2005 Annual Report 4d.Progress report. This report serves to document research conducted under a specific cooperative agreement between ARS and the University of Wisconsin (UW). Additional details of research can be found in the report of the parent CRIS project 3625-21000-047-00D, "Germplasm Enhancement of Maize Project (GEM)." This project relates to the primary objectives of the parent project which includes the development and evaluation of value-added traits such as silage nutritional quality and yield. In 2004-5 work continued breeding the GEM Quality Synthetic (GQS) using the S2 top cross system used for the Wisconsin Quality Synthetic (WQS). In 2005, 200 S1 families from GQS were selected and self pollinated under high plant density and cold stress. The resulting S2’s will be top crossed in winter nursery and put into yield trials in 2006. Other breeding work in 2005 includes further inbreeding of approximately 500 GEM families, and the addition of new GEM inbred bulks derived from two Argentina accession breeding crosses, AR16026:S1719, AR17056:N2025; a Brazilian 25% tropical breeding cross, DK212T:N11a12, and US temperate breeding cross, FS8B(T):N11a. Other GEM populations in the UW program include breeding crosses with accessions from Cuba (CUBA164:S2012, CUBA117:S1520), Brazil (BR52051:N04, DKXL370:N11a20), Mexico (CHIS775:S1911b), Argentina (AR17026:N1019), and Uruguay (UR13085:N0204). Yield trials were planted at two locations in 2005 (Madison and Arlington, WI), and nutritional evaluations are planned for neutral detergent fiber (NDF), in vitro true digestibility (IVD), crude protein (CP), and starch concentration. A significant accomplishment for FY2005 included the public release of inbred W605S in December 2004. This inbred was developed from the GEM breeding cross AR17026:N1019, and has advantages for yield (highest milk per acre yield in a 2004 trial).