2008 Annual Report 1a.Objectives (from AD-416) The proposed study will result in the development and application of sequenced-tagged-site (STS) markers for use in the marker-assisted selection of sorghum germplasm with enhanced levels of early season cold tolerance. Genomic regions associated with this trait have already been identified by the Cooperator, and it is anticipated that these markers will have a direct application in the introgression of cold tolerance genes into adapted U.S. germplasm. 1b.Approach (from AD-416) Based on a QTL map developed by the Cooperator, PCR-based molecular markers will be developed which will allow researchers to detect the presence or absence of a particular genomic region known to be associated with early season cold tolerance. Sorghum germplasm differing in its constitution, with respect to these genomic regions, will be evaluated in conjunction with the Cooperator, in order to evaluate the efficacy of this approach and the utility of these markers. 3.Progress Report Growth analysis greenhouse studies were completed for a second season, comparing a temperate-adapted and purported cold sensitive breeding line (RTx430). Assimilation and fluorescence measurements were completed at two vegetative growth stages to distinguish intrinsic biochemical bases for growth differences from physiological responses. Future physiological studies of photosynthesis will be supported by instrumentation to quantify leaf and canopy absorbance, which was acquired during this reporting period. ADODR was in regular contact with cooperator via e-mail, phone, and face-to-face meetings.