  In this work we present and discuss the observations of the Mn abundances for
247 FGK dwarfs, located in the Galactic disc with metallicity -1<Fe/H]<+0.3.
The observed stars belong to the substructures of the Galaxy thick and thin
discs, and to the Hercules stream. The observations were conducted using the
1.93 m telescope at Observatoire de Haute-Provence (OHP, France) equipped with
the echelle type spectrographs ELODIE and SOPHIE. The abundances were derived
under the LTE approximation, with an average error for the [Mn/Fe] ratio of
0.10 dex. For most of the stars in the sample Mn abundances are not available
in the literature. We obtain an evolution of [Mn/Fe] ratio with the metallicity
[Fe/H] consistent with previous data compilations. In particular, within the
metallicity range covered by our stellar sample the [Mn/Fe] ratio is increasing
with the increase of metallicity. This due to the contribution to the Galactic
chemical evolution of Mn and Fe from thermonuclear supernovae. We confirm the
baseline scenario where most of the Mn in the Galactic disc and in the Sun is
made by thermonuclear supernovae. In particular, the effective contribution
from core-collapse supernovae to the Mn in the Solar system is about 10-20%.
However, present uncertainties affecting the production of Mn and Fe in
thermonuclear supernovae are limiting the constraining power of the observed
[Mn/Fe] trend in the Galactic discs on, e.g., the frequency of different
thermonuclear supernovae populations. The different production of these two
elements in different types of thermonuclear supernovae needs to be
disentangled by the dependence of their relative production on the metallicity
of the supernova progenitor.
