The University of Massachusetts board of trustees rewrote its hiring and promotion policies yesterday to enable husbands and wives to serve on the same staff.

      The board's new policy sets competence as the only qualification for employment, tenure and promotion.

      In at least one well-publicized case, the trustees had declined to rehire a woman physics professor at Umass Boston because her husband held a tenured appointment in the same department.

      The denial of re-employment to Freda Salzman, associate professor of physics from 1965 to 1969, has evoked recent protests and petitions from the National Organization for Women and other groups seeking to ensure women's job opportunities.

      After the trustees meeting, university president Robert Wood said the new guidelines "would definitely have created a different situation" in Mrs. Salzman's case.

      However, Wood added, the trustees' ruling will not be applied retroactively, "and Mrs. Salzman's case is not considered to be pending at the moment."

      Mrs. Salzman and Wood met informally at his request Dec. 13, but she has yet to meet with him on a formal basis to exercise her right of appeal on the decision not to rehire her.

      The trustees' statement as adopted said that "demonstrated qualifications or performance" would be the sole criterion in all hiring and pay decisions.

      The trustees barred any employee from participating in a hiring or pay decision involving a family member or in-law.

      Originally accompanying the trustees' policy ruling was a plan for implementation drafted by Wood, specifying that relatives of employees must be "as well qualified as any other available candidate," a restriction not placed on other prospective employees. Other candidates need only be demonstrably competent for their jobs.

      Wood withdrew his proposal to await "further study" after a National Organization for Women (NOW) spokesman charged the policy was discriminatory. She cited recent court decisions and Federal agency rulings and suggested the implementation plan was illegal.

      The NOW contentions included an assertion that anti-nepotism rules tend in practice to work against the hiring of qualified wives of faculty members.

      In another major action, the trustees . . .