Sunflower achene hulling ability: impact of water availability and genetic

This study investigated the determinants of sunflower hulling ability by evaluating 30 commercial hybrids across eight environments over two years Variance analysis revealed that environmental factors explained 50% of the variability in hull extraction rate, while genetic factors accounted for 33%. Water availability during key developmental stages was critical: sufficient water during flowering promoted pericarp development and improved hulling, whereas non limiting water supply during grain filling reduced hulling ability, likely by increasing hull-kernel adhesion. The negative correlation between oil content and hullability (R = –0.44) was confirmed, reflecting a trade-off between oil accumulation and pericarp development. Thousand-seed weight and bulk density showed only weak associations with hullability. The model incorporating water requirement coverage during flowering and grain filling explained over 90% of the environmental effect on hullability. These findings highlight the strong environmental plasticity of hulling ability and the importance of avoiding water stress during the flowering period. While genetic improvement remains feasible, the phenotypic expression of hullability is highly sensitive to environmental conditions, particularly water availability during flowering and seed filling. This work provides a framework for breeding and agronomic strategies aimed at optimizing both seed quality and processing efficiency in sunflowers.