<input class="input_mayuscula" type="text" name="sistema_enc" value="<?php echo $alm->__GET('sistema_enc'); ?>" style="width:100%;" />

<select name="sistema_enc" class="input_mayuscula" value="<?php echo $alm->__GET('sistema_enc'); ?>">
  <option value=""></option>
  <option value="MRW">MRW</option>
  <option value="DOMESA">DOMESA</option>
  <option value="GRUPOO ZOOM">GRUPO ZOOM</option>
  <option value="TEALCA">TEALCA</option>
  <option value="SEREX">SEREX</option>
</select>