Thank you so much volovicg for your help.
But when the region is already selected, the toggling option doesn't work (i.e) After using the shortcut I have to select another nearby region on the track to select the current track on region selection, for this instead of selecting a nearby region to select the track I can manually click on the track. Also using this key command to and fro makes inconvenienced.
I'm bit confused whether I do it in the right order.
Thanks