Kiernan will continue to be involved as a committee man with the Five Nations, the International Rugby Football Board, the Irish Rugby Union and European Rugby Cup Ltd.
Hosie, 52, refereed 22 internationals before joining the Scottish Rugby Union in 1986. He has served on the Five Nations for five years, is chairman of the Laws Committee of the IRFB and is also on the Four Home Unions Tours Committee. "I am keen to follow up all the good work that Tom Kiernan achieved over the years," Hosie said.
"The Five Nations is still the jewel in the crown, and it is my wish and desire to make this competition even better."
Richard Jasinski, the 10th secretary of the Welsh Rugby Union and one of the guiding forces behind the Millennium Stadium project, has resigned his post and will leave the job he has occupied for the past 15 months at the end of October.
The 50-year-old former managing director of the Cardiff-based Powell Duffryn Standard Ltd is returning to work in the private sector.
"The WRU regrets the departure of Mr Jasinski, particularly having regard to the important role he played during a period of great transition and activity both as union secretary and as a director of Millennium Stadium plc," said a WRU spokesman.
Wales' top eight clubs will face opposition from South Africa, Canada, Namibia, Spain and Argentina in a pounds 300,000 Challenge Trophy tournament to be played in two phases this season.
The Premier League clubs will be split into two pools of four to play a domestic round of matches before Christmas. The overseas teams will come to Wales in January to play in the second phase.
Northern Transvaal will represent South Africa; Cordoba, Rosario and Tucuman will travel from Argentina, and national sides from Canada, Spain and Namibia will also play in the tournament.
The SRU has announced that Scotland A will play Northern Transvaal at a Scottish venue on 23 January, the same weekend as the senior Scotland and Under-21 teams play Italy in Treviso. Italy were unhappy about playing a senior and A fixture on the same weekend, as had been originally scheduled.
The Scots defeated Northern Transvaal during their summer tour of southern Africa, three weeks after the South African provincial side had beaten the British Lions.
The match against Northern Transvaal will follow a short tour by another southern hemisphere Super 12 side, ACT, who will play each of the four Scottish districts between 18 November and 5 December.Reuse content