Sahni, the outgoing JD(U) MLA from Morwa Assembly seat in Samastipur district, sent his resignation to the Chief Minister's Office today.
He later joined the BJP in the presence of its state unit president Mangal Pandey who welcomed him to the party-fold, saying that his decision would help the prospects of the NDA candidates at the hustings.
The minister, who hails from Nishad community, was denied ticket by the JD(U) leadership from Morwa seat which goes to polls in the first phase on October 12.