2006 Annual Report 4d.Progress report. This report serves to document research conducted under a Specific Cooperative Agreement between ARS and the University of Nebraska-Lincoln, Department of Agronomy & Horticulture. Additional details of research can be found in the report for the parent project 5440-21220-024-00D, Genetic improvement of sorghum for enhancing energy yield, nutrient availability, and disease resistance. Prior to deployment of transgenic sorghum, it will be necessary to assess and manage the risks associated with possible transgene flow to sorghum’s weedy relatives. The objective of this cooperative research project is to determine the effect of transgenes from sorghum on the fitness of shattercane × sorghum hybrids. Seed of T2 generation transgenic sorghum lines obtained from the University of California Berkeley was advanced to the T3 generation. Families were screened for HTP4, and segregating, fixed, and null families identified. Backcrossing of male sterility genes into shattercane to facilitate future crosses with GMO sorghum was continued.