He polled 468 votes to defeat five other contestants in the exercise that took place under heavy presence of security personnel.
Mr Lucky Igbokwe came a distant second with 45 votes, while the only female contestant, Mrs Ngozi Merenge, scored five votes.
Other contestants, including Dep. Gov. Ude Oko-Chukwu, Sen. Enyinnaya Abaribe, Sen. Emma Nwaka, had earlier announced their withdrawal from the race.
They were however credited with six, five and four votes, respectively.
Also, Prof. Greg Ibe, who formally defected to the All Progressives Grand Alliance on April 17, was also credited with two.
Other aspirants that withdrew from the race were Chief Ncheta Omerekpe, Mr Enyinnaya Nwafor and Mr Chima Anyaso.
However, they were credited with three, four and five votes, respectively.
The Chairman of the Primary Election Committee and former Gov. Ayo Fayose thanked the delegates for their peaceful conduct during the exercise.
In an acceptance speech, Ikonne expressed gratitude to Gov. Okezie Ikpeazu and PDP for believing in him.
He gave assurance that he would not betray such confidence.
He further assured them that he would deliver victory to the party in the general election.
He promised to tackle the huge infrastructure need of the state, create job for the youths and ensure that women were gainfully engaged, when elected.