I looked at a lot of Opuntias, there's so many of them! One thing which caught my attention is the two spines, where photos of Opuntia robusta appear to have more. I know the number of spines can vary, but how much? I found one called Opuntia bispinosa, which has varying coloured flowers but I found one which does look like yours Masud, if it's correctly named.
http://www.opuntias.co.uk/pres...
http://fotoalbum.seniorennet.b...
The site above has several pages of Opuntia..
http://fotoalbum.seniorennet.b...
According to the Plant list, Opuntia bispinosa is a synonym of Opuntia anacantha var. utkilio.
http://www.theplantlist.org/tp...
http://www.desert-tropicals.co...
The straight species appears to have orange flowers so that would explain the different flower colour.
http://cactiguide.com/cactus/?...
http://www.google.co.uk/search...
Of course I could be wrong!
Opuntia robusta monstrosa doesn't seem to fit.
http://www.google.co.uk/search...
