I have finally solved my problem. The problem is that when you use a texture with an alpha channel (transparency), maya does its own channel wich is wrong. To solve this :Open Hypershade window. By clicking . See Open Hypershade Window from official maya's documentation for more informations. Right click on your material and drag to "Graph Network". In the Graph Network, unpin "Out Alpha" to "Transparency" connection by dragging it in the void.