Search

Pre-harvest sprouting (PHS) is mainly caused by the breaking of seed dormancy in high rainfall regions, which leads to huge economic losses in wheat. In this study, we evaluated 717 Chinese wheat landraces for PHS resistance and carried out genomewide association studies (GWAS) using to 9,740 DArT-seq and 178,803 SNP markers. Landraces were grown across six environments in China and germination testing of harvest-ripe grain was used to calculate the germination rate (GR) for each accession at each site. GR was highly correlated across all environments. A large number of landraces (194) displayed high levels of PHS resistance (i.e., mean GR < 0.20), which included nine white-grained accessions. Overall, white-grained accessions displayed a significantly higher mean GR (42.7-79.6%) compared to red-grained accessions (19.1-56.0%) across the six environments. Landraces from mesic growing zones in southern China showed higher levels of PHS resistance than those sourced from xeric areas in northern and north-western China. Three main quantitative trait loci (QTL) were detected by GWAS: one on 5D that appeared to be novel and two co-located with the grain color transcription factor Tamyb10 on 3A and 3D. An additional 32 grain color related QTL (GCR-QTL) were detected when the set of red-grained landraces were analyzed separately. GCR-QTL occurred at high frequencies in the red-grained accessions and a strong correlation was observed between the number of GCR-QTL and GR (R² D 0.62). These additional factors could be critical for maintaining high levels of PHS resistance and represent targets for introgression into white-grained wheat cultivars. Further, investigation of the origin of haplotypes associated with the three main QTL revealed that favorable haplotypes for PHS resistance were more common in accessions from higher rainfall zones in China. Thus, a combination of natural and artificial selection likely resulted in landraces incorporating PHS resistance in China. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) is the germination of grains in the spike under wet conditions before harvest, which causes a severe reduction in crop yield and flour quality. The phytohormone abscisic acid plays a key role in regulating seed dormancy, which inhibits pre-harvest spouting or vivipary for many important crops. TaABI5, belonging to a family of basic leucine zipper transcription factors could regulate a subset of late embryogenesis abundant genes during seed development, was isolated and characterized. Phylogenetic analysis revealed that TaABI5 homologous gene belonged to the ABI5 subgroup of the ABF/AREB/ABI5 subfamily. TaABI5 consist of four conserved domains and one bZip domain. The expression pattern of TaABI5 indicated that it was seed-specific and accumulated at late stages of seed development. Accumulation of TaABI5 in synthetic hexaploid wheat SHW-L1 (PHS resistance) was 8.93-fold higher than that in wheat cultivar Chuanmai 32 (PHS susceptible) at 25 days post anthesis. Four expression quantitative trait loci (eQTL) of TaABI5 on chromosome 2DS, 4DS, 6DS, and 7DL were characterized from SHW-L1/Chuanmai 32 derived recombinant inbred line population. [ABSTRACT FROM AUTHOR]

BACKGROUND Viviparous-1 ( Vp-1) is a major gene affecting pre-harvest sprouting (PHS) in common wheat, and improving PHS tolerance is a crucial factor for wheat breeding. Spelt wheat is always used as the donor parent to improve resistance and quality in wheat breeding: however, the roles of the Vp-1 genes in spelt wheat and their relationship to common wheat remain uncertain. The current study aimed to isolate and characterise Vp-1 haplotypes in spelt wheat ( Triticum aestivum subsp. spelta). RESULTS In spelt wheat, a total of eight new Vp-1 haplotypes were identified: TaVp-1Ap, TaVp-1Aq and TaVp-1Ar in the A genome; TaVp-1Bj, TaVp-1Bh and TaVp-1Bi in the B genome; and TaVp-1Da and TaVp-1Db in the D genome. According to RT-PCR results, correctly spliced transcripts were more highly expressed in some haplotypes than in others, and their expression was highly associated with their distinct responsiveness to abscisic acid (ABA) exposure. The mis-splicing of Vp-1 transcripts and several indel variations detected in spelt wheat appear to have been retained through the hybridisation process. CONCLUSION Certain haplotypes detected in spelt wheat might be valuable in the breeding and selection of germplasm to improve PHS issues in wheat. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

During the Green Revolution, substantial increases in wheat (Triticum aestivum) yields were realized, at least in part, through the introduction of the Reduced height (Rht)-B1b and Rht-D1b semi-dwarfing alleles. In contrast to Rht-B1b and Rht-D1b, the Rht-B1c allele is characterized by extreme dwarfism and exceptionally strong dormancy. Recently, 35 intragenic Rht-B1c suppressor alleles were created in the spring wheat cultivar Maringá, and termed overgrowth (ovg) alleles. Here, 14 ovg alleles with agronomically relevant plant heights were reproducibly classified into nine tall and five semi-dwarf alleles. These alleles differentially affected grain dormancy, internode elongation rate, and coleoptile and leaf lengths. The stability of these ovg effects was demonstrated for three ovg alleles in different genetic backgrounds and environments. Importantly, two semi-dwarf ovg alleles increased dormancy, which correlated with improved pre-harvest sprouting (PHS) resistance. Since no negative effects on grain yield or quality were observed, these semi-dwarf ovg alleles are valuable for breeding to achieve adequate height reduction and protection of grain quality in regions prone to PHS. Furthermore, this research highlights a unique role for the first 70 amino acids of the DELLA protein, encoded by the Rht-1 genes, in grain dormancy. [ABSTRACT FROM AUTHOR]

The present study was conducted to evaluate the role of different levels of Methyl jasmonate (MeJA) i.e. control, 1, 2.5 and 5 mM to minimize pre-harvest sprouting in rice. The results suggested that MeJA (5 mM) significantly reduced germination percentage, germination energy, germination index, shoot height, root length and seedling biomass in comparison with the control treatment. This reduction was more obvious in cultivar Zhu Liang You 06 (ZY) than in Qian You No.1 (QY). The activity of antioxidative enzymes i.e. catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and malondialdehyde (MDA) contents were significantly increased after treating with 1 mM and 2.5 mM concentrations of MeJA. However, higher concentration of MeJA (5 mM) significantly reduced the activities of antioxidant enzymes, seedling biomass and increased ROS generation. The a-amylase activity was significantly decreased with seed soaking in 5 mM of MeJA as compared to the control. Gene expression analysis suggested a significant up regulation of root Amy2A and Amy3A mRNA in comparison with the shoot, by seed soaking in MeJA. Higher concentration of MeJA (5 mM) improved resistance to pre-harvest sprouting in both rice cultivars. However, little cell damage and higher ROS accumulation were also observed. [ABSTRACT FROM AUTHOR]

Taking the different sprouting methods of intact spikes，glume + grain，whole grain and half grain，we identified the sprouting resistance of 105 wheat varieties derived from domestic and overseas in the experiment. The result showed that Pre-harvest sprouting, PHS) had the great difference in different varieties， Pre-harvest sprouting percentage was 0. 72 % - 100 % and the average was 78. 09 % . It was found that most resistant variety had 1 (ONSY85) and the higher resistant varieties had 2 that were yangmai 16 and yangmai 11，resistant varieties had 4 red grains varieties，including the fengmai 36，mianyang 45，fengmai 32，yangmai 158. Pre-harvest sprouting of the seven varieties (linmai 15，fengmai 34，xiaoyan 93166，jingmai 12，zhoumai 17，yunmai 29 and x9610，respectively) was more than 98 % and easily germinaed. These accessions could be divided into 5 cluster by the K-means cluster analysis. There were significant differences and positive correlation among the germination of half grain and whole grain，germination percentage of whole grain and glume i grain，the whole grain and total head，it was indicated that the seed coat and water-soluble compounds of glumes had the remarkable effect，however the key function was the dormancy of seeds. Four spike types indicated that the panicle type had no effect on PHS. [ABSTRACT FROM AUTHOR]

Abscisic acid (ABA) is a plant hormone that plays a predominant role in the onset and maintenance of primary dormancy. Peak ABA accumulation in embryos of triticale grains was observed before any significant loss of water and was higher in Fredro, a cultivar less susceptible to pre-harvest sprouting (PHS), than in Leontino, a cultivar more sensitive to PHS. At full maturity, embryonic ABA content in Fredro was twice as high as in Leontino. Two full-length cDNAs of 9- cis -epoxycarotenoid dioxygenase ( TsNCED1 , TsNCED2 ), an enzyme involved in ABA biosynthesis, and two full-length cDNAs of ABA 8′-hydroxylase ( TsABA8′OH1 and TsABA8′OH2 ), an enzyme involved in ABA catabolism, were identified in triticale grains and characterized. The maximum transcript level of both TsNCED1 and TsNCED2 preceded the peak of ABA accumulation, suggesting that both TsNCEDs contribute to reach this peak, although the expression of TsNCED1 was significantly higher in Fredro than in Leontino. High expression of TsABA8′OH2 and TsABA8′OH1 was observed long before and at the end of the ABA accumulation peak, respectively, but no differences were observed between cultivars. The obtained results suggest that mainly TsNCED1 might be related to the higher ABA content and higher resistance of Fredro to PHS. However, Fredro embryos not only have higher ABA content, but also exhibit greater sensitivity to ABA, which may also have a significant effect on grain dormancy and lower susceptibility to PHS for grains of this cultivar. [ABSTRACT FROM AUTHOR]

A comparative analysis of genetic diversity of North American spring wheat varieties differing in resistance to pre-harvest sprouting was carried out. For identification of sources of resistance the genealogical profiles of 148 red-grained and 63 white-grained North-American spring wheat varieties with full pedigrees were calculated and estimates were made of pre-harvest sprouting. The cluster structure of the populations of red-grained and white-grained varieties was estimated. Analysis of variance revealed significant differences between the average contributions of landraces in the groups of resistant and susceptible varieties. Distribution of the putative sources of resistance in the clusters indicated that varieties having different genetic basis may have different sources of resistance. For red-grained varieties the genetic sources of resistance to pre-harvest sprouting are landraces Crimean, Hard Red Calcutta, and Iumillo, or Button, Kenya 9M-1A-3, and Kenya-U, or Red Egyptian and Kenya BF4-3B-10V1. Tracking of pedigrees showed these landraces contributed to the pedigrees, respectively, via Thatcher, Kenya-Farmer, and Kenya-58, which were likely donors of resistance for red-grained varieties. For white-grained varieties the sources of resistance were landraces Crimean, Hard Red Calcutta, Ostka Galicyjska, Iumillo, Akakomugi, Turco, Hybrid English, Rough Chaff White and Red King, and putative donors of resistance -- Thatcher, RL2265, and Frontana. The genealogical profile of accession RL4137, the most important donor of resistance to pre-harvest sprouting in North American spring wheat breeding programmes, contains almost all identified sources of resistance. [ABSTRACT FROM AUTHOR]

A long-period duration of seed dormancy helps to reduce pre-harvest sprouting (PHS) damage in common wheat when a long period of rainfall or high humidity occurs. Identification of genes or loci underlying seed dormancy duration is of high importance for investigating genetic mechanism of PHS tolerance of wheat. In the present study, the germination index (GI) of different mapping populations at 5 days (GI5), 15 days (GI15), and 30 days (GI30) after harvest (DAH) was recorded during the 2011–2012, 2012–2013, 2013–2014, and 2014–2015 cropping seasons. Field sprouting (FS) values were also determined in 2012–2013 and 2014–2015 cropping seasons. Association analysis was performed in 260 wheat varieties and advanced lines differing in seed dormancy (SD) using 557 SSR and 14 gene-specific markers for PHS/SD-related genes. The result indicated that a total of 47 loci were significantly (P < 0.01) associated with SD using both the general linear model (GLM) and mixed linear model (MLM). Five major loci were consistently detected at different post-ripening stages after harvest, including four for GI5 and GI15 on chromosomes 3AS, 3BL, 5AL, and 5BL responsible for middle-duration SD, and one for GI5, GI15, and GI30 on 2AL associated with longer-duration SD. The major locus on 2AL (designated Qsd.ahau-2AL) is likely to be a novel QTL, which was linked to Xwmc658 by mapping analysis in 165 recombinant inbred lines (RILs) derived from the Jing 411 × Wanxianbaimaizi cross and 728 F2 plants from Jimai 20 × Suiningtuotuomai. Furthermore, a CAPS marker CAPS-2AL was developed for Qsd.ahau-2AL locus and was validated using the 728 F2 plants and 201 accessions of the Chinese mini-core collection. Our results also revealed that the TaMFT-like gene on 3AS had a more significant association with dormancy duration than the other six genes underlying SD/PHS resistance in Chinese wheat germplasm. This study provides useful information for marker-assisted selection in wheat breeding and enhances our understanding of molecular genetics of SD in wheat. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) constrains wheat production worldwide by reducing both wheat grain yield and end-use quality. TaPHS1 on wheat chromosome 3AS and TaMKK3-A on chromosome 4AL are two cloned genes with major effects on PHS resistance and they are independent from grain color (GC). In this study, we used marker-assisted backcrossing (MAB) to introgress TaPHS1 and TaMKK3-A from two PHS resistant sources—‘Tutoumai A’ and ‘AUS1408′—into a sprouting-susceptible white wheat line, NW97S186. Progeny were tested in four environments to investigate individual and combined effects of those two genes. TaPHS1 significantly reduced PHS and its effect on PHS varied with environments and gene sources. In contrast, the TaMKK3-A gene also significantly reduced PHS but its effectiveness was influenced by environments. The two genes had additive effects on PHS resistance, indicating pyramiding those two quantitative trait lici (QTLs) could increase PHS resistance. The additive effects were greater in a mild environment, such as a greenhouse, than in a dry and hot environment during maturation.

O objetivo deste trabalho foi identificar as diferenças de tolerância à germinação na pré-colheita em espigas de cultivares de trigo, submetidas a um sistema de chuva artificial. Foram realizados experimentos em duas localidades do Paraná (Palotina e Cascavel) com 12 cultivares. Quando as cultivares atingiram a maturidade fisiológica, as espigas foram colhidas e secadas em temperatura ambiente por um período de 20 dias. Foram analisadas 10 espigas por cultivar e submetidas a um sistema de chuva artificial. Após o período de molhamento, foram realizadas leituras pela escala de notas de 1 a 11. As espigas foram então debulhadas e submetidas à contagem de grãos germinados e não germinados. Esses resultados possibilitaram identificar as cultivares 'Frontana', 'IAPAR 53', 'ONIX', 'CD 108' e 'IPR 85' como as de maior nível de tolerância. Considerando todas as características avaliadas, 'Frontana' foi a cultivar com maior potencial de utilização no melhoramento genético. O emprego de notas visuais de germinação na espiga foi vantajoso porque permitiu a realização de avaliações rápidas e precisas em um grande número de cultivares, sem comprometer os resultados de seleção dos genótipos tolerantes.The objective of the study was to identify the differences in pre-harvest sprouting tolerance in wheat spikes cultivars analyzed in artificial rain. Experiments were carried out in two locations of Paraná, Brazil (Palotina and Cascavel) with 12 cultivars. Spikes from plants in physiological maturation were harvested and dried at room temperature for 20 days. Ten spikes per cultivar were used and subjected to artificial rain. After the wetness duration were recorded notes from scale 1 to 11. In the next step, spikes were threshed and subjected to counting of sprouted and nonsprouted seeds. This results made possible to identify 'Frontana', 'IAPAR 53', 'ONIX', 'CD 108' and 'IPR 85' as the cultivars with the best level of tolerance. In general, Frontana was the most promising cultivar to be used in breeding programs. The use of visual grades as criteria of sprouting in the ears permitted a prompt and accurate evaluation of great number of cultivars without affecting the results of tolerant genotypes selection.

Sprouting or germination in wheat takes place as a result of the rupture of the dormancy in grain, expressed in physiological terms as the increase of α-amylases and proteases activity, which has been associated with low values of falling number. Grain sprouting has been related with high moisture and temperature at harvest and it is a serious problem in the north of Argentina. The objectives of this study were to characterize introduced and local wheat cultivars for sprouting response through falling number and, tentatively, to identify adapted materials with good behavior for this trait. A set of thirty introduced and local late and early heading wheat varieties was tested through falling number in two experiments conducted at Marcos Juárez, Argentina in 2005 and 2006. Significant differences in falling number between tested cultivars were detected with a strong interaction with environment. Late heading cultivars introductions showed significantly higher falling number values than local cultivars, and early heading cultivars introductions and local cultivars showed similar values. In the early heading cultivars group, the highest falling number value was observed in Klein Proteo, a local cultivar.En trigo el término brotado se refiere a la ruptura de la dormición en el grano, lo que expresado en términos fisiológicos es el incremento de las actividades proteásica y α-amilásica, que se asocia con valores bajos del test falling number. El brotado de grano se ha relacionado con elevada temperatura y humedad a cosecha. En este estudio se propuso caracterizar la respuesta a brotado de cultivares de trigo, locales e introducidos, a través de falling number y tentativamente, identificar materiales adaptados con buen comportamiento a brotado de grano en precosecha. Treinta variedades de trigo locales e introducidas con espigazón precoz y tardía fueron evaluadas a través del falling number en dos experimentos conducidos en Marcos Juárez, Argentina, durante 2005 y 2006. Se detectaron diferencias significativas en falling number entre los cultivares evaluados con una fuerte interacción con el ambiente. Los cultivares introducidos con espigazón tardía mostraron valores de falling number significativamente mayores que los cultivares locales, y en el grupo de espigazón precoz no se observaron diferencias significativas en falling number de cultivares introducidos y locales. Dentro del grupo de espigazón precoz el valor más alto de falling number fue observado en el cultivar local Klein Proteo.

Pre-harvest sprouting of cereals greatly reduces yield and quality of the grains. Abscisic acid (ABA) is an essential phytohormone for the induction and maintenance of seed dormancy. In this study, the ABA responsive promoter-driven ABA biosynthesis gene system was introduced to common wheat ( Triticum aestivum L.) to enhance ABA production in the embryos and pre-harvest sprouting tolerance of the grains. This system consists of a wheat ABA responsive element containing Early-Methionine-labelled ( EM ) promoter and a sorghum 9-cis-epoxycarotenoid dioxygenase ( SbNCED ) gene which encodes an ABA biosynthesis rate-limiting enzyme. Twenty-three independent single-insertion lines were obtained, from which five homozygous lines showing various SbNCED expression levels were selected. Correlations were observed between SbNCED expression, ABA accumulation in the embryos and enhanced dormancy levels of the grains. The engineered wheat grains exhibited a few day-delay in germination, which should be effective in reducing pre-harvest sprouting damage. However, the increase in ABA levels in the recombinant grains was moderate, which explains why germination was not completely suppressed. Further analysis indicated a concomitant increase in the expression of the ABA catabolic enzyme gene TaABA8'OH1 and in the levels of isoleucine-conjugated jasmonic acid, implying the presence of possible negative feedback regulation in the innate system, which should be overcome for future technology development. These findings advance an understanding of the regulatory mechanisms of hormone metabolism in seeds and facilitate the development of pre-harvest sprouting tolerance in cereal grains., Competing Interests: Conflict of interestThe authors declare that they have no competing interests., (© 2023 Japanese Society for Plant Biotechnology.)

Pre-harvest sprouting (PHS) in Sorghum bicolor is one of the main constrains for its production in the central region of Argentina, as grain maturation often coincides with rainy or high environmental humidity conditions. The obtention of more dormant genotypes with higher PHS resistance has always been a desirable trait for breeders but the typical quantitative nature of seed dormancy makes its manipulation difficult through classical breeding. Dissecting this quantitative variability into quantitative trait loci (QTL) is a main concern especially in cereal species. In this work, a sorghum segregating population including 190 families was genotyped with microsatellite markers and the SbABI5 candidate gene. A genetic map encompassing 96 markers and a total length of 1331 cM was built. Seed dormancy was phenotyped in F and F panicles in two contrasting Argentinean environments (Castelar and Manfredi). Six seed dormancy QTL for mature grains were identified ( qGI- 1, qGI- 3, qGI- 4, qGI- 6, qGI- 7 and qGI- 9) with the aid of QTL Cartographer and QTLNetwork, three of them ( qGI- 3, qGI- 7 and qGI- 9) being co-localised by both approaches. No epistasis was detected for the identified QTL but QTL-by-environment interaction was significant for qGI- 7 and qGI- 9. Interestingly, seed dormancy candidate genes SbABI3/VP1 and SbGA20ox3 were located within qGI- 3, which makes them noteworthy candidate genes for this QTL. [ABSTRACT FROM AUTHOR]

The precocious germination of cereal grains before harvest, also known as pre-harvest sprouting, is an important source of yield and quality loss in cereal production. Pre-harvest sprouting is a complex grain defect and is becoming an increasing challenge due to changing climate patterns. Resistance to sprouting is multi-genic, although a significant proportion of the sprouting variation in modern wheat cultivars is controlled by a few major quantitative trait loci, including Phs-A1 in chromosome arm 4AL. Despite its importance, little is known about the physiological basis and the gene(s) underlying this important locus. In this study, we characterized Phs-A1 and show that it confers resistance to sprouting damage by affecting the rate of dormancy loss during dry seed after-ripening. We show Phs-A1 to be effective even when seeds develop at low temperature (13 °C). Comparative analysis of syntenic Phs-A1 intervals in wheat and Brachypodium uncovered ten orthologous genes, including the Plasma Membrane 19 genes (PM19-A1 and PM19-A2) previously proposed as the main candidates for this locus. However, high-resolution fine-mapping in two bi-parental UK mapping populations delimited Phs-A1 to an interval 0.3 cM distal to the PM19 genes. This study suggests the possibility that more than one causal gene underlies this major pre-harvest sprouting locus. The information and resources reported in this study will help test this hypothesis across a wider set of germplasm and will be of importance for breeding more sprouting resilient wheat varieties. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) of wheat (Triticum aestivum L.) grains induces hydrolyzing enzymes such as α-amylase, which considerably decreases wheat product quality. PHS occurs when cool and wet weather conditions before harvest break dormancy and induce grain germination. In this study, we used PHS-tolerant varieties, Gifu-komugi (Gifu) and OS38, to characterize the mechanisms of both dormancy breakage and dormancy maintenance at low temperatures. Physiologically mature Gifu grains exhibited dormancy after imbibition at 20°C, but germinated at 15°C. In contrast, OS38 grains remained dormant even at temperatures as low as 5°C. Embryo half-grains cut out from the dormant Gifu grains germinated by imbibition at 20°C, similar to conventional varieties worldwide. However, OS38 embryo half-grains were still dormant. Hormonome and pharmacological analyses suggested that ABA and gibberellin metabolism are important for temperature-dependent dormancy maintenance and breakage. Imbibition at 15°C decreased ABA levels but increased gibberellin levels in embryos of freshly harvested Gifu grains. Additionally, low temperatures induced expression of the ABA catabolism genes, TaABA80OH1 and TaABA80OH2, and the gibberellin biosynthesis gene, TaGA3ox2, in the embryos. However, in embryos of freshly harvested OS38 grains, ABA levels were increased while gibberellin levels were suppressed at 15°C. In these dormant embryos, low temperatures induced the TaNCED ABA biosynthesis genes, but suppressed TaABA80OH2 and TaGA3ox2. These results show that the regulatory mechanism influencing the expression of ABA and gibberellin metabolism genes may be critical for dormancy maintenance and breakage at low temperatures. Our findings should help improve PHS-resistant wheat breeding programs. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting, easily influenced by the external environment, is one of the serious disasters in wheat production, and once the occurrence not only affects the yield, but also seriously affects the quality of wheat. Therefore, it is very important to develop wheat varieties with resistance to sprouting. For a more comprehensive evaluation of wheat sprouting resistance, the seed germination, whole spike germination and field intact spike germination, the basic methods to evaluate the germination of wheat, were compared and analyzed in the research by germinating test with 65 varieties and breeder's lines. The results of correlation and difference analysis showed that the germination rates obtained in the three methods were significantly positive correlated, and significantly different at the 1% level. The correlation between germination index and seed germination rate was the highest, which could better evaluate the dormancy characteristics of wheat, but could not get the overall resistance. The coefficients of variation of the seed germination and the whole spike germination were smaller, and the test conditions were easier to control, compared with the field intact spike, so they were the simple methods to evaluate the resistance of wheat spike sprouting; The average seed germination rates of most materials were the highest and the field intact spike germination rate was the smallest for the most of accessions, and the differences among the three methods reached extremely significant levels, which showed that the external environment and the external structure of wheat on spike germination was significantly affected, so it was very important to strictly control the external environment during test. Therefore, the seed germination method could be used to screen germplasm first from the dormancy, to seek resistance materials from the source, and the whole spike germination method could be used to further verify of the sprouting resistance, to evaluate the comprehensive resistance of the pre-harvest sprouting. Meanwhile, the field intact spike germination was more susceptible to natural conditions, and its variation degree was larger. Therefore, the results could be used as reference data for laboratory germination tests and it is necessary to combine the three methods in order to obtain a more accurate result. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) is one of the serious problems for wheat production, especially in rainy regions. Although seed dormancy is the most critical trait for PHS resistance, the control of heading time should also be considered to prevent seed maturation during unfavorable conditions. In addition, awning is known to enhance water absorption by the spike, causing PHS. In this study, we conducted QTL analysis for three PHS resistant related traits, seed dormancy, heading time and awn length, by using recombinant inbred lines from 'Zenkouji-komugi' (high PHS resistance) x 'Chinese Spring' (weak PHS resistance). QTLs for seed dormancy were detected on chromosomes 1B (QDor-1B) and 4A (QDor-4A), in addition to a QTL on chromosome 3A, which was recently cloned as TaMFT-3A. In addition, the accumulation of the QTLs and their epistatic interactions contributed significantly to a higher level of dormancy. QDor-4A is co-located with the Hooded locus for awn development. Furthermore, an effective QTL, which confers early heading by the Zenkouji-komugi allele, was detected on the short arm of chromosome 7B, where the Vrn-B3 locus is located. Understanding the genetic architecture of traits associated with PHS resistance will facilitate the marker assisted selection to breed new varieties with higher PHS resistance. [ABSTRACT FROM AUTHOR]

Germination percentages of wheat grains sampled at 3 grain-filling stages : yellow-ripe stage (water content 45-50%), dough-ripe stage (35-40%), and full-ripe stage (25-30%), and imbibed in water at 12°C and 20°C were examined in relation to the activities of α-amylase and endoprotease. Wheat varieties studied were Chihoku-komugi, which is susceptible to pre-harvest sprouting, and Satanta, which is resistant. Germination percentage was higher at 12°C than at 20°C in all grains sampled at all stages in both varieties, and was higher in Chihoku-komugi than in Satanta at 20°C. The activity of α-amylase in the grains at the yellow-ripe stage was higher at 12°C than at 20°C in both varieties, but that at the other 2 stages was higher only in Satanta. Endoprotease increased rapidly from 7 to 10 days after the start of imbibition, and exceeded 12 units only at 12°C in Chihoku-komugi grains at the dough and full-ripe stages. The results showed that α-amylase activity was lower than the value equivalent to 300 brabender unit (BU) in amylography when the germination percentage was 0%. Endoprotease activity exceeded 6 units when the germination percentage exceeded 90%.

Pre-harvest sprouting (PHS) of wheat reduces grain yield and quality, and it is strongly affected by seed dormancy. Therefore, identification of quantitative trait loci (QTL) for seed dormancy is essential for PHS resistance breeding. A doubled haploid (DH) population, consisting of 174 lines from the cross between Yangmai16 (YM16) and Zhongmai895 (ZM895) was used to detect QTLs for seed dormancy and grain color. For seed dormancy, a total of seven QTLs were detected on chromosomes 2A, 3A, 3D, 4D, 5B and 5D over four environments, among which Qdor.hzau-3A , Qdor.hzau-3D.1 and Qdor.hzau-3D.2 were stably detected in more than two environments. For grain color, only two QTLs, Qgc.hzau-3A and Qgc.hzau-3D were detected on chromosomes 3A and 3D, which physically overlapped with Qdor.hzau-3A and Qdor.hzau-3D.1 , respectively. Qdor.hzau-3D.2 has never been reported elsewhere and is probably a novel locus with allelic effect of seed dormancy contributed by weakly dormant parent ZM895, and a KASP marker was developed and validated in a wheat natural population. This study provides new information on the genetic dissection of seed dormancy, which may aid in further improvement for marker-assisted wheat breeding for PHS resistance.

Introduction: Pre-harvest Sprouting (PHS) seriously affects wheat quality and yield. However, to date there have been limited reports. It is of great urgency to breed resistance varieties via quantitative trait nucleotides (QTNs) or genes for PHS resistance in white-grained wheat., Methods: 629 Chinese wheat varieties, including 373 local wheat varieties from 70 years ago and 256 improved wheat varieties were phenotyped for spike sprouting (SS) in two environments and genotyped by wheat 660K microarray. These phenotypes were used to associate with 314,548 SNP markers for identifying QTNs for PHS resistance using several multi-locus genome-wide association study (GWAS) methods. Their candidate genes were verified by RNA-seq, and the validated candidate genes were further exploited in wheat breeding., Results: As a result, variation coefficients of 50% and 47% for PHS in 629 wheat varieties, respectively, in 2020-2021 and 2021-2022 indicated large phenotypic variation, in particular, 38 white grain varieties appeared at least medium resistance, such as Baipimai, Fengchan 3, and Jimai 20. In GWAS, 22 significant QTNs, with the sizes of 0.06% ~ 38.11%, for PHS resistance were stably identified by multiple multi-locus methods in two environments, e.g., AX-95124645 (chr3D:571.35Mb), with the sizes of 36.390% and 45.850% in 2020-2021 and 2021-2022, respectively, was detected by several multi-locus methods in two environments. As compared with previous studies, the AX-95124645 was used to develop Kompetitive Allele-Specific PCR marker QSS.TAF9-3D (chr3D:569.17Mb~573.55Mb) for the first time, especially, it is available in white-grain wheat varieties. Around this locus, nine genes were significantly differentially expressed, and two of them (TraesCS3D01G466100 and TraesCS3D01G468500) were found by GO annotation to be related to PHS resistance and determined as candidate genes., Discussion: The QTN and two new candidate genes related to PHS resistance were identified in this study. The QTN can be used to effectively identify the PHS resistance materials, especially, all the white-grained varieties with QSS.TAF9-3D-TT haplotype are resistant to spike sprouting. Thus, this study provides candidate genes, materials, and methodological basis for breeding wheat PHS resistance in the future., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Kou, Peng, Dong, Hu and Xu.)

Introduction: Seed dormancy (SD) significantly decreases under high temperature (HT) environment during seed maturation, resulting in pre-harvest sprouting (PHS) damage under prolonged rainfall and wet weather during wheat harvest. However, the molecular mechanism underlying HT-mediated SD remains elusiveSeed dormancy (SD) significantly decreases under high temperature (HT) environment during seed maturation, resulting in pre-harvest sprouting (PHS) damage under prolonged rainfall and wet weather during wheat harvest. However, the molecular mechanism underlying HT-mediated SD remains elusive., Methods: Here, the wheat landrace 'Waitoubai' with strong SD and PHS resistance was treated with HT from 21 to 35 days post anthesis (DPA). Then, the seeds under HT and normal temperature (NT) environments were collected at 21 DPA, 28 DPA, and 35 DPA and subjected to whole-transcriptome sequencing., Results: The phenotypic data showed that the seed germination percentage significantly increased, whereas SD decreased after HT treatment compared with NT, consistent with the results of previous studies. In total, 5128 mRNAs, 136 microRNAs (miRNAs), 273 long non-coding RNAs (lncRNAs), and 21 circularRNAs were found to be responsive to HT, and some of them were further verified through qRT-PCR. In particular, the known gibberellin (GA) biosynthesis gene TaGA20ox1 ( TraesCS3D02G393900 ) was proved to be involved in HT-mediated dormancy by using the EMS-mutagenized wheat cultivar Jimai 22. Similarly, a novel gene TaCDPK21 ( TraesCS7A02G267000 ) involved in the calcium signaling pathway was validated to be associated with HT-mediated dormancy by using the EMS mutant. Moreover, TaCDPK21 overexpression in Arabidopsis and functional complementarity tests supported the negative role of TaCDPK21 in SD. We also constructed a co-expression regulatory network based on differentially expressed mRNAs, miRNAs, and lncRNAs and found that a novel miR27319 was located at a key node of this regulatory network. Subsequently, using Arabidopsis and rice lines overexpressing miR27319 precursor or lacking miR27319 expression, we validated the positive role of miR27319 in SD and further preliminarily dissected the molecular mechanism of miR27319 underlying SD regulation through phytohormone abscisic acid and GA biosynthesis, catabolism, and signaling pathways., Discussion: These findings not only broaden our understanding of the complex regulatory network of HT-mediated dormancy but also provide new gene resources for improving wheat PHS resistance to minimize PHS damage by using the molecular pyramiding approach., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Jiang, Gao, Jiang, Liu, Jiang, Zhang, Zhang, Yan, Cao, Lu, Ma, Chang and Zhang.)

Pre-harvest sprouting is a frequent problem for wheat culture that can be simulated by laboratory-based germination. Despite reducing baking properties, wheat sprouting has been shown to increase the bioavailability of some nutrients. It was investigated whether wheat cultivars bearing distinct grain texture characteristics (BRS Guaraim, soft vs. BRS Marcante, hard texture) would have different behavior in terms of the changes in phytochemical compounds during germination. Using LC-Q-TOF-MS, higher contents of benzoxazinoids and flavonoids were found in the hard cultivar than in the soft one. Free phytochemicals, mainly benzoxazinoids, increased during germination in both cultivars. Before germination, soft and hard cultivars had a similar profile of matrix-bound phytochemicals, but during germination, these compounds have been shown to decrease only in the hard-texture cultivar, due to decreased levels of phenolic acids ( trans -ferulic acid) and flavonoids (apigenin) that were bound to the cell wall through ester-type bonds. These findings confirm the hypothesis that hard and soft wheat cultivars have distinct behavior during germination concerning the changes in phytochemical compounds, namely the matrix-bound compounds. In addition, germination has been shown to remarkably increase the content of benzoxazinoids and the antioxidant capacity, which could bring a health-beneficial appeal for pre-harvested sprouted grains.

Whether seeds germinate or maintain dormancy is decided upon through very intricate physiological processes. Correct timing of these processes is most important for the plants life cycle. If moist conditions are encountered, a low dormancy level causes pre-harvest sprouting in various crop species, such as wheat, corn and rice, this decreases crop yield and negatively impacts downstream industrial processing. In contrast, a deep level of seed dormancy prevents normal germination even under favourable conditions, resulting in a low emergence rate during agricultural production. Therefore, an optimal seed dormancy level is valuable for modern mechanised agricultural systems. Over the past several years, numerous studies have demonstrated that diverse endogenous and environmental factors regulate the balance between dormancy and germination, such as light, temperature, water status and bacteria in soil, and phytohormones such as ABA (abscisic acid) and GA (gibberellic acid). In this updated review, we highlight recent advances regarding the molecular mechanisms underlying regulation of seed dormancy and germination processes, including the external environmental and internal hormonal cues, and primarily focusing on the staple crop species. Furthermore, future challenges and research directions for developing a full understanding of crop seed dormancy and germination are also discussed. [ABSTRACT FROM AUTHOR]

Storage proteins of cereal seeds are processed during accumulation and degraded during germination primarily by cysteine proteinases. One of the mechanisms controlling the activity of these enzymes is the synthesis of specific inhibitors named phytocystatins. Here we present the complete gene sequence of a triticale ( × Triticosecale Wittm.) phytocystatin, TrcC-6 , which encodes a 152-amino acid protein with a putative 25-amino acid signal peptide. This protein has a calculated molecular mass of 16.2 kDa, and was assigned to phylogenetic group B of phytocystatins. Because TrcC-6 transcripts are present in triticale seeds, we hypothesized that this phytocystatin regulates storage protein accumulation and degradation. Therefore, changes in gene expression during the entire period of seed development and germination were examined. TrcC-6 transcripts and TrcC-6 protein levels increased during the maturation of seeds and remained high during the first hours of germination. This enabled us to conclude that TrcC-6 likely regulates seed germination by the regulation of storage protein hydrolysis. For the analysis of TrcC-6 inhibitory activity, recombinant protein was expressed in Escherichia coli BL21 (DE3) and purified. Recombinant TrcC-6 proved to be a potent inhibitor of cysteine proteinases. It inhibited the in vitro activity of papain (EC 3.4.22.2) and ficin (EC 3.4.22.3). Furthermore, native PAGE analysis revealed that recombinant TrcC-6 inhibits the activity of endogenous cysteine proteinases present in germinating seeds of triticale. Based on these results, TrcC-6 is likely one of the important factors that regulate cysteine proteinase activity during the accumulation and mobilization of storage proteins. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting in spring wheat causes significant financial loss to growers throughout the world and sprouting damage can be reduced by growing resistant genotypes. Several genetic factors, especially those related to seed dormancy, are involved in the control of pre-harvest sprouting resistance. The objective of this study was to identify quantitative trait loci (QTL) influencing pre-harvest sprouting resistance from multiple measures of dormancy at multiple germination intervals on seed harvested across multiple environments. A doubled haploid mapping population of 91 individuals derived from a cross of two Canadian white-seeded spring wheat genotypes, SC8021-V2 (pre-harvest sprouting resistant) and AC Karma (moderately susceptible to pre-harvest sprouting) was used for QTL mapping. Daily germination counts were analysed using germination index, germination resistance and percent germination at intervals of 3, 5, 7, 10, 14 and 21 days from spike samples collected from six field and one greenhouse environments in Saskatchewan, Canada. Continuous frequency distributions at certain measure-durations indicated genetic complexity of dormancy segregation in the SC8021-V2/AC Karma cross. Composite interval mapping detected significant ( p ≤ 0.05) QTL associated with resistance to pre-harvest sprouting on all 21 wheat chromosomes. Of the 26 total QTL, six were novel and the rest were detected either at the same marker or overlapping a marker interval reported in other studies. QTL expressed consistently for germination index, germination resistance and percent germination at different germination durations on chromosomes 2B, 4A, 5D and 6D. QTL identified on homoeologous chromosomes 4A, 4B and 4D with chromosome specific molecular variants of SSR marker wmc617 suggest a conserved region for controlling dormancy on group four. The majority of QTL mapped in regions known to contain factors affecting different components of pre-harvest sprouting resistance like seed dormancy, seed coat colour, ABA responsiveness and alpha-amylase activity. This study demonstrated that using multiple measures of seed dormancy at multiple intervals of germination enhanced identification of QTL affecting dormancy in white-seeded hexaploid wheat. [ABSTRACT FROM AUTHOR]

Two possible sources of resistance to pre-harvest sprouting were evaluated in quinoa. They showed dormancy at harvest and significant variations in dormancy level in response to environmental conditions experienced during seed development. The aims of this work were to evaluate the importance of seed coats in the regulation of dormancy in this species, to investigate possible mechanisms of action and to assess association of seed coat properties with changes in dormancy level caused by the environment. Accessions Chadmo and 2-Want were grown under field conditions on different sowing dates during 2 years. Seed coats were manipulated and seed germination was evaluated at different temperatures. Seed coat perforation before incubation led to faster dormancy loss in both accessions. This effect decreased with delayed sowing date, and seeds expressed a level of dormancy not imposed by coats. This suggests the presence of embryo dormancy in the genus Chenopodium. Seeds of the accession 2-Want had a significantly thinner seed coat at later sowing dates, associated with a decreasing coat-imposed dormancy, but this pattern was not detected in Chadmo. The seed coat acts as a barrier to the release of endogenous abscisic acid (ABA) in quinoa, suggested by the increase in germination and a higher amount of ABA leached from perforated seeds. ABA is able to leach from seeds with an intact seed coat, suggesting that differences in seed coat thickness may allow the leakage of different amounts of ABA. This mechanism may contribute to the observed differences in dormancy level, either between sowing dates or between accessions. [ABSTRACT FROM AUTHOR]

Mother of FT and TFL1 (MFT) participates in the regulation of seed dormancy in wheat. A single-nucleotide polymorphism (SNP) in the promoter of MFT on chromosome 3A (MFT-3A) can explain the difference in the levels of MFT-3A expression, and the difference in seed dormancy, between Chinese Spring (CS) and the CS line with a substituted chromosome 3A from Zenkoujikomugi (Zen) (CS(Zen3A)). Using a cleaved amplified polymorphic sequence (CAPS) marker for this SNP, we analyzed the distribution of the SNP in 694 cultivars, including 117 Japanese cultivars and 551 cultivars from a wheat core collection. The Zen-type SNP predominantly occurs in cultivars used in Japan, where the rainy season overlaps with the wheat harvest season. We also sequenced the ~800 bp genomic fragment amplified by the CAPS marker and categorized the sequences into 16 groups, G1–G16. Only G11 has the Zen-type SNP; all the others have the CS-type SNP. This indicates that the CS-type allele (T) is ancestral, and during cultivation, nucleotide substitution occurred to give the Zen-type allele (C), which has been adopted to improve pre-harvest sprouting tolerance. Phylogenetic analysis indicates that G11 is derived from G3, which occurs worldwide. Our results suggest that the CAPS marker provides a valuable tool to select the Zen-type MFT-3A allele in wheat breeding programs for improving pre-harvest sprouting tolerance. [ABSTRACT FROM AUTHOR]

Tibetan semi-wild wheat ( Triticum aestivum ssp. tibetanum Shao) is a hexaploid wheat resource distributed only in Tibet that has an interesting type of seed dormancy in addition to hulled glumes and brittle spikelets. A whole-genome linkage map of T. aestivum ssp. tibetanum was constructed for a population of 186 recombinant inbred lines using 645 diversity array technology (DArT) markers, 127 simple sequence repeat markers and three R- 1 genotyping markers. Seed dormancy was evaluated at five post-ripening stages from 2010 to 2013. Comprehensive quantitative trait locus (QTL) mapping by inclusive composite interval mapping analysis identified seven QTLs for seed dormancy, designated as Qsd.sau- 1B, Qsd.sau- 3A, Qsd.sau- 3B, Qsd.sau- 3D, Qsd.sau- 4A1, Qsd.sau- 4A2, and Qsd.sau- 7A, on chromosomes 1BL, 3AL, 3BL, 3DL, 4AS, 4AL, and 7AL, which explained 8.9, 7.2, 10.8, 7.0, 11.4, 9.4, and 12.7 % of phenotypic variation, respectively. Qsd.sau- 4A1 and Qsd.sau- 7A have only rarely been reported in domesticated common wheat but were prominent in T. aestivum ssp. tibetanum accession Q1028. Qsd.sau- 4A1 was associated with intense, short-duration dormancy and was recognized as an ideal QTL for wheat breeding. [ABSTRACT FROM AUTHOR]

As in other cultivated species, dormancy can be seen as a problem in cereal production, either due to its short duration or to its long persistence. Indeed, cereal crops lacking enough dormancy at harvest can be exposed to pre-harvest sprouting damage, while a long-lasting dormancy can interfere with processes that rely on rapid germination, such as malting or the emergence of a uniform crop. Because the ancestors of cereal species evolved under very diverse environments worldwide, different mechanisms have arisen as a way of sensing an appropriate germination environment (a crucial factor for winter or summer annuals such as cereals). In addition, different species (and even different varieties within the same species) display diverse grain morphology, allowing some structures to impose dormancy in some cereals but not in others. As in seeds from many other species, the antagonism between the plant hormones abscisic acid and gibberellins is instrumental in cereal grains for the inception, expression, release and re-induction of dormancy. However, the way in which this antagonism operates is different for the various species and involves different molecular steps as regulatory sites. Environmental signals (i.e. temperature, light quality and quantity, oxygen levels) can modulate this hormonal control of dormancy differently, depending on the species. The practical implications of knowledge accumulated in this field are discussed. [ABSTRACT FROM AUTHOR]