2011 Annual Report 1a.Objectives (from AD-416) Develop iceberg, romaine, and leaf lettuce cultivars with resistance to bolting, tipburn, powdery mildew, big vein and extended shelf-life. 1b.Approach (from AD-416) Field, greenhouse, laboratory, and molecular marker experiments to develop and select lettuce lines with improved performance for fall, winter, and spring planting slots in Arizona. 3.Progress Report Lettuce is the most valuable specialty crop grown in Arizona, and winter production is critical to maintaining a year round supply of high quality lettuce within the US. Growers are continually faced with pre-existing and new challenges, and pre-mature bolting, tipburn, and the diseases powdery mildew, big vein, and Fusarium wilt can lower profitability. The goal of this project is to develop landmark cultivars and breeding lines with resistance to these production constraints; seed of new cultivars will be disseminated to the lettuce industry for crop production and to develop additional cultivars. During the 2010-2011 winter production season, six field experiments were conducted to evaluate and select breeding lines and families for resistance to premature bolting, Fusarium wilt, big-vein disease, and the physiological defect tipburn. More than 420 families and breeding lines were evaluated, and 179 plants from 46 superior families were selected for additional breeding.