Interhybrid Competition Affects Sunflower Character Expression

Abstract

Field researchers are confronted with selection of the proper plot design to assure agreement of small‐scale experimental plot results with large‐scale commercial field production. The objective of this research was to investigate the effect of plot design on expression of hybrid sunflower (Helianthus annuus L.) characters. Field studies were conducted in North Dakota at three dryland sites: Carrington, Fargo, and Prosper. lnterhybrid and intrahybrid competitive situations were attained by using one‐row or two‐row hybrid arrangements with three hybrids as possible borders. Competitive effects were determined on achene yield, achene oil concentration, achene weight, test weight, days to anthesis, head diameter, plant height, and leaf number. Plot achene yield was 20% greater when the border hybrid was a semidwarf than when border hybrids were of more conventional height. Border hybrid competitive influences on achene yield were approximately twice as great for one‐row as for two‐row arrangements. Other characters influenced by interhybrid competition were test weight, head diameter, and plant height. Characters not influenced by interhybrid competition included achene weight, achene oil concentration, days to anthesis, and leaf number. Plot border rows are recommended when evaluating characters subject to interhybrid competitive influences. An alternative approach is using one‐row or two‐row arrangements and grouping hybrids similar in plant height and maturity in the same field proximity.