Abstract Diseases, particularly gummy stem blight [Didymella bryoniae (Auersw.) Rehm], downy mildew [Pseudoperonospora cubensis (Berk, and Curt.) Rostow], and powdery mildew [Sphaerotheca fuliginea (Schlecht) Poll], are major factors limiting production of muskmelon in the southern United States (Anonymous, 1962; Chiu, 1948; Ellis, 1951; Norton and Prasad, 1965; Prasad and Norton, 1967; Winstead et al., 1960). Severe economic losses have been reported in the field, in transit, and in storage. Although satisfactory control of gummy stem blight (GSB), downy mildew (DM), and powdery mildew (PM) may be accomplished with the proper application of organic fungicides during normal weather conditions, chemical control is not effective during periods of high humidity and rainfall. Furthermore, only three cultivars—Chilton, Gulfcoast, and AU-rora-are reported to be resistant to GSB (Norton, 1971; Norton, 1972; Norton et al., 1985). The discovery that plant introduction 140471 had a high level of resistance to GSB (Sowell et al., 1966) led to the initiation of an Alabama Agricultural Experiment Station muskmelon breeding program to develop multiple disease-resistant breeding lines with high yields of excellent-quality fruit (Norton and Prasad, 1965; Prasad and Norton, 1967).