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[学术文献 ] A null allele of the polyphenol oxidase gene Ppo-A1 in hexaploid wheat originates from tetraploid wheat 进入全文
Crop Science
Polyphenol oxidase (PPO) has a major effect on the time-dependent darkening of noodle products. Development of varieties with low PPO activity is one method to eliminate this problem and respond to the demands of consumers. Among the common wheat (Triticum aestivum L.) Ppo genes, Ppo-A1 has the highest effect on grain PPO activity, and several Ppo-A1 alleles with low or no activity have been reported, with the recently identified Ppo-A1i allele being the most desirable allele. In this study, reverse-transcription polymerase chain reaction analysis confirmed that this allele was not expressed and was therefore functionally null. We also determined that Ppo-A1i has an approximately 3 kb insertion in the second intron. Taking advantage of the insertion sequence, we developed a new co-dominant marker, PPO18Plus, capable of distinguishing Ppo-A1a, Ppo-A1b, and Ppo-A1i. In addition, we determined that the Ppo-A1i allele is identical to and originates from the Ppo-A1g allele of tetraploid wheat. The durum wheat (Triticum turgidum ssp. durum (Desf.) Husn.) Ppo-A1g allele has been used to improve pasta color in durum wheat breeding programs. Thus, the PPO18Plus marker developed here will be very useful in both hexaploid and durum wheat breeding programs.
[学术文献 ] Genetics of a diverse soft winter wheat population for pre-harvest sprouting, agronomic, and flour quality traits 进入全文
Fronteirs
Soft winter wheat has been adapted to the north-central, north-western, and south-central United States over hundreds of years for optimal yield, height, heading date, and pathogen and pest resistance. Environmental factors like weather affect abiotic traits such as pre-harvest sprouting resistance. However, pre-harvest sprouting has rarely been a target for breeding. Due to changing weather patterns from climate change, pre-harvest sprouting resistance is needed to prevent significant crop losses not only in the United States, but world-wide. Twenty-two traits including age of breeding line as well as agronomic, flour quality, and pre-harvest sprouting traits were studied in a population of 188 lines representing genetic diversity over 200 years of soft winter wheat breeding. Some traits were correlated to one another by principal components analysis and Pearson’s correlations. A genome-wide association study using 1978 markers uncovered a total of 102 regions encompassing 226 quantitative trait nucleotides. Twenty-six regions overlapped multiple traits with common significant markers. Many of these traits were also found to be correlated by Pearson’s correlation and principal components analyses. Most pre-harvest sprouting regions were not co-located with agronomic traits and thus useful for crop improvement against climate change without affecting crop performance. Six different genome-wide association statistical models (GLM, MLM, MLMM, FarmCPU, BLINK, and SUPER) were utilized to search for reasonable models to analyze soft winter wheat populations with increased markers and/or breeding lines going forward. Some flower quality and agronomic traits seem to have been selected over time, but not pre-harvest sprouting. It appears possible to select for pre-harvest sprouting resistance without impacting flour quality or the agronomic value of soft winter wheat.
[学术文献 ] Genetic variation for terminal heat stress tolerance in winter wheat 进入全文
Frontiers
In many regions worldwide wheat (Triticum aestivum L.) plants experience terminal high temperature stress in the grain filling stage, which is a leading cause for single seed weight decrease and consequently for grain yield reduction. An essential approach to mitigate high temperature damage is to develop tolerant cultivars using the conventional breeding approach which involves identifying tolerant lines and then incorporating the tolerant traits in commercial varieties. In this study, we evaluated the terminal heat stress tolerance of 304 diverse elite winter wheat lines from wheat breeding programs from the US, Australia, and Serbia in controlled environmental conditions. Chlorophyll content and yield traits were measured and calculated as the percentage of non-stress control. The results showed that there was significant genetic variation for chlorophyll retention and grain weight under heat stress conditions. The positive correlation between the percent of chlorophyll content and the percent of single seed weight was significant. Two possible mechanisms of heat tolerance during grain filling were proposed. One represented by wheat line OK05723W might be mainly through the current photosynthesis since the high percentage of single seed weight was accompanied with high percentages of chlorophyll content and high shoot dry weight, and the other represented by wheat Line TX04M41164 might be mainly through the relocation of reserves since the high percentage of single seed weight was accompanied with low percentages of chlorophyll content and low shoot dry weight under heat stress. The tolerant genotypes identified in this study should be useful for breeding programs to combine different tolerance mechanisms into the same variety for mitigating heat-caused grain yield loss.
[学术文献 ] Evaluation of ethyl methanesulfonate-induced in vitro mutagenesis, polymorphism and genomic instability in wheat (Triticum aestivum L.) 进入全文
SpringerLink
Wheat (Triticum aestivum L.) is highly rich in nutrients and is an important staple food for humankind. Mutation breeding offers a relatively quick method for crop improvement and it provides variation for selective breeding programs and functional gene studies. In vitro mutagenesis, coupled with in vitro regeneration procedure, can offer a wide variety of plant materials for mutagenesis; enable generation of large mutant populations in a relatively short period. Present experiments were conducted to investigate potential use of conventional chemical mutagenesis technique through ethyl methanesulfonate (EMS) for mature embryo culture in wheat. EMS mutagenesis was experimented with 4 treatment durations (2, 4, 6, and 8 h) and 5 treatment concentrations (0, 0.1, 0.2, 0.3, and 0.4%). Mature embryos were treated to detect optimum doses of mutagenesis and to estimate polymorphism and genomic instability. First of all, 50% reduction in number of regenerated plants as compared to the control (LD50) was adopted as the optimum dose. Treated and untreated mature embryos were transferred to callus induction media. EMS mutagens at different duration and concentration had significant effects on callus formation rate (%), embryogenic callus formation rate (%), responded embryogenic callus rate (%), regeneration efficiency and number of plants parameters. Based on LD50 criterion, the optimum value was achieved at 8 h duration of 0.1% EMS concentration. Secondly, inter-primer binding site (iPBS) markers was applied to investigate insertion polymorphism and genomic instability in the regenerated plants. EMS mutagenic treatments had significant effects on different effects on polymorphism and genomic instability of regenerated plants. Present findings revealed that in vitro mutagenesis might be a useful approach for accelerating breeding strategies to create enough genetic variation in wheat populations. Besides, an integrated approach can be used to carry out mutation-assisted breeding and subsequent selection of desired mutants using molecular markers in wheat.
[学术文献 ] Development and characterization of a novel common wheat–Mexico Rye T1DL·1RS translocation line with stripe rust and powdery mildew resistance 进入全文
ScienceDirect
Rye (Secale cereale L., 2n=2x=14, RR) is a significant genetic resource for improving common wheat because of its resistance to multiple diseases and abiotic-stress tolerant traits. The 1RS chromosome from the German cultivated rye variety Petkus is critical in wheat breeding. However, its weakened disease resistance highlights the need to identify new resources. In the present study, a novel derived line called D27 was developed from common wheat and Mexico Rye. Cytological observations characterized the karyotype of D27 as 2n=42=21 II. Genomic in situ hybridization indicated that a pair of whole-arm translocated Mexico Rye chromosomes were inherited typically in the mitotic and meiosis stages of D27. Experiments using fluorescence in situ hybridization (FISH) and gliadin electrophoresis showed that D27 lacked wheat 1DS chromosomes. They were replaced by 1RS chromosomes of Mexico Rye, supported by wheat simple-sequence repeat markers, rye sequence characterized amplified region markers, and wheat 40K SNP array analysis. The wheat 1DS chromosomes could not be detected by molecular markers and wheat SNP array, but the presence of rye 1RS chromosomes was confirmed. Agronomic trait assessments indicated that D27 had a higher tiller number and enhanced stripe rust and powdery mildew resistance. In addition, dough properties analysis showed that replacing 1DS led to higher viscosity and lower dough elasticity in D27, which was beneficial for cake making. In conclusion, the novel cytogenetically stable common wheat–Mexico Rye T1DL·1RS translocation line D27 offers excellent potential as outstanding germplasm in wheat breeding programs focusing on disease resistance and yield improvement. Additionally, it can be valuable for researching the rye 1RS chromosome’s genetic diversity.
[学术文献 ] Toward reducing the immunogenic potential of wheat flour: identification and characterization of wheat lines missing omega-5 gliadins encoded by the 1D chromosome 进入全文
Springer
Eleven wheat lines that are missing genes for the 1D-encoded omega-5 gliadins will facilitate breeding efforts to reduce the immunogenic potential of wheat flour for patients susceptible to wheat allergy. Efforts to reduce the levels of allergens in wheat flour that cause wheat-dependent exercise-induced anaphylaxis are complicated by the presence of genes encoding omega-5 gliadins on both chromosomes 1B and 1D of hexaploid wheat. In this study, we screened 665 wheat germplasm samples using gene specific DNA markers for omega-5 gliadins encoded by the genes on 1D chromosome that were obtained from the reference wheat Chinese Spring. Eleven wheat lines missing the PCR product corresponding to 1D omega-5 gliadin gene sequences were identified. Two of the lines contained the 1BL·1RS translocation. Relative quantification of gene copy numbers by qPCR revealed that copy numbers of 1D omega-5 gliadins in the other nine lines were comparable to those in 1D null lines of Chinese Spring, while copy numbers of 1B omega-5 gliadins were like those of Chinese Spring. 2-D immunoblot analysis of total flour proteins from the selected lines using a specific monoclonal antibody against the N-terminal sequence of omega-5 gliadin showed no reactivity in regions of the blots containing previously identified 1D omega-5 gliadins. Interestingly, RP-UPLC analysis of the gliadin fractions of the selected lines indicated that the expression of omega-1,2 gliadins was also significantly reduced in seven of the lines, implying that 1D omega-5 gliadin and 1D omega-1,2 gliadin genes are tightly linked on the Gli-D1 loci of chromosome 1D. Wheat lines missing the omega-5 gliadins encoded by the genes on 1D chromosome should be useful in future breeding efforts to reduce the immunogenic potential of wheat flour.
