Citrofortunella. Citrofortunella are a large group of commercial hybrids that cross the kumquat with other citrus. In the system of citrus taxonomy established by Swingle, kumquats were placed in a different genus, Fortunella, from Citrus, which included citron, mandarin orange, pomelo and papedas. The limequat is a citrofortunella hybrid that is the result of a cross between the Key lime and the kumquat, hybridized by Walter Tennyson Swingle in 1909.