH. Four QTLs for LL, LH, RLL, and RLH are independent from DR, HD, and PH, while there is only one region harboring QTLs for these four traits and HD. Correlation analysis and QTL mapping results indicated that LL, LH, RLL, and RLH might be important indices, like DR, for evaluating the level of resistance to rice sheath blight.     

Marker‐assisted backcross breeding to combine multiple rust resistance in wheat

A widely grown but rust susceptible Indian wheat variety HD2932 was improved for multiple rust resistance by marker‐assisted transfer of genes Lr19, Sr26 and Yr10. Foreground and background selection processes were practised to transfer targeted genes with the recovery of the genome of HD2932. The near‐isogenic lines (NILs) of HD2932 carrying Lr19, Sr26 and Yr10 were individually produced from two backcrosses with recurrent parent HD2932. Marker‐assisted background selection of NILs with 94.38–98.46% of the HD2932 genome facilitated rapid recovery of NILs carrying Lr19, Sr26 and Yr10. In the BC₂F₂ generation, NILs were intercrossed and two gene combinations of Lr19+Yr10, Sr26 + Yr10 and Lr19+Sr26 were produced. A total of 16 progeny of two gene combinations of homozygous NILs of HD2932 have been produced, which are under seed increase for facilitating the replacement of the susceptible HD2932 with three of the sixteen improved backcross lines with resistance to multiple rusts.     

QTL mapping for heading date,leaf area and chlorophyll content under cold and drought stress in two related recombinant inbred line populations (Japonica rice) and meta‐analysis

Rice is highly susceptible to drought and cold. The goal of this study was to identify the QTLs affecting the rice heading date (HD), leaf area (LA) and chlorophyll content (CC) under cold and drought stress. A total of twenty‐nine and thirty‐eight additive QTLs were detected from two crosses of ‘Dongnong422’/‘Kongyu131’ and ‘Xiaobaijingzi’/‘Kongyu131’, respectively. qHD1‐7‐1, qHD1‐7‐2, qHD1‐2‐1, qLA1‐7‐1, qLA1‐6‐3 and qCC1‐7‐1 show adaptive effects under cold treatment, while qHD2‐2‐3, qHD2‐2‐2, qLA2‐7‐3 and qCC2‐5‐1 were important for explaining the genetic mechanism during drought tolerance. Additionally, nine and five additive × environment interaction QTLs were detected for two RILs, respectively. RIL26 and RIL73 were two lines that are associated with cold and drought for HD. 339 QTLs related to HD, CC and LA of rice from database and our research were projected onto the genetic map. Nine cloned genes and nineteen homologous candidate genes related to HD, CC, cold tolerance and drought tolerance were mapped by meta‐analysis. These results lay the foundation for the fine mapping of QTLs related to HD, LA and CC for marker‐assisted selection.     

Genes for wheat stem rust resistance postulated in German cultivars and their efficacy in seedling and adult‐plant field tests

Stem rust of wheat (caused by Puccinia graminis f.sp. tritici) gained high international attention in the last two decades, but does not occur regularly in Germany. Motivated by a regional epidemic in 2013, we analysed 15 spring and 82 winter wheat cultivars registered in Germany for their resistance to stem rust at the seedling stage and tested 79 of these winter wheat cultivars at the adult‐plant stage. A total of five seedling stem rust resistance genes were postulated: Sr38 occurred most frequently (n = 29), followed by Sr31 (n = 11) and Sr24 (n = 8). Sr7a and Sr8a occurred only in two spring wheat genotypes each. Four cultivars had effective seedling resistance to all races evaluated that could only be explained by postulating additional resistance genes (‘Hyland’, ‘Pilgrim PZO’, ‘Tybalt’) or unidentified gene(s) (‘Memory’). The three winter wheat cultivars (‘Hyland’ ‘Memory’ and ‘Pilgrim PZO’) were also highly resistant at the adult‐plant stage; ‘Tybalt’ was not tested. Resistance genes Sr24 and Sr31 highly protected winter wheat cultivars from stem rust at the adult‐plant stage in the field. Disease responses of cultivars carrying Sr38 varied. Mean field stem rust severity of cultivars without postulated seedling resistance genes ranged from 2.71% to 41.51%, nine of which were significantly less diseased than the most susceptible cultivar. This suggests adult‐plant resistance to stem rust may be present in German wheat cultivars.     

Monosomic analysis of Helminthosporium leaf blight resistance genes in wheat

A set of 21 monosomic (2n ‐ 1) and the disomic (2n) lines of the ‘Chinese Spring’ cultivar were crossed with ‘Chirya‐3′, the CIMMYT synthetic wheat line which has been identified as highly resistant for Helminthosporium leaf blight disease (HLB), in order to locate the genes governing disease resistance. The F₁ and segregating populations were challenged and screened against the most virulent pure mono‐conidial HLB isolate KL‐8 (Karnal, India). The F₁ progenies of the crosses were found to be susceptible because of the recessive nature of resistance. The F₂ progeny of the control cross (‘Chinese Spring’בChirya‐3’), segregated in the ratio of 1: 15 (resistant: susceptible), indicating that resistance to HLB was controlled by a pair of recessive genes. While the F₂ progeny of 19 monosomic crosses segregated in the ratio of 1: 15 (resistant: susceptible), the progeny of the remaining two crosses, 7B and 7D, deviated significantly from the ratio, revealing that 7B and 7D were the critical chromosomes for resistance genes that were located one on each chromosome. Moreover, the critical lines, 7B and 7D, confirmed the digenic complementary recessive nature of gene action by fitting well with the overall pooled F₂ segregation ratio of 13: 51 (resistant: susceptible) as expected for digenic complementary recessive resistance. The F₃ segregation ratios of the critical crosses, based on their pooled F₂ analysis, was estimated as 19: 32: 13 (non‐segregating susceptible: segregating as susceptible and resistant: non‐segregating resistant). F₃ progenies when tested with these ratios showed goodness‐of‐fit, confirming that the two pairs of recessive resistance genes were located on chromosomes 7B and 7D.     

Characterization of correlation between grain moisture and ear rot resistance in maize by QTL meta-analysis

Ear rot (ER) in maize is a prevalent disease worldwide which reduces yield and grain quality. Grain moisture content (GM) is an important factor which impacts the fungal development of ER species. Our purpose was to identify the genomic regions of maize in the control of GM and ER resistance, and the correlations between two traits. A meta-analysis was carried out using 241 quantitative trait loci (QTL) from 29 studies to propose meta-QTL (MQTL) on a high-density genetic linkage map (IBM 2 neighbors 2008). For GM content, 44 MQTL were identified on all chromosomes except for chromosome 9, while 29 MQTL were found for ER resistance, mainly located on chromosomes 3, 6 and 7. Moreover, 14 overlapping domains for GM MQTL and ER MQTL were observed on chromosomes 2, 3, 6 and 7, mainly focused on five active regions (bins 2.08–2.09, 3.04, 3.06, 6.04–6.06 and 7.03–7.03). There were 13 genes in the overlapping domain which could be divided into five classes: stress-related gene, photosystem-related gene, architecture-related gene, dynamic-related gene and seminal-related gene. It was possibly that the five-class genes were simultaneously related with GM and ER.     

东乡野生稻抗褐飞虱QTL分析

野生稻是水稻抗褐飞虱基因的重要种质资源。应用东乡野生稻与栽培稻协青早B构建的2套材料,开展水稻抗褐飞虱基因鉴定研究。先以协青早B//协青早B/东乡野生稻BC₁F₅群体为材料,应用褐飞虱田间种群进行抗虫鉴定,检测到2个抗褐飞虱QTL,其中,qBph2位于水稻第2染色体RM29–RG157区间,东乡野生稻等位基因可降低死苗率22.2%;qBph7位于第7染色体RM11–RM234区间,东乡野生稻等位基因可降低死苗率43.7%。进一步以协青早B为轮回亲本,构建了BC₃F₃群体,应用褐飞虱生物型I、II和III进行抗虫鉴定,QTL分析表明qBph2抗褐飞虱生物型I和II,qBph7抗褐飞虱生物型I和III。这2个QTL对培育抗褐飞虱水稻品种具有重要应用价值。     

粳稻品种吉粳809的稻瘟病抗性基因分析

稻瘟病是水稻生产中危害最为严重的病害之一,种植抗病品种是抵御稻瘟病危害的有效措施。本研究利用吉粳809的2个亲本材料吉粳88与93072配制的回交分离群体进行稻瘟病人工接种,采用抗、感极端分池法定位双亲的稻瘟病抗性基因,结合基因型分析,推断吉粳809的抗性基因组成。结果表明,回交群体对强致病菌GD9-1表现为4个主效抗病基因Pi-2(t)、Pi-7-1(t)、Pi-7-2(t)和Pi-11(t)分离,对弱致病菌GD19-1表现单个主效抗病基因Pi-2(t)分离,其中Pi-2(t)基因同时抗2个菌株。除Pi-2(t)位点抗性等位基因来自吉粳88,其余3个位点的抗性等位基因均来自93072。比较基因组研究表明,Pi-2(t)可能与Pi-b等位,Pi-11(t)可能与Pi-47(t)或Pik等位,而Pi-7-1(t)和Pi-7-2(t)是2个新的抗性位点,分别与RM21260和RM8037连锁,遗传距离为0.11 cM和6.97 cM。利用与上述4个抗病位点紧密连锁的SSR标记和来自3K水稻种质资源重测序开发的55K芯片鉴定抗性位点吉粳809与双亲基因型的异同,推断吉粳809抗性基因组成,发现吉粳809携带轮回亲本吉粳88的Pi-2(t)和来自供体亲本93072的Pi-11(t) 2个基因,合理地解释了吉粳809抗性明显好于吉粳88的原因。对如何通过不同主效抗性基因聚合特别是充分利用原来抗病品种中“丧失”抗性残效基因来改良品种的稻瘟病抗性进行了讨论。     

利用双向导入系解析水稻抽穗期和株高QTL及其与环境互作表达的遗传背景效应

利用粳稻Lemont和籼稻特青相互导入构建的遗传背景基本一致的双向回交导入系群体,分别在北京和海南环境定位影响抽穗期和株高的主效QTL及其环境互作,分析QTL及其与环境互作表达的遗传背景效应。在北京和海南分别检测到影响抽穗期和株高的主效QTL 16个和17个,其中有5个主效QTL (QHd2、QHd8a、QPh3、QPh5和QPh12)在两种背景下同时被检测到,表明多数主效QTL的表达具有遗传背景特异性。两种背景下检测到影响抽穗期的3个主效QTL (QHd8a、QHd9和QHd10b)存在环境互作,其中QHd8a与海南环境的互作在两种背景下提早抽穗2~3 d,与北京环境的互作则延迟抽穗2~3 d,是影响抽穗期的一个重要主效QTL。通过与以往相同亲本来源的7个不同定位群体在不同环境下定位结果的比较,鉴定出一些在不同遗传背景和环境下稳定表达的主效QTL,如QHd3、QHd8a、QPh3和QPh4,适宜用于水稻抽穗期和株高的分子标记改良。基于QTL定位结果,本文对如何通过分子标记辅助改良品种在不同环境下的抽穗期进行了深入探讨。     

小麦抗叶锈近等基因系TcLr38 RGAs分析

摘要：为获得Lr38的抗病类似物质、为今后的相关研究奠定基础,本研究根据已知植物抗病基因的NBS-LRR(核苷酸结合位点-富含亮氨酸重复)类保守区域设计简并引物,从小麦抗叶锈近等基因系TcLr38中获得了9个小麦抗病基因同源片段D-8、A-5、B-20、C-6、F-16、A-4、B-9、C-4和D-12。这些片段都含有NB-ARC保守结构域,其中D-8、A-5、B-20、C-6、A-4、B-9、C-4和D-12与已知抗病基因的相应区域相一致,具有抗病基因NBS特征结构域激酶2a(Kinase-2)、激酶3a(Kinase-3a)和疏水结构域(HD)。     

Use of a synthetic hexaploid Triticum miguschovae for transfer of leaf rust resistance to common wheat

Summary Triticum miguschovae, a genome addition synthetic, was used as a source for transfer of leaf rust (Puccinia recondita tritici) resistance to common wheat. This synthetic, developed from two wild species Triticum militinae and Aegilops squarrosa, proves a valuable donor of the genes for leaf rust resistance. Leaf rust resistance was transferred from T. miguschovae by both dominant and recessive genes. Stable lines phenotypically similar to their recurrent parents Kavkaz and Bezostaya 1 but differing from them in a high level of leaf rust resistance were obtained. The genes for resistance in 3 selected lines differed from each other and from the known effective genes Lr9, Lr19, and Lr24. The resistance of one of them (line 1229) is controlled by two complementary interacting genes located on chromosome 7B and 1D was revealed by monosomic analysis.     

利用水稻MAGIC群体关联定位抽穗期和株高QTL

利用多亲本高代互交系(multi-parent advanced generation inter-cross,MAGIC)群体(DC1、DC2和8way)及其复合群体DC12(DC1+DC2)和RMPRIL(DC1+DC2+8way)进行关联分析定位水稻抽穗期和株高QTL。2015年和2016年分别在江西和深圳收集3个MAGIC群体抽穗期数据,2016年在两地收集株高数据,结合Rice 55K SNP芯片进行基因分型,利用关联分析方法检测到3个影响抽穗期的主效QTL(q HD3、q HD6和q HD8),分别位于第3、第6和第8染色体,且分别与已知抽穗期基因DTH3、Hd3a和Ghd8在同一区域。检测到5个影响株高的QTL(q PH1.1、q PH1.2、q PH1.3、q PH4和q PH6),其中q PH1.1和q PH1.2位于已知基因Psd1和sd1附近,其余3个QTL为影响株高的新位点,但仅在1个群体和单个环境下被检测到,QTL表达受遗传背景和环境影响大。不同MAGIC群体定位抽穗期和株高的效果不同,在8亲本MAGIC群体8way及复合群体DC12和RMPRIL分别检测到5、5和6个抽穗期和株高QTL,明显多于4亲本群体DC1的2个和DC2的4个,而且作图的精度更高,表现在定位到的QTL显著水平高和与已知基因距离更近,尤其是复合群体的联合分析(如DC12和RMPRIL)的作图优势更为明显。     

香蕉NBS-LRR类抗病基因同源序列的克隆与分析

根据已知植物抗病基因的保守区域设计引物,从香蕉基因组DNA扩增出一条与植物抗病基因同源的序列,命名为BRGA1,该同源片段含有典型的NBS-LRR类抗病基因所拥有的保守性结构p-loop、Kinase-2a、Kinase-3a和疏水结构域HD,它与部分已知NBS-LRR类抗病基因的氨基酸序列同源性为23.8%-42.7%。Northern杂交表明BRGA1在香蕉中受水杨酸调控,属诱导型表达。     

Detection and inheritance of leaf rust resistance in common wheat lines Agra Local and IWP94

Genetic studies were undertaken to determine the number and identities of leaf rust resistance genes in common wheat lines Agra Local and IWP94. The infection type arrays of the two lines with eight pathotypes (pt.) of P. triticina were different from those of lines possessing known leaf rust resistance (Lr) genes. Agra Local possessed two recessive resistance genes, one conditioning resistance to pathotype 4R9-7, and the other, a temperature-sensitive factor, gave resistance to pt. 121R127 at high temperature (27°C). IWP94 was previously demonstrated to carry Lr23. From the present study IWP94 was determined to have at least four leaf rust resistance genes. The first of these was the same recessive gene conferring resistance to pathotype 4R9-7 which was found in Agra Local. A second partially dominant gene conferred resistance to pathotype 121R127 at high temperature and two additional recessive genes governed resistance to pathotype 93R15. When present together, these two recessive genes complemented each other and provided resistance to pathotype 69R13 as well. One of the two recessive genes conferring resistance to pathotypes 93R15 and 69R13 was Lr23.     

土耳其8个小麦品种农艺性状及抗叶锈性分析

为确定8个来自土耳其的普通小麦品种在我国的应用前景,对其进行全生育期农艺性状观察,并利用44个以Thatcher为背景的近等基因系(单基因系)作为已知基因的鉴别寄主,接种8个小麦叶锈菌致病型进行苗期抗叶锈基因推导,结合成株期抗病鉴定,初步明确了这些品种(系)的抗性和可能携带的抗病基因。利用20个与Lr基因紧密连锁或共分离的分子标记,对8个土耳其小麦品种进行抗叶锈病基因的进一步鉴定。推测YJ000900中可能含有Lr1、Lr3、Lr17、Lr20;YJ000906中可能含有Lr1、Lr17、Lr20;YJ000901、YJ000902、YJ000904、YJ000905、YJ000907中可能含有Lr1;8个材料中均不含Lr9、Lr19、Lr20、Lr21、Lr24、Lr26、Lr28、Lr29、Lr34、Lr35、Lr37、Lr38和Lr47基因。结果表明,来自土耳其的8个小麦材料具有较差的抗叶锈性、抗寒和抗倒伏能力,而且产量低,不适宜于大规模推广种植,也不能作为我国小麦抗叶锈的抗源使用。     

马铃薯资源晚疫病抗性的全基因组关联分析

广谱抗性基因的挖掘是马铃薯高抗晚疫病品种选育的基础。本研究以288份国际马铃薯中心筛选的晚疫病抗性群体为试验材料,经过连续2年田间调查,计算AUDPC和sAUDPC值,评估群体晚疫病抗性;利用SLAF-seq方法进行群体简化基因组测序,通过对晚疫病抗性表型数据的全基因组关联分析,挖掘晚疫病抗性相关的遗传位点和候选基因,为晚疫病抗性品种选育和抗病机理研究提供一定的理论和材料基础。结果表明,晚疫病抗性在288份材料间存在着广泛的遗传差异;基于5种分析模型,共鉴定到82个与晚疫病抗性显著关联的位点;在关联区间关联到54个已知或可能与晚疫病抗性相关的基因。其中,23个基因为抗性基因,包括晚疫病抗性基因R1同源基因、Sw-5同源基因(R8)和Rpi-vnt1以及编码多效性耐药蛋白基因;5个基因编码MAPK蛋白和WRKY转录因子;1个基因参与茉莉酸途径;3个基因与水杨酸途径相关;6个基因是病程相关的基因;3个基因参与苯基丙酸类合成途径;其他与晚疫病抗性相关的基因,如HMGR基因(2个)、细胞色素P450(21个)。     

Genetic mapping of bph20(t) and bph21(t) loci conferring brown planthopper resistance to Nilaparvata lugens St?l in rice (Oryza sativa L.)

Brown planthopper(BPH) is one of the most serious and destructive insect pests of rice in most rice growing regions of the world. In this study, two major resistance genes against BPH have been identified in an Oryza rufipogon (Griff.) introgression rice line, RBPH54. Inheritance of the BPH resistance in RBPH54 was studied by screening the resistance in parents, F1, F2 and BC1 generations against BPH biotype 2. A population of BC3F2 lines was developed and SSR markers were employed for the gene mapping, and new markers were designed for fine mapping of the resistance genes, while sequence information of BAC/PAC clones was used to construct physical maps of the genes. The results showed that the BPH resistance in RBPH54 was governed by recessive alleles at two loci, tentatively designated as bph20(t) and bph21(t). The locus bph20(t) was fine mapped to the short arm of chromosome 6 about 2.7 cM to the upper marker RM435 and 2.5 cM to lower marker RM540 and in a 2.5 cM region flanked by two new SSR markers BYL7 and BYL8 which were developed in the present study. The other BPH resistance locus bph21(t) was initially mapped to a region 7.9 cM to upper marker RM222 and 4.0 cM to lower marker RM244 on the short arm of chromosome 10. For physical mapping, the bph20(t)-linked markers were landed on BAC/PAC clones of the reference cv., Nipponbare, released by the International Rice Genome Sequencing Project. The bph20(t) locus was physically defined to an interval of about 75 kb with clone P0514G1. Identification and location of these two genes in the present study have diversified the BPH resistance gene pool, which give benefit to the development of resistant rice cultivars, and the linkage PCR-based SSR markers for the bph20(t) and bph21(t) genes would help realize the application of the genes in rice breeding through marker-assisted selection.