The body of the woman, who is believed to have been killed in August 2013, has never been found, Ansa reported.
According to the police, Francesca Bellocco, 44, was having an affair with the head of another mafia group, Domenico Cacciola, who disappeared at the same time.
Her son, Francesco Barone, is accused of her murder and of hiding the body. It was he and his father Salvatore who reported the woman as missing.
The two families, the Cacciolas and the Bellocos, have long been at odds in the southern Italian region of Calabria.
The affair between Francesca Bellocco and Domenico Cacciola had been discovered by the families, who had tried to stop it to avoid a clan war, La Repubblica reported, but the couple reportedly carried on.
By Anna Pujol Mazzini