Summer squash (Cucurbita pepo) is an important vegetable crop which is unfortunately susceptible to many diseases, including fungal and viral plant infections. One major disease affecting C. pepo is the potyvirus Zucchini yellow mosaic virus (ZYMV). Efforts to breed disease resistant varieties of C. pepo usually involve introgressing resistance from related species such as Cucurbita moschata. Introgressing disease resistance genes from C. moschata into C. pepo is laborious, tools for marker assisted breeding in Cucurbita are lacking, and disease resistance genes introgressed into C. pepo from C. moschata landrace 'Nigerian Local' are an important source of resistance to diseases, including ZYMV, in C. pepo. Therefore the goals of this research were first to create a set of tools for studying disease resistance genes from C. moschata which could be applied to assist in breeding disease resistant C. pepo varieties, and then to use these tools to characterize ZYMV resistance in C. pepo from a C. moschata source. This involved creating a genetic linkage map using a C. pepo x C. moschata derived mapping population; sequencing candidate disease resistance genes in C. moschata and placing them on the genetic linkage map; and creating a C. pepo introgression line library with C. moschata as the donor. When these tools were created, they were then used to study ZYMV resistance introgressed from C. moschata into C. pepo by screening introgression lines for ZYMV resistance and mapping ZYMV resistance loci.