Maturation and quality of seeds of Euterpe edulis Martius assessed by imaging and X-ray densitometry

Key message

The 164 DAA maturation stage is superior in terms of germination and seedling formation, with gains of 4.2 months in relation to the last stage, and X-ray densitometry is a new and efficient technique to analyze Euterpe edulis seeds.

AbstractEuterpe edulis Martius is an endangered palm species that grows in the Atlantic Forest and the Cerrado of South America. Economic exploitation of its antioxidant-rich fruits could ensure the sustainable management of this species. However, this relies on the rapid selection of high-quality seeds from which to derive seedlings. Image analysis and X-ray densitometry can be quick, practical, and best of all, non-destructive techniques for selecting seeds, ensuring the sustainability of the species. The objective of this study was to investigate the maturation of E. edulis seeds using image analysis and X-ray densitometry. Fruits were harvested from ten matrices at different stages of maturation, from 94 days after anthesis (DAA) to 290 DAA. Seed dry mass, water content, germination, vigor, and density were quantified at each stage. At the same time, seeds were analyzed by GroundEye^® imaging, radiography, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The design was completely randomized and consisted of 29 treatments (maturation stages) and four replications with 10 seeds each. The highest dry mass was detected 255 DAA (0.83 g), in vitro germination began 115 DAA and achieved 100% from 150 DAA, and maximum vigor was observed 164 DAA, whereby 100% of seedlings appeared normal. X-ray imaging revealed dehydrated seeds and small mechanical damage, such as cracking of the pericarp. X-ray densitometry revealed that seed density increased considerably 185 DAA. SEM/EDS detected changes between maturation stages, such as the accumulation of K and Si, in the mesocarp and endocarp. Overall, E. edulis seeds presented maximum in vitro germination, vigor, percentage of normal seedlings, and physicochemical qualities 164 DAA (green epicarp), which corresponds to 126 days earlier compared with the fruits harvested 290 DAA (black epicarp) for ex vitro germination. The analyses proposed in this study, together with the analysis of seed germination and vigor throughout maturation, were promising for increasing the speed, classification accuracy, and selection of E. edulis seeds. Such analyses have a high potential since they are practical and many are non-destructive, adding cost-benefit with accurate results.