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Sunflower Performance Relative to Size and Weight of Achenes Planted¹

The research was undertaken in response to a common concern of sunflower (Helianthus annus L.) researchers and seedsmen as to whether various achene-size fractions of a seed lot will produce crops differing in performance.

The objective was to compare crops produced from large, medium, small, heavy, and ungraded achenes in yield and quality. Twelve seed lots of the major types of sunflower were separated into five grades by sieves and wind. An extra large grade representing 3% and a trash grade representing 2% of the original seed lot were additional grades included with one seed lot. Trials were planted at Rosemount, Minn., and thinned to a uniform seedling population of 61,000 plants/ha.

Sunflower achenes ranged from 18 to 52% pericarp. However, large, medium, and small achene grades contained, respectively, large, medium, and small seeds. Correlation between achene size and seed size exceeded + 0.95.

Crops produced from large, medium, small, or heavy achenes did not differ significantly in achene yield, hectoliter weight, or oil percentage. Large achenes produced significantly (5% level for human food varieties, 1% level for birdfeed varieties, and 20% level for oilseed varieties) larger achenes than the small grade, and the medium grade was intermediate.

If size-graded achenes are used in varietal trials, bias may occur in rating varieties for achene size unless the achenes planted are from similar size-fractions of the original seed lot.

Key Words: Seed size • Seed weight • Fruit and seed morphology

² Professor, University of Minnesota, St. Paul.

Received for publication March 11, 1974.