The turbulent dynamo action in a shear flow is considered by making use of
a quasilinear approximation and neglecting the back-reaction of a generated
magnetic field on turbulence. The shear can stretch turbulent magnetic fie
ld lines in such a way that turbulent motions may become suitable for the g
eneration of a large-scale magnetic field even in the absence of any strati
fication. There is no ct-effect present in our computations. The nonlocal i
ntegral representation for the mean electromotive force is derived, which i
s valid even if the turbulent length scale is comparable to that of the mea
n field. The basic result is that the presence of shear changes the type of
the equation governing the mean magnetic field so that the latter indeed c
an be generated even in the absence of rotation or large-scale stratificati
on of turbulence. To this end, however, if the turbulence field has a monot
onously falling ("turbulence-type") spectrum, a rather strong shear is need
ed. For Kepler disks the instability condition reads tau (corr) > 2 tau (ro
t)/pi, which might be fulfilled in the transition layers between star and d
isk. A system, on the other hand, consisting of random waves, large-scale m
agnetic fields and mean-field shear flow can never be stable.