By Peter Travers
November 14, 1988 12:00 PM

>Oscar loves actresses in tragic roles that let them display their heavy mettle. This fall has produced a bumper crop of contenders:

•Diane Keaton (The Good Mother) She’s heart wrenching as a divorced parent torn by a custody case in which she must choose between her child and lover.

•Jodie Foster (The Accused) She’s powerfully moving as a blue-collar victim of gang rape now looking for justice.

•Gena Rowlands (Another Woman) She’s haunting as an academic who finds that her career has cut her off from life.

•Shirley MacLaine (Madame Sousatzka) She’s dazzling as a piano teacher whose rigid standards have cost her happiness.

•Sigourney Weaver (Gorillas in the Mist) She’s electrifying as Dian Fossey, the American primatologist who gave her life to save central Africa’s mountain gorillas.