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Seed longevity is a complex process of key ecological and agronomic importance. DNA damage is a significant factor affecting seed ageing. Likewise, epigenetic changes can control gene expression and, therefore, seed response to ageing. The aim of the present work was to investigate the effect of ageing on nucleic acid stability and to identify reliable molecular markers that might help to monitor epigenetic changes within plant genetic resources during conservation. DNA profiles, evaluated by RAPD (random amplified polymorphic DNA), and methylation patterns, obtained by MSAP (methylation-sensitive amplification polymorphism), were compared in non-aged and aged Mentha aquatica seeds and plants produced by them. Germination decreased to 50% by storing seeds at 35°C and 12% wc for 28 days. RAPD profiles were 99% similar in these aged seeds compared to non-aged seeds. However, seedlings produced from the aged seeds showed a 13% dissimilarity compared to seedlings produced from the non-aged seeds. About 8% difference in the MSAP epigenetic profile was detected in seeds after storage and 16% difference was detected in the seedlings produced from them. This indicates that stress from high temperature and humidity during storage induced changes on the methylation state of seeds, and that changes were also detectable in the regenerated plants. Our results suggest that DNA integrity was compromised in seeds during ageing, and on seedlings produced by aged seeds. Genotype screening techniques such as RAPD and MSAP have the potential as markers of nucleic acid stability during seed ageing. [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]

The broad aim of this work was to study intraspecific variation of seed germination in Phillyrea angustifolia L. (Oleaceae), a species with a hard (water-permeable) endocarp. Germination of seeds from six different wild populations was correlated with traits related either to seed morphology or to environmental parameters. Germination of naked seeds (seeds without endocarp) at the optimum germination conditions was similar among populations and individuals, but great differences could be detected regarding the germination of seeds with endocarp both at inter- and intra-populational levels. Differences among populations could be related to climatic parameters and to morphometric variables of seeds with endocarp. A higher germination was associated with populations growing in habitats with more severe summer (higher temperature, lower precipitation and a longer drought period) and producing elongated seeds (lower Feret ratio and roundness). Moreover, seeds from eight different individuals within a population were tested independently, and great differences regarding the germination of seeds with endocarp could be detected among individuals. Our results suggest that the morphological variation found in P. angustifolia endocarp is both under strong maternal genetic control as well as influenced by environmental factors, as indicated by the high variability among individuals within one population and the significant correlation between climate variables and seed germination among populations. Finally, it is emphasized that standardization of plant propagation protocols should take into account the degree of intraspecific variation of Mediterranean species. [ABSTRACT FROM AUTHOR]