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Rice is a significant staple crop that provides food and livelihoods for millions of people worldwide. However, climate change and frequent cyclonic storms with heavy rains during grain maturation periods have led to a significant reduction in rice yield and quality (20–30%) due to pre-harvest sprouting (PHS) damage. PHS has become a widespread issue globally, resulting in significant economic losses for Indian farmers, amounting to billions of rupees annually and severely impacting the country’s economy. Developing protocol and PHS-resistant rice genotypes is essential to mitigate the significant economic losses experienced by farmers and meet the growing demand for food grain with the increasing population. This study was aimed to developing the efficient protocol to identify PHS-resistant rice genotypes by evaluating 96 genotypes under laboratory and field conditions at 20, 25, 30, 35 and 40 days after flowering (DAF). To evaluate the PHS resistant genotypes we have developed the efficient and standard protocol for the present study. The results showed a positive correlation between phenotypic responses under laboratory and field conditions. Based on the germination percentage exhibited under laboratory and field conditions, the genotypes were grouped into four clusters using K-clustering and dendrogram clustering analysis. Out of 96 genotypes evaluated 19 grouped as highly susceptible (45 to 88%), 14 were moderately susceptible (10 to 45%), 51 were moderately resistant (0.10 to 10.00%), and 12 were highly resistant with zero percent germination at all flowering stages. The study also evaluated the genotypes for days to germination from 20 to 40 DAF. The highly susceptible genotypes germinated earlier (3 days) than moderately susceptible and resistant genotypes (4 to 6 days). Zero days were assigned to highly resistant genotypes since no germination was recorded. In nutshell, the novel PHS-resistant rice genotypes identified in this study could serve as donors for future crop improvement programs. [ABSTRACT FROM AUTHOR]

Resistance to pre-harvest sprouting (PHS) is an agronomically important trait affecting the yield and grain quality of bread wheat. PHS resistance depends both on environmental factors and the genotypic and phenotypic properties of wheat varieties. It is known that wheat varieties with red-grain are more resistant to PHS than white-grain varieties. However, at present there are no methodological approaches that allow to unambiguously distinguish red-grain varieties according to the level of PHS resistance. The purpose of the study was to compare different methods for efficient differentiation of soft winter wheat (Triticum aestivum L.) varieties for resistance to PHS. The germination index (GI), α-amylase activity (AAA), a digital grade of the grain color and genetic bases of the wheat varieties the grain was determined in 164 winter wheat, among them 156 were red-grain. The studies were carried out at the late milk/hard dough (LM/HD; GS77-GS87) stage and the hard grain (HG; GS92-GS93) stage. Based on the dynamics of GI it was found that late LM/HD stage is the most suitable for GI evaluation. AAA was performed using the Ceralpha method and falling number (FN) evaluation. An increase in the level of AAA during grain ripening of wheat varieties was shown. A negative correlation was found between GI and FN, FN and AAA. Using the Lab color model to assess the color variation of the grain coat allow to identify 3 variants of grain color. Genetic base of wheat varieties was analyzed by means of allelic composition of the Tamyb10 gene, which participate in the formation of the red color of grain. The results indicated that digital analysis and allelic composition of the Tamyb10 cannot be used as additional criterion for separation of red-grain wheat varieties for resistance to PHS. This is despite the fact that the numerous group of the varieties contain two or more dominant Tamyb10 gene. In general, a comparison of varieties by all three parameters allow to identify a group of varieties that are most PHS resistant. This group consist of 73 red-grain varieties out of 156, while no white-grain PHS-resistant varieties were identified. [ABSTRACT FROM AUTHOR]

Rice grains are the major source of nutrition for more than half of the world's population. With increased frequencies of cyclones in the last decade during grain maturation stage of rice crop, most of the rice cultivars in lowland ecologies are getting affected by pre harvest sprouting due to flash flooding and incessant rains. Significant economic loss is incurred in the global food grain industry of cereals due to pre-harvest sprouting (PHS). It is very important to develop climate resilient varieties with PHS resistant traits introgressed in them. Well characterized PHS resistant rice genotypes with optimal dormancy that can serve as donors are need of the hour. We conducted an experiment to identify PHS resistant genotypes, and also determine to their physiological and biochemical characteristics. 96 diverse rice genotypes were evaluated for PHS resistance from 20 to 40 days after flowering (DAF). Based on their response, 16 contrasting genotypes were identified from 96 genotypes to further study the underlying mechanism of PHS resistance. The results revealed that, susceptible genotypes (8) exhibited very high germination percentage (4 to 87.5%), while resistant genotypes (8) exhibited zero germination at all the stages of study. Susceptible genotypes had higher levels of reactive oxygen species (H2O2 and O2−) and malondialdehyde (MDA) in their leaves (flag leaf) and seeds than resistant genotypes indicating a better stress protection mechanism in the resistant genotypes. The ability to imbibe moisture upon treatment also varied among the contrasting genotypes. In a nutshell, the present study revealed that better ROS scavenging mechanism, lower lipid peroxidation along with lesser moisture absorption capacity could have contributed to PHS resistance in the resistant genotypes. [ABSTRACT FROM AUTHOR]

Grain dormancy of wheat is closely associated with grain color: red-grained lines show higher dormancy than white-grained lines. The production of red pigments is regulated by R-1, Tamyb10 gene. However, the relation between grain color and dormancy remains unknown. For this study, we generated transgenic lines which were introduced a DNA fragment containing Tamyb10-D1 gene and its a 2 kb promoter including the 5′ untranslated region into white-grained wheat. Transgenic lines showed red-grained and higher dormant traits. Contents of plant hormones and gene expression of embryos at 30 days after pollination were examined in a wild type and a transgenic line. No differences were observed in the contents of plant hormones, but several genes are differentially expressed between these lines. One differentially expressed gene, TaLTP2.128, is a member of non-specific lipid transfer proteins. It was expressed higher in white grains than in red grains. A putative amino acid sequence showed similarity to that of OsHyPRP5, which is identified as QTL controlling low-temperature germinability in rice. Expression of TaLTP2.128 was increased by grain imbibition. The increasing levels were higher not only in other white-grained lines, but also in non-dormant red-grained lines. TaLTP2.128 was expressed at a quite early stage of germination. These study findings indicate that Tamyb10 regulates dormancy release by the modification of TaLTP2.128 acting as trigger of germination. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) is one of the major threats to global food security as it significantly affects cereals’ production and quality. PHS tolerance depends on diverse factors, among which phytohormones and germination-inhibitory substances (GISs) play essential roles. However, in wheat, information related to GIS in the glume is scarce. Thus, we applied LC–MS/MS-based metabolomics analysis to explore the polyphenols and phytohormones profiles of two contrasting wheat genotypes, Lincang Hulled Wheat (LHW, PHS-resistant) and Yunmai53 (Yun53, PHS-highly susceptible). Physiological tests revealed that LHW PHS-resistance is not associated with the ability of its spikelet to prevent water absorption. The total polyphenol content of the spikes and shells of LHW was significantly higher than that of Yun53, respectively. In total, 214 phenolic compounds classified mainly into phenolic acids (42.52%), flavones (23.83%), and flavonoid carbonosides (16.36%) were identified. 180 differentially accumulated polyphenols (DAPs) were uncovered, including 168 up-regulated in LHW. 24 most up-regulated DAPs (Log2FC ≥ 8) were unveiled as potential candidate GISs. Of the identified phytohormones, abscisic acid, salicylic acid, and jasmonic acid exhibited significantly higher content in LHW compared to Yun53. Whereas, Yun53 contained significantly higher levels of ethylene and gibberellin than LHW. Our findings offer new resources for PHS control in wheat.Article highlights: 168 up-regulated phenolic compounds in the PHS-resistant wheat genotype were identified. Wheat PHS resistance is associated with higher polyphenols, ABA, JA, and SA contents. 24 potential germination inhibitory polyphenols were identified for further studies. [ABSTRACT FROM AUTHOR]

Seed dormancy is an important agronomic trait under the control of complex genetic and environmental interactions, which have not been yet comprehensively understood. From the field screening of rice mutant library generated by a Ds transposable element, we identified a pre-harvest sprouting (PHS) mutant dor1. This mutant has a single insertion of Ds element at the second exon of OsDOR1 (LOC_Os03g20770), which encodes a novel seed-specific glycine-rich protein. This gene successfully complemented the PHS phenotype of dor1 mutant and its ectopic expression enhanced seed dormancy. Here, we demonstrated that OsDOR1 protein binds to the GA receptor protein, OsGID1 in rice protoplasts, and interrupts with the formation OsGID1-OsSLR1 complex in yeast cells. Co-expression of OsDOR1 with OsGID1 in rice protoplasts attenuated the GA-dependent degradation of OsSLR1, the key repressor of GA signaling. We showed the endogenous OsSLR1 protein level in the dor1 mutant seeds is significantly lower than that of wild type. The dor1 mutant featured a hypersensitive GA-response of α-amylase gene expression during seed germination. Based on these findings, we suggest that OsDOR1 is a novel negative player of GA signaling operated in the maintenance of seed dormancy. Our findings provide a novel source of PHS resistance. Key message: OsDOR1, the causal gene for the rice PHS mutant dor1, is a novel positive regulator of seed dormancy through interaction with the GID1-SLR1 complex and stabilization of the SLR1 protein in rice seeds. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) is an environmentally induced phenomenon, which causes severe yield losses in urdbean under humid weather conditions. Concerning PHS, deployment of genotypic capacity for PHS tolerance would be a feasible approach, but has not been evaluated in urdbean. Therefore, a laboratory-based study was conducted to investigate the genotypic potential of PHS tolerance in urdbean and to understand the influence of various seed and pod physical and physiological traits on PHS. A panel of 140 diverse urdbean genotypes was tested for seed and pod morphological attributes, water imbibitions patterns, fresh seed germination, germination time, and physical dormancy or hard seededness for characterizing the trait PHS. A wider variation in PHS (3–94%) was observed within the genotypes and the trait hard seededness was found as the key determinant of PHS tolerance in urdbean. The genotypes with lower PHS (< 10%) had a mean hard seededness of 77%, while, the genotypes with higher PHS (> 70%) recorded a mean hard seededness of 7%. Results further demonstrated that the persistence of hard seededness is highly genotype specific and temporal in character, which was highest in the freshly harvested seeds and decline over the storage period. The correlation results indicated that seed weight, seed length, pod water imbibitions, seed water imbibitions, mean germination time, and fresh seed germination positively influenced PHS. The large-seeded genotypes (> 4 g 100 seeds−1) showed higher PHS than the small-seeded genotypes (< 3 g 100 seeds−1). The multivariate analysis results further confirmed the positive relationship of PHS with pod water imbibitions, fresh seed germination, and 100-seed weight. The PHS tolerant genotypes PLU 302, CN 35–15, and PLU 65, which recorded hard seededness of 70–88% after harvesting, and reduced to < 24% after 60 days could be used as potential donors for the improvement of urdbean. [ABSTRACT FROM AUTHOR]

The review is devoted to pre-harvest sprouting (PHS) in soft wheat (Triticum aestivum L.) as one of the main problems faced by specialists in the field of genetics and selection of grain crops. Pre-harvest sprouting leads to a decrease in yields and economic losses. In the present work, the internal and external factors which influence PHS grain crops, as well as their interrelation, have been described. The characteristics of efficiency and features of the use of physiological biochemical and molecular genetic methods to evaluate the pre-harvest sprouting resistance of soft wheat grain are given. [ABSTRACT FROM AUTHOR]

Pre -harvest sprouting (PHS) is an important problem in cereal production reducing yield and grain quality. After decades of improvement, triticale remains particularly susceptible to PHS but no resistance genes or QTLs were identified so far in this species. As wheat shares the A and B genomes with triticale, wheat PHS resistance genes can be introgressed into triticale genome by recombination after interspecific crosses. In this project, three PHS resistance genes have been transferred from wheat to triticale by marker-assisted interspecific crosses, followed by four backcrosses. The gene TaPHS1 from the 3AS chromosome of cultivar Zenkoujikomugi (Zen) and the TaMKK3 and TaQsd1, respectively located on the 4AL and 5BL chromosomes derived both from cultivar Aus1408, were pyramided in the triticale cultivar Cosinus. Only the TaPHS1 gene increases consistently the PHS resistance in triticale. The lack of efficacy of the other two genes, especially TaQsd1, could be the result of an imperfect linkage between the marker and the gene of interest. The introduction of PHS resistance genes did not alter agronomic nor disease resistance performances of triticale. This approach leads to two new, agronomically performant and PHS-resistant triticale cultivars. Today, two breeding triticale lines are ready to enter the official registration process. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting is one of the most serious problems in rice production. Sensitive pre-harvest sprouting causes low seed quality and losses before harvesting. Seed dormancy is one of the most important traits relative to pre-harvest sprouting. In this study, the common wild rice, Oryza rufipogon W630 (strong seed dormancy) was used as a donor to improve the pre-harvest sprouting resistance of O. sativa Indica IR36 (popular cultivar in Asia). Thereafter, 170 backcross recombinant inbred lines (BRILs) at the BC2F8 generation were produced by the single seed descendant method. Their degree of dormancy was assessed and genotype was analyzed using 180 polymorphic SSR markers covering entire chromosomes. Finally, a QTL analysis was conducted by composite interval mapping to identify putative QTLs of seed dormancy and the wild allele effects to the background of typical rice cultivar IR36. Thus, two of 170 BRILs showed stronger seed dormancy compared to recurrent parent IR36. In addition, two putative QTLs for seed dormancy at chromosome 2 and 7 were also found in this population through composite interval mapping. These results indicated the stronger dormancy trait of two BRILs derived from wild rice Oryza rufipogon W630; this trait was also controlled by genetic factors. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) leads to serious economic losses because of reductions in yield and quality. To analyze the quantitative trait loci (QTLs) for PHS resistance in japonica rice, PHS rates on panicles were measured in 160 recombinant inbred lines (RILs) derived from a cross between the temperate japonica varieties Odae (PHS resistant) and Unbong40 (PHS susceptible) under two different environmental conditions—field (summer) and greenhouse (winter) environments. Genome re-sequencing of the parental varieties detected 266,773 DNA polymorphisms including 248,255 single nucleotide polymorphisms and 18,518 insertions/deletions. We constructed a genetic map comprising 239 kompetitive allele-specific PCR and 49 cleaved amplified polymorphic sequence markers. In the field environment, two major QTLs, qPHS-3FD and qPHS-11FD, were identified on chromosomes 3 and 11, respectively, whereas three major QTLs, qPHS-3GH, qPHS-4GH, and qPHS-11GH, were identified on chromosomes 3, 4, and 11, respectively, in the greenhouse environment. qPHS-11GH and qPHS-11FD had similar locations on chromosome 11, suggesting the existence of a gene conferring stable PHS resistance effects under different environmental conditions. The QTLs identified in this study can be used to improve the PHS resistance of japonica varieties, and they may improve our understanding of the genetic basis of PHS resistance. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) can result in obvious reduction of wheat grain yield and quality. Based on the sequence of barley Qsd1 gene, three homologs in common wheat were isolated, designated TaQsd1-5A, TaQsd1-5B, and TaQsd1-5D, respectively. Two CAPS (QSD1 and QSD3) and one KASP (QSD2) markers for TaQsd1-5B were developed and validated both in a natural population consisting of 351 wheat varieties and one RIL population from the cross of Yangxiaomai × Zhongyou 9507. The marker QSD1 co-segregated with a major QTL for the period of dormancy (PD) in the RIL population. The transcript levels of TaQsd1-5B were significantly higher in long-dormancy varieties (lines) than in short-dormancy varieties (lines) during seed imbibition, which is consistent with the activity of the AlaAT enzyme encoded by TaQsd1-5B. Meanwhile, we also found higher expression levels of ABA biosynthesis and signaling genes and higher endogenous ABA contents, but lower expression levels of genes for ABA catabolism in long-dormancy varieties. The allele TaQsd1-5Ba associated with longer PD was more frequently present in Chinese landrace wheats, compared with Chinese modern cultivars and foreign germplasms. These findings provide important insight into understanding the regulatory mechanism of TaQsd1 with respect to PD and molecular markers for improvement of PHS resistance in wheat breeding programs. [ABSTRACT FROM AUTHOR]

Main conclusion: Totally, 23 and 26 loci for the first count germination ratio and the final germination ratio were detected by quantitative trait loci (QTL) mapping and association mapping, respectively, which could be used to facilitate wheat pre-harvest sprouting breeding. Weak dormancy can cause pre-harvest sprouting in seeds of common wheat which significantly reduces grain yield. In this study, both quantitative trait loci (QTL) mapping and genome-wide association study (GWAS) were used to identify loci controlling seed dormancy. The analyses were based on a recombinant inbred line population derived from Zhou 8425B/Chinese Spring cross and 166 common wheat accessions. Inclusive composite interval mapping detected 8 QTL, while 45 loci were identified in the 166 wheat accessions by GWAS. Among these, four loci (Qbifcgr.cas-3AS/Qfcgr.cas-3AS, Qbifcgr.cas-6AL.1/Qfcgr.cas-6AL.1, Qbifcgr.cas-7BL.2/Qfcgr.cas-7BL.2, and Qbigr.cas-3DL/Qgr.cas-3DL) were detected in both QTL mapping and GWAS. In addition, 41 loci co-located with QTL reported previously, whereas 8 loci (Qfcgr.cas-5AL, Qfcgr.cas-6DS, Qfcgr.cas-7AS, Qgr.cas-3DS.1, Qgr.cas-3DS.2, Qbigr.cas-3DL/Qgr.cas-3DL, Qgr.cas-4B, and Qgr.cas-5A) were likely to be new. Linear regression showed the first count germination ratio or the final germination ratio reduced while multiple favorable alleles increased. It is suggested that QTL pyramiding was effective to reduce pre-harvest sprouting risk. This study could enrich the research on pre-harvest sprouting and provide valuable information of marker exploration for wheat breeding programs. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) and seed longevity (SL) are complex biological processes of major importance for agricultural production. In the present study, a recombinant inbred line (RIL) population derived from a cross between the German winter wheat (Triticum aestivum L.) cultivars History and Rubens was used to identify genetic factors controlling these two physiological seed traits. A falling number (FN) test was employed to evaluate PHS, while SL was measured using a germination test (and the speed of germination) after controlled deterioration. FN of the population was assessed in four environments; SL traits were measured in one environment. Four major quantitative trait loci (QTL) for FN were detected on chromosomes 4D, 5A, 5D, and 7B, whereas for SL traits, a major QTL was found on chromosome 1A. The FN QTL on chromosome 4D that coincided with the position of the dwarfing gene Rht-D1b only had effects in environments that were free of PHS. The remaining three QTL for FN were mostly pronounced under conditions conducive to PHS. The QTL on the long arm of chromosome 7B corresponded to the major gene locus controlling late maturity α-amylase (LMA) in wheat. The severity of the LMA phenotype became truly apparent under sprouting conditions. The position on the long arm of chromosome 1A of the QTL for SL points to a new QTL for this important regenerative seed trait. [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]

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) 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]

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]

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]

Seed dormancy (SD) is an important agronomic trait affecting crop yield and quality. In this study, one rice population of recombinant inbred lines (RILs) was used to determine the genetic characteristics of SD at the early (4 weeks after heading), middle (5 weeks after heading) and late (6 weeks after heading) development stages. The level of SD decreased with the process of seed development, and the SD was significantly affected by the heading date (HD) and temperature at the early and middle development stages. A total of eight additive quantitative trait loci (QTLs) for SD were identified at three development stages, and more QTLs were expressed at the early and late development stages. Among them, four, one and three additive QTLs were identified at the early, middle and late development stages, respectively. Epistatic QTLs and QTL-by-development interactions were detected by the joint analysis of multi-development phenotypic values, and one additive and two epistatic QTLs were identified. The phenotypic variation of SD explained by each additive, epistatic QTL and QTL × development interaction ranged from 8.0 to 13.5 %, 0.7 to 3.9 % and 1.3 to 2.8 %, respectively. One major QTL qSD7.1 for SD was tightly linked to the major QTL qHD7.4 for HD, which might be applied to reveal the relationship of SD and HD. By comparing chromosomal positions of these additive QTLs with those previously identified, five additive QTLs qSD1.1, qSD2.1, qSD2.2, qSD4.1 and qSD4.2 might represent novel genes. The best three cross combinations for the development of RIL populations were predicted to improve SD. The selected RILs and the identified QTLs might be applicable to improve the rice pre-harvest sprouting tolerance by the marker-assisted selection approach. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) of wheat greatly reduces the quality and economic value of grain, and PHS resistance is one of the most important traits in wheat breeding. Red-grained wheat varieties are generally more resistant to PHS than white-grained ones; however, some are still susceptible. The red pigment of red-grained wheat is synthesized through the flavonoid biosynthetic pathway, in which the dihydroflavonol-4-reductase gene ( DFR) is one of the genes involved in anthocyanin synthesis. In this study, a set of 120 red-grained Chinese wheat cultivars and lines with distinct PHS resistance were used to characterize TaDFR genotype variations and their association with PHS resistance. Whereas no variation or functional variation of TaDFR genes was detected on chromosomes 3A and 3D, a novel TaDFR allele, designated TaDFR- Bb, was explored on chromosome 3B. Compared with TaDFR- Ba, an 8 bp insertion (CTCTAGGA) was identified in the promoter region of TaDFR- B in most of the PHS resistant red-grained wheat varieties and advanced lines. Based on this, a CAPS marker was designed and validated with a set of Chinese red-grained wheat cultivars and lines with distinct PHS resistance. In most cases, TaDFR- Bb was associated with higher PHS resistance. An association study indicated that wheat varieties with the 8 bp insertion (average seed germination index 23.6 %) were significantly more resistant ( P < 0.01) to PHS than those without the insertion (average seed germination index 69.5 %). Further study on gene expression demonstrated that the insertion led to increased TaDFR- B expression in cultivars with PHS resistance. Transient expression of TaDFR- B in coleoptiles of wheat cv. Chinese Spring revealed that increasing TaDFR gene expression did not induce the synthesis of anthocyanins. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) reduces the quality of wheat ( Triticum aestivum L.) and the economic value of the grain. Our previous studies characterized the haplotypes of Viviparous- 1B ( Vp- 1B) and its association with PHS resistance in Chinese wheats. The objective of this study was to analyze the haplotypes of Viviparous- 1A ( Vp- 1A) and Viviparous- 1D ( Vp- 1D) in a collection of 103 widely-grown winter wheats in China, and their associations with PHS resistance. In total, 17 Vp- 1A haplotypes were explored on chromosome 3A of bread wheat, and were located in three major regions, the third intron, fifth intron and sixth exon, and designated TaVp- 1Aam, TaVp- 1Aan, TaVp- 1Aao, TaVp- 1Abm, TaVp- 1Abn, TaVp- 1Agm, TaVp- 1Ahm, TaVp- 1Ahn, TaVp- 1Aho, TaVp- 1Aim, TaVp- 1Ain, TaVp- 1Aio, TaVp- 1Ajm, TaVp- 1Ajn, TaVp- 1Akm, TaVp- 1Alm and TaVp- 1Aln, respectively. However, no allelic variation of Vp- 1D was found in this set of germplasm. Based on the haplotypes explored and their average germination index values, a novel co-dominant sequence-tagged site marker of the TaVp- 1A gene was developed and designated Vp1A3. In most cases, haplotype TaVp- 1Agm was associated with higher resistance to PHS. By combining with our previously exploited Vp1B3 marker, the efficiency of marker-assisted selection for PHS-resistant varieties was improved. Moreover, while the haplotype combination of TaVp- 1Aam and TaVp- 1Ba was associated with greater PHS susceptibility, the haplotype combinations TaVp- 1Agm and TaVp- 1Bb, TaVp- 1Agm and TaVp- 1Ba, TaVp- 1Aim and TaVp- 1Bb, and TaVp- 1Aam and TaVp- 1Bb could confer higher PHS resistance and be used as potential parental lines for molecular marker-assisted wheat breeding for PHS resistance. [ABSTRACT FROM AUTHOR]

Triticale, an artificial hybrid of wheat and rye, combines the good yield and nutritional value of wheat with good disease resistance of rye. Despite these advantages, pre-harvest sprouting (PHS) can seriously limit triticale production. Although different field and laboratory tests exist, it remains difficult to breed for PHS tolerance and mechanisms behind PHS are still elusive. As part of an integrated study focussing on the genetic and physiological background of PHS, a multidisciplinary approach was pursued monitoring α-amylase, an enzyme that is involved in PHS, both at transcriptional and post-transcriptional levels during kernel development. Plants of PHS-tolerant and PHS-susceptible varieties of wheat and triticale were grown under controlled conditions from flowering to harvest. At regular time points, kernels were harvested for germination tests, α-amylase analysis and RNA extraction. RNA extracts were used in an RT-qPCR assay to obtain expression profiles of the α- Amy1 and α- Amy2 genes. The α-amylase activity profiles during kernel development corresponded well with results from previous reports. The relative gene expression profiles revealed that α- Amy2 peaked in the beginning of kernel development, while α- Amy1 increased towards harvest maturity. Furthermore, the relative α- Amy1 expression was higher in the PHS-susceptible varieties compared to the PHS-tolerant varieties. [ABSTRACT FROM AUTHOR]

The association between high malting quality and pre-harvest sprouting (PHS) susceptibility is a key challenge when developing new malting barley varieties. A new malting barley variety Baudin has successfully combined high malting quality and PHS tolerance. A doubled haploid population was developed for mapping PHS tolerance and seed dormancy from a cross of Baudin × AC Metcalfe using 233 molecular markers. Three QTLs were mapped for seed dormancy based on the standard germination test at 24, 48 and 72 h. One major QTL was mapped to the long arm of chromosome 5H controlling seed dormancy and PHS tolerance from Baudin. Two other minor QTLs were identified from Baudin on chromosomes 3 and 7H. QTL/QTL interaction was detected for seed dormancy between chromosomes 3 and 5H. The PHS tolerance allele of the 5H QTL from Baudin contributes to higher malt yield without significant impact on diastatic power, beta-glucan content and wort viscosity. QTL from Baudin provide new sources to integrate PHS tolerance and high malting quality. [ABSTRACT FROM AUTHOR]

Grain dormancy provides protection against pre-harvest sprouting (PHS) in cereals. Composite interval mapping and association analyses were performed to identify quantitative trait loci (QTL) contributing grain dormancy in a doubled haploid (DH) barley population (ND24260 × Flagship) consisting of 321 lines genotyped with DArT markers. Harvest-ripe grain collected from three field experiments was germinated over a 7-day period to determine a weighted germination index for each line. DH lines displaying moderate to high levels of grain dormancy were identified; however, both parental lines were non-dormant and displayed rapid germination within the first two days of testing. Genetic analysis identified two QTL on chromosome 5H that were expressed consistently in each of the three environments. One QTL (donated by Flagship) was located close to the centromeric region of chromosome 5H ( qSDFlag), accounting for up to 15% of the phenotypic variation. A second QTL with a larger effect (from ND24260) was detected on chromosome 5HL ( qSDND), accounting for up to 35% of the phenotypic variation. qSDFlag and qSDND displayed an epistatic interaction and DH lines that had the highest levels of grain dormancy carried both genes. We demonstrate that qSDND in the ND24260 × Flagship DH population is positioned proximal and independent to the well-characterised SD2 region that is associated with both high levels of dormancy and inferior malt quality. This indicates that it should be possible to develop cultivars that combine acceptable malting quality and adequate levels of grain dormancy for protection against PHS by utilizing these alternate QTL. [ABSTRACT FROM AUTHOR]

Resistance to pre-harvest sprouting is an important breeding objective for cereal crops like barley and wheat. Seed dormancy, which determines the resistance or susceptibility to pre-harvest sprouting (PHS), is a complex trait. It is largely controlled by the antagonistic action of the plant hormones abscisic acid and gibberellic acid, but also has a large component of genotype × environment interaction. Recent studies have revealed a role for epigenetic changes through histone modification in controlling seed dormancy. However, the role of DNA methylation in seed development and dormancy is not known. In this study, we explored the role of ARGONAUTE4_9 class genes of the DNA methylation pathway in seed development and dormancy in barley. Our results show that the two AGO4_9 class genes in barley, i.e. AGO1002 and AGO1003, are preferentially expressed in ovaries at meiosis and in embryos 25 days after pollination (DAP). The expression of AGO1003 is two to fivefold higher than that of AGO1002 in these tissues, demonstrating differential expression of these genes. We also analysed the expression of AGO1003 in embryos of PHS-resistant and -susceptible varieties at 25 DAP and found a significant variation in the expression of this gene in seeds of dormant and non-dormant lines. The observed expression pattern of AGO1002 and AGO1003 suggests a possible role in sporogenesis and post-fertilization seed development. Indirectly these results imply a potential role of DNA methylation in seed development and seed dormancy. [ABSTRACT FROM AUTHOR]

During the last few decades, the physiological and genetic background of dormancy, and correlated pre-harvest sprouting (PHS) have been intensively investigated. Special attention has often been paid to genetic factors that may explain and predict PHS susceptible behaviour. A major candidate is the Vp1 gene which is involved in embryo development and maturation as well as in dormancy establishment. In this study, Vp1 gene expression during kernel development was studied in wheat, triticale and rye as a potential biomarker for selecting PHS tolerant varieties in cereal breeding programs. Plants of known PHS tolerant and PHS susceptible varieties were grown under controlled conditions from flowering until harvest ripeness. During that period, kernels were regularly harvested for RNA extraction and cDNA synthesis. Calibrated and normalized relative Vp1 expression levels were obtained in an RT-qPCR assay. During kernel development, Vp1 expression levels generally showed a typical peak during the soft dough stage, after which they decreased and remained low until harvest maturity. Differences in Vp1 expression levels could be observed between the PHS susceptible and PHS tolerant varieties of wheat, with the PHS tolerant variety showing higher levels of relative Vp1 expression compared to the PHS susceptible variety. In triticale, however, this difference was only seen once and could not be confirmed in further experiments. It seems that the Vp1 gene in triticale behaves in a similar way as in rye, in which no specific trends could be observed. [ABSTRACT FROM AUTHOR]

Preharvest sprouting (PHS) in spring wheat ( Triticum aestivum L.) and durum wheat ( T. turgidum L. var durum) causes significant economic losses due to a reduction in grain yield, grain functionality and viability of seed for planting. Average annual estimated losses in Canada are about $100 million. Genetic resistance to PHS reduces these losses. Development of PHS resistant cultivars is complicated by the effects of factors under genetic control, such as spike morphology, seed dormancy, environment, and kernel diseases. Resistance to PHS has been a breeding priority since the late 1960s. Development of RL4137, which is the primary source of PHS resistance in the Canada Western Red Spring market class, has led to cultivar improvements. A white-seeded derivative of RL4137 is the primary source of PHS in the Canada Prairie Spring White and Canada Western Hard White Spring wheat market classes. Procedures to select for PHS resistance vary among breeding programs, market classes and by degree of inbreeding. Methods include artificial sprouting of intact spikes, germination tests, natural weathering in field trials, artificial weathering trials, and indirect assessment of sprouting by measuring Hagberg falling number. Although many genetic loci have been attributed to preharvest sprouting resistance, application of molecular markers is currently limited due to the complex inheritance of the trait. In Canada, cultivars are characterized for their relative level of PHS resistance and the information is made available to producers. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) resistance is one of the most important traits in wheat breeding. Characterization of Viviparous- 1 ( Vp- 1) haplotypes in wheat related species will further our understanding of the role of Vp- 1 in PHS resistance of bread wheats. The present paper reported Vp- 1 haplotype analyzes of 77 accessions of wheat related species including T. monococcum and T. boeoticum (AA), T. durum (AABB), T. dicoccoides (AABB) and Ae. tauschii (DD). A total of 11 novel Vp- 1 haplotypes were identified in these species including three in T. monococcum which were designated as TmVp- 1A1, TmVp- 1A2, TmVp- 1A3, three in T. boeoticum, designated as TbVp- 1A1, TbVp- 1A2 and TbVp- 1A3, two in T. durum, designated as TduVp- 1B1 and TduVp- 1B2, and three in Ae. tauschii designated as AetVp- 1D1, AetVp- 1D2 and AetVp- 1D3, respectively. Among these haplotypes explored, TduVp- 1B1 was identical to TaVp- 1Be which was detected in a PHS resistant Chinese landrace. Semi-quantitative RT-PCR analysis demonstrated that the presence of alternatively spliced transcripts of the Vp- 1 homologues in these wheat related species. The level of correctly spliced transcripts varies among the haplotypes, and was correlated with the degree of ABA responsiveness during seed germination. It appeared that Vp- 1 mis-splicing and some indel variations in bread wheats originated from its progenitors and were retained during polyploidization. Moreover, haplotypes with better Vp- 1 splicing such as TbVp- 1A2 of T. boeoticum and TduVp- 1B1 of T. durum species might be valuable in breeding PHS tolerant wheat. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) can be a problem in malting barley ( Hordeum vulgare L.) production as it results in lower yield and reduced grade. The presence of PHS is often associated with increased activity of α-amylase, a key enzyme for breakdown of starch into simple sugars. It is difficult to measure α-amylase activity (AA) associated with PHS however, and the same quantitative trait loci (QTL) may be responsible for both PHS AA and malt AA. The objective of this paper was to investigate co-occurrence and stability of QTL controlling malt AA in a barley doubled-haploid (DH) population that was evaluated in eight environments across North America. This population consisted of 150 DH lines developed from a cross between two barley varieties (Steptoe × Morex) for the North American Barley Genome Mapping Project. Malt AA was measured on a composite 400 g sample of each DH line and parent. There were a total of 223 restriction fragment length polymorphism markers covering a total genetic distance of 1221.9 cM across the entire genome. We used an empirical Bayesian method for detecting single QTLs and epistatic QTLs for individual environments. A common QTL was counted if it co-occurred in a pair of environments. Thus, the level of QTL × environment interaction was assessed based on the total frequency of co-occurred QTLs for all possible pairs of eight environments [(8 × 7)/2 = 28]. Heritability estimates (0.62-0.89) for individual environments were moderate to high. Genetic correlations between co-occurred additive and epistatic effects are essentially zero for most environment pairs. These results indicated strong QTL × environment interaction for malt AA. While the efficacy of genome-wide selection for PHS is still unknown especially in the presence of QTL × environment interaction, using the Bayesian approach may help us better understand appropriate methods for measuring and selecting for this trait. [ABSTRACT FROM AUTHOR]

This paper describes the isolation of wheat mutants in the hard red spring Scarlet resulting in reduced sensitivity to the plant hormone abscisic acid (ABA) during seed germination. ABA induces seed dormancy during embryo maturation and inhibits the germination of mature seeds. Wheat sensitivity to ABA gradually decreases with dry after-ripening. Scarlet grain normally fails to germinate when fully dormant, shows ABA sensitive germination when partially after-ripened, and becomes ABA insensitive when after-ripened for 8-12 months. Scarlet ABA-insensitive (ScABI) mutants were isolated based on the ability to germinate on 5 μM ABA after only 3 weeks of after-ripening, a condition under which Scarlet would fail to germinate. Six independent seed-specific mutants were recovered. ScABI1, ScABI2, ScABI3 and ScABI4 are able to germinate more efficiently than Scarlet at up to 25 μM ABA. The two strongest ABA insensitive lines, ScABI3 and ScABI4, both proved to be partly dominant suggesting that they result from gain-of-function mutations. The ScABI1, ScABI2, ScABI3, ScABI4, and ScABI5 mutants after-ripen more rapidly than Scarlet. Thus, ABA insensitivity is associated with decreased grain dormancy in Scarlet wheat. This suggests that ABA sensitivity is an important factor controlling grain dormancy in wheat, a trait that impacts seedling emergence and pre-harvest sprouting resistance. [ABSTRACT FROM AUTHOR]

The expression of seed dormancy related to germination temperature was studied in 25 wheat genotypes grown in the field at two locations near Zagreb and Županja in Croatia during 2008/2009 growing season. Germination tests were conducted at 15, 20 and 25 °C at harvest maturity (Time 1) as well as after 10 days (Time 2) and 15 months (Time 3) of seed after-ripening at room temperature, respectively. Significant ( P < 0.05) differences among locations (L), temperatures (T) and genotypes (G) as well as significant L × T, G × L, G × T and G × L × T interactions were observed for weighted germination index (WGI) at both Time 1 and Time 2. At Time 3 significant differences among genotypes for germination percentage were found only at the early stages of germination. The 25 wheat genotypes responded with decreasing WGI mean values (increasing dormancy) as temperature changed from 15 to 25 °C. The rate of dormancy increase with higher germination temperature varied among genotypes. Some genotypes, having similar values of WGI at 15 °C, significantly differed from each other at 25 °C and vice versa. This indicates that the range of germination temperatures included in the present study is useful when testing genotypes for their temperature-dependent dormancy potential. The number of genotypes with WGI values significantly different from the mean, as a measure of the power of germination test to detect differences in dormancy level among genotypes, as well as heritability estimates for WGIs were the highest at Time 1 for 15 °C and at Time 2 for 20 °C. [ABSTRACT FROM AUTHOR]

Few Chinese high yielding white-grained wheat cultivars possess sufficient dormancy to avoid pre-harvest sprouting (PHS). Because the field evaluation of PHS is difficult, the identification of informative molecular markers is a priority for improving the level of dormancy. In this report, the effectiveness of phenotypic and genotypic selection was compared. Four microsatellite loci Xbarc57, Xbarc294, Xbarc310 and Xbarc321, mapped on the short arm of chromosome 3A, were used for selection in white-grained wheat F lines which were also selected on the basis of their grain filling rate (GFR). One of these (later designated cv. Zhongmai911) was further selected on the basis of its allelic constitution at the four SSR loci. This cultivar combines a high level of PHS resistance with high grain yield. The results suggested that rapid GFR and PHS resistance can be bred simultaneously. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) greatly reduces the quality and economic value of wheat grain. In this study, a total of 168 International Maize and Wheat Improvement Center (CIMMYT) wheat germplasm lines were examined to characterize the haplotypes of Vp- 1A, Vp- 1B and Vp- 1D, which are located on the long arms of chromosomes 3A, 3B and 3D, respectively. Among them, five new alleles of Vp- 1Aa (the wild allele) were identified on chromosome 3A, and designated as Vp- 1Ab, Vp- 1Ac, Vp- 1Ad, Vp- 1Ae and Vp- 1Af, respectively . The main difference between Vp- 1Aa and the newly identified alleles was in the numbers of CTT repeats located in the third intron, but Vp- 1Af also had 6 and 2 bp deletions at positions 2860-2865 bp and 2880-2881 bp, and possessed five SNPs within the same intron region. In the Vp- 1B locus, several alleles ( Vp- 1Ba, Vp- 1Bb, Vp- 1Bc, Vp- 1Bd, Vp- 1Be and Vp- 1Bf) have already been identified. In the present material only two, the already known allele Vp- 1Bc, and a new one, designated as Vp- 1Bg, were detected. Compared with Vp- Ba, Vp- 1Bg had additional insertion of TCC at position 2372 bp and a 9 bp change from CTGCATC AC to GCATCAGTG at 2417-2425 bp. However, no polymorphism was detected in Vp- 1D. The frequencies of Vp- 1Aa Vp- 1Ab, Vp- 1Ac, Vp- 1Ad, Vp- 1Ae, and Vp- 1Af were 65, 10, 11, 4, 5 and 5%, respectively. For Vp- 1B, 155 out of the 168 lines were Vp- 1Bc; the remaining 13 were Vp- 1Bg. Analyses of the germination index (GI) and abscisic acid (ABA) sensitivity showed that genotypes with Vp- 1Ab or Vp- 1Af showed higher PHS resistance than the ones with other alleles, suggesting that they might be valuable for CIMMYT breeding program or germplasm introduction. The results presented here will underpin the introduction of germplasm from CIMMYT and the improvement of PHS resistance, both in CIMMYT and elsewhere. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting refers to the precocious germination of the grain in the spike prior to harvest as a result of moist weather conditions at harvest time. From the agricultural viewpoint, it is necessary to impose an exogenous dormancy to wheat seeds in order to improve the resistance of seed to pre-harvest sprouting. In this regard, we found that clove bud essential oil is a strong inhibitor for wheat seed germination. The extract obtained from clove bud by supercritical fluid extraction using CO as solvent minimized the number of extracts to two compounds, eugenol and eugenyl acetate. Eugenol, as the main constituent of the oil, was responsible for its strong inhibitory activity in wheat seeds. The aqueous solution of clove bud oil was submitted to germination assay at various concentrations from 50 to 400 mg/L. Complete inhibition of seed germination was recorded when the concentration was 400 mg/L. Roots and sprouts have similar sensitivity to inhibitory effect. In an empirical study, the synergistic cooperation of eugenol and eugenyl acetate from clove bud oil in the inhibition of seed germination was found to be a 1:1 ratio. The clove bud essential oil is widely available and will broaden the horizon of applications for natural and safe inhibitors in the fields. [ABSTRACT FROM AUTHOR]

The allelic variations of Vp-1B have been confirmed to have close association with seed dormancy (SD) and pre-harvest sprouting (PHS) of Chinese wheat in previous research, but little was known regarding whether the alleles of two other orthologs of Vp1 on 3AL ( Vp-1A) and 3DL ( Vp-1D) are also present and related to these traits. In view of this, 11 primer pairs flanking the whole sequences of these two orthologs were designed to investigate their allelic variations. The results identified six alleles of Vp-1A using the primer pair A17-19 among 81 wheat cultivars and advanced lines, which were designated as Vp-1Aa, Vp-1Ab, Vp-1Ac, Vp-1Ad, Vp-1Ae, and Vp-1Af. Except for Vp-1Ac, the other five alleles were proven novel, but no allelic variation was found in Vp-1D. On sequence analysis of alleles of Vp-1A, five deletions were observed, all occurring in the same region holding many TTC repeats. Of the six alleles detected in this study, four ( Vp-1Aa, Vp-1Ac, Vp-1Ae, and Vp-1Af) were generally distributed in varieties exhibiting higher average germination index (GI, range 0.46-0.56) and spike sprouting (SS, range 39.6-49.4%); however, the alleles Vp-1Ab and Vp-1Ad were distributed in genotypes carrying higher SD (GI 0.19-0.26) and stronger PHS resistance (SS 12.3-17.2%). On Spearman correlation analysis, the allele Vp-1Ab had significantly negative correlation with GI (−0.479) and SS (−0.542) at the 0.01 level, and the three alleles Vp-1Aa, Vp-1Ac, and Vp-1Ae had significantly positive correlation with GI [0.311 (0.05 level), 0.401 (0.01 level), and 0.294 (0.05 level)] and SS [0.283 (0.05 level), 0.309 (0.05 level), and 0.266 (0.05 level)]. The other alleles, including Vp-1Ad and Vp-1Af, also exhibited correlation, albeit not significant, with these two traits. This negative correlation showed that Vp-1Ab helped to improve SD and PHS tolerance, but Vp-1Aa, Vp-1Ac, and Vp-1Ae appeared to exert the opposite effect. To further confirm the association between alleles of Vp-1A and the two traits, a recombinant inbred line (RIL) population with 157 lines was genotyped using the primer pair A17-19, developed from the cross between Wanxianbaimaizi ( Vp-1Ab) and Jing411 ( Vp-1Ac). General linear model analysis indicated that variation in Vp-1A had a significant ( P < 0.001) association with the two traits, explaining 23.4% of the variation in GI and 16.7% of the variation in SS in the population across three crop seasons. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) in bread wheat is a major abiotic constraint reducing yield and influencing the production of high quality grain. In China both spring and winter wheat regions are affected by PHS. Sichuan lies in southwest China, where the most of rainfall occurs during April to September when wheat is harvested. The present investigation was conducted to identify the allelic variability of Vp1, a gene that plays a role in maintenance and induction of dormancy, among Sichuan landraces and recent cultivars with different dormancy levels and to find potential sources of PHS resistance for breeding. Sichuan landrace and cultivar wheat accessions had a wide range of dormancy levels. The average germination index (GI) of Sichuan landrace accessions was 0.232, whereas at 0.674 it was much higher for cultivars. The different dormancy levels between landraces and cultivars indicated that pre-harvest sprouting resistance might have been neglected in recent Sichuan wheat breeding programs. The average GI of white grained accessions was higher than for red grained accessions. Particular Vp-1B gene fragments were specific in landraces or cultivars and in white or red grained accessions. The results indicated that Vp-1B markers could be used to distinguish cultivars and landraces. Significant relationships between certain Vp-1B allelesand GI of Sichuan wheat accessions were shown by Spearman's rank correlation analysis. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) in developing wheat ( Triticum aestivum L.) spikes is stimulated by cool and wet weather and leads to a decline in grain quality. A low level of harvest-time seed dormancy is a major factor for PHS, which generally is a larger problem in white-grained as compared to red-grained wheat. We have in this study analyzed seed dormancy levels at the 92nd Zadok growth stage of spike development in a doubled-haploid (DH) white wheat population and associated variation for the trait with regions on the wheat genome. The phenotypic data was generated by growing the parent lines Argent (non-dormant) and W98616 (dormant) and 151 lines of the DH population in the field during 2002 and 2003, at two locations each year, followed by assessment of harvest-time seed dormancy by germination tests. A genetic map of 2681 cM was constructed for the population upon genotyping 90 DH lines using 361 SSR, 292 AFLP, 252 DArT and 10 EST markers. Single marker analysis of the 90 genotyped lines associated regions on chromosomes 1A, 2B, 3A, 4A, 5B, 6B, and 7A with seed dormancy in at least two out of the four trials. All seven putative quantitative trait loci (QTLs) were contributed by alleles of the dormant parent, W98616. The strongest QTLs positioned on chromosomes 1A, 3A, 4A and 7A were confirmed by interval mapping and markers at these loci have potential use in marker-assisted selection of PHS resistant white-grained wheat. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) in wheat ( Triticum aestivum L.) is a significant problem. Introgression of genes controlling grain dormancy into white-grained bread wheat is one means of improving resistance to PHS. In this study seven dormant (containing the SW95-50213 and AUS1408 sources) × non-dormant crosses were produced to investigate the effectiveness of selection for grain dormancy in early segregating generations. Each generation (F1–F4) was grown in a temperature controlled glasshouse with an extended photoperiod (i.e. continuous light). F2 and F3 generations were subject to selection. Five hundred harvest-ripe grains were tested for germination over a 14 day period, and the 100 most dormant grains were retained and grown-on to produce the next generation within each cross. The response to selection was assessed through analysis of the time to 50% germination (G50) in the F2, F3 and F4 generations. In addition, changes in marker class frequencies for two SSR markers (barc170 and gpw2279) flanking a known quantitative trait locus (QTL) for grain dormancy on chromosome 4A were assessed in DNA from F2 plants selected from early germinating (non-dormant) and late germinating (dormant) phenotypic extremes within each cross. Selection for grain dormancy in the F2 and F3 generations effectively recovered the dormant phenotype in all seven crosses, i.e. the F4 generation was not significantly different from the dormant parent. Further, selection based on individual F2 grains changed marker class frequencies for the 4A dormancy QTL; in most cases eliminating the marker class homozygous for the non-dormant alleles. Application of this screening method will enable breeders to better select for grain dormancy and may lead to development of new cultivars offering effective resistance to PHS in the near future. [ABSTRACT FROM AUTHOR]

Wheat pre-harvest sprouting (PHS) is an undesired trait, which often reduces yield and downgrades end-use quality of grain. Viviparous-1B ( Vp-1B), a regulator gene located on chromosome 3B, has previously been proved to be involved in inducing grain dormancy of wheat. In order to obtain some new or useful alleles associated with PHS tolerance of white-grained wheat, we developed a gene-specific marker (Vp1-b2) to identify allelic variations of Vp-1B using denaturing PAGE in micro-core collections of Chinese wheat and landraces. As a main component observed genetic variation for PHS, seed dormancy evaluated by germination index (GI) was determined at dough-yellow ripening stage in the present study. The results indicated that six alleles of Vp-1B, in our study, were discovered among 276 Chinese wheat varieties. Of these alleles, two variants were validated to be novel alleles and designated as Vp-1Be and Vp-1Bf, respectively. By investigating the association between allelic variations of Vp-1B and seed dormancy, we found allele of Vp-1Ba always inclined to weak seed dormancy and susceptibility to PHS. Up to 62.2% genotypes carrying the allele had high GI value with a range of 0.51–1.00, only 14.4% genotypes had low GI value under 0.30. On the contrary, other variants such as Vp-1Bb, Vp-1Bc, Vp-1Bd, Vp-1Be and Vp-1Bf mostly occurred in varieties with higher PHS tolerance, which average of GI values were 0.204, 0.227, 0.296, 0.256 and 0.186, respectively. In Chinese wheat germplasms, Vp-1Ba and Vp-1Bc showed the most widespread distribution followed by Vp-1Bb; other alleles fell into less used varieties. Our research confirmed rich allelic variation of Vp-1B occurred in micro-core collections of Chinese wheat and landraces, which may be useful for improving PHS tolerance as breeding parents. [ABSTRACT FROM AUTHOR]

A framework linkage map comprising 214 molecular marker (SSR, AFLP, SAMPL) loci was prepared using an intervarietal recombinant inbred line (RIL) mapping population of bread wheat. The RIL population that was developed from the cross SPR8198 (red-grained and PHS tolerant genotype) × HD2329 (white-grained and PHS susceptible genotype) following single seed descent segregated for pre-harvest sprouting (PHS). The RIL population and parental genotypes were evaluated in six different environments and the data on PHS were collected. Using the linkage map and PHS data, genome-wide single-locus and two-locus QTL analyses were conducted for PHS tolerance (PHST). Single-locus analysis following composite interval mapping (CIM) detected a total of seven QTL, located on specific arms of five different chromosome (1AS, 2AL, 2DL, 3AL and 3BL). These seven QTL included two major QTL one each on 2AL and 3AL. Two of these seven QTL were also detected following two-locus analysis, which resolved a total of four main-effect QTL (M-QTL), and 12 epistatic QTL (E-QTL), the latter involved in 7 QTL × QTL interactions. Interestingly, none of these M-QTL and E-QTL detected by two-locus analysis was involved in Q × E and Q × Q × E interactions, supporting the results of ANOVA, where genotype × environment interaction were non-significant. The QTL for PHS detected in the present study may be efficiently utilized for marker-aided selection for enhancing PHST in bread wheat. [ABSTRACT FROM AUTHOR]

In spite of the availability of laboratory and field tests there is still a major problem to select pre-harvest sprouting (PHS) tolerant triticale varieties in a reliable, field-independent way. One approach to minimize the influence of environmental conditions and physio-morphological traits on PHS detection is using molecular genetic tools. The ‘viviparous’ Vp1 gene has been repeatedly described to play an important role in dormancy in wheat. A quantitative RT-PCR assay based on the expression of the Vp1 gene has been developed. Specific primers were designed for detecting Vp1 in both wheat and triticale. The expression levels of Vp1 were normalized using reference genes and relatively quantified with the comparative Ct-method. However, the first results indicate that the achieved Vp1 expression levels at 50 days post anthesis are not useful to select for PHS tolerance, both in wheat and triticale. This negative outcome so far is possibly due to the existence of several splicing events or to the late assaying moment in the kernel development, when Vp1 expression is found to be low. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) of wheat greatly reduces the quality and economic value of grain, and PHS tolerance is one of the most important traits in wheat breeding. Two new Vp-1B alleles were identified in wheat genotypes with distinct PHS tolerance and ABA responsiveness and designated as Vp-1Bb and Vp-1Bc. These alleles had an insertion of 193-bp and a deletion of 83-bp in the third intron in the region of B3 domain, respectively. Further analysis indicated that different Vp-1B alleles showed different expression and responsiveness to ABA exposure at transcriptional level, implying that they may regulate PHS tolerance. Based on these alleles, a STS marker Vp1B3 was developed and validated among a set of 89 Chinese wheat accessions. The results indicated that Vp1B3 may be useful as an efficient and reliable co-dominant marker in the evaluation of wheat germplasm for PHS tolerance and marker-assisted breeding for PHS tolerant cultivars. Moreover, analysis of a collection of 490 EU winter wheat varieties revealed not only the prevalence of Vp-1B alleles but also a new allele Vp-1Bd which does not occur in Chinese wheats. [ABSTRACT FROM AUTHOR]

Preharvest sprouting (PHS) in spring wheat ( Triticum aestivum L.) causes significant economic losses due to a reduction in grain functionality, grain yield and viability of seed for planting. Genetic resistance to PHS reduces these losses. Development of PHS resistant cultivars is complicated by the effects of genotype, environment, kernel diseases and spike morphological factors. RL4137 has consistently exhibited high levels of resistance to PHS over years and environments. The mean PHS scores of Canada Western Red Spring (CWRS) wheat cultivars with RL4137 in their ancestry are lower than that of CWRS wheat cultivars without. RL4137 has two mechanisms for PHS resistance, one associated with kernel color and the other not associated with kernel color. RL4137 was the source of PHS resistance in white wheats HY361, AC Vista, Snowbird, Kanata, and Snowstar, all of which had significantly lower PHS scores than the white-seeded check, Genesis. Known DNA markers relating to PHS were used to compare haplotypes with and without RL4137 in the ancestry. Coefficients of parentage also demonstrated the relationship. Because cultivars that have RL4137 in their ancestry were grown on about 77% of the spring wheat area for 2003–2007, RL4137 continues to contribute to protecting market grade from preharvest sprouting. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) in spring wheat ( Triticum aestivum L.) is a major downgrading factors for grain producers and can significantly reduce end-use quality. PHS resistance is a complex trait influenced by genotype, environment and plant morphological factors. A population of 185 doubled haploid (DH) lines from the spring wheat cross ‘RL4452/AC Domain’ were used as the mapping population to detect quantitative trait loci (QTLs) associated with three PHS traits, germination index (GI), sprouting index (SI) and falling number (FN). Six major QTLs linked with PHS traits were mapped on bread wheat chromosomes 3A, 3D, 4A (2 loci), 4B and 7D. ‘AC Domain’ alleles contributed to PHS resistance on 3A, 4A (locus-2) and 4B, and ‘RL4452’ alleles contributed resistance on 3D, 4A (locus-1) and 7D. QTLs detected on chromosome 4B controlling FN ( QFN.crc-4B), GI ( QGI.crc-4B) and SI ( QSI.crc-4B) were coincident, and explained the largest amount of phenotypic variation in FN (22%), GI (67%) and SI (26%), respectively. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) causes immediate loss of seed viability, making barley ( Hordeum vulgare L.) grains worthless for malting purposes. Grain dormancy release rate in barley crops is genetically and environmentally controlled. A 2 year experiment was conducted to evaluate the effect of soil nitrogen and water availability during grain filling on the dormancy release pattern (and then on the PHS susceptibility) for five malting barley commercial cultivars. Drought and well-irrigated control treatments were imposed from anthesis onwards, and contrast nitrogen fertilization treatments were applied at tillering. Nitrogen availability showed no effects on dormancy release. Drought during grain filling accelerated dormancy release with respect to well-irrigated control in 2004, but not in 2005 year. Mean temperatures during the last stages of grain filling were much higher (ca. 6°C) in 2005 than in 2004, indicating that high-dormancy loss promoting temperatures had masked drought effects on dormancy release. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) in wheat ( Triticum aestivum L.) can be a significant problem, causing deleterious effects on grain quality. However, the adverse impacts of PHS can be reduced by introgressing genes controlling grain dormancy into white-grained bread wheat. Screening for grain dormancy typically involves germination testing of harvest-ripe grain grown in a glasshouse or field. However, the more uniform environmental conditions provided by temperature controlled glasshouses (i.e. controlled environmental conditions—CEC) may provide significant benefits for the assessment of grain dormancy. In this study, the dormancy phenotype of grain grown under CEC incorporating an extended photoperiod, was compared with 2 years of data from field grown material. Four dormant double haploid lines (derived from SW95-50213 and AUS1408) and two locally adapted non-dormant cultivars EGA Gregory and EGA Wills were compared in three replicated experiments grown under CEC (22 ± 3°C and 24 h photoperiod). The germination response of harvest-ripe grain was examined to assess the expression of grain dormancy. Two measures of germination, the predicted time to 50% germination ( G50) and a weighted germination index, both clearly differentiated dormant and non-dormant lines grown under CEC. In addition, levels of grain dormancy were similar to field-grown plants. These results demonstrated that CEC with an extended photoperiod can be used for rapid and reliable characterisation of grain dormancy in fixed lines of bread wheat. [ABSTRACT FROM AUTHOR]

Hard white wheat ( Triticum aestivum L.) is a value-added product because of its processing advantages over red wheat; however, white wheat tends to be more susceptible to pre-harvest sprouting (PHS). To identify quantitative trait loci (QTLs) associated with PHS tolerance, we developed a doubled haploid (DH) mapping population from the cross AC Domain (red seeded) × White-RL4137 (white seeded). A genetic map was constructed using microsatellite markers located on chromosome groups 3, 4, 5 and 6. A population of 174 DH lines was characterized for important aspects of PHS including sprouting index, germination index, Hagberg falling number and seed coat colour. A total of 11 QTLs were identified on group 3 chromosomes and on chromosome 5D. Seven QTLs associated with the PHS traits were found to be co-incident with seed coat colour on chromosomes 3A, 3B and 3D. The 5D PHS QTL was notable because it is independent of seed coat colour. [ABSTRACT FROM AUTHOR]

Pre-harvest sprouting (PHS) is a complex trait controlled by multiple genes with strong interaction between environment and genotype that makes it difficult to select breeding materials by phenotypic assessment. One of the most important genes for pre-harvest sprouting resistance is consistently identified on the long arm of chromosome 4A. The 4AL PHS tolerance gene has therefore been targeted by Australian white-grained wheat breeders. A new robust PCR marker for the PHS QTL on wheat chromosome 4AL based on candidate genes search was developed in this study. The new marker was mapped on 4AL deletion bin 13-0.59-0.66 using 4AL deletion lines derived from Chinese Spring. This marker is located on 4AL between molecular markers Xbarc170 and Xwg622 in the doubled-haploid wheat population Cranbrook × Halberd. It was mapped between molecular markers Xbarc170 and Xgwm269 that have been previously shown to be closely linked to grain dormancy in the doubled haploid wheat population SW95-50213 × Cunningham and was co-located with Xgwm269 in population Janz × AUS1408. This marker offers an additional efficient tool for marker-assisted selection of dormancy for white-grained wheat breeding. Comparative analysis indicated that the wheat chromosome 4AL QTL for seed dormancy and PHS resistance is homologous with the barley QTL on chromosome 5HL controlling seed dormancy and PHS resistance. This marker will facilitate identification of the gene associated with the 4A QTL that controls a major component of grain dormancy and PHS resistance. [ABSTRACT FROM AUTHOR]