phenoSeeder - A robot system for automated handling and phenotyping of individual seeds

The enormous diversity of seed traits is an intriguing feature and critical for the overwhelming success of higher plants. In particular seed mass is generally regarded to be key for seedling development but is mostly approximated by using scanning methods delivering only 2D data, often termed "seed size". However, 3D traits such as volume or mass of single seeds are very rarely determined in routine measurements. Here we introduce a device named phenoSeeder which enables handling and phenotyping of individual seeds of very different sizes. The system consists of a pick-and-place robot and a modular setup of sensors which can be versatilely extended. Basic biometric traits detected for individual seeds are 2D data from projections, 3D data from volumetric measures, and mass from which also seed density is calculated. Each seed is tracked by an ID and, after phenotyping, can be planted, sorted or individually stored for further evaluation or processing, e.g., in routine seed-to-plant tracking pipelines. By investigating seeds of Arabidopsis (Arabidopsis thaliana), rapeseed (Brassica napus) and barley (Hordeum vulgare) we observed that, even for apparently round-shaped seeds of rapeseed, correlations between projected area and mass of seeds were much weaker than between volume and mass. This indicates that simple projections may not deliver good proxies for seed mass. Though throughput is limited, we expect that automated seed phenotyping on a single seed basis can contribute valuable information for applications in a wide range of wild or crop species including seed classification, seed sorting or assessment of seed quality.