Discover has announced that beginning September 16, its credit and debit cards will be compatible with Apple Pay. Discover is also giving cardholders who add a card to Apple Pay a Cashback Bonus if they use that card with Apple Pay by the end of 2015.
From Discover:
From September 16, to the end of the year, cardmembers who pay with their Discover card using Apple Pay will automatically earn an extra 10% Cashback Bonus on up to $10,000 of in-store purchases. Discover it Miles, Miles and Escape cardmembers will earn an extra 10 miles per dollar on up to $10,000 of in-store purchases.
It should be noted that September 16 is the release date for iOS 9, and you might need to update to the new OS on your iPhone in order to add your Discover card. iOS 9 will bring support for store reward cards in Apple Pay as well.
Source: Discover