Without seeds, how do you think navel oranges are grown?
Well, citrus growers sometimes graft buds of one tree onto another. A bud from a lime tree, for example, can be inserted into a slit in the bark of a lemon tree. If the graft works, the bud receives sap from the tree and grows, branching out and bearing fruit. I bet navel oranges are grown by grafting buds onto other trees.
Buds
Where did the very first navel orange bud came from?
The very first bud came from a mutant, seedless orange tree that appeared on a plantation in Brazil.
In the wild, a mutant tree that produced seedless fruit would simply die out, but orange growers thought seedless oranges were a great idea, so they grafted a bud onto another tree, then grafted buds from that tree onto another, and so on.
Original Mutant Tree
Every navel orange in the world can be traced back to that original mutant tree in Brazil.
Most seedless fruits don't come from genetic mutations. Bananas, for example, first came from a cross between two closely related plants, that produced seedless, or sterile, fruit.