2007 Annual Report 1a.Objectives (from AD-416) The objective of this cooperative research project is to determine if host plant tolerance to hardlock is controlled by a genetic system consisting of one or a few genes or by a genetic system consisting of numerous genes that are inherited in a quantitative way. 1b.Approach (from AD-416) Several F2 populations, developed by Cooperator and putatively segregating for hardlock tolerance, will be evaluated under field conditions at Cooperators's breeding station in Sellers, SC, and ARS' Pee Dee Research and Education Center in Florence, SC. A total of 400 plants per population will be space planted, evaluated, and scored for tolerance to hardlock at the end of the growing season at each location. Parental lines used to develop the F2 populations and a check cultivar known to exhibit extreme hardlock susceptibility will also be evaluated and scored for tolerance to hardlock. Leaf samples will be harvested from 10 randomly selected plants within each parent plot and the susceptible check cultivar plot. All leaf samples will be stored at -80 degrees C for possible future DNA analysis. Data collected from each location and F2 population will be input into a personal computer. The population data will be tested against expected single gene and two-gene genetic ratios to determine if hardlock tolerance is simply inherited. 3.Progress Report This report serves to document research conducted under a non-funded cooperative agreement (6657-21000-005-04N) between ARS and Bayer Crop Science International. Additional details of research can be found in the report of the parent project 6657-21000-005-00D, Enhancing the Sustainability of Cotton Production in the Southeast USA. The objective of this cooperative research project is to determine if host plant tolerance to hardlock is controlled by a genetic system consisting of one or a few genes or by a genetic system consisting of numerous genes that are inherited in a quantitative way. A total of 400 progeny, representing several different F2 families putatively segregating for hardlock tolerance, were evaluated and scored for tolerance to hardlock in two field trials during 2006. Data collected from each location and F2 population was tested against expected single gene and two-gene genetic ratios to determine if hardlock tolerance is simply inherited. Initial results suggest that genetic tolerance to hardlock is quantitatively inherited and controlled by many genes. To confirm the heritability of hardlock tolerance or susceptibility, F3 progeny rows from randomly selected and self-pollinated F2 individuals are currently being evaluated and scored for tolerance to hardlock in two locations during 2007. This research will provide a scientific basis for strategies to employ toward developing improved cotton germplasm lines with tolerance to hardlock and other abiotic stress. Project progress was monitored at least quarterly throughout the year via teleconference, email, and visits to the ARS and cooperator facilities.