Grapes are an important symbol.

Grapes were a symbol of the bounty of the promised land. Check out this report when the spies went to search the land, they "cut down from thence a branch with one cluster of grapes, and they bare it between two upon a staff" 

Isaiah teaches about our good works with a symbol of good grapes and wild grapes or sour grapes.

"What could have been done more to my vineyard, that I have not done in it? wherefore, when I looked that it should bring forth grapes, brought it forth wild grapes?"

Grapes and vines are symbolic of the Savior.

This prophecy about Judah clearly points toward the Savior, "The sceptre shall not depart from Judah, nor a lawgiver from between his feet, until Shiloh come; and unto him shall the gathering of the people be. Binding his foal unto the vine, and his ass's colt unto the choice vine; he washed his garments in wine, and his clothes in the blood of grapes"

Jesus himself taught that He is the True Vine:

"I am the vine, ye are the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing."