A rapid and sensitive method to assess seed longevity through accelerated aging in an invasive plant species.
Background: Seed longevity and vigor assessment is crucial for efficient ex situ biodiversity conservation in genebanks but may also have potential applications for the understanding of ecological processes and in situ biodiversity conservation. In fact, one of the factors determining the persistence of invasive species, a main threat to global biodiversity, is the generation of soil seed banks where seeds may remain viable for several years. Artificial seed aging tests using high temperatures and high relative humidity have been described for seed longevity estimation but have been mainly optimized for species with commercial interest. Thus, the aim of the study is to define a rapid and sensitive method to assess seed longevity and vigor through accelerated aging in the worldwide distributed invasive species Carpobrotus edulis to provide tools to biodiversity managers to evaluate invasive potential and develop effective post-eradication plans. Results: Slow seed deterioration rate was obtained when C. edulis seeds were subjected to common accelerated aging temperatures (43-45°C). This contrasts with the rapid viability decay between 24-72 h when seeds were subjected to temperatures superior to 55°C, a strong inflection point for this species' thermosensitivity. Relative humidity also played a role in defining seed survival curves, but only at high temperatures, speeding up the deterioration process. The selected aging conditions, 55°C at 87% relative humidity were tested over two C. edulis populations and three measures were proposed to parametrize the differential sigmoidal seed survival curves, defining the seed resistance to deterioration (L5, aging time where 95% of seeds maintain their viability), medium longevity (L50, 50% of seeds lose their viability) and lethal aging time (L95, 95% of viability loss). Conclusions: An accelerated aging test at 55°C and 87% relative humidity constitutes a rapid and sensitive method that can be performed within a working week, allowing managers to easily test seed vigor and longevity. This test may contribute to assess invasive potential, design effective monitoring programs and soil seed bank eradication treatments.