Factors contributing to the variability in sunflower achene dehulling efficiency

This study aims to identify the morphological and anatomical factors that influence the dehulling capacity of sunflower achenes, a critical issue for the oilseed industry. Four cultivars grown at two sites over two cultivation years were examined. The study is based on observations from transverse sections of achenes, enabling measurement of the area of the achenes, embryos, and pericarp, as well as the length of contact zones between the pericarp and the embryo. Calculations were used to evaluate pericarp thickness, filling rate, and contact rate. Dehulling capacity does not simply depend on achene size or oil content but rather results from a complex balance between pericarp rigidity (as determined by its thickness) and the presence of gaps or adhesion zones at the pericarp/embryo interface. Genetic factors influence pericarp thickness and the propensity for hull/kernel contact. Environmental conditions impact the supply of water at both the flowering and seed-filling stages. The flowering period is crucial for pericarp development, and water stress during this period results in thinner pericarps and smaller achenes that are more difficult to dehull. The filling rate increases when water needs during seed filling are met, whereas the contact zones depend on the interaction between water supplies during both stages. In summary, the findings validate the role of the hull/kernel interface in dehulling and provide fresh avenues for selecting varieties with superior technological quality in sunflower achenes.