Not all rootstock is the same, as your last paragraph indicated. Various rootstock provide different a
properties. While some are more phylloxera resistant, others might be more drought resistant. And still others might provide more vigor. When planting a vineyard on rootstock, careful consideration of the needs of the vineyard should be taken into account to get the best results.
Also, within the last few years, a study out of the Oregon State University Extension Service shows that dropping fruit generally does not make better wine.
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