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1.
Several species of wheat stem sawflies (WSS) are pests of wheat, including Cephus cinctus Norton in North America. Larvae feed inside the stems and cut the stem near plant maturity. The primary means of control is resistance due to solid stems, largely controlled by a locus on chromosome 3B (Qss.msub‐3BL). Cultivars that differed for WSS resistance, but with similar stem solidness, were crossed to determine the genetic basis for the differences. The cultivar ‘Scholar’ is susceptible, while ‘Conan’ shows resistance. Scholar and Conan possessed different alleles at Qss.msub‐3BL. Both alleles conferred solidness, yet the Conan allele conferred higher WSS resistance. An allele from Conan on chromosome 4A also decreased infestation and stem cutting. The 3B and 4A alleles from Conan acted in an additive fashion to provide increased WSS resistance without increasing stem solidness. Stem solidness has long been used by breeders as a proxy for WSS resistance because of its simplicity. Our results suggest that other resistance mechanisms may complement solid stems.  相似文献   

2.
Stripe rust of wheat caused by the fungal pathogen is a destructive foliar disease of wheat. Thus, it is crucial step to characterize the resistant germplasm for stripe rust in a diverse germplasm pool for their ultimate utilization in efficient crop rust resistance breeding. In the present study, we followed two pronged strategies involving integrated phenotypic and molecular characterization of 440 diverse wheat germplasm lines for rust resistance. The germplasm panel was extensively evaluated in field epiphytotic conditions during two consecutive years. After rigorous screening, 72 accessions were successfully revealed as resistant to moderately resistant to stripe rust. Subsequently, entries were then evaluated for their field agronomicperformances, considering prerequisites for serving as a donor germplasm,particularly for yield and 33 potential rust-resistant accessions were identified. Furthermore, to detect the sources of resistance, accessions were molecular characterized for potential race-specific resistance genes Yr5, Yr10,Yr15, and effective adult plant resistance (APR) gene Lr34/Yr18/pm38. We identified the 22 accessions possessing one or more single resistance genes and two accessions were observed with at least three of them. Moreover, Lr34/Yr18/pm38 was determined to confer resistance when observed along with any of the race-specific genes. Thus, the study not only provides proof of concept methodology to identify candidate resistant sources from large germplasm collections but simultaneouslyconfirmed the contribution of combining race-specific andnon-specific APR genes. The finding could further assist in the potential deployment of resistant genes directly into the stripe rust breeding program by involving marker-assisted approaches.  相似文献   

3.
Numerous stripe rust resistance genes have been identified from wheat, and new virulent races of Puccinia striiformis f. sp. tritici have also emerged in recent years. Deployment of diverse combinations of resistance genes is an efficient way to combat virulent evolution of strip rust pathogen. In this study, publically available molecular markers were used to identify the distribution of 36 Yr genes in 672 wheat accessions. The effectiveness of Yr genes individually and in combinations was also evaluated in field conditions. The result showed effective resistance of some recently applied genes, such as Yr15 and Yr65. It also showed the lost efficacy of some once widely used genes, such as Yr9 and Yr10. Moreover, significant additive effects were observed in some gene combinations, such as Yr9 + Yr18 and Yr30 + Yr46. Proper deploying of Yr genes and utilizing the positive interactions will be helpful for durable resistance breeding in wheat.  相似文献   

4.
The stem solidness trait in wheat has been the most effective mechanism for management of the wheat stem sawfly (WSS) for six decades. However, recent results have shown that in certain genotypes, the degree of stem solidness is not a useful indicator of WSS resistance. A morphological characterization of solidness expression indicated that in the genotype ‘Conan’, very solid pith undergoes rapid retraction during stem maturation, resulting in significantly less solidness at maturity. In other solid‐stemmed genotypes, including the standard WSS‐resistant cultivar ‘Choteau’, dense pith in the stem remains nearly unchanged throughout plant development. In cage trials, ‘Conan’ plants were less preferred for oviposition by the WSS when paired with ‘Choteau’ plants. Field bioassays using near‐isogenic lines differing for alleles at Qss.msub‐3BL showed that the Conan allele provides higher levels of early stem solidness and rapid pith retraction during stem maturation. These results suggest that the traditional approach for increasing WSS resistance by selecting for increasing stem solidness needs to be modified to consider temporal variations in pith expression associated with alleles at Qss.msub‐3BL.  相似文献   

5.
Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is an important insect pest which causes severe economic losses in wheat (Triticum spp.). Among the various U.S. RWA biotypes, biotype 1 (RWA1) and biotype 2 (RWA2) are the most prevalent and most virulent on cultivated genotypes. Although many sources of resistance to these biotypes are available among landraces, their relatedness should be characterized to permit their more efficient use in breeding programs. In this study, 38 hexaploid accessions resistant to biotype 1 and/or biotype 2 were evaluated for genetic diversity based on amplified fragment length polymorphisms (AFLP). Fifteen AFLP selective primer combinations were used to genotype these accessions, resulting in 893 amplicons. Of these, 274 (30.6%) informative polymorphic bands were used for genetic diversity analysis. Genetic similarity coefficients ranged from 0.47 to 0.87 among the resistant accessions, indicating high genetic diversity among them. Cluster analysis grouped the 38 accessions into two major clusters, I and II, including resistant lines for RWA1 and RWA2. The study indicated that accessions in the National Small Grains Collection conferring RWA1 or RWA2 resistance comprise a diversified population which should support introgression efforts and provide genetic diversity for future breeding for RWA resistance.  相似文献   

6.
Pre-harvest sprouting (PHS) causes significant yield loss and degrade the end-use quality of wheat, especially in regions with prolonged wet weather during the harvesting season. Unfortunately, the gene pool of Triticum durum (tetraploid durum wheat) has narrow genetic base for PHS resistance. Therefore, finding out new genetic resources from other wheat species to develop PHS resistance in durum wheat is of importance. A major PHS resistance QTL, Qphs.sicau-3B.1, was mapped on chromosome 3BL in a recombinant inbred line population derived from ‘CSCR6’ (Triticum spelta), a PHS resistant hexaploid wheat and ‘Lang’, a PHS susceptible Australian hexaploid wheat cultivar. This QTL, Qphs.sicau-3B.1, is positioned between DArT marker wPt-3107 and wPt-6785. Two SCAR markers (Ph3B.1 and Ph3B.2) were developed to track this major QTL and were used to assay a BC2F8 tetraploid population derived from a cross between the durum wheat ‘Bellaroi’ (PHS susceptible) and ‘CSCR6’ (PHS resistant). Phenotypic assay and marker-assisted selection revealed five stable tetraploid lines were highly PHS resistant. This study has successfully established that PHS-resistance QTL from hexaploid wheat could be efficiently introgressed into tetraploid durum wheat. This tetraploid wheat germplasm could be useful in developing PHS resistant durum cultivars with higher yield and good end-use quality.  相似文献   

7.
Septoria tritici blotch (STB), caused by the ascomycete fungus Zymoseptoria tritici (also known as Mycosphaerella graminicola), is one of the most devastating foliar wheat diseases worldwide. Host resistance is the most effective strategy for management of the disease. A factor that complicates the determination of resistance is its reported interaction with heading date (Hd) and plant height (Ph). In this study, we report findings from a genome-wide association study of resistance to STB in a world-wide collection of 96 wheat accessions. The collection was evaluated under conditions of artificial infection for seedling and adult plant STB resistance, Hd and Ph in field trials. Marker-trait associations (MTAs) were detected using a mixed linear model. STB disease severities showed significant phenotypic variation. In total, 73 MTAs involving STB resistance were detected. The chromosomal locations of some of them were similar to known Stb genes or quantitative trait loci; whereas others were detected in new genomic regions. The field experiment showed evidence of genetic association between STB resistance and Hd, but only for a few genotypes. This was corroborated at the molecular level, where a total of eight genomic regions associated with STB resistance were located in similar positions to MTAs for Hd. New genomic regions associated with STB resistance found here could be useful in wheat breeding aimed at controlling STB after validation in relevant genetic backgrounds  相似文献   

8.
NBS (nucleotide binding site) genes, one type of the most important disease-resistance genes in the plant kingdom, are usually found clustered in genome. In this study, a total of 2288 full-length NBS protein-coding sequences were isolated from the wheat (Triticum aestivum L.) genome, and 903 TaNBSs of which were found expressed in wheat. Meanwhile, 2203 microsatellite loci were detected within 1061 scaffolds containing TaNBS. The distribution of these microsatellite loci across wheat homologous groups (HG) is 20% HG2, 16% HG7, 15% HG1, 15% HG6, 12% HG4, 12% HG5 and 10% HG3. We developed 1830 NBS-related microsatellite (NRM) markers for the microsatellite loci on TaNBS-scaffold sequences.Among them, 342 NRM markers were developed for HG2 with the largest number of microsatellite loci, and 69 out of these markers were anchored to the wheat genetic map using mapping population. Then, a total of 26 2AS-NRM markers, nine 2BL-NRM markers and nine 2DL-NRM markers were integrated into the genetic maps carrying Yr69, Pm51 and Pm43, respectively. Finally, candidate sequences, within the gene clusters where Yr5 and Sr21 located, were analyzed according to the genomic position information of TaNBS and NRM markers. These NRM markers have clear chromosome locations and are correlated with potential disease resistance sequences, which can be manipulated to mapping or adding linkage markers of disease-resistance genes or QTLs, especially for those in the NBS gene clusters.  相似文献   

9.
Hessian fly is an important pest of wheat on the North American continent and the temperate Mediterranean drylands. Yield losses caused by this insect in Morocco are the heaviest in the Mediterranean region and are estimated to be 36% on average. Genetic resistance to Mediterranean Hessian fly biotypes has not been found in durum wheat, although large numbers of durum accessions were screened. Genes for resistance were found in common wheat; some of which are transferable to durum. However, there is a need to broaden the genetic base for resistance in durum wheat. The objective of this work was to introgress resistance from selected Triticum araraticum and T. carthlicum accessions using multiple backcross methodology. The experimental recipient durum wheat included numerous adapted and high‐yielding lines. Testing for Hessian fly resistance under controlled conditions and field yield data showed that this programme yields Hessian fly‐resistant durum lines with good yields and adaptation.  相似文献   

10.
The root lesion nematode Pratylenchus thornei is widely distributed in Australian wheat (Triticum aestivum) producing regions and can reduce yield by more than 50%, costing the industry AU$50 M/year. Genetic resistance is the most effective form of management but no commercial cultivars are resistant (R) and the best parental lines are only moderately R. The wild relatives of wheat have evolved in P. thornei-infested soil for millennia and may have superior levels of resistance that can be transferred to commercial wheats. To evaluate this hypothesis, a collection of 251 accessions of wheat and related species was tested for resistance to P. thornei under controlled conditions in glasshouse pot experiments over two consecutive years. Diploid accessions were more R than tetraploid accessions which proved more R than hexaploid accessions. Of the diploid accessions, 11 (52%) Aegilops speltoides (S-[B]-genome), 10 (43%) Triticum monococcum (A m -genome) and 5 (24%) Triticum urartu (A u -genome) accessions were R. One tetraploid accession (Triticum dicoccoides) was R. This establishes for the first time that P. thornei resistance is located on the A-genome and confirms resistance on the B-genome. Since previous research has shown that the moderate levels of P. thornei resistance in hexaploid wheat are dose-dependent, additive and located on the B and D-genomes, it would seem efficient to target A-genome resistance for introduction to hexaploid lines through direct crossing, using durum wheat as a bridging species and/or through the development of amphiploids. This would allow resistances from each genome to be combined to generate a higher level of resistance than is currently available in hexaploid wheat.  相似文献   

11.
The allopolyploidization event that created cultivated oilseed rape Brassica napus L, followed by intense breeding, reduced its genetic diversity. Resynthesized (RS) B. napus L. obtained by interspecific hybridization between genotypes of B. rapa L. and B. oleracea L. can be a valuable source for broadening genetic diversity in cultivated oilseed rape. In this study, we determined the extent of DNA polymorphism among natural accessions of oilseed rape, resynthesized B. napus, their parental species and double-low quality semi-RS lines carrying the Rfo gene. Using 10 selected primer combinations, 522 polymorphic AFLP markers were scored in the complete set of 100 Brassica sp. To detect relationships between these genotypes, a cluster analysis was performed using the Jaccard’s distance. Resynthesized allopolyploids clustered directly between their diploid parents. Cultivated accessions of oilseed rape created a compact group away from resynthesized allopolyploids as well as semi-RS lines. The natural oilseed rape group, which consists of 49 cultivars and breeding lines of oilseed rape, is characterized by lower genetic diversity than the group of 33 accessions of resynthesized oilseed rape, and the analysis showed that the double-low quality semi-RS lines represent a specific genetic variation of B. napus. The de novo resynthesized B. napus lines and the semi-RS lines of double-low quality generated from them, provide a significant opportunity for enrichment the gene pool of oilseed rape.  相似文献   

12.
Association mapping is a method to identify associations between target traits and genetic markers based on linkage disequilibrium (LD) of a quantitative trait locus. Synthetic hexaploid wheat (SHW) is derived from a cross between Triticum durum Desf. and Aegilops tauschii Coss. that enhances genetic diversity and broadens breeding resources. In this study, phenotypic diversity in 110 wheat accessions (86 SHW germplasm specimens and 24 conventional wheat varieties) was evaluated quantitatively for yield characteristics of grains per spike, thousand kernel weight, and spike length. Phenotypic data were collected over two years at two locations, and 1785 alleles were detected (mean 6.59), ranging from 3 to 11 alleles per locus. The average genetic diversity index was 0.749, with a range from 0.239 to 0.923. The polymorphic information content (PIC) ranged from 0.145 to 0.968, with a mean value of 0.695. The genetic diversity index and PIC indicated that genome B > D > A. Accessions were grouped into three subgroups based on STRUCTURE and unweighted pair-group with arithmetic mean clustering. The mean LD decay across the genome was 11.78 cM. Association mapping between traits and simple sequence repeat markers was performed using the generalized linear model approach. Forty-six SSR loci were significantly associated with the measured agronomic traits in two geographic locations. Together, these results broaden our knowledge of how to harness elite genes and genetic diversity in SHW in genomic and marker-assisted selection.  相似文献   

13.
The cabbage root fly Delia radicum L. (Diptera: Anthomyiidae) is one of the major pests of many Brassica crops in the temperate areas of Europe and North America. At present, turnip (B. rapa ssp. rapa L.) varieties resistant to the pest does not exist. With the aim to fill this gap, a no-choice tolerance test of 56 accessions among turnips, turnip tops and turnip greens was performed under controlled conditions by introducing D. radicum eggs. Plant survival, leaf and root conditions, pupae number and weight significantly varied among plant accessions. Ten putatively resistant and ten susceptible accessions (control group) were selected from this first screening, transplanted in the field and exposed to natural infestation to detect antibiosis and antixenosis mechanisms. Both in the laboratory and in the field, pupae number significantly varied within accessions and between resistant and susceptible group, although pupal weight did not, indicating the absence of antibiosis effect on this early stage. In the field, the number of galleries was significantly lower in the resistant group in comparison with the control. Resistant accessions had smaller size, and a smaller, white and mostly buried root. Within the resistant and susceptible accessions, larger plants harboured more pupae, however purple roots were those most preferred, and the hosted pupae weighed most. Three accessions from the resistant group (MBGBR0178, MBGBR0570 and MBGBR0371) stand out for resistance to D. radicum possibly through antixenosis mechanisms.  相似文献   

14.
Summary Fusarium head blight (FHB) is a serious disease of wheat worldwide that may cause substantial yield and quality losses. Breeding for FHB-resistant cultivars is the most cost-effective approach to control FHB. The objective of the present study was to determine the relationship of resistance between new resistant sources and Sumai 3 using five simple sequence repeat (SSR) markers closely linked to the major QTL for FHB resistance on chromosome arms 3BS and 6BS. All five SSR markers were highly polymorphic between Sumai 3 (and its derivatives) and susceptible Canadian wheat lines. Most of the Sumai 3-derived Chinese wheat accessions and three Canadian FHB-resistant lines had all the Sumai 3 SSR marker alleles on chromosome arms 3BS and 6BS. The Chinese landrace Wangshuibai and two Japanese accessions Nobeokabozu and Nyu Bai had the same banding patterns as Sumai 3 for all five SSR marker alleles, and another Chinese landrace Fangshanmai had three of the five SSR markers in common with Sumai 3, and therefore most likely carries the same QTL as Sumai 3 on 3BS and 6BS. The Brazilian cultivar Frontana had no alleles in common with Sumai 3 on either QTL, and the Chinese landrace Hongheshang had only one of the five SSR markers in common with Sumai 3, therefore likely carrying resistance genes different from Sumai 3. The Italian cultivar Funo is not the donor of either the 3BS QTL or 6BS QTL. All five SSR seem to be effective candidates for marker-assisted selection to increase the level of resistance to FHB in wheat breeding programs.  相似文献   

15.
Iranian wheat landrace accessions (IWAs) were collected from country‐wide farm fields and market places in 1935 by a professor at the University of Tehran and shared with University of California at Davis, California. IWAs were further submitted to the genebank of International Maize and Wheat Improvement Center (CIMMYT), Mexico. 2,403 IWAs from CIMMYT’s genebank were assayed by DArT‐seq technology to assess genetic diversity. No apparent ecogeographic patterns related to genetic diversity were detected, probably due to long‐term transport and frequent interchange of landraces among farmers. A multivariate clustering procedure combining genotypic and phenotypic information was used in selecting a core‐set, which represented 15% of the hexaploid wheat accessions included in this study. This subset captured an estimated 93% of rare (frequency <0.05) alleles. Multisite phenotypic data (India, Mexico) validated the ability of the core‐set in detecting useful variants. Potential donor accessions for multiple traits (disease resistance, zinc concentration) were identified from the core‐set for wheat‐breeding. This report illustrates a breeder friendly robust core‐set formulation strategy for harnessing the useful genetic variation stored in the genebanks.  相似文献   

16.
Septoria tritici blotch (STB), caused by fungal agent Zymoseptoria tritici (previously known as Mycosphaerella graminicola) is a devastative foliar wheat diseases globally. Importance and potential threat of STB have been discussed historically and geographically. This paper reviews information on the Z. tritici—wheat pathosystem and proposes approaches to identify resistance genes and to advance in breeding for STB resistance. Screening of resistant lines/cultivars, QTL mapping analysis within genetic populations derived from crosses, detection of new resistance gene(s) and finally application of Stb gene carrier line/cultivar in crosses are the major stages of a practical wheat-breeding program against STB of wheat. Phenotyping and genotyping outputs on the top of each other should confirm each other, so it needs to expose a resistance gene carrier line/cultivar in the epidemic condition at seedling/adult plant stage to confirm resistance performance of detected gene(s) in the real condition. On the other word, detecting an associated QTL to resistance should not be considered as the end of investigation. Climate change resulted geographical disease pattern conversion where some diseases became more important in some area where they had not been serious in the past and vice versa. Hence, a reconsideration of wheat disease importance zone is necessary to predict regions where STB is and will be a limitation for wheat yield improvement.  相似文献   

17.
Hessian fly (Mayetiola destructor (Say)) is a major pest in wheat producing areas of United States, Canada, Europe, and North Africa but has not been found in Australia. Host plant resistance is thought to involve a similar strategy used against plant pathogen, and in this study, we sought to investigate whether disease-resistance gene markers can also be useful in selecting against Hessian fly attack. The genome-wide association study involved 251 wheat genotypes of diverse origin and 72 SNPs, selected on the basis of significant similarity of their associated contig sequences to putative disease resistance genes. A novel statistical approach for genome-wide scan was applied, which utilised genotype data scored as Null alleles in the mixed model, instead of deleting or treating them as missing alleles. The analyses identified four markers with significant associations at the 5% level, after applying the false discovery rate. These were located on chromosomes 4A, 4B, 5A and 7D, with the 5A locus mapping to the cluster of major genes that confer resistance to multiple Hessian fly biotypes. Amongst the diverse wheat accessions analysed, most of the susceptible phenotypes carried the A–G–C–C haplotype at the BS00064369, BS00007416, BS00077047 and HfrDrd_nt_143 loci, respectively. When heterozygotes were excluded, all the Australian wheat accessions carried this allelic combination. The combination of alleles conferring resistance depended on the origin of the wheat accessions, with ICARDA accessions carrying a preponderance of the C–C–CG–T. Of the 11 USA accessions used for this study, only Lola carried a favourable combination of alleles for resistance at these loci.  相似文献   

18.
Fusarium head blight (FHB) caused by Fusarium species, is among the most devastating wheat diseases, causing losses in numerous sectors of the grain industry through yield and quality reduction, and the accumulation of poisonous mycotoxins. A germplasm collection of spring and winter wheat, including nine reference cultivars, was tested for Type II FHB resistance and deoxynivalenol (DON) content. Genetic diversity was evaluated on the basis of Simple Sequence Repeat (SSR) markers linked to FHB resistance quantitative trait loci (QTLs) and Diversity Arrays Technology (DArT) markers. The allele size of the SSR markers linked to FHB resistance QTLs from known resistance sources was compared to a germplasm collection to determine the presence of these QTLs and to identify potentially novel sources of resistance. Forty-two accessions were identified as resistant or moderately resistant to Fusarium spread, and two also had very low DON concentrations. Genetic relationships among wheat accessions were generally consistent with their geographic distribution and pedigree. SSR analysis revealed that several resistant accessions carried up to four of the tested QTLs. Resistant and moderately resistant lines without any known QTLs are considered to be novel sources of resistance that could be used for further genetic studies.  相似文献   

19.
Genetic resistance to common bunt is a cost-effective, environmentally friendly, and sustainable approach to controlling the disease. To date, 16 race specific common bunt resistance genes (Bt1-Bt15 and Btp) have been reported in wheat. However, a limited number have been mapped and few markers have been identified, which limits the usage of molecular markers in a marker-assisted breeding program. A total of 125 synthetic hexaploid wheats (SHWs) were evaluated for reactions to a mixture of common bunt races under field conditions in Turkey in 2016 and 2017. The objectives of this study were to identify common bunt resistant genotypes, identify genomic regions conferring resistance to common bunt using 35,798 genotyping-by-sequencing derived single nucleotide polymorphisms (SNPs), and investigate the significant SNPs present within genes using the functional annotations of the underlying genes. We found 29 resistant SHWs that can be used in wheat breeding. The genome-wide association study identified 15 SNPs associated with common bunt resistance and a haplotype block comprising three SNPs in perfect linkage disequilibrium. Five of them were novel and were located on chromosomes 2A, 3D, and 4A. Furthermore, seven of the 15 SNPs were found within genes and had annotations suggesting potential role in disease resistance. This study identified several favorable alleles that decreased common bunt incidence up to 26% in SHWs. These resistant SHWs and candidate genomic regions controlling common bunt resistance will be useful for wheat genetic improvement and could assist in further understanding of the genetic architecture of common bunt resistance.  相似文献   

20.
Pepper huasteco yellow vein virus (PHYVV) is the main virus of pepper crop in Mexico. No resistant cultivars are available and resistance breeding is hampered by the lack of knowledge of heritability (h 2) of PHYVV resistance. This is a continuation of previous studies and the objectives were to analyze the h 2 and the behavior of the resistant trait to PHYVV. Four resistant assays were done with three resistant wild lines (UAS12, UAS13 and UAS10) of Capsicum annuum in the S4, S5, S6 and S7 generation under greenhouse conditions. Plants from all tests were inoculated with PHYVV through Bemisia tabaci. Line UAS12 was the most resistant showing a significantly proportion of resistant plants, less disease symptoms and longer incubation time, followed by the lines UAS13 and UAS10 in all assays. Distribution of symptoms showed a bimodal tendency in all the trials, suggesting that two groups of genes are involved in this resistance trait. The lines UAS12, UAS13 and UAS10 showed the same pattern of response to selection with an average of h 2 of 0.17, 0.06, 0.02 and 0.00 in the S4, S5, S6 and S7, respectively. These results indicate that all lines responded positively to the selection in the S4, S5 and S6, whereas in the S7 there was no response by the possible exhaustion of variation. Line UAS12 is the most promising genotype and the lines UAS13 and UAS10 are genetic resources that can be supplemented to breed the resistance of PHYVV. These results provides basic information for resistance breeding.  相似文献   

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