If you write genres that have hardly any crossover such as horror and romance, you might need different agents most likely down the line unless you self-publish one of the genres on the side. If you're a new author, don't worry about this yet. Try to get an agent for one genre you write first. Pick the genre you're most passionate about and work with it and focus on the other at a later time. Who knows? You might get lucky and meet an agent that represents both of what you write. But, it is not uncommon to have different agents if the genres you write for are so split in the audiences there is hardly any crossover. If you get an agent, maybe your agent can lead you to someone who represents your other work.