  A class of modified gravity, known as $f(R)$-gravity, has presently been
applied to Cosmology as a realistic alternative to dark energy. In this paper
we use the most recent Type-Ia Supernova (SNe Ia) data, the so-called
\emph{Union} sample of 307 SNe Ia, to place bounds on a theory of the form
$f(R)=R - \beta/R^n$ within the Palatini approach. Given the complementarity of
SNe Ia data with other cosmological observables, a joint analysis with
measurements of baryon acoustic oscillation peak and estimates of the {\rm CMB}
shift parameter is also performed. We show that, for the allowed intervals of
$n$, $\Omega_{mo}$, and $\beta$, models based on $f(R) = R - \beta/R^{n}$
gravity in the Palatini approach can produce the sequence of
radiation-dominated, matter-dominated, and accelerating periods without need of
dark energy.
