Puglia, the 'heel' of the Italian peninsula is well regarded for its hot climate, ripe red wines, though only recently because of quality. The hot, flat terrain was well suited to bulk wine production and agriculture and only recently have trends begun to change. Wine making in Puglia dates back to the ancient Greek settlers, who brought many of the local grape vines with them, and today the quality is improving dramatically. The struggle for local producers in Puglia is to tame the arid climate and the high sugar levels that develop in the grapes. Primitivo is the most distinctive product, with Primitivo di Manduria a well regarded dry red DOC and the region's only DOCG wine being the sweet Primitivo di Manduria Dolce Naturale. Recently, geneticists confirmed that the Primitivo grape is actually just an early ripening clone of Zinfandel (which originated in Croatia). The increased popularity for Primitivo has been a boon for the region (some California wine makers have even started labeling their wine Primitivo!). Negroamaro is also a distinctively Apulian grape, and true to its name produces a slightly bitter, deeply colored, and tannic wine. Notable DOC wines also include Castel del Monte, (made mostly from Uva di Troia and Aglianico), Salice Salentino (made mostly from Negroamaro), and Galatina (a blend of many varietals). Other Italian varietals are found here in quantity, including Montepulciano, Malvasia Nera, and Sangiovese; these are frequently permitted in most local DOC blends.