C. melo because most authors/databases (say The Plant List) don't recognise any infraspecific taxa within C. melo
C. melo subsp. melo because GRIN data base treats it so, but also lists C. melo subsp. agrestis var. agrestis, because wild populations of C. melo are more commonly listed under subsp. agrestis. This should help
- Sebastian, P. et al. 2010. Cucumber (Cucumis sativus) and melon (C. melo) have numerous wild relatives in Asia and Australia, and the sister species of melon is from Australia. Proc. Natl. Acad. Sci. U.S.A. 107:14269–14273. [as Cucumis melo subsp. agrestis].