Genetic and comparative genomics mapping reveals that a powdery mildew resistance gene Ml3D232 originating from wild emmer co-segregates with an NBS-LRR analog in common wheat (Triticum aestivum L.)

Powdery mildew caused by Blumeria graminis f. sp. tritici is one of the most important wheat diseases worldwide and breeding for resistance using diversified disease resistance genes is the most promising approach to prevent outbreaks of powdery mildew. A powdery mildew resistance gene, originating from wild emmer wheat (Triticum turgidum var. dicoccoides) accessions collected from Israel, has been transferred into the hexaploid wheat line 3D232 through crossing and backcrossing. Inoculation results with 21 B. graminis f. sp. tritici races indicated that 3D232 is resistant to all of the powdery mildew isolates tested. Genetic analyses of 3D232 using an F₂ segregating population and F₃ families indicated that a single dominant gene, Ml3D232, confers resistance in the host seedling stage. By applying molecular markers and bulked segregant analysis (BSA), we have identified polymorphic simple sequence repeats (SSR), expressed sequence tags (EST) and derived sequence tagged site (STS) markers to determine that the Ml3D232 is located on chromosome 5BL bin 0.59–0.76. Comparative genetic analyses using mapped EST markers and genome sequences of rice and Brachypodium established co-linearity of the Ml3D232 genomic region with a 1.4 Mb genomic region on Brachypodium distachyon chromosome 4, and a 1.2 Mb contig located on the Oryza sativa chromosome 9. Our comparative approach enabled us to develop new EST–STS markers and to delimit the genomic region carrying Ml3D232 to a 0.8 cM segment that is collinear with a 558 kb region on B. distachyon. Eight EST markers, including an NBS-LRR analog, co-segregated with Ml3D232 to provide a target site for fine genetic mapping, chromosome landing and map-based cloning of the powdery mildew resistance gene. This newly developed common wheat germplasm provides broad-spectrum resistance to powdery mildew and a valuable resource for wheat breeding programs.     

pmX: a recessive powdery mildew resistance gene at the Pm4 locus identified in wheat landrace Xiaohongpi

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is one of the most devastating foliar diseases of wheat and imposes a constant challenge on wheat breeders. Xiaohongpi, a Chinese landrace of wheat (Triticum aestivum L.), shows resistance to powdery mildew during the entire growth stage in the field and under controlled conditions. The F₁ plants from cross of the powdery mildew susceptible cultivar Yangmai158 with Xiaohongpi were susceptible to isolate Bgt19, the locally most prevalent Bgt isolate. In the derived F₂ population and F₃ progenies, the resistance segregation deviated significantly from the one-gene Mendelian ratio. However, marker analysis indicated that only one recessive gene conferred the resistance, which co-segregated with Xsts-bcd1231 that showed co-segregation with Pm4a in different studies. Allelism test indicated that this recessive resistance gene, designated as pmX, is either allelic or tightly linked to Pm4a. The pmX gene was different from Pm4 alleles in resistance spectrum. Examination of the genotype frequencies at pmX and the linked marker loci in the F₂ population showed that a genetic variation favoring the transmission of Xiaohongpi alleles could be the cause of deviated segregation. Mapping of the pmX-linked markers using Chinese Spring deletion lines indicated that it resides in the 0.85–1.00 bin of chromosome 2AL.     

<Emphasis Type="Italic">Pm61</Emphasis>: a recessive gene for resistance to powdery mildew in wheat landrace Xuxusanyuehuang identified by comparative genomics analysis

Key message

A single recessive powdery mildew resistance gene Pm61 from wheat landrace Xuxusanyuehuang was mapped within a 0.46-cM genetic interval spanning a 1.3-Mb interval of the genomic region of chromosome arm 4AL.

Abstract

Epidemics of powdery mildew incited by the biotrophic fungus Blumeria graminis f. sp. tritici (Bgt) have caused significant yield reductions in many wheat (Triticum aestivum)-producing regions. Identification of powdery mildew resistance genes is required for sustainable improvement of wheat for disease resistance. Chinese wheat landrace Xuxusanyuehuang was resistant to several Bgt isolates at the seedling stage. Genetic analysis based on the inoculation of Bgt isolate E09 on the F₁, F₂, and F_2:3 populations produced by crossing Xuxusanyuehuang to susceptible cultivar Mingxian 169 revealed that the resistance of Xuxusanyuehuang was controlled by a single recessive gene. Bulked segregant analysis and simple sequence repeat (SSR) mapping placed the gene on chromosome bin 4AL-4-0.80-1.00. Comparative genomics analysis was performed to detect the collinear genomic regions of Brachypodium distachyon, rice, sorghum, Aegilops tauschii, T. urartu, and T. turgidum ssp. dicoccoides. Based on the use of 454 contig sequences and the International Wheat Genome Sequence Consortium survey sequence of Chinese Spring wheat, four EST-SSR and seven SSR markers were linked to the gene. An F₅ recombinant inbred line population derived from Xuxusanyuehuang?×?Mingxian 169 cross was used to develop the genetic linkage map. The gene was localized in a 0.46-cM genetic interval between Xgwm160 and Xicsx79 corresponding to 1.3-Mb interval of the genomic region in wheat genome. This is a new locus for powdery mildew resistance on chromosome arm 4AL and is designated Pm61.

     

New wheat-rye 5DS-4RS·4RL and 4RS-5DS·5DL translocation lines with powdery mildew resistance

Powdery mildew is one of the serious diseases of wheat (Triticum aestivum L., 2n = 6 × = 42, genomes AABBDD). Rye (Secale cereale L., 2n = 2 × = 14, genome RR) offers a rich reservoir of powdery mildew resistant genes for wheat breeding program. However, extensive use of these resistant genes may render them susceptible to new pathogen races because of co-evolution of host and pathogen. Therefore, the continuous exploration of new powdery mildew resistant genes is important to wheat breeding program. In the present study, we identified several wheat-rye addition lines from the progeny of T. aestivum L. Mianyang11 × S. cereale L. Kustro, i.e., monosomic addition lines of the rye chromosomes 4R and 6R; a disomic addition line of 6R; and monotelosomic or ditelosomic addition lines of the long arms of rye chromosomes 4R (4RL) and 6R (6RL). All these lines displayed immunity to powdery mildew. Thus, we concluded that both the 4RL and 6RL arms of Kustro contain powdery mildew resistant genes. It is the first time to discover that 4RL arm carries powdery mildew resistant gene. Additionally, wheat lines containing new wheat-rye translocation chromosomes were also obtained: these lines retained a short arm of wheat chromosome 5D (5DS) on which rye chromosome 4R was fused through the short arm 4RS (designated 5DS-4RS·4RL; 4RL stands for the long arm of rye chromosome 4R); or they had an extra short arm of rye chromosome 4R (4RS) that was attached to the short arm of wheat chromosome 5D (5DS) (designated 4RS-5DS·5DL; 5DL stands for the long arm of wheat chromosome 5D). These two translocation chromosomes could be transmitted to next generation stably, and the wheat lines containing 5DS-4RS·4RL chromosome also displayed immunity to powdery mildew. The materials obtained in this study can be used for wheat powdery mildew resistant breeding program.     

部分小麦近缘物种材料的白粉病抗性鉴定

鉴定了170份小麦近缘物种材料苗期对北京地区流行的小麦白粉菌小种的抗性表现,包括引自美国和欧洲的斯卑尔脱小麦81份,密穗小麦27份,中国的西藏半野生小麦4份,和引自 CIMMYT 的人工合成六倍体小麦58份。结果表明,3份斯卑尔脱小麦表现抗病,它们是瑞士品种 Hubel 和 Lueg 以及德国的原始品种69Z6.245(编号 PI348085)。人工合成六倍体小麦中有19份材料表现高抗至免疫。密穗小麦材料中有2份(即美国材料 DN-2263和 Coda)表现抗病。4份西藏半野生小麦苗期都不抗小麦白粉病。     

Identification and mapping of <Emphasis Type="Italic">MLIW30</Emphasis>, a novel powdery mildew resistance gene derived from wild emmer wheat

Powdery mildew, caused by Blumeria graminis f.sp. tritici (Bgt), is a destructive foliar disease of common wheat in areas with cool or maritime climates. Wild emmer wheat, Triticum turgidum ssp. dicoccoides, the progenitor of both domesticated tetraploid durum wheat and hexaploid bread wheat, harbors abundant genetic diversity related to resistance to powdery mildew that can be utilized for wheat improvement. An F₂ segregating population was obtained from a cross between resistant bread wheat line 2L6 and susceptible cultivar Liaochun 10, after which genetic analysis of F₂ and F₂-derived F₃ families was performed by inoculating plants with isolate Bgt E09. The results of this experiment demonstrated that powdery mildew resistance in 2L6, which was derived from wild emmer wheat accession IW30, was controlled by a single dominant gene, temporarily designated MLIW30. Nineteen SSR markers and two STS markers linked with MLIW30 were acquired by applying bulked segregant analysis. Finally, MLIW30 was located to the long arm of chromosome 4A and found to be flanked by simple sequence repeat markers XB1g2000.2 and XB1g2020.2 at 0.1 cM. Because no powdery mildew resistance gene in or derived from wild emmer wheat has been reported in wheat chromosome 4A, MLIW30 might be a novel Pm gene.     

Genetic analysis of a novel broad-spectrum powdery mildew resistance gene from the wheat-<Emphasis Type="Italic">Agropyron cristatum</Emphasis> introgression line Pubing 74

Main conclusion

A novel broad-spectrum powdery mildew resistance gene PmPB74 was identified in wheat- Agropyron cristatum introgression line Pubing 74. Development of wheat cultivars with broad-spectrum, durable resistance to powdery mildew has been restricted by lack of superior genetic resources. In this study, a wheat-A. cristatum introgression line Pubing 74, originally selected from a wide cross between the common wheat cultivar Fukuhokomugi (Fukuho) and Agropyron cristatum (L.) Gaertn (2n = 4x = 28; genome PPPP), displayed resistance to powdery mildew at both the seedling and adult stages. The putative alien chromosomal fragment in Pubing 74 was below the detection limit of genomic in situ hybridization (GISH), but evidence for other non-GISH-detectable introgressions was provided by the presence of three STS markers specific to A. cristatum. Genetic analysis indicated that Pubing 74 carried a single dominant gene for powdery mildew resistance, temporarily designated PmPB74. Molecular mapping showed that PmPB74 was located on wheat chromosome arm 5DS, and flanked by markers Xcfd81 and HRM02 at genetic distances of 2.5 and 1.7 cM, respectively. Compared with other lines with powdery mildew resistance gene(s) on wheat chromosome arm 5DS, Pubing 74 was resistant to all 28 Blumeria graminis f. sp tritici (Bgt) isolates from different wheat-producing regions of northern China. Allelism tests indicated that PmPB74 was not allelic to PmPB3558 or Pm2. Our work showed that PmPB74 is a novel gene with broad resistance to powdery mildew, and hence will be helpful in broadening the genetic basis of powdery mildew resistance in wheat.

     

Pm50: a new powdery mildew resistance gene in common wheat derived from cultivated emmer

Fungal diseases of wheat, including powdery mildew, cause significant crop, yield and quality losses throughout the world. Knowledge of the genetic basis of powdery mildew resistance will greatly support future efforts to develop and cultivate resistant cultivars. Studies were conducted on cultivated emmer-derived wheat line K2 to identify genes involved in powdery mildew resistance at the seedling and adult plant growth stages using a BC₁ doubled haploid population derived from a cross between K2 and susceptible cultivar Audace. A single gene was located distal to microsatellite marker Xgwm294 on the long arm of chromosome 2A. Quantitative trait loci (QTL) analysis indicated that the gene was also effective at the adult plant stage, explaining up to 79.0 % of the variation in the progeny. Comparison of genetic maps indicated that the resistance gene in K2 was different from Pm4, the only other formally named resistance gene located on chromosome 2AL, and PmHNK54, a gene derived from Chinese germplasm. The new gene was designated Pm50.     

Genetic analysis and detection of the gene MlLX99 on chromosome 2BL conferring resistance to powdery mildew in the wheat cultivar Liangxing 99

Key message

The effectiveness of wheat cultivar Liangxing 99 against powdery mildew was shown to be controlled by a single dominant gene located on a new locus of chromosome 2BL in the bin 2BL2-0.35-0.50.

Abstract

Liangxing 99, one of the most widely grown commercial cultivars in the winter wheat (Triticum aestivum) producing regions in northern China, was shown to provide a broad spectrum of resistance to Blumeria graminis f. sp. tritici (Bgt) isolates originating from that region. Using an F₂ population and F_2:3 lines derived from a cross of Liangxing 99 × Zhongzuo 9504, genetic analysis demonstrated that a single dominant gene, designated MlLX99, was responsible for the resistance of Liangxing 99 to Bgt isolate E09. The results of molecular analysis indicated that this gene is located on chromosome 2BL and flanked by the SSR marker Xgwm120 and EST-STS marker BE604758 at genetic distances of 2.9 and 5.5 cM, respectively. Since the flanking markers of MlLX99 were previously mapped to the bin 2BL2-0.36-0.50, MlLX99 must be located in this chromosomal region. MlLX99 showed a different resistance reaction pattern to 60 Bgt isolates from Pm6, Pm33, and PmJM22, which were all previously mapped on chromosome 2BL, but differed in their positions from MlLX99. Due to its unique position on chromosome 2BL, MlLX99 appears to be a new locus for resistance to powdery mildew. Liangxing 99 has shown superior yield performance and wide adaptation to different agricultural conditions, which has resulted in its extensive use as a wheat cultivar in China. The identification of resistance gene MlLX99 facilitates the use of this cultivar in the protection of wheat from damage caused by powdery mildew.     

Microsatellite mapping of a Triticum urartu Tum. derived powdery mildew resistance gene transferred to common wheat (Triticum aestivum L.)

A powdery mildew resistance gene from Triticum urartu Tum. accession UR206 was successfully transferred into hexaploid wheat (Triticum aestivum L.) through crossing and backcrossing. The F₁ plants, which had 28 chromosomes and an average of 5.32 bivalents and 17.36 univalents in meiotic pollen mother cells (PMC), were obtained through embryos rescued owing to shriveling of endosperm in hybrid seed of cross Chinese Spring (CS) × UR206. Hybrid seeds were produced through backcrossing F₁ with common wheat parents. The derivative lines had normal chromosome numbers and powdery mildew resistance similar to the donor UR206, indicating that the powdery mildew resistance gene originating from T. urartu accession UR206 was successfully transferred and expressed in a hexaploid wheat background. Genetic analysis indicated that a single dominant gene controlled the powdery mildew resistance at the seedling stage. To map and tag the powdery mildew resistance gene, 143 F₂ individuals derived from a cross UR206 × UR203 were used to construct a linkage map. The resistant gene was mapped on the chromosome 7AL based on the mapped microsatellite makers. The map spanned 52.1 cM and the order of these microsatellite loci agreed well with the established microsatellite map of chromosome arm 7AL. The resistance gene was flanked by the microsatellite loci Xwmc273 and Xpsp3003, with the genetic distances of 2.2 cM and 3.8 cM, respectively. On the basis of the origin and chromosomal location of the gene, it was temporarily designated PmU.     

Transfer and mapping of a gene conferring later-growth-stage powdery mildew resistance in a tetraploid wheat accession

Wheat powdery mildew is a severe foliar disease and causes significant yield losses in epidemic years. Breeding and using resistant cultivars is the most widely employed strategy to curb this disease. To identify and transfer powdery mildew resistance genes in wild emmer wheat accession TA1410 into common wheat, a resistant F3 line derived from the cross of TA1410 × durum wheat line Zhongyin1320 was crossed with common wheat cultivar Yangmai158. The homozygous resistant BC5F2 lines derived from the backcross with Yangmai158 exhibited susceptibility at seedling stage and conferred increasing resistance when the plants were closer to heading stage. In two segregating BC5F3 families investigated at heading stage, the segregation of the resistance fit a 3:1 ratio, suggesting that a single dominant gene controls the resistance. This resistance gene, designated HSM1, was mapped to the 0.6-cM Xmag5825.1–Xgwm344 interval on chromosome 7AL and co-segregated with Xrga-C3 and Xrga-C6. A mapping position comparison with other powdery mildew resistance genes on this chromosome suggested that HSM1 belongs to the Pm1 resistance gene cluster. HSM1 is a useful candidate gene for resistance breeding, particularly in winter-wheat growing areas.     

Chromosomal Location and Comparative Genomics Analysis of Powdery Mildew Resistance Gene Pm51 in a Putative Wheat-Thinopyrum ponticum Introgression Line

Powdery mildew (PM) is a very destructive disease of wheat (Triticum aestivum L.). Wheat-Thinopyrum ponticum introgression line CH7086 was shown to possess powdery mildew resistance possibly originating from Th. ponticum. Genomic in situ hybridization and molecular characterization of the alien introgression failed to identify alien chromatin. To study the genetics of resistance, CH7086 was crossed with susceptible genotypes. Segregation in F₂ populations and F_2:3 lines tested with Chinese Bgt race E09 under controlled conditions indicated that CH7086 carries a single dominant gene for powdery mildew resistance. Fourteen SSR and EST-PCR markers linked with the locus were identified. The genetic distances between the locus and the two flanking markers were 1.5 and 3.2 cM, respectively. Based on the locations of the markers by nullisomic-tetrasomic and deletion lines of ‘Chinese Spring’, the resistance gene was located in deletion bin 2BL-0.89-1.00. Conserved orthologous marker analysis indicated that the genomic region flanking the resistance gene has a high level of collinearity to that of rice chromosome 4 and Brachypodium chromosome 5. Both resistance specificities and tests of allelism suggested the resistance gene in CH7086 was different from previously reported powdery mildew resistance genes on 2BL, and the gene was provisionally designated PmCH86. Molecular analysis of PmCH86 compared with other genes for resistance to Bgt in the 2BL-0.89-1.00 region suggested that PmCH86 may be a new PM resistance gene, and it was therefore designated as Pm51. The closely linked flanking markers could be useful in exploiting this putative wheat-Thinopyrum translocation line for rapid transfer of Pm51 to wheat breeding programs.     

Quantitative trait loci mapping of adult-plant resistance to powdery mildew in Chinese wheat cultivar Lumai 21

Powdery mildew, caused by Blumeria graminis f. sp. tritici, is a major fungal disease in common wheat (Triticum aestivum L.) worldwide. The Chinese winter wheat cultivar Lumai 21 has shown good and stable adult plant resistance for 19 years. The aim of this study was to map quantitative trait loci (QTLs) for resistance to powdery mildew in a population of 200 F₃ lines from the cross Lumai 21/Jingshuang 16. The population was tested for powdery mildew reaction in Beijing and Anyang in the 2005–2006 and 2006–2007 cropping seasons, providing data for 4 environments. A total of 1,375 simple sequence repeat (SSR) markers were screened for associations with powdery mildew reactions, initially in bulked segregant analysis. Based on the mean disease values averaged across environments, broad-sense heritabilities of maximum disease severity and area under the disease progress curve were 0.96 and 0.77, respectively. Three QTLs for adult plant resistance were detected by inclusive composite interval mapping. These were designated QPm.caas-2BS, QPm.caas-2BL and QPm.caas-2DL, respectively, and explained from 5.4 to 20.6% of the phenotypic variance across environments. QPm.caas-2BS and QPm.caas-2DL were likely new adult plant resistance QTLs flanked by SSR markers Xbarc98–Xbarc1147 and Xwmc18–Xcfd233, respectively. These markers could be useful for improving wheat powdery mildew resistance in breeding programs.     

Molecular detection of a gene effective against powdery mildew in the wheat cultivar Liangxing 66

Since it was commercialized in 2008, Liangxing 66 is one of the most widely grown cultivars of wheat (Triticum aestivum L.) in winter and facultative wheat-producing regions in northern China. This cultivar displays broad-spectrum resistance to isolates of powdery mildew. To identify the powdery mildew resistance gene in Liangxing 66, genetic analysis and molecular mapping were conducted using the F₂ populations and F_2:3 families derived from the reciprocal crosses of Liangxing 66 and the susceptible cultivar Jingshuang 16. A single dominant gene, tentatively designated PmLX66, conferred resistance in Liangxing 66 to the powdery mildew isolate E09. The results of molecular mapping indicated that this gene was located on the short arm of chromosome 5D and flanked by SCAR203 and Xcfd81 at genetic distances of 0.4 and 2.8?cM, respectively, which is similar to the position of locus Pm2. However, PmLX66 and Pm2 showed different reactions to five of the 42 isolates of powdery mildew tested. Together, these results indicated that PmLX66 was most likely an allele of Pm2. Based on its superior yield and agronomic performance, in combination with powdery mildew resistance, Liangxing 66 is useful as a promising parent for control of powdery mildew and for the development of new disease-resistant cultivars.     

Germin-like proteins (GLPs) in cereal genomes: gene clustering and dynamic roles in plant defence

The recent release of the genome sequences of a number of crop and model plant species has made it possible to define the genome organisation and functional characteristics of specific genes and gene families of agronomic importance. For instance, Sorghum bicolor, maize (Zea mays) and Brachypodium distachyon genome sequences along with the model grass species rice (Oryza sativa) enable the comparative analysis of genes involved in plant defence. Germin-like proteins (GLPs) are a small, functionally and taxonomically diverse class of cupin-domain containing proteins that have recently been shown to cluster in an area of rice chromosome 8. The genomic location of this gene cluster overlaps with a disease resistance QTL that provides defence against two rice fungal pathogens (Magnaporthe oryzae and Rhizoctonia solani). Studies showing the involvement of GLPs in basal host resistance against powdery mildew (Blumeria graminis ssp.) have also been reported in barley and wheat. In this mini-review, we compare the close proximity of GLPs in publicly available cereal crop genomes and discuss the contribution that these proteins, and their genome sequence organisation, play in plant defence.     

Mapping of novel powdery mildew resistance gene(s) from <Emphasis Type="Italic">Agropyron cristatum</Emphasis> chromosome 2P

Key message

A physical map of Agropyron cristatum 2P chromosome was constructed for the first time and the novel powdery mildew resistance gene(s) from chromosome 2P was(were) also mapped.

Abstract

Agropyron cristatum (L.) Gaertn. (2n = 28, PPPP), a wild relative of common wheat, is highly resistant to powdery mildew. Previous studies showed that wheat-A. cristatum 2P disomic addition line II-9-3 displayed high resistance to powdery mildew, and the resistance was attributable to A. cristatum chromosome 2P. To utilize and physically map the powdery mildew resistance gene(s), 15 wheat-A. cristatum 2P translocation lines and three A. cristatum 2P deletion lines with different chromosomal segment sizes, obtained from II-9-3 using ⁶⁰Co-γ ray irradiation, were characterized using cytogenetic and molecular marker analysis. A. cristatum 2P chromosomal segments in the translocations were translocated to different wheat chromosomes, including 1A, 4A, 5A, 6A, 7A, 1B, 2B, 3B, 7B, 3D, 4D, and 6D. A physical map of the 2P chromosome was constructed with 82 STS markers, consisting of nine bins with 34 markers on 2PS and eight bins with 48 markers on 2PL. The BC₁F₂ populations of seven wheat-A. cristatum 2P translocation lines (2PT-3, 2PT-4, 2PT-5, 2PT-6, 2PT-8, 2PT-9, and 2PT-10) were developed by self-pollination, tested with powdery mildew and genotyped with 2P-specific STS markers. From these results, the gene(s) conferring powdery mildew resistance was(were) located on 2PL bin FL 0.66–0.86 and 19 2P-specific markers were identified in this bin. Moreover, two new powdery mildew-resistant translocation lines (2PT-4 and 2PT-5) with small 2PL chromosome segments were obtained. The newly developed wheat lines with powdery mildew resistance and the closely linked molecular markers will be valuable for wheat disease breeding in the future.

     

Radiation-induced translocations with reduced Haynaldia villosa chromatin at the Pm21 locus for powdery mildew resistance in wheat

Haynaldia villosa Schur. (syn. Dasypyrum villosum Candargy, 2n = 2x = 14, genome VV), a species related to wheat, is highly resistant to powdery mildew. The powdery mildew resistance gene Pm21 from H. villosa was introduced into common wheat by means of a translocation line T6VS·6AL, where the 6VS chromosome arm of H. villosa was joined at the centromere with wheat chromosome arm 6AL. To develop small alien translocations, especially interstitial translocations of small alien chromosome segments, we irradiated mature female gametes of a T6VS·6AL translocation line with gamma rays. More than 20 new translocations and deletions of 6V chromatin were obtained and subsequently used to map Pm21. Pm21 was located in a small region (FL 0.45–0.58) by genomic in situ hybridization, molecular marker analysis, and powdery mildew response. Two homozygous translocation lines with small H. villosa chromosome fragments carrying Pm21 were identified by fluorescence in situ hybridization and molecular marker analysis: an interstitial translocation in which a small fragment of 6VS is inserted into chromosome 4B and a terminal translocation with a small fragment of 6VS inserted into 1A. These small alien translocations are being transferred into an adapted elite wheat background by backcrossing to allow their easy use in breeding programs.     

抗白粉病基因PmCH1302的遗传分析及染色体定位

CH1302是以来源于中间偃麦草的八倍体小偃麦TAI7047为桥梁亲本选育的高抗白粉病的小麦新品系,对白粉菌多个流行小种均表现出良好抗性。为了解其抗白粉病基因来源及其在染色体上的位置,对绵阳11×CH1302的F_1、F_2及F_(2∶3)家系进行了遗传分析,推断其抗白粉病基因可能来源于中间偃麦草,暂将其命名为PmCH1302。利用i Select 90K SNP芯片对抗、感病池进行扫描,发现位于2AL染色体上的多态性位点最多,为313个,占全部多态性位点的9.79%,且集中于2AL染色体100~105 c M和150~155 cM两个区域附近。在上述位点选取SSR标记,筛选出3对与Pm CH1302连锁的分子标记,Xwmc522、Xgwm356和Xgwm526,其中Xgwm356和Xgwm526位于Pm CH1302两侧,连锁距离分别为3.1 c M和7.8 cM。利用遗传图谱以及中国春缺体、双端体将PmCH1302定位于小麦2AL染色体上。进一步与位于2AL上的Pm4、Pm50比较发现,PmCH1302可能是位于2AL上的一个新基因或等位基因。     

Genetic control of the wheat Triticum monococcum L. resistance to powdery mildew

Using hybrid analysis and test-clone method, 102 accessions of Triticum monococcum L. from the collection of the Vavilov All-Russia Institute of Plant Industry have been studied. This species of wheat has been found to by considerably polymorphic with respect to the resistance to the fungus Erysiphe graminis DC. f. sp. tritici Marchal. causing powdery mildew. The resistance of most accessions to the fungus population and clones is determined by dominant genes. In rare cases, the resistance was determined by recessive genes or one, two, or three oligogenes. A group of einkorn wheat accessions has been found in which the resistance to powdery mildew was determined by the same dominant factor or different but closely linked ones. Recessive resistance genes of T. monococcum differ from the recessive gene pm5 determining the resistance of T. aestivum plants. The genome of T. monococcum contains various genes of resistance to powdery mildew and is a potential source of effective genes to be used when selecting cultivated species of wheat for immunity.     

Adult plant and seedling resistance to powdery mildew in a Triticum aestivum × Triticum militinae hybrid line

In the progeny of a cross between the common wheat cultivar Tähti and Triticum militinae, a member of the timopheevii group of tetraploid wheats, several hybrid lines were selected that are characterized by improved seedling and adult plant resistance (APR) to powdery mildew. An F₂ single-seed descendant mapping population segregating for seedling resistance and APR to powdery mildew was analysed for the identification of quantitative trait loci (QTL). The main QTL responsible for APR was detected on the long arm of chromosome 4A tightly linked to the Xgwm160 locus on a T. militinae translocation explaining up to 54% of phenotypic variance. The same translocation influenced seedling resistance to powdery mildew upon inoculation of plants with a synthetic population of Blumeria graminis DC. f. sp. tritici, and explained 28–33% of the phenotypic variance.