[Orgmode] Difference if exporting a table to latex

[Seweryn Kokot]

Hello,

First I had a table

<code>
| M_r | /33.22/ |
</code>

in an .org file and exporting the table to latex gave the following

\begin{center}
\begin{tabular}{ll}
 M$_r$  &  \emph{33.22}  \\
\end{tabular}
\end{center}

Then as I needed more control so I moved to a .tex file. This time, using a 
radio table, the converted table is quite different i.e. no $$ around _r, and 
no \emph env.

<code>
% BEGIN RECEIVE ORGTBL test1
\begin{tabular}{ll}
M_r & /33.22/ \\
\end{tabular}
% END RECEIVE ORGTBL test1

\begin{comment}
#+ORGTBL: SEND test1 orgtbl-to-latex
| M_r | /33.22/ |
\end{comment}
</code>

Is it a bug in `orgtbl-to-latex' or how I can get the same behaviour as in 
exporting from an .org file?