There's quite a bit more than just the giant fruit. Here's all the similarities I've thought of so far:
•Story opens with a giant, overgrown vegetable created to win a prize
•Mutant vermin overrun fields eating the produce and threatening said prize
•An experiment is designed to rid vermin of desire to eat vegetables
•Experiment goes wrong
•Main character mutates into a vermin hybrid, but this fact is hidden from the other main characters for one act
•Attacks on garden continue, this time performed by the hybrid main character
•Aforementioned giant veggie is used as bait to lure hybrid so the procedure can be reversed
•Once all is set right, the vermin are moved to a sanctuary where they can eat to their hearts' content.
That's...a lot of similarities. All the plot points are basically the same.