2007 Annual Report 1a.Objectives (from AD-416) Develop landmark cultivars, advanced generation breeding lines and information for use by other breeders. Problems facing the lettuce industry will be addressed using genetic approaches that are suited to coastal, desert, and interior valley locations, to the various types of lettuce, and to the demands of different production and marketing approaches. 1b.Approach (from AD-416) Evaluate cultivars and PI accessions for useful traits. Plant trials in coastal and desert districts to evaluate yield, head size, and shape, color and various disease, insect, and stress resistances. Look for tipburn, rib blight, pink rib, lettuce chlorosis, and bolting. Continue statewide trials of cultivars and breeding lines. Groups of lines with single or combined resistances will be grown in field trials for evaluation under commercial conditions. Documents Trust with California Lettuce Research Board (#58-5305-4-450). Formerly 5305-21000-011-02T. Log 25764. 3.Progress Report This report serves to document research conducted under a trust fund agreement between ARS and the California lettuce Research Board. Additional details of research can be found in the report for the parent CRIS 5305-21000-011-00D; Evaluation, Enhancement, Genetics, and Breeding of Lettuce, Melons and Closely Related Species. Our objectives are to incorporate resistance to several diseases and insects into crisphead and mixed lettuce cultivars and breeding lines. In 2006, major efforts targeted resistance to lettuce big vein disease, lettuce drop /Sclerotinia species, Verticillium wilt, Fusarium root rot, lettuce dieback/tombusviruses, bacterial leaf spot, corky root, leafminer, lettuce aphid, tipburn and multiple disease resistance. Minor programs addressed adaptation to low desert conditions, nutritional content, as well as resistance to powdery mildew and yellow spot. In all programs, horticultural traits, adaptation, and resistance to tipburn are considered essential. In 2006, we identified new candidate sources of resistance to yellow spot and race 2 isolates of Verticillium dahliae. We confirmed resistance in previously identified germplasm to big vein disease, Verticillium wilt, and lettuce aphid. Selections were taken from breeding populations, and advanced breeding lines were evaluated, as part of breeding for resistance to big vein disease, lettuce drop, Verticillium wilt, powdery mildew, dieback, bacterial leaf spot, corky root, leafminer, tipburn, bolting, and for increased nutritional content. Three iceberg breeding lines with Verticillium wilt resistance were released as germplasm. Genetic studies concurrent with breeding programs are being conducted to determine the inheritance of resistance to bacterial leaf spot, big vein disease, lettuce mosaic virus, lettuce drop, leafminers, and Verticillium wilt. Publications during 2006-2007 included reports of original research on big vein disease, Verticillium wilt, and tipburn resistance, a germplasm release for verticillium wilt, and a book chapter on lettuce breeding. This project is monitored through twice yearly written and oral reports.