Technical Abstract: Understanding the relationship between plant morphology and disease resistance is crucial to successful breeding, particularly resistance to lettuce drop caused by Sclerotinia minor. Latin type lettuce cultivars are small plants with upright leaves longer than they are wide, similar to romaine type cultivars but considerably shorter. The objective of this research was to determine the segregation for plant height in romaine x Latin crosses and characterize the effect of height on lettuce drop resistance derived from the Latin cultivar Eruption. The frequency of short plants was conditioned by a single recessive gene in F1, F2 and F3 families from nine romaine x Latin crosses tested in 2007, 2008, and 2009 field experiments. The gene, named short leaf 1 (sl1), affects only leaf length in rosette plants and is morphologically distinct from other dwarfing genes. In two S. minor infested field experiments with 75 F3 romaine x Eruption families, no difference in disease incidence was detected between short (sl1, sl1), tall (Sl1, Sl1) or segregating families. Therefore, development of romaine cultivars from crosses with ‘Eruption’ is feasible.