  The stability of the ion-temperature gradient mode in quasisymmetric
stellarators is assessed. This is performed using a set of analytical estimates
together with linear gyrokinetic simulations. The peak growth rates, their
corresponding real frequencies and wave-vectors are identified. A comparison is
made between a first-order near-axis expansion model and eleven realistic
designs obtained using numerical optimization methods. It is found that while
the near-axis expansion is able to replicate the growth rates, real frequencies
and perpendicular wave-vector at the inner core (both using simplified
dispersion relations and first-principle gyrokinetic simulations), it leads to
an overestimation of the growth rate at larger radii. An approximate analytic
solution of the ITG dispersion relation for the non-resonant limit suggests
growth rates could be systematically higher in quasi-axisymmetric (QA)
configurations compared to quasi-helically (QH) symmetric ones. However except
for very close to the axis, linear gyrokinetic simulations do not show
systematic differences between QA and QH configurations.
