Seed Bank Persistence Research Articles

Comparative pericarp biomechanics and germination physiology of Raphanus raphanistrum and Raphanus pugioniformis indehicent fruits.

The biomechanical, morphological and ecophysiological properties of plant seed/fruit structures are adaptations that support survival in unpredictable environments. High phenotypic variability of noxious and invasive weed species such as Raphanus raphanistrum (wild radish) allow diversification into new environmental niches. Dry indehiscent fruits (thick and lignified pericarp [fruit coat] enclosing seeds) have evolved many times independently. Here, we demonstrate that the hard pericarp of Raphanus species (Brassicaceae) imposes mechanical dormancy by preventing full phase-II water uptake of the enclosed seeds. A multiscale biomechanics and imaging (microscopy, X-ray, finite element stress simulation, puncture force analysis) approach was used to comparatively investigate the indehiscent fruits of R. raphanistrum (global weed), R. pugioniformis (endemic weed) and R. sativus (cultivated radish). This demonstrated that the apparently unilocular fruits of Raphanus species develop from two fused valves, that pericarp rupture to permit germination is confined to the midvalve regions (MVR), and that each MVR contains a predeterimed breaking zone which is biomechanically defined by the internal shape of the seed chambers. Direct biomechanical analysis revealed great variability in within-fruit and between-fruits pericarp resistences. We conclude that variability in pericarp-imposed dormancy provides a bet-hedging strategy to affect soil seed bank persistence and prolong the germinability period.

Environmental drivers of seed persistence and seedling trait variation in two Neltuma species (Fabaceae)

Abstract The endemic tree Neltuma caldenia Burk. and the shrub Neltuma flexuosa var depressa F.A. Roig (Fabaceae; subfam: Mimosoideae) are two promising species from the central region of Argentina, with high potential for use in the restoration of disturbed environments, for extensive livestock grazing and apiculture. Both species have seeds with physical dormancy. Ecological study of native species is important from the point of view of rehabilitation of degraded areas by natural regeneration or via seed-based programmes. The objective of this study was to evaluate soil seed bank persistence and seedling traits to understand variation among different populations of each of the study species growing along an ecological gradient and to identify potential components driving this variation. Home environments influenced seed bank persistence, which was higher in populations originating from more arid and unpredictable environments where it could act as a bet-hedging strategy between years and seasons. We also observed differences associated with seedling growth traits between the species and populations. Populations with higher seed persistence were associated with greater seedling growth in N. caldenia. The rapid elongation rate of N. caldenia seedlings growing in large populations and unstable environments could help their ability to escape drought by accessing deeper soil moisture and would confer a high relative competitive ability. In contrast, N. f. var depressa displayed higher seed persistence, which was associated with more arid and unstable conditions and correlated with lower seedling growth, possibly due to an inbreeding depression effect, resulting from the presence of mother plants in low-densities or being isolated from other individuals. There was no effect of population size on seed persistence. To better understand seed persistence and associated seedling trait variation, future studies need to consider the genotype, environment and landscape conditions.

Russian thistle (Salsola tragus) ecology in wheat cropping systems of the Pacific Northwest

Abstract Russian thistle (Salsola tragus L.) is a significant summer annual weed in the semi-arid Pacific Northwest (PNW), causing yield losses of up to 50%. Understanding the biology and ecology of S. tragus is vital for developing effective integrated weed management (IWM) strategies. This study focused on 1) S. tragus emergence and seedbank persistence in two cropping systems: fallow–winter wheat (Triticum aestivum L.) and spring wheat–fallow–winter wheat rotations, and 2) S. tragus plant biomass and viable seed production in fallow and spring wheat fields. A four-year experiment (2020-2023) was conducted at the Columbia Basin Agriculture Research Center (CBARC) in Adams, OR, using a randomized block design with four replications. Salsola tragus seeds were sprinkled only at the beginning of the experiment, and seedling numbers were recorded throughout. Most seedlings emerged in the first year, with the highest rates in spring wheat (72%) and fallow (32%), followed by significantly lower rates (0.25-5%) in subsequent years. Seedling emergence began in late March and early April for the first two years but was delayed to May for the third year. Plant biomass and viable seed production were greater in fallow than in spring wheat, with early-season plants having more biomass than later-emerging plants. Plants emerged between early and mid-May produced the most viable seeds. Viable seed production was very low until it peaked in mid-September. Findings indicated that most S. tragus seedlings emerged in the first year after dispersal coinciding with spring precipitation and lasting approximately two months. Additionally, most S. tragus plants produce viable seeds in September, and seeds persist in the soil for more than two years. These results demonstrate the need for growers to control S. tragus emergence to prevent reinfestations and ultimately the need to control S. tragus plants before September to prevent the species from producing viable seed.

Soil salinity regulates spatial-temporal heterogeneity of seed germination and seedbank persistence of an annual diaspore-trimorphic halophyte in northern China

Background and aimsSeed heteromorphism is a plant strategy that an individual plant produces two or more distinct types of diaspores, which have diverse morphology, dispersal ability, ecological functions and different effects on plant life history traits. The aim of this study was to test the effects of seasonal soil salinity and burial depth on the dynamics of dormancy/germination and persistence/depletion of buried trimorphic diaspores of a desert annual halophyte Atriplex centralasiatica.MethodsWe investigated the effects of salinity and seasonal fluctuations of temperature on germination, recovery of germination and mortality of types A, B, C diaspores of A. centralasiatica in the laboratory and buried diaspores in situ at four soil salinities and three depths. Diaspores were collected monthly from the seedbank from December 2016 to November 2018, and the number of viable diaspores remaining (not depleted) and their germinability were determined.ResultsNon-dormant type A diaspores were depleted in the low salinity “window” in the first year. Dormant diaspore types B and C germinated to high percentages at 0.3 and 0.1 mol L-1 soil salinity, respectively. High salinity and shallow burial delayed depletion of diaspore types B and C. High salinity delayed depletion time of the three diaspore types and delayed dormancy release of types B and C diaspores from autumn to spring. Soil salinity modified the response of diaspores in the seedbank by delaying seed dormancy release in autum and winter and by providing a low-salt concentration window for germination of non-dormant diaspores in spring and early summer.ConclusionsBuried trimorphic diaspores of annual desert halophyte A. centralasiatica exhibited diverse dormancy/germination behavior in respond to seasonal soil salinity fluctuation. Prolonging persistence of the seedbank and delaying depletion of diaspores under salt stress in situ primarily is due to inhibition of dormancy-break. The differences in dormancy/germination and seed persistence in the soil seedbank may be a bet-hadging strategy adapted to stressful temporal and spatial heterogeneity, and allows A. centralasiatica to persist in the unpredictable cold desert enevironment.

The evaluation of secondary seed dormancy potentials of spring Brassica napus L. genotypes and the relationship with seed germination, vigor, and seed quality traits

AbstractVolunteer canola (Brassica napus L.) is defined as canola germinating and emerging after the intended cropping season, and it continually ranks as a top occurring weed on the Canadian prairies. Seed dormancy is the physiological mechanism enabling the seed to remain viable in the soil seedbank for extended periods of time. Specifically, canola has a high likelihood of being induced into secondary seed dormancy under adverse environmental conditions not suitable for germination. A reduction of secondary seed dormancy in modern canola varieties may result in lower seedbank persistence; however, the effect of reducing dormancy on other seed traits is not known. This study examined a diverse collection of spring B. napus genotypes produced in differing maternal environments for secondary seed dormancy as well as seed germination, vigor, and seed quality traits. Genotype contributed the most to total variability (46%), the interactions between genotype and environment had a moderate contribution (28%), and very little contribution from maternal environment alone (4%) was observed for the secondary seed dormancy trait. The remaining variability (22%) was allocated to the residuals. No association was observed between secondary seed dormancy and germination time or seed vigor traits in genotypes examined. Significant associations with secondary seed dormancy were detected for primary dormancy, total protein, seed fiber components, glucosinolates content, seed geographical origin, and fatty acid composition. According to the results of this study, the reduction of secondary seed dormancy as a breeding objective in canola breeding programs is feasible as the trait is largely genetically controlled. Furthermore, direct selection against secondary seed dormancy is unlikely to have adverse effects on canola seed germination and vigor given no associations were detected in the current study.

The Effect of Heat Shock on Seed Dormancy Release and Germination in Two Rare and Endangered Astragalus L. Species (Fabaceae).

Many Astragalus species exhibit seeds with physical dormancy (PY), but little is known about the ecological context of this dormancy. We focused on A. maritimus and A. verrucosus, two threatened Sardinian endemic species inside the subgenus Trimeniaeus Bunge. Fresh seeds collected from the only two respective known populations were used to investigate the effect of mechanical scarification, heat shock, and water imbibition processes on PY release and germination. PY can be overcome through mechanical scarification of the water-impermeable seed coats, while no dormancy break was detected, nor a subsequent increase in seed germination due to fire-induced heat. This suggests that fire does not trigger dormancy release and seed germination in these species. The seeds tolerate relatively high heat shock temperatures (up to 120 and 100 °C for A. verrucosus and A. maritimus, respectively), but after 120 °C for 10 min, the number of dead seeds increases in both species. These facts suggest the capacity to develop a soil seed bank that can persist after fires and delay germination until the occurrence of optimal conditions. As regards water imbibition, both Astragalus species did not show the typical triphasic pattern, as germination started without further water uptake. This study emphasizes the significance of understanding germination processes and dormancy in threatened species. In fire-prone ecosystems, PY dormancy plays a crucial role in soil seed bank persistence, and it may be selectively influenced by post-fire conditions. Understanding such adaptations provides useful insights into conservation strategies.

Mechanical soil disturbance in a pine savanna has multiyear effects on plant species composition

AbstractSoil disturbance threatens native perennial grasslands and savannas worldwide, including pine savannas of the North American Coastal Plain. Disk harrows are used in the region to plow linear features for firebreaks to contain prescribed fires, to manage game and other wildlife, and to reduce wildfire hazard to protect forest resources. However, the long‐term response of vegetation to these disturbances has not been well investigated. Our aim was to compare vegetation changes over time (0–9 years) following repeated disturbance by disking and a single disturbance by disking for firebreaks with undisturbed vegetation within a native pine savanna. We hypothesized that (1) a single disking event has multiyear effects on plant species composition and abundance because of the loss of perennial, dispersal‐limited species, but that partial survival of propagules allows the recovery to be more complete than following repeated disturbance, and (2) post‐disturbance changes are determined by species' life‐history characteristics resulting in a successional trajectory toward the undisturbed community. We established 10 plots within a repeated‐disturbance firebreak and a single‐disturbance firebreak, and in undisturbed vegetation (n = 30). We identified plant species within the plots six times over nine years, categorized plant species by life span, seed bank persistence, and dispersal mechanism, and assessed changes in the plant community using ordination. Changes in species composition in both repeated and single disturbance treatments showed a pattern consistent with succession toward the undisturbed plant community, but vegetation in neither disturbance treatment matched undisturbed treatment conditions within the nine years of study. Repeated‐disturbance plots progressed from a high occurrence of annuals to species with persistent seed banks and wind‐dispersed species. Single‐disturbance plots were more strongly associated with perennials, species lacking a persistent seed bank, and species dispersed by vertebrate consumption, but not to the same degree as undisturbed plots, although differences decreased slightly over time. Our results relating to narrow mechanical soil disturbances in pine savanna vegetation are consistent with studies concluding that similar but larger scale disturbances have long‐term degradational effects on the plant community. Therefore, conservation management plans should consider the possible negative long‐term effects of soil disturbance on native perennial herbaceous plant communities.

Seed longevity and germination of the emerging invasive species wavyleaf basketgrass (Oplismenus undulatifolius) under varied light regimes

AbstractInvasive nonindigenous species pose a serious threat to native biodiversity and ecosystem functioning. Understanding how species’ performance varies under conditions in the current and invaded range can help to predict the dynamics of the invading species in its new environment. Plants with the ability to alter growth in response to variation in light conditions may be favored in landscapes that experience frequent disturbance, as these species may be able to exploit a wide range of niches. Seedbank persistence may also play a critical role in successful plant invasion, as extended seed viability may increase the chance of outlasting unfavorable conditions, maintain population genetic diversity, and allow reinvasions. This study investigated seed longevity and the effect of light intensity on germination of wavyleaf basketgrass [Oplismenus undulatifolius (Ard.) Roem. & Schult.], a newly established invasive species in U.S. mid-Atlantic forest understories. Oplismenus undulatifolius seeds were collected across 5 yr from the original site of introduction in Maryland, USA, and stored in standard lab conditions, then subjected to germination trials under four light conditions in a controlled growth chamber. Seeds remained viable for at least 9 yr, and light intensity did not significantly impact seed germination. Our study demonstrates the importance of evaluating environmental and temporal effects on germination traits, because the scope of surveillance in the field may need to be expanded based on new information about environmental tolerance. Long-term monitoring may also be necessary to effectively control invasive plant populations capable of forming a persistent seedbank.

Agronomic characteristics, insect pollinators, and seedbank persistence of a novel oilseed crop, chia (Salvia hispanica L.) in eastern China

Chia (Salvia hispanica L.), a member of the Lamiaceae family, is a newly emerging crop species in China, gaining extensive attention worldwide as a potential dietary oil and pharmaceutical resource. However, there are few reports on the cultivation or field evaluation of chia in China. The present study was conducted to evaluate the agronomic performance of chia, including the determination of the suitable seeding window and seed yield potential. Data were also collected on flower-visiting insects, flowering phenology, and seedbank persistence of chia for providing baseline information on weed risk assessment for the potential of crop introduction in China. Results showed that chia seeded between late-Apr. and middle-May produced a greater seed yield (mean: 686.6 kg ha−1; ranges: 324.5–1034 kg ha−1) compared to that of seeded at other dates (mean: 136.6 kg ha−1; ranges: 0–311.0 kg ha−1). While the content of individual saturated and unsaturated fatty acids of the chia seed oil varied with seeding date and genotype, the unsaturated fatty acids, including C18:1 (oleic acid), C18:2 (linoleic), and C18:3 (linolenic) were the most abundant fatty acid in chia seed oil, accounting for approximately 87 % of the total oil content. At the present location, even though the chia seeding dates varied from mid-Mar. to end-Jun., the plants could still complete the whole crop lifecycle with similar dates for the specific phenological stage. Moreover, chia flowers attracted a diverse group of pollinating insects from the Hymenoptera, Diptera, Lepidoptera, and Coleoptera. Eastern honeybees (Hymenoptera) and syrphid flies (Syrphidae) were the most abundant insect species, accounting for 25.4 % and 25.8 % of all insect pollinators, respectively. While the chia cannot persist in the seedbank during the spring growing season, the seeds from the late fall harvest could be partially dormant in the soil seedbank with the potential for generating the weed control problem in the subsequent crops. The baseline information obtained from this study would help understand the potential ecological risk of chia and serve a valuable reference for introduction of chia production in China.

Comparing the performance of machine learning methods in predicting soil seed bank persistence

Soil seed banks are pivotal for understanding plant population life histories and elucidating plant-environment relationships. Although experimental exploration of persistent seed banks yields valuable insights, it is often time-consming, labor-intensive, and costly. Consequently, the development of efficient computational methods like machine learning techniques is crucial to augment traditional fieldwork and enhance our capacity for effective seed bank data analysis and interpretation. In this study, we collated a dataset of 398 observations from the TRY database, encompassing measurements such as seed thickness, seed length, seed width, seed dry mass, and seed bank type. Notably, some species' seed bank types within this dataset are identified as having a soil seed bank, without distinguishing between persistent or transient seed banks. Our primary objective was to utilize this data to predict whether a species' soil seed bank is persistent or transient. To this end, we evaluated the performance of four classic machine learning methods—Adaptive Boosting (Adaboost), Artificial Neural Network (ANN), Random Forest (RF), and Support Vector Machine (SVM)—in predicting seed bank types. We gauged the performance of each model using five metrics: Accuracy, AUC (Area Under the Curve), kappa, sensitivity, and specificity. Among the four models examined, the ANN model proved to be the most effective in predicting the persistence of soil seed banks, suggesting its efficacy in predicting seed bank types based on a limited number of independent variables. This study underscores the potential of machine learning methods in soil seed bank research and paves the way for future investigations. It can potentially aid in crafting conservation strategies by enhancing our understanding of plant population dynamics.

Evaluating seedbank stimulants for wild oat and volunteer cereal management on the Canadian Prairies

Wild oat is a widespread threat to annual crop production on the Canadian Prairies. Infestations are difficult to manage due to a persistent seedbank, complex dormancy, a long emergence window, herbicide resistance, and seed shatter corresponding to crop harvest timings. The study objective was to evaluate the efficacy of potassium nitrate (KNO3) and pyroligneous acid for promoting germination and emergence of wild oat and volunteer wheat, barley, and oat. A total of 24 repeated experiments were conducted using freshly produced seeds to ensure adequate endodormancy. Wheat and barley demonstrated no endodormancy following seed formation and rapidly emerged with moisture. All species imbibed but did not germinate in Petri dishes within pyroligneous acid solutions of 5%–100%. Dormancy release was observed within 0.1% and 1% pyroligneous acid solutions. KNO3 did not stimulate germination or emergence for any species and was inhibitory at 125 kg N ha−1. Pyroligneous acid increased wild oat emergence with 50% and 100% solutions applied at 200 L ha−1 in the first study and with 10% solutions in the second study. Emergence inhibition was noted for oat, barley, and wheat with pyroligneous acid applications. This research further confirms that pyroligneous acid may stimulate wild oat emergence and confirms activity on freshly matured seed.

Persistent, viable seedbank buffers serotinous bishop pine over a broad fire return interval

BackgroundIn ecosystems where fire has been excluded, pyrosilviculture can restore some processes historically maintained by fire while mitigating risk where fire is inevitable. Pyrosilviculture in crown fire-adapted forests is, however, limited by insight into the temporal window of fire return matching canopy seedbank development. Here, we characterized demographic responses to fire and non-native pine pitch canker infection in a chronosequence of serotinous bishop pine stands burned at high-severity to quantify (1) temporal patterns of seedbank development given seed viability and density, cone production, and tree density, and (2) pine pitch canker incidence across tree ages and sizes to assess how infection might impact stand and seedbank development. We use our findings to elucidate pyrosilvicuture as a means of restoring fire given practical challenges of reintroducing high-severity fire in crown-fire adapted forests embedded within wildland urban interfaces (WUI).ResultsBishop pine produces an abundant, viable seedbank within eight years that persists across developmental stages and age classes. Seed abundance and viability are exceptionally high at even the earliest age (median > 600,000 seeds ha− 1 and 97% viability at 6 years) and remain high, with the oldest stands (36 years) maintaining median densities of > 500,000 seeds ha− 1 and viability of 95%. We additionally learned that pine pitch canker infection is most severe during the sapling stage (8–10 years post-fire), likely altering stand development trajectories as well as potentially limiting recruitment, and thus the aerial seedbank, into the canopy.ConclusionsIn bishop pine and equally-fecund serotinous species, pyrosilviculture appears a viable management tool across a broad fire return window given the early development and persistence of a robust, viable seedbank, allowing managers flexibility in restoring fire to promote forest persistence while simultaneously mitigating wildfire risk. Moreover, pyrosilviculture in pine pitch canker infected stands may also provide disease mitigation. Although the long-term effects of pine pitch canker infection remain unknown, bishop pines’ viable, persistent seedbank suggests that managers can ignite prescribed fire across a broad return interval — as short as eight years and as long as several decades — to promote bishop pine persistence, mitigate disease infection rates, and reduce wildfire risk in WUI-adjacent ecosystems.

Long-term seed bank persistence in a stochastic desert environment.

Seed banks, the collection of viable seeds in the soil, are particularly important determinants of population survival in highly variable environments. Predictions of increased stochasticity in the amount and timing of precipitation in desert environments raise the question of how seed banks of desert species will respond to climate change, and ultimately, whether these species will persist. Here, we present data from our long-term studies of germination requirements and seed bank dynamics in a rare desert gypsophile perennial, Arctomecon californica (Las Vegas bearpoppy). Arctomecon californica is a relatively short-lived plant that recruits from seed in sequences of unusually favorable years. We used germination experiments, an in situ seed bank study, and a 15-year field seed retrieval study to examine factors affecting seed bank persistence. In the germination study, a majority of seeds remained dormant, despite a wide variety of treatments, suggesting that a large proportion of the seed dispersed each year has cue-nonresponsive dormancy. Our in situ seed bank study showed that seed density varied widely between sites, among transects, and among samples within a transect. The patchiness of seeds in the soil highlights the importance of protecting large areas where A. californica populations are known to have existed in the past. The seed retrieval study provided strong evidence that this species has a long-lived seed bank in which only a small fraction of seeds (roughly 5%) become nondormant each year, allowing seed banks of this species to last up to 20 years without a seed production event. Whether this impressive life-history strategy can maintain the species in the face of climate change depends on the future frequency of the well-timed precipitation that allows for the establishment of new cohorts of adult plants.

More warm‐adapted species in soil seed banks than in herb layer plant communities across Europe

Abstract Responses to climate change have often been found to lag behind the rate of warming that has occurred. In addition to dispersal limitation potentially restricting spread at leading range margins, the persistence of species in new and unsuitable conditions is thought to be responsible for apparent time‐lags. Soil seed banks can allow plant communities to temporarily buffer unsuitable environmental conditions, but their potential to slow responses to long‐term climate change is largely unknown. As local forest cover can also buffer the effects of a warming climate, it is important to understand how seed banks might interact with land cover to mediate community responses to climate change. We first related species‐level seed bank persistence and distribution‐derived climatic niches for 840 plant species. We then used a database of plant community data from grasslands, forests and intermediate successional habitats from across Europe to investigate relationships between seed banks and their corresponding herb layers in 2763 plots in the context of climate and land cover. We found that species from warmer climates and with broader distributions are more likely to have a higher seed bank persistence, resulting in seed banks that are composed of species with warmer and broader climatic distributions than their corresponding herb layers. This was consistent across our climatic extent, with larger differences (seed banks from even warmer climates relative to vegetation) found in grasslands. Synthesis. Seed banks have been shown to buffer plant communities through periods of environmental variability, and in a period of climate change might be expected to contain species reflecting past, cooler conditions. Here, we show that persistent seed banks often contain species with relatively warm climatic niches and those with wide climatic ranges. Although these patterns may not be primarily driven by species' climatic adaptations, the prominence of such species in seed banks might still facilitate climate‐driven community shifts. Additionally, seed banks may be related to ongoing trends regarding the spread of widespread generalist species into natural habitats, while cool‐associated species may be at risk from both short‐ and long‐term climatic variability and change.

Sobrevivência e distribuição do banco de sementes de arroz daninho após 22 anos de cultivo de arroz em diferentes sistemas

ABSTRACT: Weedy rice (Oryza sativa L.) is the most problematic weed in rice fields due to the few control management alternatives to control it, because of the genetic similarity with the crop. Different cropping systems (regarding soil preparation before sowing) have been used as options to control the persistence and emergence of the weed seedbank. Therefore, the objective of this study was to evaluate the longevity and vertical distribution of weedy rice seeds in the soil seedbank after 22 years of different rice cropping systems. Data was analyzed as a two-way factorial, with cropping systems carried out for 22 years [no-tillage (NT), conventional tillage (CT), wet direct-seeded (WDS)] as one factor and sampling depth (0-2, 2-5, 5-10 and 10-20 cm) as the other factor. The number of whole and deteriorated seeds per m-2 were assessed, as well as the viability (%). No effect between the systems were detected up to 5 cm, however at 5-10 cm CT and WDS showed higher amount of seeds, and WDS at 10-20 cm. As the sampling depth increased, NT showed fewer amount of seeds, while less reduction of the soil seedbank was observed in WDS. CT and WDS spread viable seeds in the soil profile from 0 to 20 cm depth. After 22 years there are viable weedy rice seeds up to 10 cm of depth in the three cropping systems and there is no difference among them up to 5 cm of depth, demonstrating the serious problem of the seedbank for this species.

Hybridization rate and fitness of hybrids produced between the tetraploid Camelina rumelica and hexaploid Camelina sativa

Pre-release risk assessment of genetically modified (GM) Camelina sativa (L.) Crantz requires a careful evaluation of the reproductive compatibility with its closely-related Camelina species. Camelina rumelica Velen. is a naturalized weed occurring in C. sativa production region in the northwestern China. In this study, a large number of reciprocal crosses was conducted between the tetraploid C. rumelica and hexaploid C. sativa. The F1 hybrids were produced by the tetraploid C. rumelica (♀) × hexaploid C. sativa (♂) at the rate of one hybrid for 217 ovules pollinated, and one hybrid for 220 ovules pollinated in the reciprocal direction. All F1 hybrids required vernalization treatment to induce timely flowering and showed the significant lower pollen viability (< 2%) compared to the parental lines. Despite that the F1 failed to backcross with the parental lines, selfed seeds (F2) were obtained from F1 hybrids plants. The F2 hybrids showed some degree of restored pollen viability (about 20%) and successfully produced seeds by both backcrossing and self-pollination. A similar pattern was observed in the field, with F1 hybrids showing self-compatibility and reduced seed production potential. It is worthwhile to mention that all F1 and F2 plants grew well both in the greenhouse and field conditions, but with the significant lower seed production ability. A portion of selfed F2 seeds from naturally shattering persisted in the soil seedbank during summer period and subsequently germinated in late fall. By contrast, other F2 seeds may have been dormant in the soil seedbank and germinated the following spring. These altered life-cycle related traits in hybrids generates the novel ecological concerns on the persistence and population dynamics of transient hybrids in the seedbank. In summary, this study provided the evidence that the tetraploid C. rumelica and hexaploid C. sativa, which have the sympatric distributions and overlapped flowering periods, gene flow between them probably could occur. Although the rate was relatively low (about 0.5%), the introgression of life-cycle related traits into C. sativa population could alter its key life-cycle traits and raise the concerns on the soil seedbank persistence and invasiveness of transient hybrid in C. sativa production region in the northwestern China.

New directions in weed management and research using 3D imaging

AbstractRecent innovations in 3D imaging technology have created unprecedented potential for better understanding weed responses to management tactics. Although traditional 2D imaging methods for mapping weed populations can be limited in the field by factors such as shadows and tissue overlap, 3D imaging mitigates these challenges by using depth data to create accurate plant models. Three-dimensional imaging can be used to generate spatiotemporal maps of weed populations in the field and target weeds for site-specific weed management, including automated precision weed control. This technology will also help growers monitor cover crop performance for weed suppression and detect late-season weed escapes for timely control, thereby reducing seedbank persistence and slowing the evolution of herbicide resistance. In addition to its many applications in weed management, 3D imaging offers weed researchers new tools for understanding spatial and temporal heterogeneity in weed responses to integrated weed management tactics, including weed–crop competition and weed community dynamics. This technology will provide simple and low-cost tools for growers and researchers alike to better understand weed responses in diverse agronomic contexts, which will aid in reducing herbicide use, mitigating herbicide-resistance evolution, and improving environmental health.

Assessing Seedbank Longevity and Seed Persistence of the Invasive Tussock Grass Nassella trichotoma Using in-Field Burial and Laboratory-Controlled Ageing

The ability to produce highly dense and persistent seedbanks is a major contributor to the successful widespread establishment of invasive plants. This study seeks to identify seed persistence and seedbank longevity for the invasive tussock grass Nassella trichotoma (Nees.) Hack. ex Arechav in order to recommend management strategies for preventing re-emergence from the seedbank. To determine the seedbank longevity and persistence, two experiments were conducted: (i) seeds were buried at four depths (0, 1, 2, and 4 cm) and collected and assessed for viability, seed decay, and in-field germination after 6, 9, 12, 15, and 18 months of field burial; and (ii) seeds were exposed to artificial ageing conditions (60% RH and 45 °C) for 1, 2, 5, 9, 20, 30, 50, 75, 100, and 120 days, and viability was determined through germination tests and tetrazolium tests. Less than 10% of the seeds collected after 12 months of in-field burial were viable. The artificial ageing treatment found germination declined to 50% after 5.8 days, further suggesting that N. trichotoma seeds are short lived. The results from both experiments indicate that N. trichotoma has a transient seedbank, with less than 10% of the seeds demonstrating short-term persistence. It is likely the persistent seeds beyond 12 months were exhibiting secondary dormancy as viable seeds did not germinate under optimal germination conditions. The “Best Practice Guidelines” recommend monitoring for seedbank recruitment for at least three years after treating N. trichotoma infestations. The results of this study support this recommendation as a small proportion of the seeds demonstrated short-term persistence.

Plant life span and persistence of soil seedbanks predict the emergence of herbicide resistance in noxious weeds

AbstractPlant control methods have been developed to reduce weed species that are often problematic in agricultural systems. However, these methods can create new challenges, such as herbicide resistance. Determining which plant traits are associated with herbicide resistance can assist managers in identifying species with the potential to develop herbicide resistance and to better understand factors contributing to the evolution of herbicide resistance. We used random forest models to model herbicide resistance of noxious weeds as a function of 10 biological and ecological plant characteristics. Three noxious weed characteristics—plant life span, seedbank persistence, and occurrence in riparian or wetland microsites—predicted herbicide resistance with 87% accuracy. Species with persistent seedbanks and with short life spans (i.e., annuals) that occurred outside riparian or wetland areas were most likely to develop herbicide resistance. Short life spans indicate short generation times enabling faster evolution for herbicide resistance. Persistent seedbanks may increase the survival of resistant genotypes within a population or may be co-selected as an alternate form of escape from control methods. Species occurring in riparian or wetland microsites may be a case of “avoidance” rather than resistance, as managers typically avoid applying herbicide in these areas. Currently, 47 of the noxious weed species analyzed in this study are herbicide resistant, and our models identified an additional 63 species with traits that are highly associated with herbicide resistance, potentially indicating species that are at risk of developing resistance under conducive conditions. Further data-driven analyses with more plant traits and species from around the world could help refine current risk assessment of herbicide-resistance development.

Rising atmospheric CO2 concentration affect weedy rice growth, seed shattering and seedbank longevity

AbstractWeedy rice (Oryza sp.) is one of the most troublesome global weeds in cultivated rice. Its troublesome status is associated with characteristics such as seed shattering and dormancy, allowing for long‐term reinfestation and persistence in rice fields. However, the role of rising carbon dioxide levels (CO2) and other climate variables on these characteristics has not, to date, been assessed. The current research objectives were to evaluate two aspects related to climatic change, increased CO2 concentration (400 ± 50 μmol mol−1 and 700 ± 50 μmol mol−1) and water management (continuous and alternate‐wetting drying), to assess plant development, seed shattering and seedbank longevity of weedy rice. Our results indicated that elevated CO2 (700 ± 50 μmol mol−1) increased weedy rice growth and biomass, seed shattering and lengthened viability within the seedbank. Water management did not affect weedy rice growth, seed shattering and seed dormancy. These results suggest that in areas where weedy rice is dominant, its seed bank persistence and potential competition may be exacerbated with rising CO2 levels, with negative consequences for rice production.