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Cumulative oxidation of cellular macromolecules during storage reduces seed longevity. This study was undertaken to unravel the physiological and biochemical changes in rice seeds that contribute to deterioration during storage. Rice seeds maintained at three different seed moisture contents (SMC; 10, 12 and 14%) were stored in airtight glass jars. Half of the jars were flushed with nitrogen gas to provide modified oxygen conditions, while the other half were sealed with natural air (21% O2). Seed quality in terms of germination and antioxidant defence mechanisms was monitored after 3 and 6 months of storage at 25°C. The results showed that seeds performed better when stored at low SMC (10 and 12%), whereas the deterioration process accelerated in seeds stored at higher SMC (14%). Coupling high SMC with the availability of oxygen in the storage environment produced a negative effect on seed quality and longevity. Results from the antioxidant analysis showed more activity in seeds stored with oxygen at high SMC (14%) compared to lower SMC stored in modified oxygen conditions. Therefore, it is recommended that storage with low moisture levels (12%) or below (10%) is the best to preserve rice seed quality. However, at higher moisture levels (14%), the availability of oxygen in storage is more harmful to seed lifespan and quality. [ABSTRACT FROM AUTHOR]

Post-fire flowering (PFF) species resprout, flower and disperse seeds within weeks after fire. This may be an important strategy to recruit new individuals and colonize the gaps opened by fire. The seeds released in the post-fire environment may interact with byproducts derived from plant burning, and the resulting ash may have compounds that can promote the germination of various seeds, particularly those with permeable coats. In the Cerrado ecoregion, PFF is a strategy commonly observed in the species of the ground layer, but their seeds are rarely investigated. So, we examined the quality and the germination of the seeds of 13 species that disperse seeds within 3 months after fire. We estimated the amount of empty, filled and predated seeds for each species, and tested the germination with or without ash. There was a clear separation in seed quality as dicots produced 35–75% filled seeds but grasses <15%. Pre-dispersal predation was only observed for dicots (<10%). Ash stimulated the germination of two out of the three dormant species but inhibited the germination of three non-dormant species. Overall, the seeds produced in response to fire are an important source of genetic variability in an ecosystem that has resprouting as the main persistence strategy. As most species have non-dormant seeds, ash may only be important to stimulate the germination of few PFF species. Even so, ash can be completely washed away by rains before seeds are dispersed and may not have an effect under field conditions. [ABSTRACT FROM AUTHOR]

The J. Derek Bewley Career Lectures presented at the triennial meetings of the International Society of Seed Science support early-career seed scientists by providing retrospective views, from those late in their careers, of lessons learned and future implications. Ambition, ability, inspiration, foresight, hard work and opportunity are obvious career requirements. The importance of mentoring and teamwork combined with the clear communication of results, understanding and ideas are emphasized. The role of illustration in research, and its dissemination, is outlined: illustration can support hypothesis development, testing and communication. Climate change may perturb the production of high-quality seed affecting conservation as well as agriculture, horticulture and forestry. An illustrative synthesis of the current understanding of temporal aspects of the effects of seed production environment on seed quality (assessed by subsequent seed storage longevity) is provided for wheat (Triticum aestivum L.) and rice (Oryza sativa L.). Seed science research can contribute to complex global challenges such as future food supplies from seed-propagated crops in our changing climate whilst conserving biological diversity (through seed ecology and technologies such as ex situ plant genetic resources conservation by long-term seed storage in genebanks), but only if that research can be – and then is – applied. [ABSTRACT FROM AUTHOR]

To maximize seed longevity, seeds should be harvested at optimal maturity, that is, when seeds have acquired maximum physiological quality before deterioration begins. The aim of this study was to map the variation in temporal patterns of lentil (Lens culinaris Medik.) seed quality development when grown across four regeneration environments, which differ in the level of temperature and humidity control throughout the growing season, at the Australian Grains Genebank. Seeds of two lentil accessions (76080 and 76072) were harvested at different stages throughout development, commencing at 21 d after 50% anthesis until a maximum of 130 d. At each harvest, physiological quality traits, including germinability (fresh and dried seeds) and seed longevity, were determined, as well as seed dry weight and moisture content. Seeds of both accessions, and in all environments, started to accumulate physiological quality early on in development but did not reach their maximum until 3–54 d after mass maturity. The temporal patterns of desiccation tolerance and storage longevity were highly influenced by the environmental conditions during the maturation drying phase, affecting both 'when' maximum quality was attained and for how long it was maintained, thereafter. Seeds did not show a typical developmental response, rather variation was observed in seed quality development both between and within accessions grown in the different environments. The poorest storage longevity was seen when seeds of both accessions were grown in the cooler, temperature-controlled glasshouse, and the maximum longevity was observed in the warmer, semi-protected environments of the green and the big igloo for accessions 76080 and 76072, respectively. [ABSTRACT FROM AUTHOR]

For endozoochorous species, the quality component of seed dispersal effectiveness depends in part on the treatment seeds receive in the animal's gut. Covering a variety of taxa, diet, digestion system and body size of Prosopis flexuosa seed dispersers, we analysed differences among species in (1) mean retention time of ingested seeds, (2) recovery of viable seeds, (3) seed germination in comparison with seeds collected from trees and (4) germination of seeds after two different periods of retention in the gut. Feeding experiments were conducted with captive individuals of Dolichotis patagonum, Lycalopex gymnocercus, Rhea americana, Chelonoidis chilensis and Lama guanicoe. On the first day, we provided them with fruits containing controlled amounts of seed, and on the subsequent days, we collected faeces in order to recover seeds. We performed germination and viability tests on seeds coming from faeces and collected from trees. The results showed differences among species in the mean retention time of seeds. Chelonoidis chilensis had the longest mean retention time, but its effect on seed recovery and germination was similar to that of the other species, except for L. guanicoe, which showed the lowest seed recovery. When scarification and promotion of seed germination were considered, herbivorous mammals and tortoises (L. guanicoe, D. patagonum and C. chilensis) were the ones increasing germinability, whereas R. americana and L. gymnocercus did not significantly increase final seed germination percentage, which was similar to that for seeds collected from trees. P. flexuosa seeds receive a variety of treatments from endozoochorous dispersers, which might result in an overall fitness benefit for a plant living in unpredictable environments. [ABSTRACT FROM AUTHOR]

Recent evidence points to relationships between intra-specific seed mass variation and viability loss in response to ageing stress. However, little is known about how seed quality may change temporally in response to such stress. Here we examined seed–water relations of mass-separated Rudbeckia mollis seeds to better understand physiological status among mass classes. We then evaluated seed viability and vigour changes in response to various storage conditions or post-storage vigour tests (a 41°C, 75% RH stress for up to 45 d). We found similar pre-storage physiology among mass classes. However, seeds of lower mass deteriorated up to 1.5-fold faster than heavier seeds under certain conditions. Stressing seeds after storage resulted in distinct vigour differences among mass classes. For example, vigour in lower mass seeds tended to decline more compared to heavier seeds following storage in a climate-controlled room. Alternatively, vigour loss varied among mass classes following storage in a non-climate-controlled shed. Our results highlight the importance of distinguishing between pre-sowing storage and post-storage vigour effects when quantifying relative levels of viability loss among seeds of different mass. Furthermore, differential responses to storage and ageing stress among mass classes may have important implications for post-storage regeneration and subsequent population dynamics. [ABSTRACT FROM AUTHOR]

Drought and high temperature each damage rice (Oryza sativa L.) crops. Their effect during seed development and maturation on subsequent seed quality development was investigated in Japonica (cv. Gleva) and Indica (cv. Aeron 1) plants grown in controlled environments subjected to drought (irrigation ended) and/or brief high temperature (HT; 3 days at 40/30°C). Ending irrigation early in cv. Gleva (7 or 14 days after anthesis, DAA) resulted in earlier plant senescence, more rapid decline in seed moisture content, more rapid seed quality development initially, but substantial decline later in planta in the ability of seeds to germinate normally. Subsequent seed storage longevity amongst later harvests was greatest with no drought because with drought it declined from 16 or 22 DAA onwards in planta, 9 or 8 days after irrigation ended, respectively. Later drought (14 or 28 DAA) also reduced seed longevity at harvest maturity (42 DAA). Well-irrigated plants provided poorer longevity the earlier during seed development they were exposed to HT (greatest at anthesis and histodifferentiation; no effect during seed maturation). Combining drought and HT damaged seed quality more than each stress alone, and more so in the Japonica cv. Gleva than the Indica cv. Aeron 1. Overall, the earlier plant drought occurred the greater the damage to subsequent seed quality; seed quality was most vulnerable to damage from plant drought and HT at anthesis and histodifferentiation; and seed quality of the Indica rice was more resilient to damage from these stresses than the Japonica. [ABSTRACT FROM AUTHOR]

The long-standing hypothesis that seed quality improves during seed filling, is greatest at the end of seed filling, and declines thereafter (because seed deterioration was assumed to begin then), provided a template for research in seed quality development. It was rejected by investigations where seed quality was shown to improve throughout both seed development and maturation until harvest maturity, before seed deterioration was first observed. Several other temporal patterns of seed quality development and decline have also been reported. These are portrayed and compared. The assessment suggests that the original hypothesis was too simple, because it combined several component hypotheses: (a) the seed improvement (only) phase ends before seed deterioration (only) commences; (b) there is only a brief single point in time during seed development and maturation when, in all circumstances, seed quality is maximal; (c) the seed quality improvement phase coincides perfectly with seed filling, with deterioration only post-seed filling. It is concluded that the search for the single point of maximum seed quality was a false quest because (a) seed improvement and deterioration may cycle (sequentially if not simultaneously) during seed development and maturation; (b) the relative sensitivity of the rates of improvement and deterioration to environment may differ; (c) the period of maximum quality may be brief or extended. Hence, when maximum quality is first attained, and for how long it is maintained, during seed development and maturation varies with genotype and environment. This is pertinent to quality seed production in current and future climates as it will be affected by climate change and a likelihood of more frequent coincidence of brief periods of extreme temperatures with highly sensitive phases of seed development and maturation. This is a possible tipping point for food security and for ecological diversity. [ABSTRACT FROM AUTHOR]

We studied the variability of germination, dormancy and viability loss of Hirschfeldia incana seeds in relation to seed size. Seeds were stored at 35°C under humid [75% relative humidity (RH)] or dry (33% RH) conditions. Seed germination and electrolyte leakage were evaluated periodically. Small seeds had lower longevity at humid or dry storage conditions (5 or 407 days, respectively) than large or intermediate seeds (7–9 or 536–727 days, respectively). Moreover, H. incana shows variability in seed dormancy related to seed size within a population, with small seeds having lower dormancy (13%) than intermediate (50%) or large seeds (72%). Dormancy was partially released after a short storage at 35°C and humid conditions. Under dry storage conditions, endogenous dormancy cycles were observed for over a year, and longer times of storage had a dormancy-breaking effect through dry after-ripening. Results suggest a dual strategy producing non-dormant seeds with low longevity that will germinate immediately after dispersal, and seeds with greater longevity that will delay germination. Membrane permeability increased linearly with ageing at both humid and dry storage (R 2 = 0.60). Small seeds showed greater conductivity than intermediate or large seeds (0.7, 0.4 or 0.3 mS g–1 dry weight, respectively, at the 80% germination). The conductivity test could be used to evaluate the quality of H. incana seeds and would allow us to identify dormant (non-germinating) seed lots as viable. However, the influence of storage conditions and variability within a seed population on seed longevity should be taken into account when evaluating seed quality. [ABSTRACT FROM AUTHOR]

Many seed quality tests are conducted by first randomly assigning seeds into replicates of a given size. The replicate results are then used to check whether or not any problems occur in the realization of the test. The two main tools developed for this verification are the ratio of the observed variance of the replicate results to a theoretical variance and the tolerance for the range of the results. In this paper, we derive the theoretical distribution and its related properties of the sequence of numbers of seeds with a given quality attribute present in the replicates. From these theoretical results, we revisit the two quality checking tools widely used for the germination test. We show a precaution to be taken when relying on the variance ratio to check for under- or over-dispersion of the replicate results. This has led to the development of tables providing credible intervals of the variance ratio. The International Seed Testing Association tolerance tables for the range of the results are also compared with tolerances computed from the exact theoretical distribution of the range, leading us to recommend a revision of these tables. [ABSTRACT FROM AUTHOR]

In nature, fruit and seed production in many plants have been shown to be pollen limited. Pollen limitation is demonstrated when open-pollinated plants that are hand-supplemented (Ps) with outcross pollen produce more fruits and/or seeds than open-pollinated controls that are not hand-pollinated (Po). There are three categories of results in such studies: Ps > Po, Ps = Po and Ps < Po, in which case pollen limitation indices are positive, zero and negative, respectively. In an index widely used to calculate pollen limitation, 1 – (Po/Ps), the bounds for Ps ≥ Po are 0 to + 1, whereas the bounds for Ps < Po are 0 to –∞. The first aim of this review was to show how the pollen limitation index can be modified so that the bounds of Ps < Po are 0 and –1, whereupon the index gives equal weight to the best performer (Ps or Po) and worst performer (Ps or Po). In addition to seed quantity, pollen supplementation can affect seed quality, including germinability. Thus, our second aim was to summarize the results of studies that have also tested the effect of pollen limitation on seed germination. In short, the 30 case studies in 15 families, 16 genera and 18 species that we identified show that seed germination percentage increased, was not affected or decreased by pollen supplementation in 12, 11 and seven cases, respectively. The effect of pollen limitation on seed germination, which can be quite large, has not been considered in developing population growth models to determine the effect of pollen limitation on λ. [ABSTRACT FROM AUTHOR]

Multispectral imaging is a new technology that is being deployed to assess seed quality parameters. Examples of applications in the detection and identification of fungi on seeds are presented, together with an example of the technology used for maturity determination in sugar beet seed. Results from multispectral imaging are compared with reference methods, and a high correlation is found. Applications of the technique for varietal discrimination and insect damage are also presented. There is a need for non-destructive, reliable and fast techniques, and it is concluded that multispectral imaging has potential for seed quality assessment, in particular for those components associated with surface structure and chemical composition, seed colour, morphology and size. [ABSTRACT FROM AUTHOR]

Rapid, non-destructive methods for measuring seed germination and vigour are valuable. Standard germination and seed vigour were determined using 81 soybean seed lots. From these data, seed lots were separated into high and low germinating seed lots as well as high, medium and low vigour seed lots. Near-infrared spectra (950–1650 nm) were collected for training and validation samples for each seed category and used to create partial least squares (PLS) prediction models. For both germination and vigour, qualitative models provided better discrimination of high and low performing seed lots compared with quantitative models. The qualitative germination prediction models correctly identified low and high germination seed lots with an accuracy between 85.7 and 89.7%. For seed vigour, qualitative predictions for the 3-category (low, medium and high vigour) models could not adequately separate high and medium vigour seeds. However, the 2-category (low, medium plus high vigour) prediction models could correctly identify low vigour seed lots between 80 and 100% and the medium plus high vigour seed lots between 96.3 and 96.6%. To our knowledge, the current study is the first to provide near-infrared spectroscopy (NIRS)-based predictive models using agronomically meaningful cut-offs for standard germination and vigour on a commercial scale using over 80 seed lots. [ABSTRACT FROM AUTHOR]

The resilience of seed quality in rice (Oryza sativa L.) to flooding was investigated. Pot-grown plants of the japonica cv. Gleva, the indica cv. IR64, and the introgressed line IR64-Sub1 were submerged in water, to simulate flooding, for 3‒5 days at different stages of seed development and maturation. Mean seed weight, pre-harvest sprouting, ability to germinate, and subsequent longevity in air-dry storage were assessed. Whereas seed quality in both IR64 and IR64-Sub1 was resilient to submergence, in Gleva the longer the duration of submergence and the later in development when plants were submerged the greater the pre-harvest sprouting. Thousand seed dry weight was reduced more by submergence in Gleva than IR64 or IR64-Sub1. At harvest maturity, few pre-harvest sprouted seeds were able to germinate upon rehydration after desiccation to 11‒12% moisture content. Seed longevity of the non-sprouted seed fraction in air-dry hermetic storage (40°C, 15% moisture content) was not affected greatly by submergence, but longevity of the japonica rice was less than that of the indica rices due to the former's steeper seed survival curves. Longevity of the two indica rices was predicted well by the seed viability equation and previously published estimates of viability constants for rice. The greater dormancy of IR64 and IR64-Sub1, compared with Gleva, enhanced resilience to pre-harvest sprouting and reduced thousand seed dry weight from plant submergence. There was little or no effect of plant submergence on subsequent air-dry storage longevity of non-sprouted seeds in any genotype. [ABSTRACT FROM AUTHOR]

Seed quality is of great importance in optimizing the cost of crop establishment. Rapid and non-destructive seed quality detection methods must therefore be developed for agriculture and the seed production industry. This review focuses primarily on non-destructive techniques, namely machine vision, spectroscopy, hyperspectral imaging, soft X-ray imaging, thermal imaging and electronic nose techniques, for assessing the quality of agricultural seeds. The fundamentals of these techniques are introduced. Seed quality, including chemical composition, variety identification and classification, insect damage and disease assessment as well as seed viability and germinability of various seeds are discussed. We conclude that non-destructive techniques are accurate detection methods with great potential for seed quality assessment. [ABSTRACT FROM PUBLISHER]

Dormancy has evolved in plants to restrict germination to favourable growth seasons. Seeds from most crop plants have low dormancy levels due to selection for immediate germination during domestication. Seed dormancy is usually not completely lost and low levels are required to maintain sufficient seed quality. Brassica napus cultivars show low levels of primary seed dormancy. However, B. napus seeds are prone to the induction of secondary dormancy, which can lead to the occurrence of volunteers in the field in subsequent years after cultivation. The DELAY OF GERMINATION 1 (DOG1) gene has been identified as a major dormancy gene in the model plant Arabidopsis thaliana. DOG1 is a conserved gene and has been shown to be required for seed dormancy in various monocot and dicot plant species. We have identified three B. napus genes with high homology to AtDOG1, which we named BnaA.DOG1.a, BnaC.DOG1.a and BnaC.DOG1.b. The transcripts of these genes could only be detected in seeds and showed a similar expression pattern during seed maturation as AtDOG1. In addition, the BnaDOG1 genes showed enhanced transcript levels after the induction of secondary dormancy. These results suggest a role for DOG1 in the induction of secondary dormancy in B. napus. [ABSTRACT FROM AUTHOR]