According to the recipe in BYO, which had input from the SN brewers Torpedo
Bittering - Magnum at 60 minutes
Taste - Magnum & Crystal at 5 minutes (28g each)
Dry Hop - Magnum, Crystal & Citra Dry Hoped (19g each)
All for a 5US Gal ~20L batch
The hops in Corona are as far as I know all extract, probably pre-isomerised and UV stabilised (see Tetra, Hexa, Hydro) so what they are made from is totally irrelevant, these extracts have no varietal character - just bitterness. So I suspect the hop are very carefully selected on price.
Topaz - the Australian variety - holds the world record for kg of Alpha/ Hectare, it was developed as an Extract producing variety, personally I quite like it as both a bittering and late hop.
Mark