A couple months ago, I devoted my column space to what has become the de facto “signature variety” for Long Island wine country: merlot. There are approximately 700 acres of merlot planted on Long Island — roughly 30 percent of the total vineyard acreage — and there are reasons for that. It grows and ripens dependably and consistently, even in all but the most horrid of vintages. That’s important here and why it’s the backbone of the industry.  But the East End isn’t like many parts of Europe where regulations dictate what grapes can be grown where. Long Island growers…