Rout said he would work for the ouster of the Patnaik government in the Assembly elections scheduled to be held along with the Lok Sabha polls.
Pradhan said his joining the BJP will strengthen the party in the state.
Rout had been a minister in all the four governments headed by Patnaik and was seen to be close to him before falling out with the BJD president.
He is the second BJD bigwig to switch over to the saffron camp. Recently, Bijayant Panda also joined the BJP.
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