"Leucistic" is a specific gene.
To my knowledge, this gene has NOT yet been found in Pantherophis guttattus though it exists in other Pantherophis-genus snakes (most notably Texas rat snakes).
You could theoretically use a Leucistic Texas Rat, breed it to a corn, breed the offspring together to get leucistic animals that are part corn, breed them to corns, breed back the babies to get leucistic animals that are slightly more corn... but they will still be Texas Rat hybrids... and there's a chance that the stroppy temperament that some Texas Rats show will carry through just as much as the pretty blue-eyed-white colour does.
Heck, I've got a female Leucistic Texas rat, a spare male corn... but they aren't going to be breeding, because I just don't think there's a market for a breed of potentially-stroppy and potentially-bug-eyed "North American Rat Snakes" over here... by which I mean "Pantherophis soup".