Level Of Dormancy Research Articles

Alteration in the balance between ABA and GA signaling mediates genetic variation in induction and retention of dormancy during seed maturation in wheat

Induction and retention of dormancy are among the physiological processes that take place during seed maturation; however, the molecular mechanisms underlying these events are poorly understood in wheat. This study revealed that seed maturation in wheat is associated with decreases in abscisic acid (ABA) and gibberellin (GA) levels irrespective of dormancy level exhibited by the seeds mainly via expression of specific ABA (TaCYP707A1) and GA (TaGA3ox2, TaGA2ox3 and TaGA2ox6) metabolism genes. Consistently, ABA to GA level ratio decreased during maturation in both highly dormant and low-dormant seeds with no apparent difference in the ratio of their levels between the two seed samples. Our data, however, showed a close association between the induction and retention of dormancy during seed maturation and modulation of the balance between ABA and GA signaling via expression of specific genes that acts as positive regulators seed response to ABA (TaPYL5 and TaABI5) and GA (TaGAMyb). Consistently, the highly dormant and low-dormant seeds exhibited substantial variation in their sensitivity to ABA and GA during their maturation. The findings of this study highlight that genetic variation in induction and retention of dormancy during wheat seed maturation can be mediated by a shift in balance between seed sensitivity to ABA and GA independent of a shift in balance between their levels.

Evaluation of postharvest age and dormancy-breaking methods on Echinochloa crus-galli seed germination

Barnyardgrass (Echinochloa crus-galli) is one of the most troublesome weeds in irrigated rice cultivation and has increasingly impacted rainfed crops due to the emergence of herbicide-resistant populations. Understanding its germination dynamics is crucial for developing and implementing effective management strategies. Additionally, since barnyardgrass research relies on growing plants from seeds, its dormancy characteristics are of particular interest. The present study aimed to evaluate the influence of postharvest age on barnyardgrass seed germination and the effectiveness of different dormancy-breaking methods in susceptible and herbicide-resistant populations. Germination rate (G), germination speed index (GSI), and seed viability, assessed using the topographic tetrazolium test, were measured in seed lots with four different postharvest ages: two years, one year, two months, and one day postharvest. The seeds were subjected to 15 dormancy-breaking methods, including temperature variation and the use of solutions containing H2SO4, KNO3, and GA3. Seeds that were one or two years old showed germination rates exceeding 90%, regardless of the method used. In contrast, seeds aged two months or one day postharvest only germinated when exposed to 40°C for seven days, with G values of 25.2% and 5.9%, respectively. Both herbicide-susceptible and resistant barnyardgrass populations exhibited similar dormancy levels and responses to dormancy-breaking methods. The results indicate that newly harvested seeds have high dormancy levels, and specific methods are only partially effective in overcoming barnyardgrass seed dormancy.

After-Ripening and Stratification Improve the Germination of the Cakile maritima Scop. (Brassicaceae) from the Apulia Region, Italy

Understanding seed germination is crucial for refining the propagation techniques of Cakile maritima, a wild halophyte species with significant potential for biosaline agriculture. However, research on seed germination within intact fruits of this species is limited. Four trials were conducted to study the seed germination of a population from the Apulia region. The focus was on seeds that had undergone after-ripening for 3 years (20AR3) or 2 years (20AR2) (both collected in 2020), or 1 year (22AR1) (collected in 2022), and freshly harvested seeds in 2022 (22AR0) and 2023 (23AR0). The seeds were either incubated as naked or moist-stratified within intact fruits. A portion of 2022 AR0 siliques was submerged in saline water before stratification. The naked seeds collected in 2022 and 2020 (22AR0 and 20AR2) did not germinate, whereas a portion of the 23AR0 (67%), 20AR3, and 22AR1 (45%, irrespective of after-ripening) lots quickly (T50 = 3.5 days) germinated, underlining a lower dormancy level for seeds harvested or dry stored in 2023. Seed germination in the intact fruits was lower than the naked seeds, confirming the role of the pericarp in inducing seed dormancy. Stratification of the shelled seeds was much more effective in improving the germination time (140 days) and levels in the 23AR0 (81%), 20AR3, and 22AR1 (66%, irrespective of after-ripening) lots than in the 22AR0 (34%) and 20AR2 (61%) ones, which required 240 days to germinate. The saline solution imbibition of fruit seems only to delay the occurrence of the maximum emergence. The physiological seed dormancy of this C. maritima population has been proven, which may be variable in depth according to the year of fruit collection, ranging from intermediate to non-deep.

Characterization of Escherichia coli Persisters from Biofilm Culture: Multiple Dormancy Levels and Multigenerational Memory in Formation.

Persister cells (PCs), a subpopulation occurring within normal cells, exhibit a transient tolerance to antibiotics because of their dormant state. PCs are categorized into two types: type I PCs, which emerge during the stationary phase, and type II PCs, which emerge during the logarithmic phase. Using the conventional colony-forming method, we previously demonstrated that type I PCs of Escherichia coli form more frequently in air-solid biofilm culture than in liquid culture. In the current study, we modified a cell filamentation method as a more efficient and rapid alternative for quantifying PCs. This modified method yielded results consistent with those of the conventional method with 103-104 times higher sensitivity and less detection time, within several hours, and further revealed the existence of multiple levels of type I PCs, including a substantial number of deeply dormant cells. This study also discovered a potential epigenetic memory mechanism, spanning several generations (four or six cell divisions), which influences type II PC formation based on prior biofilm experience in E. coli.

Contribution of the alternative pathway on spring rejuvenation of alfalfa

Alfalfa often suffers from low temperature during spring rejuvenation, so it is important to improve the cold tolerance of alfalfa leaves for its smooth rejuvenation, and the alternative pathway (AP) could effectively improve the plant's tolerance. In this study, the contribution of AP on spring rejuvenation of alfalfa was investigated in Xinmu No.4 and Gannong No.5 with different fall dormancy levels. Though the protein and AP capacity were decreased during the rejuvenation, the ratio of AP/TP were increased in two alfalfa varieties, compared to those in alfalfa before overwintering. This indicated that AP had positive response to alfalfa rejuvenation. The limitation of AP significantly affected the leaf length, leaf width and growth rate of greening alfalfa, showing that AP played an important role in alfalfa rejuvenation. Inhibition of AP resulted in a significant decrease in Pn, Ci, Gs and stomatal structure deformity, suggestion that AP affected photosynthesis by influencing stomatal development during rejuvenation. AP reduces oxidative damage to PSII core protein repair in alfalfa leaves and optimizes photosynthesis by up-regulating NADP-MDH activity, decreasing the accumulation of excess reducing power in the chloroplasts, and by increasing SOD and POD activities and decreasing the accumulation of hydrogen peroxide. The higher proportion of AP keeps it more tolerant to low temperature for rejuvenation in Xinmu No.4 with a lower fall dormancy level.

A comprehensive phenotypic and genotypic evaluation of Spanish groundnuts from diverse crosses to identify superior and stable donors for fresh seed dormancy

Breeding high yielding groundnut cultivars with 2–3 weeks of fresh seed dormancy, particularly in Spanish-type cultivars, enhances the sustainability of agriculture in groundnuts. In this context, we conducted a comprehensive phenotypic and genotypic evaluation of advanced breeding lines developed in the genetic background of Spanish types. By employing multi-phenotyping and marker data, we identified PBS 15044, 16004, 16013, 16015, 16016, 16017, 16020, 16021, 16026, 16031, 16035, 16037, 16038, 16039, 16041, and 16042 with 2–3 weeks dormancy (> 90%).The various parametric and non-parametric estimates identified the stable fresh dormant genotypes with one or more superior economic trait. PBS 16021, 15044, 16038, and 16039 identified with high hundred pod weight (HPW) were also reported having high intensity of dormancy (> 90% for up to 3 weeks); PBS 15044, 16016, PBS 16038 and PBS 16039 with high hundred kernel weight (HKW) also reported with up to 3 weeks fresh seed dormancy; and PBS 16013, 16031, and 16038 with up to 3 weeks fresh seed dormancy had high shelling percentage (SP). They can be used to develop lines with the desired level of dormancy, and high yields, by designing appropriate breeding strategies.

Programmed temperature control for inactivation of Clostridium perfringens spores in cooked chicken with different germinants

This study designed a new programmed temperature control (PTC) process for cooked chicken, aiming to increase the efficacy of Clostridium perfringens spore inactivation through inducing spore germination at different levels of dormancy. The results showed that the use of PTC treatment in the presence of germinant AGFK (a mixture of l-asparagine, D-glucose, D-fructose, and KCl) lead to a reduction of exceeding 6 lg CFU/mL spores in a model system after being subjected to 90 °C for 20 min. A significant up-regulation of gerKA, gerKC and gerAA relative expression suggested that the PTC treatment may induce more spore germination. Meanwhile, there was an observed rise in the release of pyridine-2,6-dicarboxylic acid, accompanied by a steady decline in refractivity. In the cooked chicken meat undergone a cooling process, the number of C. perfringens spores were reduced by approximately 5 lg CFU/g after the PTC treatment and heated at 90 °C for 20 min. In conclusion, the PTC treatment can effectively enhance the inactivation of C. perfringens spores by inducing more spore germination at different levels of dormancy during cooked meat preparation.

A Method of Coupling Lucerne Quality with Meteorological Data to Evaluate the Suitability of Hay Harvest

The alfalfa harvest time is determined by the alfalfa growth stage and the weather factors at that time, which will affect the yield and quality of the alfalfa hay. Addressing issues like the lack of precise harvesting timing and underutilized production potential of lucerne, this study is based on the internal(fall dormancy level, crude protein, acid, neutral detergent fiber, relative feed value) and external factors(air temperature, precipitation, wind speed, ground temperature, relative humidity, solar radiation) affecting the quality of lucerne, as well as the relevant experimental data of the existing literature and the weather factors within 24 h after the lucerne harvest.Using principal component analysis to calculate the weights of the above indicators, the harvest suitability score formula was constructed to determine the harvesting time, harvesting method and harvesting stubble. Huanghua City was used as an example to confirm the method’s effectiveness in guiding for determining the optimal harvest date of lucerne in the city. Key findings include the following: The hay quality of the first two crops of alfalfa in Huanghua City was higher than that of the third and fourth crops, and the optimal harvest stage of alfalfa was before the precipitation concentration period, which was consistent with other local research results and weather characteristics, and the method was feasible. Precipitation was the most significant factor affecting the lucerne harvest. The effects of other weather factors on hay quality varied with precipitation conditions. The temperature was the second important factor when daily precipitation is less than 1 mm, and the wind speed became the second important factor when the daily precipitation is less than 10 mm and more than 1 mm. Under low suitability and high precipitation, it may be advisable to convert hay harvest to silage to maximize economic benefits. This research could help agricultural decision-makers to develop precise harvesting strategies, and further improve lucerne production efficiency.

A wheat heat shock transcription factor gene, TaHsf-7A, regulates seed dormancy and germination

Heat shock transcription factors (Hsfs) play multifaceted roles in plant growth, development, and responses to environmental factors. However, their involvement in seed dormancy and germination processes has remained elusive. In this study, we identified a wheat class B Hsf gene, TaHsf-7A, with higher expression in strong-dormancy varieties compared to weak-dormancy varieties during seed imbibition. Specifically, TaHsf-7A expression increased during seed dormancy establishment and subsequently declined during dormancy release. Through the identification of a 1-bp insertion (ins)/deletion (del) variation in the coding region of TaHsf-7A among wheat varieties with different dormancy levels, we developed a CAPS marker, Hsf-7A-1319, resulting in two allelic variations: Hsf-7A-1319-ins and Hsf-7A-1319-del. Notably, the allele Hsf-7A-1319-ins correlated with a reduced seed germination rate and elevated dormancy levels, while Hsf-7A-1319-del exhibited the opposite trend across 175 wheat varieties. The association of TaHsf-7A allelic status with seed dormancy and germination levels was confirmed in various genetically modified species, including Arabidopsis, rice, and wheat. Results from the dual luciferase assay demonstrated notable variations in transcriptional activity among transformants harboring distinct TaHsf-7A alleles. Furthermore, the levels of abscisic acid (ABA) and gibberellin (GA), along with the expression levels of ABA and GA biosynthesis genes, showed significant differences between transgenic rice lines carrying different alleles of TaHsf-7A. These findings represent a significant step towards a comprehensive understanding of TaHsf-7A's involvement in the dormancy and germination processes of wheat seeds.

Analysis of the global transcriptome and miRNAome associated with seed dormancy during seed maturation in rice (Oryza sativa L. cv. Nipponbare)

BackgroundSeed dormancy is a biological mechanism that prevents germination until favorable conditions for the subsequent generation of plants are encountered. Therefore, this mechanism must be effectively established during seed maturation. Studies investigating the transcriptome and miRNAome of rice embryos and endosperms at various maturation stages to evaluate seed dormancy are limited. This study aimed to compare the transcriptome and miRNAome of rice seeds during seed maturation.ResultsOryza sativa L. cv. Nipponbare seeds were sampled for embryos and endosperms at three maturation stages: 30, 45, and 60 days after heading (DAH). The pre-harvest sprouting (PHS) assay was conducted to assess the level of dormancy in the seeds at each maturation stage. At 60 DAH, the PHS rate was significantly increased compared to those at 30 and 45 DAH, indicating that the dormancy is broken during the later maturation stage (45 DAH to 60 DAH). However, the largest number of differentially expressed genes (DEGs) and differentially expressed miRNAs (DEmiRs) were identified between 30 and 60 DAH in the embryo and endosperm, implying that the gradual changes in genes and miRNAs from 30 to 60 DAH may play a significant role in breaking seed dormancy. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses confirmed that DEGs related to plant hormones were most abundant in the embryo during 45 DAH to 60 DAH and 30 DAH to 60 DAH transitions. Alternatively, most of the DEGs in the endosperm were related to energy and abiotic stress. MapMan analysis and quantitative real-time polymerase chain reaction identified four newly profiled auxin-related genes (OsSAUR6/12/23/25) and one ethylene-related gene (OsERF087), which may be involved in seed dormancy during maturation. Additionally, miRNA target prediction (psRNATarget) and degradome dataset (TarDB) indicated a potential association between osa-miR531b and ethylene biosynthesis gene (OsACO4), along with osa-miR390-5p and the abscisic acid (ABA) exporter-related gene (OsMATE19) as factors involved in seed dormancy.ConclusionsAnalysis of the transcriptome and miRNAome of rice embryos and endosperms during seed maturation provided new insights into seed dormancy, particularly its relationship with plant hormones such as ABA, auxin, and ethylene.

Thermal regulation of dormancy in Echinochloa crus‐galli (L.) P. Beauv. seeds: Development of a model to predict the temporal ‘window’ of emergence in the field

AbstractPredicting weed emergence is of vital importance for weed management, since the seedling stage is the most effective plant stage for the application of control practices. In weeds species whose seeds present dormancy, as in Echinochloa crus‐galli, predicting emergence requires understanding how the environment regulates seed dormancy level. In the present work we studied the environmental regulation of dormancy in E. crus‐galli seeds. For this, E. crus‐galli seeds were stored under different conditions: (i) moist at 5, 10 and 15°C (stratification) and (ii) dry at 15 and 25°C (dry after‐ripening) for 80 days. During storage the seeds were tested for germination at regular intervals under a wide thermal range (10–30°C). The results showed that the changes in dormancy level were associated with a widening of the thermal range permissive for seed germination, which was mainly explained by a decrease in its lower limit temperature (Tl). This decrease in Tl was higher when the seeds were stratified at 10°C than at 5 and 15°C. Seeds exposed to dry after‐ripening showed an extremely low rate of dormancy release. Obtained results were used to establish functional relationships able to predict the temporal ‘window’ of field emergence of E. crus‐galli as a function of soil temperature.

MKK3 Cascade Regulates Seed Dormancy Through a Negative Feedback Loop Modulating ABA Signal in Rice

BackgroundWith the increasing frequency of climatic anomalies, high temperatures and long-term rain often occur during the rice-harvesting period, especially for early rice crops in tropical and subtropical regions. Seed dormancy directly affects the resistance to pre-harvest sprouting (PHS). Therefore, in order to increase rice production, it is critical to enhance seed dormancy and avoid yield losses to PHS. The elucidation and utilization of the seed dormancy regulation mechanism is of great significance to rice production. Preliminary results indicated that the OsMKKK62-OsMKK3-OsMPK7/14 module might regulate ABA sensitivity and then control seed dormancy. The detailed mechanism is still unclear.ResultsThe overexpression of OsMKK3 resulted in serious PHS. The expression levels of OsMKK3 and OsMPK7 were upregulated by ABA and GA at germination stage. OsMKK3 and OsMPK7 are both located in the nucleus and cytoplasm. The dormancy level of double knockout mutant mkk3/mft2 was lower than that of mkk3, indicating that OsMFT2 functions in the downstream of MKK3 cascade in regulating rice seeds germination. Biochemical results showed that OsMPK7 interacted with multiple core ABA signaling components according to yeast two-hybrid screening and luciferase complementation experiments, suggesting that MKK3 cascade regulates ABA signaling by modulating the core ABA signaling components. Moreover, the ABA response and ABA responsive genes of mpk7/14 were significantly higher than those of wild-type ZH11 when subjected to ABA treatment.ConclusionMKK3 cascade mediates the negative feedback loop of ABA signal through the interaction between OsMPK7 and core ABA signaling components in rice.

Breeding for reduced seed dormancy to domesticate new grass species.

Introducing new grass species into cultivation has long been proposed as beneficial to increase the sustainability and diversity of productive systems. However, wild species with potential tend to show high seed dormancy, causing slow, poor, and unsynchronized seedling emergence. Meanwhile, domesticated species, such as cereals, show lower seed dormancy, facilitating their successful establishment. In this work, we conduct a review of phenotypic variation on seed dormancy and its genetic and molecular basis. This quantitative and highly heritable trait shows phenotype plasticity which is modulated by environmental factors. The level of dormancy depends on the expression of genes associated with the metabolism and sensitivity to the hormones abscisic acid (ABA) and gibberellins (GA), along with other dormancy-specific genes. The genetic regulation of these traits is highly conserved across species. The low seed dormancy observed in cereals and some temperate forages was mostly unconsciously selected during various domestication processes. Emphasis is placed on selecting materials with low seed dormancy for warm-season forage grasses to improve their establishment and adoption. Finally, we review advances in the domestication of dallisgrass, where seed dormancy was considered a focus trait throughout the process.

Genetic, Epigenetic, and Environmental Control of Seed Dormancy and Germination.

Seed germination is controlled by a combination of the seed dormancy level and environmental conditions such as light, temperature, moisture, and nitrate levels. Seed dormancy is programed genetically, but it is also sensitive to maternal environmental conditions before and after anthesis. Recent developments in molecular genetics and bioinformatics have greatly enhanced our understanding of the molecular mechanisms of seed dormancy and germination in model plants and economically important crop species. This chapter focuses on temperature as an environmental factor and discusses the genetic and epigenetic mechanisms of dormancy and germination.

Map-Based Cloning of the Causal Gene for a Seed Dormancy Quantitative Trait Locus in Barley.

Seed dormancy is an important agronomic trait in cereal crops. Throughout the domestication of cereals, seed dormancy has been reduced to obtain uniform germination. However, grain crops must retain moderate levels of seed dormancy to prevent problems such as preharvest sprouting in wheat (Triticum aestivum) and barley (Hordeum vulgare). To produce modern cultivars with the appropriate seed dormancy levels, it is important to identify the genes responsible for seed dormancy. With recent advances in sequencing technology, several causal genes for seed dormancy quantitative trait loci (QTLs) have been identified in barley and wheat. Here, we present a method to identify causal genes for seed dormancy QTLs in barley, a method that is also applicable to other cereals.

Assessment of Dormancy Level and Germination Ability of Seeds with Physiological Dormancy.

Germination test is fundamental and commonly used technique for seed dormancy and germination studies, and proper assessment of dormancy level and germination ability of a given set of seeds is prerequisite for most of the studies. However, germination is very sensitive to imbibition conditions, and dormancy development is also sensitive to growth conditions of the mother plants. In this chapter, we describe tips for plant growth and germination test mainly for physiological and molecular genetic studies with Arabidopsis. This protocol can be applied for other plant species with relatively small seeds and for various studies to analyze the effect of light, phytohormones, and other chemicals in seed germination.

Seed Dormancy and Germination in Alfalfa (Medicago falcata L.)

Background: Medicago falcata L. (M. falcata L.) is widely distributed in Xinjiang and Inner Mongolia, which is a significant source of resistance genes. Its seeds have a high level of physical dormancy (PD). The current study aimed to study the dormancy characteristics, water absorption characteristics and methods for releasing hard seeds of M. falcata L., to reveal the the relationship between seed coat structure and water absorption and to understand the dormancy characteristics, which can provide theoretical basis for seed dormancy and seed biology research. Methods: Seed germination rate (GR), absorption, germination inhibitor activity and initial site of water entry into seeds were measured to investigate the causes of seed dormancy. Treatments to break dormancy included: (1) sandpaper sanding, (2) ultrasonic treatment for 30 min after sandpaper sanding, (3) 98% sulfuric acid immersion (5,10, 20, 40, 60 and 120 min) and (4) hot water immersion at different temperatures (50, 60, 70, 80 and 90oC) for 10 min, 20 min and 30 min. Result: The results showed that the hard rate of untreated seeds was 99.33% and the hard rate after the seed coat was scratched was 1.33%. Based on the inhibitory activity test of M. falcata L. seeds, high concentration seed extract has an inhibitory effect on the growth of other seeds. The toludine staining test showed that the hilum and microscope are the initial and main parts for seed water absorption. The germination rate of seeds after soaking in 98% sulfuric acid for 40 minutes and ultrasonic treatment with sandpaper for 30 minutes is higher than 94%, which is an effective method to relieve the PY of M. falcata L. seeds.

Slow Release of GA3 Hormone from Polymer Coating Overcomes Seed Dormancy and Improves Germination.

Seed dormancy often hinders direct seeding efforts that are attempting to restore degraded landscapes. Gibberellic acid (GA3) can be applied to physiologically dormant seeds to induce germination, but this hormone is rarely effective, as it can degrade or be leached from the seed. We tested different polymer matrixes (polylactic acid, polyvinylpyrrolidone, and ethylcellulose) to apply and slowly release GA3 to the seed. These polymers were tested as seed coatings in either a powder, liquid, or a combination of powder and liquid forms. We found that a liquid ethylcellulose/GA3 coating generally outperformed the other polymers and applications methods using our test species Penstemon palmeri. With this top-performing treatment, seed germination was 3.0- and 3.9-fold higher at 15 °C and 25 °C, respectively. We also evaluated the liquid ethylcellulose/GA3 coating on P. comharrenus, P. strictus, P. pachyphyllus, and P. eatonii. Again, the coating had a strong treatment response, with the degree of difference related to the relative level of dormancy of the species. Growth studies were also performed in pots to ensure that the side effects of GA3 overdosing were not present. Here, we found minimal differences in root length, shoot length, or biomass between plants grown from untreated and GA3-coated seeds.

Exploring life-history traits of an endangered plant (Vicia biennis L.) to support the conservation of marginal populations

We aimed to investigate the reproduction-related traits of Vicia biennis L., an endangered and poorly known wetland species in its western marginal populations (in Hungary), and discuss the conservational and ecological implications. We measured the mass, viability, and physical dormancy of half-year-old seeds in five in-situ collected seed lots, while potential seed longevity (i.e., seed bank type) was estimated from repeatedly germinating subsamples from four ex-situ collected seed lots for 3–8 years. Plant survival, flowering, and seed production were studied in different light-, irrigation-, and competition conditions in a botanical garden experiment. We found that 1) half-year-old seeds have a high germination capacity (78–100%), 2) and high level of physical dormancy (72–100%) in all examined Hungarian populations, and 3) the seeds can preserve their germination capacity for more than five years, although their viability sharply decreases, probably falling below 10% within ten years, when they are stored at room temperature. The results of the botanical garden experiment suggested that 1) the species is annual, not biennial; 2) it shows strong sensitivity to precipitation and low competitiveness for water; and 3) it can produce hundreds of seeds even in suboptimal (dry or shady) conditions. Although the species was found to be well-adapted to a temporally heterogeneous environment, its future vulnerability can increase depending on the duration of dry seasons. Further investigation of genetic diversity and soil seed bank is needed to estimate the actual vulnerability of the species while strengthening the populations through seed sowing, and additional vegetation control in the habitats is suggested.

Impact of water stress during reproductive development on seed dormancy in Bromus diandrus Roth and Lolium rigidum Gaudin

Context Bromus diandrus Roth and Lolium rigidum Gaudin are important weeds of cereal-based cropping systems of Australian agriculture. Adaptation to environmental stresses, protracted seed germination and herbicide resistance have made these weeds serious threats to crop production. Aims Studies were undertaken to determine the impact of moisture stress during reproductive development on the extent of seed dormancy and the expression of genes involved with gibberellic acid and abscisic acid synthesis. Methodology A pot study was undertaken at two locations, with two populations each of B. diandrus and L. rigidum. Water stress was applied from either the GS31 or GS60 stage until seed maturation, along with a well-watered treatment. Seeds of stressed vs well-watered treatments were assessed for seed dormancy and the expression of ABA1 and GA20ox genes using quantitative polymerase chain reaction. Results The seeds from GS31 treatment, where plants experienced the longest water stress, were most dormant in both weed species. Water stress treatments altered the expression of the GA20ox gene, which was correlated with the level of dormancy in seeds of B. diandrus and L. rigidum. Conclusions This investigation has provided clear evidence of the impact of water stress on seed dormancy and on expression of genes involved in regulating seed dormancy in these weed species. Implications As spring rainfall in the Australian agricultural landscape is highly variable, weeds are likely to experience variable levels of water stress during reproductive development, which in turn is likely to influence seed dormancy, weed seedling emergence and effectiveness of pre-sowing weed management next season.