"We are here to defend Italian farming, which is at risk throughout the
country due to an unprecedented crisis caused by the drop in prices below production costs in key sectors of Made in Italy," farmers' association Coldiretti said.
The price of tomatoes has plunged 43 percent from last year, while that of oranges has dropped 30 percent and the price of durum wheat - used to make pasta - is down 27 percent, Coldiretti said in a statement.
"Attackers of Made in Italy attack Italy itself," chanted the protesters, who had gathered in Bari despite the rain, sheltering under umbrellas in Coldiretti yellow, against a backdrop of dozens of blue and green tractors.
The farmers, hit by a mild winter and competition from Moroccan tomatoes, Egyptian strawberries and Tunisian olive oil - all beneficiaries of an EU tax deal - want EU-wide mandatory origin labelling for their products.
They have also suffered from a Russian embargo brought in to retaliate against EU sanctions over Ukraine, which cost the Italian food sector alone €240 million ($268 million) in 2015, according to Coldiretti.