Researchers from Tel Aviv University in Israel studied a collection of ancient texts, art, artifacts and plant remains such as fossil pollen grains, charcoals, seeds.
Until the first century AD, the only citrus produce available to the ancient Romans were the extremely rare and inordinately expensive citrons and lemons, they said.
"Today, citrus orchards are a major component of the Mediterranean landscape and one of the most important cultivated fruits in the region. But citrus is not native to the Mediterranean Basin and originated in Southeast Asia," said Dafna Langgut, from Tel Aviv University in Israel.
"All other citrus fruits most probably spread more than a millennium later for economic reasons," she added.
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At first, Romans only had access to rough-skinned citrons, also known as etrogim - mostly rind and dry, tasteless flesh. The citron arrived in Rome from what is now Israel.
The earliest botanical remains of the citron were identified in a Persian royal garden near Jerusalem and dated to the 5th-4th centuries BC.
It is presumed that it spread from there to other locations around the Mediterranean, researchers said.
It appears that the citron was considered a valuable commodity due to its healing qualities, symbolic use, pleasant odour and rarity, researchers said.
Only the rich could have afforded it. Its spread therefore was helped more by its high social status, its significance in religion and its unique features, rather than its culinary qualities, they said.
Sour oranges, limes and pomelos were introduced to the West by Muslim traders via Sicily and the Iberian Peninsula much later, in the 10th century AD, Langgut said.
Researchers found that the sweet orange associated with Israel today only dates as far back as the 15th century and was the product of a trade route established by the Genoese and, later, the Portuguese.
The sticky-sweet mandarin was introduced to the Mediterranean in the beginning of the 19th century, they said.
"It wasn't until the 15th century that the sweet orange arrived on European tables. By the time mandarins appeared in the 19th century, citrus fruits were considered commonplace. They were cash crops rather than luxury items," said Lanngut.