Colonies of Genoa and Venice in Palestine also took on agricultural ventures in their concessions. They especially cultivated Sugar for export to Europe. Sugar cane had been introduced in Palestine by the Arabs. To work on the sugar fields, Italian colonists utilized slaves or serfs of Arab or Syrian origin, or local serfs. Sugar manufacturing began in Tyre. In the 13th century, Sugar production continued to increase in Palestine, and merchants could export it duty-free through the port of Acre until its conquest in 1291. This sugar exploitation system pioneered in the Kingdom of Jerusalem is seen as a precursor to the sugar plantations in the Americas.