Showing papers in "Seed Science and Technology in 2020"

Seed dormancy and dormancy-breaking conditions of 12 West African woody species with high reforestation potential in the forest-savanna ecotone of Côte d'Ivoire

Abstract: Information on the regeneration ecology of native woody species of the forest-savanna ecotone of West Africa is scarce, which is a major impediment to their optimal utilization in large-scale restoration programmes. The scattered information that is available for some of these species reveals that freshly matured seed are dormant. However, environmental heterogeneity among different habitats may results in inter-population seed dormancy variation. Thus, our objective was to re-examine the dormancy of 12 species from the forest-savanna ecotone that have been targeted for reforestation. Specifically, we aimed to examine the water-permeability of the seeds and explore the effectiveness of acid scarification and heat treatment to alleviate dormancy. Four species belonging to families other than Fabaceae and Malvaceae had water-permeable seeds. Two of them had nondormant (ND) seeds, and seeds of the other two species had a mixture of ND and other kinds of dormancy (possibly physiological dormancy, PD). Most species of Fabaceae and Malvaceae had water-impermeable seeds. All seeds of three species had physical dormant (PY), and some seeds of the remaining species had PY, while others were ND or had PD. Acid-scarification was effective in breaking PY and in augmenting imbibition and germination of non-PY seeds, while heat treatment was moderately effective in breaking dormancy. In general, acid scarification for 1-30 minutes and heat treatment for one hour at 55-75°C were optimal to enhance seed germination, depending on species. The present study has wide practical implications for park conservationists and restoration ecologists interested in producing bulk quantities of high-quality planting stocks of native woody species for large-scale restoration programmes.

Germination performance and biochemical changes under drought stress of primed rice seeds

Abstract: Seed priming may improve germination performance of rice under drought. The present study was conducted to investigate the dynamics of seed biochemical changes during priming and post-priming germination under drought and to correlate those biochemical properties with the germination performance of primed seeds. The priming treatments were non-priming as control, hydro-priming and osmo-priming at -0.3, -1.0 and -2.2 MPa. All seeds were germinated under different levels of drought stress: 0 MPa as control, -0.2, -0.4, -0.6 and -0.8 MPa. The germination performance of hydro- and osmo-primed seeds at -0.3 and -1.0 MPa under severe stress (-0.8 MPa) was better compared with control and osmo-primed seeds at -2.2 MPa. Hydro-priming and osmopriming at -0.3 MPa significantly improved germination performance while germinated seeds of -1.0 MPa osmoprimed seeds recorded the highest root and total seedling length. Proline accumulation was significantly higher in seeds that were hydro-primed or osmo-primed at -0.3 or -1.0 MPa as compared with non-primed control seeds and seeds osmo-primed at -2.2 MPa. In addition, proline was significantly correlated with the starch and glucose content and α-amylase activity. Higher α-amylase activity would accelerate the process of starch hydrolysis into soluble sugar for embryo growth and development resulting in enhanced germination processes

Determination of tobacco (Nicotiana tabacum) seed vigour using controlled deterioration followed by a conductivity test

Abstract: Seeds of eight lots of four tobacco varieties differing in vigour were studied. The initial germination percentage (GPUT) was 81-100% and the controlled greenhouse emergence percentage (CEP) was 55-91%. All seeds were treated by controlled deterioration (CD) at 20% moisture content and 45°C for 24 hours, then some seeds were subjected to a standard germination test and the rest of the seeds were subjected to a conductivity test. The electrical conductivity (EC) of seed soak water was measured every six hours up to 54 hours. The results showed that relative conductivity after CD (RCCD) was highly significantly correlated with GPCD after 30 to 48 hours soaking (r = -0.9324 to -0.9409, P < 0.001). After 36 and 42 hours, RCCD was significantly correlated (P < 0.01) with CEP (correlation coefficients of -0.9120 and -0.9137, respectively). Therefore, it is suggested that measuring relative conductivity after CD could be used to rank tobacco seed lots for vigour. In addition, the best seed soaking time for EC measurement is 36 to 42 hours, with respect to both efficiency and accuracy.

Differentiation of alfalfa and sweet clover seeds via multispectral imaging

Abstract: It is hard to remove sweet clover seeds from alfalfa seed lots by conventional methods, affecting the purity of seed lots and resulting losses in for alfalfa hay production as well as seed yield. However, the discrimination of sweet clover seed contaminates in alfalfa seed lots is difficult without special training. In this study, multispectral imaging with object-wise multivariate image analysis was evaluated for its potential to separate sweet clover and alfalfa seeds. Principal component analysis (PCA), linear discrimination analysis (LDA), partial least squares discriminant analysis (PLSDA), AdaBoost and support vector machine (SVM) methods were applied to classify seeds of sweet clover and alfalfa according to their morphological features and spectral traits or a combination thereof. The results showed that an excellent classification could be achieved based on a combination of morphological features and spectral data in a tested data set. Seed classification accuracy was up to 99.58% in a validation set with the LDA model, which was better than the PLSDA (68.19%), AdaBoost (96.95%) and SVM (98.47%) models. Thus, multispectral imaging together with chemometric multivariate analysis is a promising technique to identify sweet clover seeds in alfalfa seed lots with high efficiency.

Vermicompost priming stimulated germination and seedling emergence of onion seeds against abiotic stresses

Abstract: The present study elucidates the effect of matrix priming with vermicompost (VCP) on germination and seedling emergence of two onion seed lots under drought, salt and temperature stress conditions. Seeds treated with water was considered as hydropriming (HP) and untreated (NP) seeds were taken as control. Treated and untreated seeds were exposed to different levels of drought (10 and 15% PEG), salt (50 and 100 mM NaCl) and temperature (30 and 35°C) stresses. Priming with vermicompost improved the performance of onion seed as indicated by higher germination and seedling growth under stress conditions. Catalase, superoxide dismutase and ascorbate peroxidase activities were found to be significantly (P < 0.05) higher in the vermicompost treated seeds than hydroprimed and untreated seeds.

Effects of temperature, gibberellic acid, and KNO3 treatments on seed germination of the wild plant Maesa japonica

Abstract: We investigated the morphological characteristics of Maesa japonica seeds and the optimal conditions for germination. The seeds were exalbuminous, and their length and width were 0.85 ± 0.09 mm and 0.77 ± 0.05 mm, respectively. We tested germination at 15, 20, 25, 30 and 35°C; the optimum temperature for germination was 30°C (64% germination). To test the effects of gibberellic acid (GA3) and KNO3 on germination, the seeds were soaked in solutions containing 0, 0.2, 0.5, 1.0, 1.5 or 2.0 g GA3 L-1 or 0, 0.05, 0.10, 0.20 or 0.50 g KNO3 L-1 before sowing for germination. KNO3 treatment increased germination percentage and speed. Soaking in GA3 concentrations over 1.0 g L-1 stimulated 100% germination after 13 days. A presoaking treatment that combined 1.0 g GA3 L-1 and 0.2 g KNO3 L-1 promoted germination speed and shortened the time in which half of the seeds germinated. Overall, we determined that the best method for germination of Maesa japonica seeds was pre-soaking in 1.0 g GA3 L-1 and 0.2 g KNO3 L-1 at 4°C in the dark for 24 hours, followed by incubation at 25–30°C in a 16-hour light, 8-hour dark cycle for 10 days.

Toxicity of seed-applied pesticides to Azospirillum spp.: an approach based on bacterial count in the maize rhizosphere

Abstract: The objective of this work was to investigate the impact of pesticides on the survival of the plant growth- promoting bacteria Azospirillum in the surface of coated seeds as well as in the maize rhizosphere. Our results showed that the greater the time that the bacteria are in contact with the seed surface, the higher the cell mortality. In uncoated maize seeds, inoculation increased bacterial concentration in root tissues and ensured superior plant growth up to 12 hours of Azospirillum contact with the seed surface, while for the coated seeds, a similar performance was observed only up to six hours of exposure.

Automated seed testing by 3D X-ray computed tomography

Abstract: In this paper, a fully automated CT-scanner is presented, which has been developed for testing of sugar beet seeds in industrial production environment. The system is simple to use, and no special training is needed for staff. The system has high throughput and the evaluation of volume images is performed automatically by dedicated image processing software. Quantitative measures of various characteristics of the parts of the seed (volume, thickness, weight) for each individual seed of a sample of 400 seeds are obtained. From these measurements, quality parameters can be derived to control seed processing.

Management of seed-borne Sirococcus conigenus on Norway spruce by fungicide seed treatment

Abstract: Seedling blight caused by Sirococcus conigenus was recently reported on Norway spruce (Picea abies) from Norwegian forest nurseries. The inoculum source was found to be infected seeds. In a Petri dish assay, the fungicide fludioxonil + difenoconazole was, among other fungicides, found to inhibit mycelial growth of S. conigenus. This fungicide is formulated as a seed treatment and registered for cereals in Norway, and was chosen for an experiment to control S. conigenus on Norway spruce seeds. Samples from two naturally infected seed lots were treated with half, normal and double dose of the recommended rate for cereals. Together with untreated control samples, treated seeds were tested in the laboratory for efficacy against S. conigenus on potato dextrose agar (PDA) in Petri dishes and for germination potential on filter paper. We also recorded seed emergence in soil of one of the seed lots in a growth chamber and in a forest nursery. On agar, the fungus was not detected after seed treatment with fludioxonil + difenoconazole at any of the three dosages, but it was present in the control. Germination on filter paper and emergence in soil was high in both treated and untreated control seeds with no signs of detrimental effects from any of the three fungicide doses.

Temperature fluctuation improves oil palm (Elaeis guineensis) dura × pisifera seed germination.

Abstract: Oil palm is mainly propagated using dura × pisifera (D × P) hybrid seeds. Among the issues in D × P seed production are relatively poor seed germination and uniformity, despite heat treatment at 40°C to break dormancy. The conditions for germination post-heat-treatment may be a contributing factor. This study aimed to evaluate and compare the effect of constant 30°C or ambient temperature fluctuation at two different locations, Sime Darby Oil Palm Breeding Seed Processing Renggam, Johor and the Seed Production Unit (SPU) Banting, Selangor on oil palm D × P seed germination. At both locations, final mean germination percentage and speed were higher at fluctuating temperatures compared with constant 30°C. Under fluctuating conditions, the Oil Palm Breeding Seed Processing Renggam environment resulted in higher germination (85.8%) compared with SPU Banting (69.8%). Thus, the higher temperature amplitude (difference between daily maximum and minimum temperatures) was an important factor, resulting in higher germination. Therefore, oil palm can be germinated under ambient temperature conditions to obtain higher germination than under constant temperature, avoiding the need for maintaining expensive constant temperature germination rooms. In addition, a sufficiently high temperature amplitude can be beneficial in improving the ability to germinate and the speed of germination.

Correlation between historical data of the germination test and of the tetrazolium test in coffee seeds by GAMLSS.

Abstract: In the Brazilian National System of Seeds and Seedlings, coffee seeds are evaluated by the germination or tetrazolium test. However, differences have been observed between the results of these tests in various studies, especially when the seeds have a lower level of quality. Given this situation, the aim of this study was to evaluate the correlation between historical data of results of the germination test and of the tetrazolium test in samples of coffee seeds using Generalized Additive Models for Location, Scale and Shape (GAMLSS). Historical data of results of the germination test and of the tetrazolium test of coffee seeds originating from different cultivars and different crop seasons were used. The zero-or-one inflated beta GAMLSS is suitable for fitting data from the germination test and from the tetrazolium test. The estimate of viability by the tetrazolium test varies according to the germination percentage class. There are greater GAMLSS correlations between the percentages of normal seedlings and of viability in the tetrazolium test for germination values above 70%, and low correlations below this value, showing that evaluation of coffee seeds based only on the tetrazolium test may not correspond to actual physiological performance.

Seed filling determines seed vigour of superior and inferior spikelets during hybrid rice (Oryza sativa) seed production

Abstract: Growth and development of spikelets are asynchronous during hybrid rice seed production. However, knowledge is limited about the variation in seed vigour between superior and inferior spikelets. The main objective of this study was to evaluate the differences in seed vigour between superior and inferior spikelets of hybrid rice, and to explore the mechanisms associated with such variations with regards to seed filling characteristics and starch accumulation. Field experiments were conducted in 2017 and 2018, and seed vigour parameters, seed filling characteristics and starch accumulation were determined. We found that significant differences were recorded in seed vigour parameters between superior and inferior spikelets. Germination percentage (GP) and vigour index (VI) of superior spikelets were higher than that of inferior spikelets, irrespective of year or variety. Moreover, significant differences were observed in seed filling characteristics and starch accumulation between superior and inferior spikelets. Lower total starch content, amylose content and amylopectin content were recorded in inferior spikelets with low seed filling rate and long seed filling duration. Superior spikelets with high seed filling rate and short seed filling duration increased final seed weight by 23.9 and 22.3% for each variety, respectively. Therefore, these results raise the possibility that seed filling influences the starch accumulation and seed weight, and is closely associated with differences in the vigour of seeds from superior and inferior spikelets during hybrid rice seed production.

Effect of storage temperature on occurrence of secondary dormancy in buckwheat seeds

Abstract: Buckwheat (Fagopyrum spp.) is an important crop in many parts of the world, and many varieties have been developed. One of the important breeding issues to be addressed is the low resistance to preharvest-sprouting which causes loss in yields and quality of buckwheat grain. The occurrence of dormancy in cultivated buckwheat, including presence of secondary dormancy has yet to be clarified. In this study, we investigated the effects of storage temperature and periods using nine common buckwheat (Fagopyrum esculentum), seven Tartary buckwheat (Fagopyrum tataricum) and one wild buckwheat (Fagopyrum homotropicum). In some Tartary buckwheats stored at 5°C, the germination of seeds stored 10 days harvest was significantly less than the germination of seeds collected and sown at harvest maturity; the germination of other germplasm, including common buckwheat, was not affected by storage. This result indicates that Tartary buckwheat can acquire secondary dormancy. In addition, the wild buckwheat did not germinate at any storage temperature up to 30 days after harvest maturity; therefore, this buckwheat is considered to be promising breeding material for increasing resistance to preharvest-sprouting resistance.

High and differential strontium tolerance in germinating dimorphic seeds of Salicornia europaea

Abstract: Salicornia europaea, a highly salt-tolerant halophyte, is potentially resistant to other metals because plant stress tolerance partly relies on common physiochemical mechanisms. Large median seeds and small lateral seeds of S. europaea have high salt tolerance and display contrasting germination responses. Thus, we hypothesised that dimorphic seeds of S. europaea might also have high and differential strontium (Sr) tolerance during germination. Both types of seeds were incubated in different SrCl2 concentrations at 25°C. 0-300 mmol L-1 SrCl2 did not significantly affect germination of median seeds. However, for lateral seeds, relatively high concentrations (≥ 200 mmol L-1) dramatically inhibited germination. The simulated critical value (when germination percentage is 50%) was 502 mmol L-1 for median seeds and 224 mmol L-1 for lateral seeds. Dimorphic seeds of S. europaea are highly tolerant to Sr stress and large median seeds display higher tolerance. The results suggest that direct seeding of large seeds of S. europaea might be an effective method to remediate heavy Sr-polluted soils.

Thirty-year monitoring and statistical analysis of 50 species' germinability in genebank medium-term storage suggest specific characteristics in seed longevity

Abstract: A total of 401,293 germination test results accumulated over 30 years for 110,819 seed lots of 50 species and 4 sub-species stored at –1°C and 30% relative humidity was analysed to assess seed longevity. The Kaplan- Meier estimator was used to perform comprehensive analysis, including censored observations due to seed lot regeneration or substitution. The Weibull distribution was used to model the observed and censored death times for each survival curve and its parameters were used as the common indicator. Interspecific differences in seed longevity, the time until the germination percentage falls below 85% of its initial value, were observed. The shortest and longest seed longevity periods were 8.4 and 127.1 years for Panicum maximum and Cucumis sativus, respectively. Moreover, intra-specific differences in seed longevity were observed at different levels of domestication and geographical distribution of origin. For example, the average seed longevity of six-row Hordeum vulgare landraces that originated from southern Europe showed 2.5 times that of the average of this species. Here, reference materials for setting appropriate intervals of germination testing are presented.

Dry-storage and light exposure reduce dormancy of Arabian desert legumes more than temperature

Abstract: Propagation and conservation of desert plants are assisted by improved understanding of seed germination ecology. The effects of dry-storage on dormancy and germination were studied in seven desert legumes. Mature seeds were collected in summer 2017 and germinated within one week of collection (fresh) and after six months (dry-storage) under two temperature and two light regimes. Seed weight of two species increased 22-55% within 24 hours of water imbibition but others increased ≤ 7%. Germination ranged from 0-32% in fresh and 2-92% in dry-stored seeds, indicating a mix of non- and physically-dormant seeds at maturity. Dry-storage at ambient room temperature was effective at relieving dormancy, though the extent was species-dependent. Germination percentage increased in response to light exposure during incubation, while the effect of temperature was species-dependent. This variable response to dormancy alleviation may assist to spread the population risk of seedling survival in the harsh and variable environment of the Arabian desert.

First report on the germination requirement of Pterygopleurum neurophyllum seeds

Abstract: Pterygopleurum neurophyllum is a class II endangered species and Red list class CR species in Korea. In this study, we considered the effects of cold stratification on embryo development in P. neurophyllum seeds, and analysed the effect of temperature and light conditions, immersion time in 50% H2SO4 and GA3 concentration on subsequent germination. The embryo of P. neurophyllum seeds showed elongation after four weeks of cold stratification (4°C) and embryo length was significantly increased after eight weeks. Germinated seeds were observed after 12 weeks of cold stratification. The cold-stratified (12 weeks) seeds showed the highest germination (23.1%) at 20°C. After 30 minutes H2SO4 immersion, germination of cold-stratified seeds was 29.4%. The GA3 concentration study showed the highest germination for seeds treated with 0.5 g L-1 GA3 (37.2%). The maximum germination across all treatment combinations was 79.8% for seeds given 30 minutes of 50% H2SO4 treatment and 12 weeks of cold stratification and then treated for 24 hours in 0.5 g L-1 GA3.

Seed treatment with 5-azacytidine reduces ageing-induced damage in onion seeds

Abstract: The effect of treating aged onion seeds with 5-azacytidine (5-aza) on germination and vigour was evaluated. Seeds of two onion varieties, 'Bhima Raj' (BRJ) and 'Bhima Red' (BRD) were treated with 0, 10, 25 or 50 μg mL–1 5-azacytidine (a DNA demethylating agent). In comparison with the control treatment (0 μg mL–1 5-azacytidine), treatment with 5-azacytidine enhanced seed germination, seedling length, seedling dry weight and seed vigour indices. 5-azacytidine treatment also increased the activity of superoxide dismutase (SOD) and total antioxidant capacity (TAC). Seed treatment with 5-azacytidine has the potential to enhance the viability and vigour of aged onion seeds. This study provides phenotypic and biochemical data for further exploring the role of DNA methylation in understanding the process of seed ageing.

Effect of dry heat on seed germination of Desmodium and Stylosanthes species

Abstract: Mechanical scarification with a scalpel is the best treatment to break physical dormancy and reach high germination percentages in many legumes. However, it is highly time-consuming. Given the ecological relationship between the presence of physical dormancy and high temperatures in tropical grasslands, dry heat treatment could also promote breaking of physical dormancy in Desmodium and Stylosanthes species. This study assessed seed germination of several accessions of nine species of Desmodium and Stylosanthes. Seeds were treated with dry heat (80°C for 30 minutes) and scarified with a scalpel to determine whether dry heat is a reliable alternative treatment to overcome physical dormancy. Mechanical scarification with a scalpel was effective and resulted in high germination for all species. In S. guianensis, both treatments had an equivalent effect, making dry heat a feasible alternative. Dry heat could also be a reliable alternative in D. heterocarpon, D. velutinum, S. hamata, and S. scabra, but tetrazolium tests may be necessary to confirm viability. For D. barbatum and D. scorpiurus, dry heat could be an alternative but further research is needed to confirm this, while in S. capitata and S. viscosa dry heat is not a reliable alternative.

Germination of Bromus auleticus after different treatments to release seed dormancy

Abstract: Bromus auleticus is a cool season perennial C3 grass, recognised as a forage plant genetic resource and used for native grasslands restoration. It is native to the campos biome, found in southern Brazil, Uruguay and central Argentina. Its forage yield is comparable with tall fescue. Seed dormancy is a problem to evaluate germination and for commercialisation of this species. Using four recently harvested seed lots of three different genotypes, we tested six different treatments to release dormancy: a control (mean germination 52%); 0.05 and 0.1% gibberellic acid; KNO3; pre-chilling + KNO3; and pre-chilling (mean germination across seed lots and treatments, 87%). Pre-chilling + KNO3 and pre-chilling were the best treatments to break dormancy, with mean germination times (MGT) reduced to half (8.7 and 9.3 days-1) that of the untreated control (19.2 days-1). The treatment with KNO3 alone did not yield uniform results across seed lots; when combined with pre-chilling, final germination did not increase but showed more consistent results. The use of 0.05% gibberellic acid was less efficient than pre-chilling to reduce the MGT of 17.2 days-1, but it could be considered as an alternative treatment for seed lots in which the germination results are needed fast and has the additional advantages of avoiding exposing seeds to cold stress. Furthermore, if seeds are contaminated with fungi, it reduces growth time and contamination effects.

Effect of high temperature drying on seed longevity of Bambara groundnut (Vigna subterranea) accessions

Abstract: In this paper, we considered the effects of different drying regimes on the subsequent longevity of Bambara groundnut seeds. Freshly harvested Bambara groundnut seeds from 27 genebank accessions were divided into five samples. One sample (control) was immediately dried at 17°C/15% RH and the other samples were dried at 45°C/35% RH for up to eight days, before transfer to 17°C/15% RH. After drying, seed moisture content was raised to 10.9% before packing the seeds in aluminium foil packets and placing at 45°C. Samples were removed at regular intervals for germination tests to compare seed longevity. Initial drying at the higher temperature resulted in a faster reduction in seed moisture content. The effect of the different drying regimes on subsequent longevity was not significant for most accessions. Nonetheless, the seed longevity of smaller-seeded accessions was perhaps enhanced by initial drying at a higher temperature; in contrast, initial drying at 17°C appeared to be the best drying treatment for larger-seeded accessions. Overall, the results suggest that initial drying at a higher temperature was beneficial for reducing processing time and for some accessions would be beneficial for seed longevity, but further work is required to understand for which seed lots.