While over 90% of German wine grapes grown are the principal varieties discussed in Part I, many other wine grapes are found in Germany, with around 135 varieties being grown, many in very small quantities. This chart shows a selection of the numerous cross-breeds produced by German agricultural scientists and growers, in the never-ending quest to improve yields, protect against fungal infections and enhance quality. Though few of these have proved as successful as the principal varieties, and many have declined over time, some have grown in popularity and have taken their place alongside the principal varieties, such as Bacchus and Regent.