Answer: It seems to me that large pumpkin varities are more succeptible than others to cracking on the main stem or "trunk" from which all the vines grow. If vines are wilting, perhaps the cracks are severe enough to restrict water, but you'd think the moisture stress would be equal among the vines. Perhaps the wilting vine isn't well rooted along its length. Roots that spring from leaf axils along a vine do route a lot of water to that vine. Try burying the leaf axils (the spot where the leaves emerge from the vine) and see if resulting root growth makes a difference.
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