Im thinking about buying a mother board for mining that has a slot pci express 1.0, I want to know if it is a problem to mine with a GPU R9 290, i will lose hashrate?
In general, no. Mining on the vast majority of algorithms does not require much PCIe bandwidth. Mining with your card in a x16 v1.0 slot will be fine. Most people with multi-GPU rigs use risers that connect their cards to x1 slots and don't notice a difference between having it directly into an x16 v3.0 slot.