  It is shown that a certain sum rule for soft supersymmetry-breaking scalar
masses, which has been recently found in a certain class of superstring models,
is universal for gauge-Yukawa unified models. To explain this coincidence, we
argue that the low-energy remnant of the target-space duality invariance in the
effective supergravity of compactified superstrings can be identified with the
(broken) scale invariance in gauge-Yukawa unified models, and that gauge-Yukawa
unification which is indispensable for the sum rule to be satisfied follows
from the matching of anomalies.
