Fate: The pearl was grown from a piece of sand lying on the ocean floor, its existence purely happened by chance. This lends to the theme of fate because a pearl's creation is just that: made by fate.
Fortune: Due to the pearl's rarity a monetary value was assigned to it, making it a materialistic item worth a large sum of money. Once Kino returns with it, he brags about all he can do and buy with the money from its sale.
Greed/Evil: By the end of the novella, the pearl is coveted and represents all the evil and greed in the world. The pearl only brought death and destruction to the family, as it attracted thieves who desired it.