Recent advances in agricultural biotechnology have produced many new crop varieties with valuable transgenic traits. These varieties are being, and will continue to be, marketed alongside conventional non-transgenic varieties. As a result, seed purity in commercial seed lots is of particular importance to both seed consumers and seed producers. A key step in the seed production process is the design of sampling and testing procedures used to evaluate seed lot purity. However, due to uncertainties in such methods, there is always a risk of incorrectly rejecting or accepting a seed lot. This paper discusses factors that should be considered when designing and implementing seed purity testing procedures to manage this misclassification risk – especially with regard to the presence or absence of transgenic traits. Many sources of uncertainty in both seed lot sampling and in the assay methods are described, and recommendations for reducing their impact are provided. This paper also explains the statistical concepts of misclassification risk as it affects seed producers and seed consumers. Sampling plans and formulas for determining the sample sizes necessary to control these misclassification errors when accepting or rejecting seed lots are also provided. Both simple, single-stage testing plans and the, often more efficient, double-stage testing plans are described. Testing seed pools rather than individual seeds is introduced as another way of adding efficiency to the testing process. Formulas are given for determining, from a seed sample, the confidence limits for the actual purity level of a commercial lot.

Correlative evidence indicates that sucrose and α-galactosyl-sucrose oligosaccharides (raffinose family oligosaccharides; RFOs) may be involved in seed longevity. Priming treatments (hydration in water or osmotic solutions followed by drying) can improve short-term seed performance but often result in reduced seed longevity. As RFOs are metabolized quickly following seed imbibition, loss of RFOs during priming could lead to more rapid deterioration in dry storage. This hypothesis was tested by measuring sucrose and oligosaccharide contents and potential longevity of primed seeds. Raffinose contents of whole lettuce (Lactuca sativa L.) seeds declined during hydration and priming and were correlated with decreased median potential viability (p50). However, this relationship was less significant when only the embryonic axes were analysed. In tomato (Lycopersicon esculentum Mill.) and impatiens (Impatiens balsamina L.) seeds, planteose was the major galactosyl-sucrose oligosaccharide and only small quantities of RFOs were present. Planteose contents declined during priming in seeds of both species, while sucrose contents increased or remained constant. Post-priming treatments that restored longevity in primed impatiens and tomato seeds were not accompanied by consistent changes in RFO or planteose contents. Our data do not rule out a role for oligosaccharides in seed longevity, but they make it unlikely that changes in oligosaccharide contents alone are responsible for the reduction in longevity due to priming or its restoration by post-priming treatments.

Embryonic axes of tea (desiccation sensitive) and pea (desiccation tolerant) were dried at different rates or stored at different water contents to distinguish between damage associated with the immediate effects of water loss and the longer-term effects of a partially hydrated state. No loss of viability was observed if pea axes were dried sufficiently rapidly (from 1.8 to 0.1 g H2O g-1dry mass (g/g) within 5 d). However, viability was lost in tea axes dried below 0.5 g/g (approximately -15 MPa) even if axes were dried within 1 h. Death in tea axes dried to moisture contents less than 0.5 g/g probably resulted from the removal of water necessary for cellular structural integrity (i.e. desiccation damage sensu stricto). When axes of both species were dried at slower rates, viability losses were observed at water potentials between about -3 and -15 MPa. The timing for this type of damage was species dependent, occurring within 2 d for tea and after 5 d for pea, and may be explained by higher oxidative activity in tea compared to pea. Embryos of both species with water potentials below -3 MPa were lethally damaged if oxygen consumption exceeded 1000–5000 μmol O2 g-1dry mass. Recalcitrant seeds are different than orthodox seeds because the former do not survive drying below a critical water content, regardless of the drying rate. Rapid drying is required for accurate assessment of the critical water content. Slow drying leads to metabolic imbalance and artefactual assessment of the critical water content for desiccation damage. Both tea and pea seeds were susceptible to damage from metabolic imbalances, suggesting that the predominant stress from slow drying is ageing.

Homologues of the pea SBP65, a late embryogenesis abundant (LEA) biotinylated protein that behaves as a putative sink for the free vitamin biotin during embryo development, were characterized biochemically in various plant species, including soybean, lentil, peanut, rape, cabbage, carrot and sugarbeet. Based on sequence homologies, the genome of Arabidopsis thaliana contains a gene putatively encoding a homologue of pea SBP65. These proteins exhibit two remarkable features. First, they only accumulate in seeds, particularly during late stages of embryo development. The results strongly suggest that these seed-specific biotinylated proteins belong to the class of plant proteins called seed maturation proteins, which are presumed to play major roles in embryo development. Secondly, covalent attachment of biotin occurs at a lysine residue within a conserved motif of (V/M)GKF, which shows no resemblance to the highly conserved AMKM tetrapeptide that houses the target lysine residue in the well-characterized biotin-dependent carboxylases and decarboxylases. These findings highlight novel structural features for protein biotinylation.

Patterns of seed mass variation in the perennial spurge Euphorbia characias(L.) (Euphorbiaceae) in three populations from north-east Spain were examined. Mature inflorescences have a distinctive structure, with a distal umbrella of rays subtending dichotomously grown cyathia. Under the umbrella, cyathia are loosely arranged on rays growing from the bases of leaves. Seed characteristics were studied, especially in relation to position along the inflorescence. Maximum inflorescence height had no effect on seed set or seed mass. Seed set did not differ between populations. Flower position along the inflorescence had a marked effect on seed set and seed mass. Seed set was higher in the distal (upper) portion of the inflorescence. Seeds from the distal area had a greater mass than those from lower parts of the inflorescence. Seeds were planted in the field and observed under natural weather conditions. The bigger seeds from the higher position in the inflorescence produced seedlings with a greater percentage emergence, which, in addition, had an increased percentage establishment than seedlings originating from the smaller seeds from lower areas of the inflorescence. For the three populations considered together, seeds from the basal (lower) portion of the inflorescence were reduced in germination by 51% and establishment by 59%. No differences in seedling dry mass were observed. Seed dispersal-related structures (elaiosome and elaiosome/load ratio) did not vary in relation to position or population. Positional effects on female performance – seed quantity and quality – may be a very strong selective pressure for the peculiar flower disposition in the architecture of E. characias.

Schismus arabicus is a common annual grass occurring in the Negev Desert of Israel. Under unpredictable distribution and very small amounts of rain, as well as massive seed predation, this species has developed complementary sets of survival strategies that are influenced by biotic and abiotic environmental factors. One of these strategies is the phenotypic germination plasticity due to distinct caryopsis size groups. These groups occur in different percentages in the seed population, according to plant age at the time of seed development and maturation, but are not influenced by photoperiod. The size of the tiny, dust-like caryopses has an influence on the range of temperatures required for germination, the speed of germination and the final germination percentage reached between 5 and 30°C. These survival characteristics contribute to making S. arabicus one of the most common annual plant species in large areas of the Saharo-Arabian deserts and Irano-Turanian regions.