Variability in oil content among heads and seeds within heads of sunflowers (Helianthus annuus L.)

Oil contents were determined by nuclear magnetic resonance on four samples, each consisting of six seeds, from each of three ring positions (outer, middle, and inner) for 10 heads from each of two open‐pollinated varieties and two inbred lines of sunflowers. The largest source of variability for three of the entries was due to differences among heads. Variability due to seed position in the head was the largest for the fourth entry. When averaged over all entries, % oil was the highest for seeds samples from the middle ring position. In studies in which oil content is determined on single seeds or small samples, error variation can be reduced by sampling from either of the outer two ring positions, rather than sampling from the inner position or at random.