AUGUSTA — Gov. John R. McKernan, issuing his first veto of the 1990 legislative session Monday, rejected a bill to change the composition of the board that oversees Maine’s technical college system.

McKernan said he endorses a requirement in the bill that the system’s trustees develop and update a five-year plan. But he said he objects to a provision that would remove the commissioners of the Labor Department and the Economic and Community Development Department as ex-officio trustees.

“The mission of the technical college system is inextricably related to the services and resources” provided by the two state agencies, the Republican governor said in a written message to lawmakers.

McKernan cited a projected shortage of Maine workers that is expected to reach 35,000 by 1995. The Labor Department, which administers $18 million a year in job-training money, and the Economic and Community Development Department, which pumps about $13 million into programs designed to create or preserve jobs, can both help the system meet the state’s needs, he said.

“Because there is no rational reason to strip the technical colleges of their direct access to the guidance of the state’s highest labor and economic development leaders, and because the technical colleges clearly benefit from the expertise of these leaders, I urge you to sustain this veto,” he wrote.