What varieties are allowed to produce Champagne?

Like almost all European wine regions, the Champagne region was devastated by phylloxera in the late 19th century, and this changed its history.
What is phylloxera and what does it have to do with the varieties allowed in the Champagne specification? Phylloxera is a vine pest that was imported to France on vine cuttings from America. At one stage in its life cycle, phylloxera feeds on the vine roots, piercing them and creating wounds that promote the growth of infections that eventually block the flow of nutrients and kill the plant.
While native American vines evolved with the louse and thus developed defenses against its attack, European vines lacked such protection. Fortunately, it was discovered that grafting European vines onto American rootstocks combated the effects of phylloxera. Today, the vast majority of European vineyards are grafted.

Before phylloxera, far more grape varieties were grown in Europe than today. More than a hundred varieties were registered in some French regions, while today there are only a handful. Historically, winemakers have always preferred to keep their vineyards as diverse as possible. This tended to protect crops from total catastrophe: if one variety failed to ripen or was attacked by a disease, at least some of the other varieties would produce crops and the winemaker would still have an income or wine to drink.

When growers were forced to replant because of phylloxera, however, they focused on the varieties known to work best in their region: the easiest to grow, the most abundant, the most disease-resistant, and those that produced the easiest fruit and wines to sell. This is why Pinot Noir (about 38 percent of today's plantings in Champagne), Pinot Meunier (about 32 percent) and Chardonnay (about 30 percent) dominated plantings throughout the Champagne region.
tWhat are the rarest grape varieties in Champagne? The least known grape varieties among those allowed to produce Champagne are Arbanne, Pinot Gris, Pinot Blanc and Petit Meslier. If we add to these Pinot Noir, Pinot Meunier and Chardonnay, there are seven varieties allowed in Champagne.

Is there a champagne that uses all seven permitted grape varieties? Aurélien Laherte 's Les 7 champagne uses all seven permitted grape varieties.