  In some models of N=1 supersymmetric SU(M) gauge dynamics (hep-th/9503163 and
hep-th/9707244), the tension of a string ending on q external quarks is
proportional to sin(pi q/M), q=1,..., M-1. In this paper we calculate the
ratios of the q-string tensions using the recently derived type IIB gravity
duals of N=1 SUSY gauge theories. Far in the IR these gravity duals contain a
three-sphere with M units of R-R 3-form flux which, upon S-duality, turns into
NS-NS 3-form flux. The confining q-string is described by a D3-brane wrapping a
two-sphere inside the three-sphere with q units of world volume flux. For one
of the gravity dual backgrounds (Maldacena-Nunez) a D3-brane probe calculation
exactly reproduces the sin(pi q/M) dependence, while for another
(Klebanov-Strassler) we find approximate agreement. We speculate on the
connection of the q-string tensions with D-brane tensions in the SU(2) WZW
model.
