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1.
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.  相似文献   

2.
D. M. Tucker    C. A. Griffey    S. Liu    M. A. Saghai Maroof   《Plant Breeding》2006,125(5):430-436
Three quantitative trait loci (QTL) associated with adult plant resistance (APR) to powdery mildew (Blumeria graminis) in wheat (Triticum aestivum) cultivar ‘Massey’ were mapped in a previous study. The three QTL were located on chromosomes 2A, 2B and 1B, and explained 50% of the total phenotypic variation. A 293 recombinant inbred line (RIL) breeding population (UJ) derived from the cross of ‘USG 3209’, a derivative of ‘Massey’, and ‘Jaypee’ was used to evaluate the potential effectiveness of marker‐assisted selection (MAS) for APR. Powdery mildew severities of the 293 UJ RILs were evaluated in 2002 (F5 : 6) and 2003 (F6 : 7) under natural disease pressure in the field. The 293 RILs were also evaluated for disease severity in a 2004 (F7 : 8) greenhouse experiment using a composite of five different isolates of B. graminis. Selection of RILs possessing the QTL on chromosome 2A, and to a lesser extent, the one on chromosome 1B was effective in identifying powdery mildew resistance in both greenhouse and field experiments. Overall, selecting RILs with QTL on chromosomes 2A and 2B was most successful in identifying highly resistant RILs, which had mean mildew severities of 4.4% and 3.2% in 2002 and 2003 field experiments, respectively. Breeders implementing MAS programs for APR to powdery mildew via selection of RILs containing the two QTL on chromosomes 2A and 2B likely will obtain RILs having high levels of resistance in the field, however combining all three QTL may ensure greater durability.  相似文献   

3.
Powdery mildew, caused by Podosphaera xanthii (syn. Sphaerotheca fuliginea ex Fr. Poll.), is one of the most economically important foliar diseases in cucumber (Cucumis sativus L.). Cucumber parental line ‘Kyuri Chukanbohon Nou 5 Go’, developed from weedy cucumber line CS-PMR1, is highly resistant to powdery mildew and is promising breeding material. We performed quantitative trait locus (QTL) analysis using double-digest restriction-site-associated DNA sequencing (ddRAD-Seq) in a population from a cross between ‘Kyuri Chukanbohon Nou 5 Go’ and the Japanese native cultivar ‘Kaga-aonaga-fushinari’, which is susceptible to powdery mildew. The resistance of the population and its parents was evaluated using leaf disc assays and image analysis. We detected one major QTL on Chr. 5 that was effective at both 20°C and 25°C and one minor QTL on Chr. 1 effective at 20°C. We detected two additional QTLs in subpopulation: one on Chr. 3 effective at 20°C and one on Chr. 5 effective at both 20°C and 25°C in a position different from the major QTL. The resistance alleles at all four QTLs were contributed by ‘Kyuri Chukanbohon Nou 5 Go’. The results of this study can be used to develop practical DNA markers tightly linked to genes for powdery mildew resistance.  相似文献   

4.
Y. Bougot    J. Lemoine    M.T. Pavoine    H. Guyomar'ch    V. Gautier    H. Muranty    D. Barloy 《Plant Breeding》2006,125(6):550-556
Powdery mildew is one of the major diseases of wheat in regions with a maritime or semi‐continental climate which can strongly affect grain yield. The objective of the study was to identify and compare quantitative resistance to powdery mildew of line RE9001 at the adult plant and vernalized seedling stages. RE9001 has no known Pm gene and shows a high level of adult plant resistance in the field. Using 104 recombinant inbred lines (RILs) of an RE9001 × ‘Courtot’ F8 population, a genetic map was developed with 363 markers distributed over 26 linkage groups and covering 3825 cM. The global map density was 1 locus/10.3 cM. RILs were assessed under field and tunnel greenhouse conditions for 2 years in two locations. Eleven quantitative trait loci (QTL) were detected at the adult stage and they explained 63% of the variation, depending on the environment. Three QTLs were found, at least, in the two environments. One QTL from RE9001, mapped on chromosome 2B, was stable in each environment. This QTL, QPm.inra.2B, explained 10.3–36.6% of the variation and could be mapped in the vicinity of the Pm6 gene. At the vernalized seedling stage, one QTL detected by the isolate 93‐27 could be an allele of the Pm3g gene present in ‘Courtot’. No residual effect of the Pm3g gene was detected at either stage. Markers flanking the QTL 2B could be useful tools to combine resistance to powdery mildew in wheat cultivars.  相似文献   

5.
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.  相似文献   

6.
Powdery mildew (PM, caused by Podosphaera fusca) and downy mildew (DM, caused by Pseudoperonospora cubensis) are important diseases of cucumber (Cucumis sativus). Breeding for resistance has been undertaken since the 1940s, but underlying resistance genes have not been functionally analysed yet. The published genome sequence of cucumber catalyses the search for such genes. Genetic studies have indicated that resistances to PM and DM in cucumber are often inherited recessively, which indicates the presence of susceptibility genes (S-genes). Therefore we analyzed the cucumber genome for homologs of functionally proven S-genes known from other plant species. We identified 13 MLO-like genes in cucumber, three of which cluster in Clade V, the clade that contains all known MLO-like susceptibility genes to powdery mildews in other dicots. The expression of one of these three genes, CsaMLO1, located on chromosome 1, was upregulated after PM inoculation. It co-localizes with a QTL for PM resistance previously identified. Also homologs of the susceptibility genes PMR4 and PMR5 are located at this QTL. The second MLO-like gene from Clade V (CsaMLO8) resides in a recessively inherited major QTL for PM resistance at the bottom of chromosome 5, together with a PMR6-like gene. Two major QTL for DM recessive resistance at the top of chromosome 5 co-localize with CsaDMR6-2, which is homologous to the DMR6 susceptibility gene in Arabidopsis. This study has identified several candidate genes for susceptibility to PM and DM in cucumber that may explain QTL for recessively inherited resistance, reported earlier.  相似文献   

7.
【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。  相似文献   

8.
玉米霜霉病的分子遗传学研究进展   总被引：1，自引：0，他引：1  
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  相似文献   

9.
B. Chaitieng    A. Kaga    O. K. Han    X. W. Wang    S. Wongkaew    P. Laosuwan    N. Tomooka  D. A. Vaughan 《Plant Breeding》2002,121(6):521-525
Both restriction fragment length polymorphism (RFLP) and amplified fragment length polymorphism (AFLP) analyses were employed to map a new source of resistance to powdery mildew in mungbean. Disease scores of an F2 population derived from the cross between a moderately resistant breeding line VC1210A and a susceptible wild relative (Vigna radiata var. sublobata, accession TC1966) showed a continuous distribution and was treated as a quantitative trait. Although no significant quantitative trait loci (QTL) that can explain the variation was detected by QTL analysis based on the reconstructed RFLP linkage map, new marker loci associated with resistance were discovered by AFLP analysis. The RFLP loci detected by two of the cloned AFLP bands are associated with resistance and constitute a new linkage group. A major resistance quantitative trait locus was found on this linkage group that accounted for 64.9% of the variation in resistance to powdery mildew. One of the probes developed in this study has the potential to assist in breeding for powdery mildew resistance in mungbean.  相似文献   

10.
Genetic diversity of maize inbred lines in relation to downy mildew   总被引：2，自引：0，他引：2  
A major emphasis in maize breeding in Asian countries has been the improvement for resistance to downy mildew, a serious disease that causes significant yield losses. A total of 102 inbred lines, including lines from Asian breeding programs, Mexico, USA and Germany, were analyzed with 76 SSR markers to measure diversity and investigate the effect of selection for downy mildew resistance. A mean polymorphism information content of 0.59, with a range of 0.14 to 0.83, was observed. Diversity at the gene level showed an average of 5.4 alleles per locus and a range of two to 16 alleles per locus, with a total of 409 alleles. About half of the alleles in the Asian lines had frequencies of 0.10 or less, and only 2% had frequencies > 0.80, indicating the presence of many alleles, and thus a high level of diversity. Some of the high-frequency alleles were in chromosomal regions associated with disease resistance. However, the frequencies of alleles in three SSR loci that are linked to a QTL for resistance to downy mildews in Asia were not significantly different in the subtropical/tropical Asian lines as compared to all the lines in the study. Lines from the US, Germany, and China, comprised three clusters of temperate maize(GS = 0.31), while those from India, Indonesia, Philippines, Thailand, Vietnam and CIMMYT comprised seven indistinct clusters of subtropical and subtropical maize (GS = 0.29). We conclude that maize breeding activity in Asia has not caused a decline in the overall amount of diversity in the region. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

11.
Downy mildew of sunflower, caused by the Oomycete, Plasmopara halstedii is at present controlled by major resistance genes. However, the pathogen has shown a considerable capacity for changes in virulence and these resistance genes are overcome only a few years after they have been introduced into new sunflower varieties. This paper presents research for quantitative, non-race-specific resistance independent of major genes. The reaction of cultivated sunflower genotypes to field attack by downy mildew was studied over 4 years in several environments and in the presence of the two most common races in France: 703 and 710. An experimental protocol with pre-emergence irrigation was developed, making it possible to observe downy mildew reaction whatever the weather conditions. Significant levels of partial resistance were observed in about 50 inbred sunflower lines among the 800 observed. These results suggest that it should be possible to select for non-race-specific downy mildew resistance and to include it in modern varieties. However, since this non-specific resistance is partial, it may be necessary to combine it with major gene resistance. Possible strategies are discussed to obtain durable resistance to downy mildew.  相似文献   

12.
Sunflower lines RHA‐274, HA‐61 and RHA‐325 were studied for their resistance to race 330 of downy mildew (Plasmopara halstedii). The same inbred line, with normal (HA‐89) or sterile cytoplasm (cmsHA‐89) was used in all the crosses as susceptible parent, and, in each cross, only one genotype of the resistant parent was studied. The resistant‐to‐susceptible ratios obtained in the BC1 and F2 progenies from the crosses of the lines RHA‐274 and HA‐61 to cmsHA‐89 and HA‐89, respectively, suggested that, in each resistant line, two dominant genes are responsible for resistance to this downy mildew race. One of the genes (A) is epistatic to the other (B), and the recessive allele b in homozygosity is also epistatic to aa, with plants carrying aabb genotypes being resistant. Resistance to race 330 seemed to be controlled by two complementary genes in the sunflower inbred line RHA‐325, the dominant allele of one of them being present in cmsHA‐89. In the genotypes HA‐89 or cmsHA‐89, the existence of genes that modify the expected segregations following the crosses with resistant parents is proposed. It is concluded that, although major genes have been described as responsible for monogenic resistance to downy mildew, other types of regulation of this character, such as complementarity and epistatic relationships, do occur.  相似文献   

13.
Bacterial wilt caused by Ralstonia solanacearum is one of the most devastating diseases of tomato. Tomato cultivar ‘Hawaii 7996’ has been shown to have stable resistance against different strains under different environments. This study aimed to locate quantitative trail loci (QTLs) associated with stable resistance using 188 recombinant inbred lines (RILs) derived from ‘Hawaii 7996’ and ‘West Virginia 700.’ A new linkage map with good genome coverage was developed, mainly using simple sequence repeat markers developed from anchored bacterial artificial chromosome or scaffold sequences of tomato. The population was evaluated against phylotype I and phylotype II strains at seedling stage or in the field in Indonesia, Philippines, Taiwan, Thailand, and Reunion. Two major QTLs were identified to be associated with stable resistance. Bwr-12, located in a 2.8-cM interval of chromosome 12, controlled 17.9–56.1 % of total resistance variation. The main function of Bwr-12 was related to suppression of internal multiplication of the pathogen in the stem. This QTL was not associated with resistance against race 3-phylotype II strain. Bwr-6 on chromosome 6 explained 11.5–22.2 % of the phenotypic variation. Its location differed with phenotype datasets and was distributed along a 15.5-cM region. The RILs with the resistance allele from both Bwr-12 and Bwr-6 had the lowest disease incidence, which was significantly lower than the groups with only Bwr-12 or Bwr-6. Our studies confirmed the polygenic nature of resistance to bacterial wilt in tomato, and that stable resistance in ‘Hawaii 7996’ is mainly associated with Bwr-6 and Bwr-12.  相似文献   

14.
A partial resistance to maize mosaic virus (MMV) and maize stripe virus (MStV) was mapped in a RILs population derived from a cross between lines MP705 (resistant) and B73 (susceptible). A genetic map constructed from 131 SSR markers spanned 1399 cM with an average distance of 9.6 cM. A total of 10 QTL were detected for resistance to MMV and MStV, using composite interval mapping. A major QTL explaining 34–41% of the phenotypic variance for early resistance to MMV was detected on chromosome 1. Another major QTL explaining up to 30% of the phenotypic variation for all traits of resistance to MStV was detected in the centromeric region of chromosome 3 (3.05 bin). After adding supplementary SSR markers, this region was found to correspond well to the one where a QTL of resistance to MStV already was located in a previous mapping study using an F2 population derived from a cross between Rev81 and B73. These results suggested that these QTL of resistance to MStV detected on chromosome 3 could be allelic in maize genome.  相似文献   

15.
While the cultivated soybean, Glycine max (L.) Merr., is more recalcitrant to pod dehiscence (shattering-resistant) than wild soybean, Glycine soja Sieb. & Zucc., there is also significant genetic variation in shattering resistance among cultivated soybean cultivars. To reveal the genetic basis and develop DNA markers for pod dehiscence, several research groups have conducted quantitative trait locus (QTL) analysis using segregated populations derived from crosses between G. max accessions or between a G. max and G. soja accession. In the populations of G. max, a major QTL was repeatedly identified near SSR marker Sat_366 on linkage group J (chromosome 16). Minor QTLs were also detected in several studies, although less commonality was found for the magnitudes of effect and location. In G. max × G. soja populations, only QTLs with a relatively small effect were detected. The major QTL found in G. max was further fine-mapped, leading to the development of specific markers for the shattering resistance allele at this locus. The markers were used in a breeding program, resulting in the production of near-isogenic lines with shattering resistance and genetic backgrounds of Japanese elite cultivars. The markers and lines developed will hopefully contribute to the rapid production of a variety of shattering-resistant soybean cultivars.  相似文献   

16.
One population of pearl millet (Pennisetum glaucum (L.) R. Br.) highly susceptible to downy mildew (Sclerospora graminicola (Sacc.) Schroet.) was subjected to two cycles of recurrent selection for downy mildew resistance using a modified greenhouse screening method. The response to selection was evaluated under greenhouse and field conditions using 50 random S1 progenies and 50 random full-sib progenies from each cycle bulk. Significant progress over cycles of selection was observed in all evaluation trials. These results demonstrated that, in a susceptible population, recurrent selection effectively increased the level of resistance to downy mildew. The modified greenhouse method for assessing resistance to downy mildew effectively differentiated genotypes and had the advantages of greater rapidity and suitability for use throughout the year, independent of season. A rapid decline of genotypic variance was observed in advanced cycles of selection, indicating that a small number of genes controls downy-mildew resistance in this population. The comparison of genotypic and error variance components from S1 progenies and full-sib progenies suggested that full-sib progenies can be used successfully in recurrent selection for increased downy-mildew resistance.  相似文献   

17.
Downy mildew (Pseudoperonospora cubensis) is the most devastating disease in muskmelon (Cucumis melo). A generation mean analysis study was designed to determine the types of gene action and estimate the heritability for resistance to downy mildew in four selected crosses of muskmelon. Generation mean analysis revealed that genetic dominance may be of greater importance for expression of resistance to downy mildew in both greenhouse and field experiments and in all the crosses. The F1 mean was significantly lesser than the mid-parent value and skewed towards resistant parent in all the crosses. Negative sign associated with gene effects indicated, in those crosses, that disease level could be decreased in relation to midparent. All the crosses expressed significant and positive additive (d) gene effects. Dominance (h) and dominance × dominance (l) gene effects had opposite sign in all crosses and both experiments, which implied duplicate type of gene action. High mid-parent heterosis in all the crosses indicated strong dominance effects (as combination of parental alleles) for resistance to downy mildew. In all the crosses, both resistant and susceptible parent contributed one or more dominant/partially dominant factors for resistance. Estimates of broad-sense heritability were high and relatively consistent in both experiments. The two different screening experiments showed that fixable gene effects (d + i) were lower than the non-fixable gene effects (h + l) in all the crosses indicating greater role of non-additive effects in the inheritance of resistance to downy mildew. Resistance to downy appeared to be controlled mainly by dominance effects, therefore the inbred lines IIHR 121 and IIHR 122 could be used strategically to exploit heterotic effects.  相似文献   

18.
Fusarium graminearum could cause serious yield loss of soybean. Host resistance could offer an economical and effective way to control F. graminearum. The aims of this study were to identify and confirm quantitative trait loci (QTLs) underlying resistance to F. graminearum, and to analyse the genetic effects of pyramid resistance QTL on resistance level. A total of 140 F2:14 recombinant inbred lines (RILs) were constructed via the cross between 'Hefeng 25' (moderate resistance to F. graminearum) and 'Conrad' (resistance to F. graminearum). The molecular genetic linkage map was constructed based on 164 simple sequence repeat (SSR) markers. A total of seven QTLs underlying F. graminearum resistance, located on six chromosomes, were identified. Among these seven identified QTLs, beneficial allele of qFG-1, qFG-2 and qFG-3 derived from 'Hefeng 25' and beneficial allele of qFG-4, qFG-5, qFG-6, qFG-7 derived from 'Conrad'. Of these seven identified QTLs, qFG-1, qFG-3, qFG-4 and qFG-5 were novel for F. graminearum resistance. Four pairs of QTLs with significant epistatic effects were found. The accumulation of resistance QTL was positively correlated with decreases in disease severity index, which was valuable for improving efficiency of marker-assistant breeding in F. graminearum resistance.  相似文献   

19.
Plant height is an important plant architecture trait that determines the canopy structure, photosynthetic capacity and lodging resistance of upland cotton populations. To understand the genetic basis of plant height for marker-assisted breeding, quantitative trait loci (QTL) analysis was conducted based on the genetic map of recombinant inbred lines (RILs) derived from the cross “CRI12 × J8891” (Gossypium hirsutum L.). Three methods, including composite interval mapping, multiple interval mapping and multi-marker joint analysis, were used to detect QTL across multiple environments in the RILs and in the immortalized F2 population developed through intermating between RILs. A total of 19 QTL with genetic main effects and/or genetic × environment interaction effects were identified on 15 chromosomes or linkage groups, each explaining 5.8–14.3 % of the phenotypic variation. Five digenic epistatic QTL pairs, mainly involving additive × additive and/or dominance × dominance, were detected in different environments. Seven out of eight interacting loci were main-effect QTL, suggesting that these loci act as major genes as well as modifying genes in the expression of plant height. The results demonstrate that additive effects, dominance and epistasis are all important for the genetic constitution of plant height, with additive effects playing a more important role in reducing plant height. QTL showing stability across environments that were repeatedly detected by different methods can be used in marker-assisted breeding.  相似文献   

20.
G. Backes    G. Schwarz    G. Wenzel  A. Jahoor 《Plant Breeding》1996,115(5):419-421
A quantitative trait loci (QTL) analysis of quantitative powdery mildew resistance was performed on 216 doubled haploid lines derived from a cross between the winter-barley varieties ‘Igri’ and ‘Danilo’ using 67 RFLP loci. Resistance to powdery mildew was determined in the field with natural infection and on detached primary leaves with a specific isolate. The major QTL found in both sets of analysis mapped to the same chromosomal region. No further QTL could be found in the analysis based on detached leaves and one additional minor QTL was found in the analysis based on field data.  相似文献   

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