Pre-Harvest Sprouting In Wheat Research Articles

Genome-Wide Association Study of Preharvest Sprouting in Wheat.

Genome-wide association study (GWAS) is widely used to characterize genes or quantitative trait loci (QTLs) associated with preharvest sprouting and seed dormancy. GWAS can identify both previously discovered and novel QTLs across diverse genetic panels. The high-throughput SNP arrays or next-generation sequencing technologies have facilitated the identification of numerous genetic markers, thereby significantly enhancing the resolution of GWAS. Although various methods have been developed, the fundamental principles underlying these techniques remain constant. Here, we provide a basic technological flow to perform seed dormancy assay, followed by GWAS using population structure control, and compared itwith previous identified QTLs and genes.

The GATA transcription factor TaGATA1 recruits demethylase TaELF6-A1 and enhances seed dormancy in wheat by directly regulating TaABI5.

Seed dormancy is an important agronomic trait in crops, and plants with low dormancy are prone to preharvest sprouting (PHS) under high-temperature and humid conditions. In this study, we report that the GATA transcription factor TaGATA1 is a positive regulator of seed dormancy by regulating TaABI5 expression in wheat. Our results demonstrate that TaGATA1 overexpression significantly enhances seed dormancy and increases resistance to PHS in wheat. Gene expression patterns, abscisic acid (ABA) response assay, and transcriptome analysis all indicate that TaGATA1 functions through the ABA signaling pathway. The transcript abundance of TaABI5, an essential regulator in the ABA signaling pathway, is significantly elevated in plants overexpressing TaGATA1. Chromatin immunoprecipitation assay (ChIP) and transient expression analysis showed that TaGATA1 binds to the GATA motifs at the promoter of TaABI5 and induces its expression. We also demonstrate that TaGATA1 physically interacts with the putative demethylase TaELF6-A1, the wheat orthologue of Arabidopsis ELF6. ChIP-qPCR analysis showed that H3K27me3 levels significantly decline at the TaABI5 promoter in the TaGATA1-overexpression wheat line and that transient expression of TaELF6-A1 reduces methylation levels at the TaABI5 promoter, increasing TaABI5 expression. These findings reveal a new transcription module, including TaGATA1-TaELF6-A1-TaABI5, which contributes to seed dormancy through the ABA signaling pathway and epigenetic reprogramming at the target site. TaGATA1 could be a candidate gene for improving PHS resistance.

TAMFT-3A and TAMFT-3B2 homeologs are associated with wheat preharvest sprouting.

The phenomenon of preharvest sprouting (PHS), caused by rain after physiological maturity and prior to harvest, negatively affects wheat (Triticum aestivum L.) production and end use. Investigating the genetics that control PHS resistance may result in increased control of seed dormancy. Multiple genes involved in the development of seed dormancy are associated with PHS. In this study, the TaMFT (3A, 3B1, 3B2, 3D), TaMKK3-4A, and TaVP1-3B genes were assessed for association with PHS in a double-haploid line (DHL) hard red winter wheat population derived from a BC1 cross between the cultivars Loma and Warhorse, where Loma was the recurrent and PHS susceptible parent. The 162 BC1 DHL lines were grown over two field seasons and PHS susceptibility was assessed by measuring PHS resistance in physiologically mature heads. The PHS variation was associated with the TaMFT-A and the B2 homeolog with Loma carrying mutant forms of each gene. No sequence variation between Loma and Warhorse was detected in the exons of the TaMFT-B1 and D homeologs. No association between PHS resistance and TaMKK3-4A or TaVp1-3B variation was observed, though Loma and Warhorse vary for TaMKK3-4A and TaVp1-3B mutations reported to be PHS associated. Previous research has shown TaMFT-3A as having a large impact on PHS resistance. In the current study, the TaMFT-3A and TaMFT-3B2 alleles each explained 14% of observed PHS variation. Markers for both TaMFT-3A and TaMFT-3B2 should be used in selecting for increased wheat dormancy and PHS resistance.

Pre-harvest Sprouting Tolerance of Triticale Genotypes in Brazil

Pre-harvest sprouting (PHS) represents one of the main factors, which causes yield, technological and physiological losses in triticale seeds (X Triticosecale Wittmack). This work aimed to rate the variability and identify potential pre-harvest sprouting tolerant sources in triticale genotypes. Based on that, 32 triticale and three wheat genotypes were sown in 2016, 2017 and 2018 growing seasons, in Londrina-PR, Brazil. After the ears harvesting, these were submitted to simulate raining, for sprouting induction, through nebulization in a greenhouse. After nebulization, ears were sun dried, later hand threshed to determain, grain germination percentage (GERM) and hectoliter weight (HW). Additionally, it was determined grains HW of ears, whom were not submitted to nebulization, as well as the whole meal flour falling number (FN). The experiment design was completely randomized design, with two replications, and the experimental unit was made of 20 ears. The data collected were subjected to analysis of variance (ANOVA) and Scott-Knott test. Frontana, ND 674 and Quartzo are a source of tolerance to PHS in wheat. In triticale genotypes, genetic variability was observed for GERM, FN, and HW prior and after nebulization. The triticale genotypes BRS Netuno, BRS Saturno, TCL 15116, X 092181, Tiguera 1 and Tiguera 8, where tolerant towards PHS.

Grain Yield and Its Associations With Pre-harvest Sprouting in Wheat

This study aimed to evaluate direct and indirect effects of agronomic traits importance on grain yield with focus in pre-harvest sprouting. Experiment was conducted in 2017 crop season, and conducted in a randomized block design, with three replications, with eight wheat cultivars (BRS Sábia, CD 105, CD 1104, CD 1440, Frontana, Jadeíte 11, Mirante and ORS Vintecinco). Grain yield and its components were evaluated, as well as other important traits such as pre-harvest sprouting. Data were submitted to variance analysis; and phenotypic, genotypic and environmental correlations were estimated to understand grain yield expression, direct and indirect effects of its components were evaluated through path analysis. Cultivar BRS Sabiá showed shorter cycle, cultivar CD 1104 was highlighted in number of spikes per area, hectoliter weight and grain yield. And cultivars Frontana, CD 1440 and ORS Vintecinco presented the best tolerances pre-harvest sprouting. Grain yield showed high and positive phenotypic and genotypic correlations with number of ears per square meter. Furthermore, high positive direct effect of pre-harvest sprouting on grain yield, revels lower tolerance for cultivars with high grain yield. Number of spikes per square meter showed intermediate and positive direct effect and pre-harvest sprouting had the greatest direct effect on grain yield.

Impact of Preharvest Sprouting on Endogenous Hydrolases and Technological Quality of Wheat and Bread: A Review

The cereal-based food industry faces the challenge to produce food of high and uniform quality to meet consumer demands. However, adverse weather conditions, including prolonged and repeated rainfall, before harvest time evoke germination of the kernels in the ear of the parent plant, which is known as preharvest sprouting (PHS). PHS results in the production of several hydrolytic enzymes in the kernel, which decreases the technological quality of wheat and causes problems during processing of the flour into cereal-based products. Therefore, wheat that is severely sprouted in the field is less suitable for products for human consumption, and is often discounted to animal feed. Up till now, most knowledge on PHS is obtained by research on laboratory-sprouted wheat as a proxy for field-sprouted wheat. Knowledge on PHS in the field itself is more scarce. This review gives a comprehensive overview of the recent findings on PHS of wheat in the field, compared to knowledge on controlled sprouting. The physiological and functional changes occurring in wheat during PHS and their impact on wheat and bread quality are discussed. This review provides a useful background for further research concerning the potential of field-sprouted wheat to be used as raw material in the food industry.

Wheat miR9678 Affects Seed Germination by Generating Phased siRNAs and Modulating Abscisic Acid/Gibberellin Signaling.

Seed germination is important for grain yield and quality and rapid, near-simultaneous germination helps in cultivation; however, cultivars that germinate too readily can undergo preharvest sprouting (PHS), which causes substantial losses in areas that tend to get rain around harvest time. Moreover, our knowledge of mechanisms regulating seed germination in wheat (Triticum aestivum) remains limited. In this study, we analyzed function of a wheat-specific microRNA 9678 (miR9678), which is specifically expressed in the scutellum of developing and germinating seeds. Overexpression of miR9678 delayed germination and improved resistance to PHS in wheat through reducing bioactive gibberellin (GA) levels; miR9678 silencing enhanced germination rates. We provide evidence that miR9678 targets a long noncoding RNA (WSGAR) and triggers the generation of phased small interfering RNAs that play a role in the delay of seed germination. Finally, we found that abscisic acid (ABA) signaling proteins bind the promoter of miR9678 precursor and activate its expression, indicating that miR9678 affects germination by modulating the GA/ABA signaling.

Impact of Preharvest Sprouting of Wheat (Triticum aestivum) in the Field on Starch, Protein, and Arabinoxylan Properties.

To obtain detailed knowledge on possible changes in the properties of starch, proteins, and arabinoxylan as a result of field preharvest sprouting (PHS), three wheat varieties were harvested at maturity and several weeks later when severe PHS had occurred. Falling number values of flour dropped from 306 to 147 s (Sahara), 382 to 155 s (Forum), and 371 to 230 s (Tobak). Blocking of α-amylase activity demonstrated that the decline in falling number and changes in RVA pasting and gelation properties were not caused by changes in intrinsic starch properties as a result of PHS. PHS had no influence on the SDS-extractability and molecular weight distribution of the proteins. For arabinoxylan, incipient breakdown was noticed, leading to a higher amount and average degree of polymerization of water extractable arabinoxylan. Results show that strategies to cope with severely PHS in wheat should focus on blocking enzyme activities.

Evolution and Distribution of Hydrolytic Enzyme Activities during Preharvest Sprouting of Wheat (Triticum aestivum) in the Field.

To date, research on preharvest sprouted (PHS) wheat has mostly been conducted on kernels germinated under laboratory conditions, which differ widely from conditions in the field. To obtain detailed knowledge of the evolution of hydrolytic enzyme activities in PHS wheat (Triticum aestivum), a broad collection of samples from three varieties was obtained by harvesting before, at, and after maturity. Delaying harvest time coupled with periods of heavy rainfall caused sprouting in the kernels, observed as a drop in Falling Number and an increase in α-amylase activity. The appearance of α- and β-amylase, peptidase, and endoxylanase activity during field sprouting was independent from each other. Consequently, Falling Number could not be used to predict activity of other hydrolytic enzymes. When differentiating endogenous from kernel-associated microbial enzymes, results showed that α- and β-amylase and peptidase activity of PHS kernels were predominantly of endogenous origin, whereas endoxylanase activity was largely from microbial origin.

Correction: Polymorphic Homoeolog of Key Gene of RdDM Pathway, ARGONAUTE4_9 class Is Associated with Pre-Harvest Sprouting in Wheat (Triticum aestivum L.)

Correction: Polymorphic Homoeolog of Key Gene of RdDM Pathway, ARGONAUTE4_9 class Is Associated with Pre-Harvest Sprouting in Wheat (Triticum aestivum L.)

Repeatability of Pre-Harvest Sprouting in Wheat

This study aimed to detect genotypic differences in the resistance to sprouting of wheat grains, evaluate the effectiveness of different methods for inducing sprouting and identify, using repeatability estimates, the minimum number of spikes necessary for the adequate evaluation of the percentage of grain sprouting in the spike in order to assist in the selection of superior genotypes in breeding programs. Spikes from four wheat cultivars (Frontana, IPR Catuara, Quartzo and BRS 220) were evaluated using three methods for inducing grain sprouting in the spike (water immersion, rainfall simulation and germination chamber). To determine the most efficient method, repeatability coefficients were estimated through analysis of variance, principal components analysis and structural analysis based on correlation and covariance matrices. The induction of sprouting by immersion in water was the most effective method for indicating genotypic differences and may be used in breeding programs for this purpose. The repeatability method based on the components of covariance was more efficient. A minimum of 11 spikes is required to make a high-reliability estimate of the percentage of sprouted grains in the spike.

Polymorphic Homoeolog of Key Gene of RdDM Pathway, ARGONAUTE4_9 class Is Associated with Pre-Harvest Sprouting in Wheat (Triticum aestivum L.)

Resistance to pre-harvest sprouting (PHS) is an important objective for the genetic improvement of many cereal crops, including wheat. Resistance, or susceptibility, to PHS is mainly influenced by seed dormancy, a complex trait. Reduced seed dormancy is the most important aspect of seed germination on a spike prior to harvesting, but it is influenced by various environmental factors including light, temperature and abiotic stresses. The basic genetic framework of seed dormancy depends on the antagonistic action of abscisic acid (ABA) and gibberellic acid (GA) to promote dormancy and germination. Recent studies have revealed a role for epigenetic changes, predominantly histone modifications, in controlling seed dormancy. To investigate the role of DNA methylation in seed dormancy, we explored the role of ARGONAUTE4_9 class genes in seed development and dormancy in wheat. Our results indicate that the two wheat AGO4_9 class genes i.e. AGO802 and AGO804 map to chromosomes 3S and 1S are preferentially expressed in the embryos of developing seeds. Differential expressions of AGO802-B in the embryos of PHS resistant and susceptible varieties also relates with DNA polymorphism in various wheat varieties due to an insertion of a SINE-like element into this gene. DNA methylation patterns of the embryonic tissue from six PHS resistant and susceptible varieties demonstrate a correlation with this polymorphism. These results suggest a possible role for AGO802-B in seed dormancy and PHS resistance through the modulation of DNA methylation.

Cloning and Characterization of a Critical Regulator for Preharvest Sprouting in Wheat

Sprouting of grains in mature spikes before harvest is a major problem in wheat (Triticum aestivum) production worldwide. We cloned and characterized a gene underlying a wheat quantitative trait locus (QTL) on the short arm of chromosome 3A for preharvest sprouting (PHS) resistance in white wheat using comparative mapping and map-based cloning. This gene, designated TaPHS1, is a wheat homolog of a MOTHER OF FLOWERING TIME (TaMFT)-like gene. RNA interference-mediated knockdown of the gene confirmed that TaPHS1 positively regulates PHS resistance. We discovered two causal mutations in TaPHS1 that jointly altered PHS resistance in wheat. One GT-to-AT mutation generates a mis-splicing site, and the other A-to-T mutation creates a premature stop codon that results in a truncated nonfunctional transcript. Association analysis of a set of wheat cultivars validated the role of the two mutations on PHS resistance. The molecular characterization of TaPHS1 is significant for expediting breeding for PHS resistance to protect grain yield and quality in wheat production.

Effects of Meteorological Factors During Grain Development on Pre-harvest Sprouting in Wheat

登熟期間中の気象がコムギの穂発芽の発生に及ぼす影響について，ガラス室および圃場で栽培した穂発芽耐性の異なる農林61号とシロガネコムギを対象に解析した．開花期から成熟期の間に採取した穂を吸水させ，15℃，10日間過湿状態に置いた時の穂全体の発芽率を穂発芽率として解析の対象とした．ガラス室において開花期から成熟期までの気温を13℃から25℃の範囲で一定に制御した結果，登熟期間中の平均気温と成熟期の穂発芽率には有意な正の相関が認められた．圃場では年次や作期により登熟期間中の気温および降水日数，積算降水量は変動し，登熟期間中の平均気温と成熟期の穂発芽率の相関はガラス室と比較して低かった．開花から成熟までの登熟段階を，気温から推定した子実含水率により10％毎に区分し，段階別の気象と成熟期の穂発芽率との関係について解析した結果，2品種に共通して子実含水率50％から生理的成熟期までの平均気温と穂発芽率に有意な正の相関が認められた．農林61号では，同じ登熟段階の降水日数と穂発芽率との間にも正の相関が得られた．また積算降水量はいずれの段階においても穂発芽率との相関は認められなかった．これらのことから，子実が急速に乾燥する直前の時期の高温と雨ぬれの継続により，成熟期の穂発芽の発生危険度が高まることが示唆された．

Proteomic analysis of developing rye grain with contrasting resistance to preharvest sprouting

Significant differences in the two-dimensional electrophoresis patterns of proteins from developing rye grain were found to be associated with resistance and susceptibility to preharvest sprouting (PHS). Mass spectrometry of individual spots showing different abundance in PHS-resistant and PHS-susceptible lines identified proteins involved in: reaction to biotic and abiotic stresses, including oxidative stress, energy metabolism and regulation of gene expression. Highly differentiated abundance of proteins found in developing grain suggest that the diversification of processes leading to developing PHS resistance or PHS susceptibility starts from an early stage of grain development. A part of the identified proteins in rye grain were also reported to be associated with PHS in wheat and rice, which suggests that some mechanisms affecting precocious germination might be common for different cereal species.Electronic supplementary materialThe online version of this article (doi:10.1007/s13353-012-0127-8) contains supplementary material, which is available to authorized users.

Sivb 2003 Congress Symposium Proceeding: Mutation- and Transposon-Based Approaches for the Identification of Genes for Pre-Harvest Sprouting in Wheat

This article reviews techniques for gene identification and cloning in allohexaploid bread wheat (Triticum aestivum L.). Gene identification and cloning in wheat are complicated by the large size and high redundancy of the genome. Both classical mutagenesis and transposon tagging are important tools for the study of grain dormancy and plant hormone signaling in wheat. While classical mutagenesis can be used to identify wheat mutants with altered hormone sensitivity, it can be difficult to clone the corresponding genes. We review the techniques available for gene identification in wheat, and propose that transposon-based activation tagging will be an important tool for wheat genetics.

Effects of Drought and High Temperature During Maturation on Preharvest Sprouting of Hard White Winter Wheat

Preharvest sprouting of wheat (Triticum aestivum L.) is affected greatly by conditions after ripening, but effects of conditions during maturation are not clear. The objective of this research was to ascertain the effects of drought and high temperature during maturation on susceptibility of wheat to preharvest sprouting after ripening. ‘Betty’ hard white winter wheat was grown at 25/20 °C day/night until anthesis, when plants were subjected to no drought (field moisture capacity) and drought (−1.7 MPa leaf water potential) at 15/10, 22.5/17.5, and 30/25 °C until physiological maturity. Drought had little effect, but high temperature reduced all yield components. Neither stress affected α-amylase enzyme, but high temperature increased polyphenol oxidase enzyme, probably by increasing the proportion of bran in kernels. Grain protein percentage and SDS sedimentation were highest at the intermediate temperature. The germination promptness index of the grain, a measure of the rate and magnitude of sprouting, was increased by drought and unaffected by temperature. We concluded that drought during maturation increased susceptibility of wheat to preharvest sprouting, and high temperature reduced yield and might reduce quality of grain for noodles by increasing activity of polyphenol oxidase enzyme.

A Five-Minute Field Test for On-Farm Detection of Pre-Harvest Sprouting in Wheat

Field trials have shown that the extent of preharvest sprouting after rainfall can vary markedly between and within fields. Testing of grain from different fields or parts of fields before harvest would permit separate harvesting and binning of damaged grain from sound grain, and financial losses resulting from downgrading of the crop could be reduced. An immunochromatography method, based on detection of alpha-amylase isozymes, using specific antibodies was developed for field-level detection of preharvest sprouting in wheat (Triticum aestivum L.). In the test, alpha-amylase from ground grain is extracted with a salt solution and two drops of the extract is added to a zone on a disposable card. The result appears in less than 5 min. If the grain is sprouted, amylases in the samples become sandwiched between gold-labeled and immobilized antibodies, and a maroon band appears in the test window. Color intensity depends on the extent of weather damage, with good (negative) correlations between test color and Falling Number in large sets of samples comprising many cultivars. Precision is as good as or better than the Falling Number test. Methods for obtaining representative samples from a standing wheat crop were developed, and an extensive trial of the new method with farmers and elevator company staff was conducted in late 1998. Six wheat samples varying in Falling Number were tested blindly by a group of 75 farmers and grain handling company staff, with the vast majority obtaining correct results for each sample. The method should be suited for rapid screening on-farm prior to harvest, use at elevators, or as a rapid laboratory test.

RFLP Analysis of Genomic Regions Associated with Resistance to Preharvest Sprouting in Wheat

Resistance to preharvest sprouting (PHS) is difficult to incorporate into new varieties because heritability is low and selection is limited to one generation per year. Our objective was to identify genomic regions containing quantitative trait loci (QTL) associated with resistance to PHS in two recombinant inbred (R) populations of white wheat (Triticum aestivum L. em. Thell.) by restriction fragment length polymorphism (RFLP) markers. One population consisted of 78 RI lines from the cross of NY6432‐18 (NY18) × ‘Clark's Cream’ (CC). The second population consisted of 138 RI lines from the cross between sib lines NY18 and NY6432‐10 (NY10). The NY18/CC and NY18/10 populations were evaluated for PHS in six and seven environments, respectively, by examining physiologically mature spikes under simulated rainfall. The three parental lines were surveyed for polymorphism with 195 low‐copy RFLP clones. Individual RI lines from the NY18/CC and NY18/NY10 populations were probed with 37 and 27 polymorphic clones, respectively. Eight regions of the genome (four from each population) were significantly associated with resistance to PHS. Based on multiple regression, specific sets of markers and their interactions accounted for 44% of the genetic variance for PHS in the NY18/CC and 51% in the NY18/NY10 populations. These markers could find utility in breeding programs as indirect selection criteria for improvement of PHS resistance.