2009 Annual Report 1a.Objectives (from AD-416) To produce, with the aid of traditional breeding approaches, a sunflower with improved resistance to the herbicide Atrazine (triazine), and to determine the mode of inheritance of such resistance. 1b.Approach (from AD-416) Traditional breeding with chemical mutagenesis was used to produce lines derived from HA 821 and HA 382 with point mutations scattered throughout the genome. One or more of these point mutants provide resistance to triazine. Research is ongoing to determine the mode of resistance of each of the potential sources, and also to determine transmittance of the resistance to hybrids. After the mode of resistance is determined, purification of resistant lines will continue until a pure line is available for joint release by USDA-ARS and Kansas State University. 3.Progress Report This past year we collectively began physiological trials with presumed herbicide-resistant parental lines and hybrids made from them to see if the gene action of the resistance is additive or dominant in hybrids. This is an important facet of the research in that it will tell us if we need to have the resistance genes on both the male and female sides of the hybrid, or just in one of the parents. Preliminary results indicate that there is good resistance to atrazine herbicide in hybrids formed with the USDA line RHA 373. Additional information will be gathered from laboratory and greenhouse screening of hybrids and the experimental inbred lines this year. The ADODR monitors research progress by quarterly meetings with the Cooperator's personnel and by site visits to field plot locations.