Seed Germination Traits Research Articles

Variation in thermal and hydrotime requirements for seed germination of Chaco seasonally dry forest species in relation to population environmental conditions and seed mass

AbstractThermal and hydrotime requirements for seed germination can vary with the species, environment in which the seeds developed and/or seed mass. We investigated seed germination responses to temperature and water potential of Aspidosperma quebracho‐blanco, Bulnesia retama, Parasenegalia visco, Parkinsonia praecox and Tecoma stans, all of which are native tree species of Chaco seasonally dry forests in northwest Argentina. We determined inter‐and intraspecific variability in seed germination through thermal and hydrotime models and correlated model parameters with environmental variables of seed provenance and seed mass. Seeds of all species germinated to high percentage over a range of temperatures. Seeds of A. quebracho‐blanco, P. praecox and T. stans were more tolerant to water stress than those of B. retama and P. visco. Thermal and hydrotime parameters for germination varied amongst species and populations. There was a negative correlation between thermal (θT(50)) and hydrotime (θH) constants and base temperature (Tb) and water potential (Ψb(50)). Seed mass correlated negatively with Tb and positively with θT(50). Species and populations were grouped according to thermal and hydrotime parameters and seed mass but not according to seed provenance. These results suggest that seed germination traits related to temperature, water potential and seed mass are species specific, and the variations within a species are probably due to a high phenotypic plasticity. These species showed a complex set of germination strategies that give them a competitive advantage in different environments, depending on dispersal time, seed mass and local environmental conditions during the germination period.

Genome-Wide Association Studies Provide Insights Into the Genetic Architecture of Seed Germination Traits in Maize

Seed germination is an important agronomic trait that affects crop yield and quality. Rapid and uniform seed germination traits are required in agricultural production. Although several genes are involved in seed germination and have been identified in Arabidopsis and rice, the genetic basis governing seed germination in maize remains unknown. Herein, we conducted a genome-wide association study to determine the genetic architecture of two germination traits, germination speed, and consistency, in a diverse panel. We genotyped 321 maize inbred populations with tropical, subtropical, or temperate origins using 1219401 single-nucleotide polymorphism markers. We identified 58 variants that were associated with the two traits, and 12 of these were shared between the two traits, indicating partial genetic similarity. Moreover, 36 candidate genes were involved in seed germination with functions including energy metabolism, signal transduction, and transcriptional regulation. We found that favorable variants had a greater effect on the tropical subpopulation than on the temperate. Accumulation of favorable variants shortened germination time and improved uniformity in maize inbred lines. These findings contribute significantly to understanding the genetic basis of maize seed germination and will contribute to the molecular breeding of maize seed germination.

Identification of candidate genes involved in salt stress response at germination and seedling stages by QTL mapping in upland cotton.

Salinity is a major abiotic stress at critical stages of seed germination and seedling establishment. Germination rate (GR) and field emergence rate (FER) are the key traits that determine the basic number of plants stand under field conditions. To explore molecular mechanisms in upland cotton under salt stress, a population of 177 recombinant inbred lines, and their parents were evaluated for seed germination traits (GP, germination potential; GR; FW, fresh weight; DW, dry weight; GL, germinal length) and seedling traits (FER; SH, seedling height; NL, number of main stem leaves) in 2016–2018. Based on the linkage map contained 2,859 single nucleotide polymorphism and simple sequence repeat markers, traits under salt stress (E1) and normal conditions (E2), and in the converted relative index (R-value) dataset of 3 years’ trials were used to map quantitative trait loci (QTL). A total of 3 QTL and 2 clusters were detected as salt-tolerant QTL. Three QTL (qGR-Chr4-3, qFER-Chr12-3, and qFER-Chr15-1) were detected under salt stress conditions and R-value dataset, which explained variance of phenotype 9.62–13.67%, and 4.2–4.72%, 4.75–8.96%, respectively. Two clusters (Loci-Chr4-2 and Loci-Chr5-4) harboring the QTL for 4 germination traits (GR, FER, GL, and NL) and 6 seedling traits (GR, FER, DW, FW, SH, and NL) were detected related under salt stress. A total of 691 genes were found in the candidate QTL or clusters. Among them, 4 genes (Gh_A04G1106, Gh_A05G3246, Gh_A05G3177, and Gh_A05G3266) showed expression differences between salt-sensitive and -tolerant lines under salt stress conditions, and were assigned as candidate genes in response to salt stress. The consistent salt-tolerance QTL identified in both germination and seedling stages will facilitate novel insights into effective utilization of cotton genetic resources.

Soil moisture level and substrate type determine long-term seed lifespan in a soil seed bank

AimsSeeds are usually classified as short- or long-term persistent. It is still hardly understood how environmental conditions influence seed persistence. The study aimed to monitor the long-term effects of different moisture and substrate on seed persistence.MethodsSeeds of three Rumex species buried in autumn 2009 in combinations of moisture and substrate were exhumed in spring 2015 and 2021 to test their persistence in the soil after 5.5 and 11.5 years, respectively. Long-term persistence data were compared with data from previous short-term experiment for the same species and environmental conditions reported in Abedi et al. (Plant Soil 374:485-495, 2014).ResultsNo seeds of R. acetosa were found viable after 1.5 years. Seeds of R. acetosella retained viability after 11.5 years mostly in dry-loam (~ 60%) and moist-sand (~ 25%) test conditions and moisture levels were identified as the main driver. R. maritimus retained ≥ 80% viability in moist and wet test conditions and > 40% in the dry test conditions.ConclusionsFor one (R. acetosella) of the three investigated species, the classification of soil seed bank type depended on environmental conditions, emphasizing the need to introduce a more detailed classification scheme for soil seed persistence and to include the information about extrinsic parameters in databases. However, in the other two species with transient (R. acetosa) and long-term persistent (R. maritimus) seed banks, there are rather intrinsic parameters that affect seed viability. Hence, both site-specific environmental factors as well as seed germination traits need full consideration in the classification of future soil seed bank studies.

Restoration seedbanks for mined land restoration

Restoration seedbanks have become a key infrastructure resource in efforts to restore damaged and degraded environments across the globe. Large‐scale ecological restoration typically utilizes large volumes of valuable, usually wild‐collected seeds, but insufficient knowledge of seed biology (including storage requirements in some cases) and ecology for many species continues to hamper the utility of restoration seedbanks to meet this rising demand. Poor germination and establishment when seeds are deployed from seedbanks can stem from factors such as premature seed collection, low seed quality, poor processing, handling and storage, variable seed quality from year to year, and, critically, insufficient understanding of seed dormancy, seed germination traits, and the ecological requirements for germination stimulation. While these factors may impact the success of seed‐based ecological restoration both synergistically and idiosyncratically, they can be universally addressed by adopting best practice principles in seedbank management and operation and through an improved understanding of the seed biology and ecology of stored species. Drawing upon an industry case study in seedbanking for post‐mining ecological restoration, we outline how optimizing seed storage conditions and a focus on seed biology and ecology in the operation of a restoration seedbank can deliver broad and immediate benefit and cost‐efficiency to native seed use. Such improvements are crucial in developing more effective approaches for returning biodiverse plant communities to highly modified landscapes and are foundational for meeting the aspirations for ecological restoration at global scales in the coming decade.

Source-sink relationship in wheat as affected by defoliation and spikelet removal

The relationship between source and sink affects the accumulation of grain dry matter in crops such as wheat. Wheat is a plant of high economic importance. The leaves are known as the source due to the production of photosynthetic materials. Photosynthetic materials made by the leaves are stored inside the seeds and the seeds are called the sink. Laboratory and field experiments were conducted to assess the impact of defoliation intensity and spikelet removal on seed yield, yield components, and germination traits of produced seeds in wheat. At the field experiment, studied factors included defoliation intensities (removal of 0, ½, and all leaves per plant) and spikelet removal (½ spikelet removal, no spikelet removal). Seeds produced under maternal plant conditions were assessed at the laboratory experiment. Results showed that wheat, Pishtaz cultivar, reacted to source and sink manipulation. Complete defoliation with ½ spikelet removal causes dramatically reduction of stem and leaf weight and spike weight. Under no leaf removal, ½ spikelet removal reduced wheat seed yield. Defoliation intensity and ½ spikelet removal had no significant effect on seed germination traits.  Wheat, cv. Pishtaz had little ability in changing seed size as one of the factors of sink strength under high photosynthate so the cultivar is more sink- than source- limited. Keywords: germination, leaf removal, maternal plant environment, seed vigour, Triticum aestivum

Regeneration from seed in herbaceous understorey of ancient woodlands of temperate Europe.

European ancient woodlands are subject to land use change, and the distribution of herbaceous understorey species may be threatened because of their poor ability to colonize isolated forest patches. The regeneration niche can determine the species assembly of a community, and seed germination traits may be important descriptors of this niche. We analysed ecological records for 208 herbaceous species regarded as indicators of ancient woodlands in Europe and, where possible, collated data on seed germination traits, reviewed plant regeneration strategies and measured seed internal morphology traits. The relationship between plant regeneration strategies and ecological requirements was explored for 57 species using ordination and classification analysis. Three regeneration strategies were identified. Species growing in closed-canopy areas tend to have morphological seed dormancy, often requiring darkness and low temperatures for germination, and their shoots emerge in early spring, thus avoiding the competition for light from canopy species. These species are separated into two groups: autumn and late winter germinators. The third strategy is defined by open-forest plants with a preference for gaps, forest edges and riparian forests. They tend to have physiological seed dormancy and germinate in light and at higher temperatures, so their seedlings emerge in spring or summer. Seed germination traits are fundamental to which species are good or poor colonizers of the temperate forest understorey and could provide a finer explanation than adult plant traits of species distribution patterns. Seed dormancy type, temperature stratification and light requirements for seed germination are important drivers of forest floor colonization patterns and should be taken in account when planning successful ecological recovery of temperate woodland understories.

Effect of Laser Biostimulation on Germination of Wheat

HighlightsThe effect of laser biostimulation on wheat germination was explored using a single- and dual-wavelength (DW) laser.An 80 mW green-infrared DW laser treatment significantly enhanced several germination traits of wheat.The effect of a 100 mW single-wavelength red laser on wheat germination was non-significant.Abstract. Laser biostimulation of seeds has established itself as a safe and sustainable alternative to genetic modification or chemical use to enhance plant germination and growth. A knowledge gap, however, exists to define optimal laser parameters for different seeds as inappropriate irradiation may seriously damage or destroy germinability. To this end, the effect of laser biostimulation on germination of Canada Western Red Winter (CWRW) wheat seeds was evaluated using two low power portable lasers: 1) a single-wavelength red laser (659 nm) and 2) a dual-wavelength (DW) green/infrared laser [531 and 810 nm (ratio ~10:1)]. The seeds were pretreated with laser light before germination tests for 5, 10, and 15 minutes using total power densities of ~14.2 and 11.3 mW/cm2, respectively. Laser treatment with a DW laser for a duration of 10 min was found to be the most efficient as it significantly enhanced mean germination time, germination rate index, germination speed, number of roots, and hypocotyl length by 14.3%, 15.2%, 15.2%, 31.8%, and 60.9%, respectively, with respect to control samples. The effect of single-wavelength red laser on CWRW wheat seed germination traits was not statistically significant. To the best of our knowledge, this study is the first on evaluating the effect of DW laser treatments in plant biostimulation and introduces a new pathway for manipulating the germination, growth, and development of seeds/plants. Keywords: Agriculture, Biostimulation, Dual-wavelength laser, Laser, Wheat.

Effects of diesel-engine exhaust emissions on seed germination and seedling growth of Brassicaceae family using digital image analysis.

This paper describes a multi-phase investigation into the direct effect of diesel exhaust emission on seed germination traits and biochemical changes responsible for observed effects in seeds belongs to the Brassica family. Diesel exhaust emissions were collected in germination boxes and seeds were exposed to diesel exhaust pollutants for durations of 30 to 120min with 30min intervals. Observed effects include seed germination inhibition, changes in seeds' antioxidants activity, and protein content. The lowest seed germination of canola (71 %) and arugula (84 %) was observed when seeds were exposed to 120min of diesel exhaust pollution. Seed exposure to diesel exhaust emission for 60min, caused a 23 % and 8 % decline of germination index of canola and arugula, respectively. The maximum seed soluble protein for canola (3.72mg/g FW) was observed in seeds exposed to 120min diesel exhaust pollution declined to 1.65mg/g FW, and 0.60mg/g FW after 60 and 30min exposure to diesel exhaust, respectively. The maximum protein content of arugula seeds (0.95mg/g FW) was observed in the control treatment and it was reduced to 0.72mg/g FW and 0.53mg/g FW after 60 and 90min exposure to diesel exhaust pollution. Catalase activity was significantly reduced as canola seed exposure to diesel exhausted was increased while there were no statistically significant changes for catalase activity of arugula seeds. All evidence suggested that time of exposure was the key phytotoxic component of exhaust emissions, and highlights the potential for detrimental effects of vehicle emissions on agro-ecosystems.

Gain from genomic selection for a selection index in two-row spring barley.

New breeding programs are faced with many challenges including evaluation of unknown germplasm, initiation of breeding populations that will satisfy short- and long-term breeding goals, and implementation of efficient phenotyping strategies for multiple traits. Genomic selection (GS) is a potentially valuable tool for recently established breeding programs to quickly accelerate genetic gain. Genomic selection on selection index (SI) values may increase gain over phenotypic selection but empirical studies remain limited. We compared gain in overall SI value for height, heading date, preharvest sprouting (PHS) resistance, and spot blotch resistance and component traits in two cycles of GS with one round of phenotypic selection (PS) in two-row spring malting barley (Hordeum vulgare L.). Higher realized gain for SI value, height, and PHS was observed with GS compared with PS but GS did not result in significant gain for heading date and spot blotch. Genetic variances for height and heading date, which had small index weights, were not reduced with GS but variances were substantially reduced for heavily weighted PHS and correlated seed germination traits. Inbreeding was increased by GS compared with PS but restricted mating of high breeding value individuals limited potential inbreeding. Our results indicate GS is a useful method to improve selection on index values with different weights.

Seed germination traits predict seedling emergence rather than survival of Stipa breviflora in populations along a latitude gradient

AbstractSeed germination is a key stage for successful seedling establishment, and thus it should be considered when selecting the seed source for ecological restoration. However, how seed germination traits of wild species in the laboratory contribute to seedling emergence and establishment under natural conditions is not well known. In this study, seeds from 12 populations collected in 2017 and 14 additional populations collected in 2018 of Stipa breviflora were used for laboratory germination tests and field seedling establishment evaluation in the Alxa Desert and at Yuzhong on the Loess Plateau. Depending on germination conditions, seed germination percentage showed a positive, negative, or no correlation with the latitude of seed collection. Seedlings derived from seeds collected in southern populations had a higher establishment percentage in southern growing sites than those from northern populations, and vice versa, suggesting that populations are locally adapted at the seedling survival stage. Germination in laboratory was generally positively correlated with seedling emergence in the field. There was positive relationship between lab germination and field seedling survival at Yuzhong Station, while negative relationship was observed at Alxa Station. These results suggested that high germination percentages could be adaptive or maladaptive depending on offspring growth conditions. Thus, seed source selection based on germination traits should take offspring growing conditions into consideration.

Nutrient availability and pH level affect germination traits and seedling development of Conyza canadensis

Reducing pesticide application in agricultural land is a major challenge for the twenty-first century. Responses of weed seed’s germination and seedling’s early development to chemical soil conditions around the seed may be a promising way to aid weed control in a no-till system. Thus, the objective of this work was to test, under controlled conditions, whether different chemical conditions affect the germination and development of horseweed [Conyza canadensis (L.) Cronquist]. We used, as treatment, solutions containing different nutrients (P, K, Ca, and Mg), separately and in combination, and at two pH levels (4.8 and 6.5). Phosphorus alone inhibited horseweed seed germination at ~ 7 times while had ~ 4 times reduction in final germination percentage and germination speed index for both pH tested. Other nutrients tested had a no-effect in germination speed index compared to the control treatment. Potassium alone or associated with other ions (P, Ca, and Mg) at pH 4.8 had a synergistic effect on seedling development (root and shoot length). In the same way, K associated with Mg was synergistic to the root length at pH 6.5. Seeds in the control treatment (distilled water) presented a high germination speed index at pH 6.5, while at low pH this parameter was higher when in association with KMg, PMg and Ca. The findings demonstrate that seed germination traits and seedling development of horseweed depend on nutrient kind exposure and pH conditions in the seed environment. This work suggests that adequate topsoil management (i.e., pH and nutrient availability) may aid to reduce weed germination, because, it consists of an important factor of weed occurrence in agricultural areas.

Acorn germination and oak (Quercus brantii Lindl.) seedling development dramatically affected by spatial position of maternal trees from Ilam gas refinery, Iran

Air pollution from industrial areas is an environmental stress on trees that can seriously endanger the future of forests. Ancient Persian oak trees (Quercus brantii Lindl.) in the semi-arid forests of the Zagros are exposed to various environmental stresses such as air pollution from the Ilam gas refinery, which causes many challenges in forest regeneration and afforestation, thus jeopardizing forest sustainability or restoration. The aim of this study was to investigate the effect of toxic pollutants emitted from a gas refinery operation on seed germination and morphological characteristics of seedlings from maternal trees that are located at different distances (1000, 1500, 2000, 2500 and 10,000 m) and directions (east and west) from the facility. The results showed that oak seedlings grown from acorns collected at a distance of 10,000 m had the highest values in various seed germination and seedling developmental measures and morphological traits such as leaf and root mass, number and length compared to other distances of 1000, 1500, 2000 and 2500 m from the gas refinery. Highest values in seed germination, and seedling emergence and growth occurred at distances furthest from the refineries. Also, direction from the refinery significantly (p < 0.05) effected root growth, with larger seedlings occurring from acorn collected west of the refinery. The results of principal component analysis and discriminate analysis showed that, of the traits observed, various seed germination traits were most sensitive to gaseous toxic pollutants emitted from this source. Based on all studied traits, seedlings from acorns collected at 10,000 m from the facility were easily distinguished from seedlings of acorns collected at closer distances. It can be concluded that refinery toxic pollutants caused significant adverse changes in germination and seedling growth from acorns collected from oak trees located near (less than 10,000 m) to the source of air pollution. It is recommended that such pollution sources should be established far away from forest areas, and if constructed, be equipped with appropriate technologies such as flare gas recovery (FGR) to reduce emission of toxic pollutants and other emissions such as sulfur dioxide (SO2) and hydrogen sulfide (H2S) from the gas refinery. It is also strongly recommended that acorns collected for restoration measures come from maternal trees growing at a distance >10,000 m, and especially to the west of gas refineries.

Effect of Nitrogen Addition on Selection of Germination Trait in an Alpine Meadow on the Tibet Plateau.

Seed germination requirements may determine the kinds of habitat in which plants can survive. We tested the hypothesis that nitrogen (N) addition can change seed germination trait-environmental filter interactions and ultimately redistribute seed germination traits in alpine meadows. We determined the role of N addition on germination trait selection in an alpine meadow after N addition by combining a 3-year N addition experiment in an alpine meadow and laboratory germination experiments. At the species level, germination percentage, germination rate (speed) and breadth of temperature niche for germination (BTN) were positively related to survival of a species in the fertilized community. In addition, community-weighted means of germination percentage, germination rate, germination response to alternating temperature and BTN increased. However, germination response to wet-cold storage (cold stratification) and functional richness of germination traits was lower in alpine meadows with high-nitrogen addition than in those with no, low and medium N addition. Thus, N addition had a significant influence on environmental filter-germination trait interactions and generated a different set of germination traits in the alpine meadow. Further, the effect of N addition on germination trait selection by environmental filters was amount-dependent. Low and medium levels of N addition had less effect on redistribution of germination traits than the high level.

Management of Source-Sink Balance for Maintaining Seed Vigor and Storability of Maize

Defoliation was the major factor which directly affected to maize seed yield and quality basis on source-sink relationship. Thus, the objectives were to study the effect of source-sink balance management on corn seed vigor and storability and to determine the effect of defoliation treatments on maize yield, yield components and produced seed germination traits. The experiment was arranged basis on Split-Plot in Randomized Complete Block Design with four replications. Main plot was the pattern of leave cutting with 5 levels: D1 = control, (without defoliating), D2 = complete defoliation, D3 = defoliating only under the ear, D4 = remain 2 top leaves, D5 = remain ear leaf. Sup-plot was leaf cutting dates which were C1 = 7 days after silking, C2 = 10 days after silking, C3 = 13 days after silking and C4 = 16 days after silking. Complete defoliation severely reduced ear weight, row number per ear, seed number per ear and 100 - seed weight (P<5%). Defoliation treatments had much more significantly affected on produced seed germination and seed vigor traits. Leaf defoliation intensity and leaf position affected total dry matter. Conclusion, the leaf defoliation only below ears was useful for source-sink balance management, because it promoted the seed qualities and vigor following to principle of parasitic sink elimination.

Germination responses to water potential and temperature variation among provenances of Pinus yunnanensis

Provenance selection plays a major role for the afforestation success, resilience and persistence of forests into the future. Understanding the germination response to water potential and temperature among provenances is crucial for forest restoration initiatives. However, afforestation programs often neglect the seed germination traits from a selected provenance, threatening natural or artificial regeneration in future. In this study, we assessed the impact of water potential (0 and -0.2 MPa) and temperature (20, 25, and 30°C) on germination of Pinus yunnanensis seeds from 15 provenances. We found a clear effect of seed provenance on the germination percentage and mean germination time. In general, the lower water potential (-0.2 MPa) led to a reduction of germination percentage for most provenances, especially at 30°C; and the higher temperature (30°C) and water potential (0 MPa) resulted in low mean germination time. Germination percentage and mean germination time responses to water potential and temperature varied among provenances. We observed that germination percentage was significantly positively correlated with annual mean temperature, mean temperature of driest quarter and seed mass associated with the provenance, but significantly negatively correlated with annual mean precipitation, and mean precipitation of driest quarter and wettest quarter. Significant relationships between mean germination time and those variables were contrary to germination percentage. However, the significance of these relationships varied in all the treatments. Therefore, we conclude that germination of P. yunnanensis seeds from different provenances adapt diversely to abiotic stresses; this is likely to be important for provenance selection in future reforestation. Our results highlight that future re-forestation efforts need to critically evaluate larger numbers of provenances to understand thresholds limiting performance and establishment success.

Relationship of seed pericarp color with seed quality in sugar beet (Beta vulgaris L. var. altissima Döll)

Quantitative traits of seed pericarp color were used to evaluate the sugar beet (Beta vulgaris L.) seed quality. These traits were measured on 10 single cross hybrids along with the male parent produced in three locations, Ardebil, Firouzkooh and Karaj, Iran. The quantitative traits included 9 color traits based on which the traits L*(Lightness/Luminance), a*(Red/Green color), b*(Blue/Yellow), RGB (Red–Green–Blue) and HSV (Hue- Saturation-Value) were measured. Results showed significant differences among the hybrids for seed pericarp color. The hybrids were classified into four clusters. Cluster C2 which had the least L*, b*, R, G as well as quantity of color value (V) and included the SC (231*SB37), SC (231*SB17) and SC (231*SB16) single crosses, contained high quality seeds. The quantitative color traits were significantly correlated with some seed germination traits. Sugar beet seed pericarp color traits were related to female parent not to male parent and displayed significant correlations with the ratio of embryo to seed pericarp weight. In conclusion, analysis of quantitative traits of sugar beet seed pericarp color can be used to determine the time of maturity, to group the cultivars and to rank the seed quality.

Identification and fine mapping of qGR6.2, a novel locus controlling rice seed germination under salt stress

BackgroundRice growth is frequently affected by salinity. When exposed to high salinity, rice seed germination and seedling establishment are significantly inhibited. With the promotion of direct-seeding in Asia, improving rice seed germination under salt stress is crucial for breeding.ResultsIn this study, an indica landrace Wujiaozhan (WJZ) was identified with high germinability under salt stress. A BC1F2 population derived from the crossing WJZ/Nip (japonica, Nipponbare)//Nip, was used to quantitative trait loci (QTL) mapping for the seed germination rate (GR) and germination index (GI) under H2O and 300 mM NaCl conditions. A total of 13 QTLs were identified, i.e. ten QTLs under H2O conditions and nine QTLs under salt conditions. Six QTLs, qGR6.1, qGR8.1, qGR8.2, qGR10.1, qGR10.2 and qGI10.1 were simultaneously identified under two conditions. Under salt conditions, three QTLs, qGR6.2, qGR10.1 and qGR10.2 for GR were identified at different time points during seed germination, which shared the same chromosomal region with qGI6.2, qGI10.1 and qGI10.2 for GI respectively. The qGR6.2 accounted for more than 20% of phenotypic variation under salt stress, as the major effective QTL. Furthermore, qGR6.2 was verified via the BC2F2 population and narrowed to a 65.9-kb region with eleven candidate genes predicted. Based on the microarray database, five candidate genes were found with high transcript abundances at the seed germination stage, of which LOC_Os06g10650 and LOC_Os06g10710 were differentially expressed after seed imbibition. RT-qPCR results showed the expression of LOC_Os06g10650 was significantly up-regulated in two parents with higher levels in WJZ than Nip during seed germination under salt conditions. Taken together, it suggests that LOC_Os06g10650, encoding tyrosine phosphatase family protein, might be the causal candidate gene for qGR6.2.ConclusionsIn this study, we identified 13 QTLs from a landrace WJZ that confer seed germination traits under H2O and salt conditions. A major salt-tolerance-specific QTL qGR6.2 was fine mapped to a 65.9-kb region. Our results provide information on the genetic basis of improving rice seed germination under salt stress by marker-assisted selection (MAS).

Nitrogen Application Modifies the Seed and Oil Yields and Fatty Acid Composition of Nicotiana tabacum

Tobacco is traditionally an industrial crop that is used for manufacturing cigarettes. However, due to health concerns and global tobacco control movements, alternative uses of tobacco are urgently needed to support tobacco farmers and vendors. Tobacco is also an oilseed crop with an oil yield ranging from 30% to 40 of its dry weight. However, there is still no information on the effects of nitrogen application on tobacco seed yield and seed oil production. The objective of this study was to evaluate the effects of N fertilization (90, 120, 150, and 180 kg·ha−1 N) on the seed yield, oil content, fatty acid composition, and seed germination characteristics of tobacco plants at two locations. The results showed that applying increasing amounts of N to tobacco plants significantly increased their total seed yields and oil content. Nitrogen application also modified the fatty acid composition of the seed oil, as more unsaturated fatty acids were produced under the increasing N application rate treatments than under the control. Moreover, increasing the N application rate generally significantly increased the yields of individual fatty acids as well. Nevertheless, the increased seed oil content and altered fatty acid composition did not affect seed germination traits, as the seed germination potential and rate showed no obvious change among treatments or the control. The height and size of the tobacco plants also increased with the increasing N application rate, which would be beneficial for increasing biomass production for bioenergy. This study shows for the first time the feasibility of increasing the seed and oil yields and modifying the fatty acid composition of tobacco plants by increasing N addition.

Geographical variation in germination traits of the salt-marsh cordgrassSpartina alterniflorain its invasive and native ranges

AbstractAimsGermination is the earliest life-history transition of a plant species. It determines the ecological breadth and geographic ranges of a species and has major effects on its invasion potential. The largest spread of the invasive salt-marsh cordgrass Spartina alterniflora in China, where it extends to latitudes lower than its native range in North America, provides an opportunity to examine germination trait variation across latitudes within and among its invasive and native ranges.MethodsWe studied seed germination traits of S. alterniflora using seeds collected from 10 locations across latitudes in its invasive range (China, 20°–40° N) and 16 locations across latitudes in its native range (USA, 27°–43° N) in growth chambers with 0 PSU sterilized distilled water. We further evaluated how climate and tide range in the original locations influenced germination traits.Important FindingsNative populations showed higher (~10%) germination percentage and significantly higher (~20%) germination index than invasive populations did, but invasive populations germinated significantly earlier (~3 days) than native populations. Germination percentage and germination index increased with latitude in the invasive range but decreased with latitude in the native range. The mean germination time decreased with latitude in the invasive range and paralleled that in the native range. Germination percentage and germination index were negatively correlated with mean daily temperature (Tmean), mean daily maximum temperature (Tmax) and mean daily minimum temperature (Tmin), and inversely correlated with Tmean, Tmax and Tmin in the native range. However, the mean germination time was positively correlated with Tmean, Tmax and Tmean in both ranges. Our results demonstrate that invasive and native populations have evolved different latitudinal clines in germination percentage and index, but the mean germination time of the invasive population mirrored the latitudinal cline observed in the native range, suggesting that germination strategy across latitudes may change during invasion process.