Yes, it will work just fine. In fact, here are Gigabyte's words:
1 x PCI Express x16 slot, running at x16 (PCIEX16)
(The PCIEX16 slot conforms to PCI Express 3.0 standard.)
* For optimum performance, if only one PCI Express graphics card is to be installed, be sure to install it in the PCIEX16 slot.