In this YouTube video at 12:29, you can see that DOTS the Seedot has Bide and Harden.
As for why this is the case, the Seedot that you receive will always be the same level as the Ralts you trade over. In this example, the Ralts sent over was level 4, so the Seedot is also level 4. At level 4, Seedot learns Bide and Harden and no other moves. You can see what moves the Seedot will have by referencing it's learnset in Emerald.
Source for same level claim. In the third paragraph, it says, "Prior to Generation V, every Pokémon has the same level as the Pokémon it was traded for."
Hope I helped!