  The purpose of the paper is to derive linkage principle for modular
representations of ortho-symplectic supergroups. We follow the approach of Doty
and investigate in detail the representation theory of the orthosymplectic
group $OSP(2|1)$ and that of its Frobenius thickening. Using the description of
flags and adjacent Borel supersubgroups we derive first the strong linkage for
the Frobenius thickening $G_rT$ of the orthosymplectic supergroup $G$ of type
$SpO(2m|2n+1)$ and $SpO(2m|2n)$. Based on this, we derive the linkage principle
for orthosymplectic supergroup $SpO(2m|2n+1)$ and $SpO(2m|2n)$.
