Erroll B. Davis Jr., who has led the University System of Georgia since 2006, today announced that he would retire when his five-year contract expires next June. In announcing his departure he cited his contract and the need for his successor to establish a relationship with the state’s next governor. (Gov. Sonny Perdue, a Republican, is ineligible to seek another term.) Mr. Davis, a former energy executive, earned plaudits for bringing business efficiencies to the 35-institution system during several years of tight budgets. Recently he received negative publicity over his long tenure on BP’s Board of Directors, a spot he relinquished shortly before the company’s April oil-rig accident.