Grigor Dimitrov beats qualifier Mackenzie McDonald in five sets
Third seed wins 4-6 6-2 6-4 0-6 8-6
GB's Edmund through to third round
Kyrgios beats Troicki 7-5 6-4 7-6 (7-2)
Nadal beats Mayer in straight sets
Wozniacki saves match points on way to tough win
Image source, ReutersJamie Murray and Brazilian partner Bruno Soares are in doubles action later today, around 04:30 GMT, with the fifth seeds facing Americans Frances Tiafoe and Donald Young.
Naomi Broady and Anna Smith are already out, however, losing 6-2 6-1 to fourth seeds Lucie Safarova and Barbora Strycova from the Czech Republic earlier.
Image source, Getty ImagesSo what sort of test does Kyle Edmund expect Denis Istomin to pose?
"He's obviously one of those guys that's always really solid, really professional, always around the same ranking. You know what you're going to get with him," said Edmund.
"He's going to bring out a level that's going to be tough to beat because he's that solid a player."
Image source, ReutersKyle Edmund claimed the best win of his career to reach the second round, knocking out 11th seed Kevin Anderson in five sets with a 6-7 (4-7) 6-3 3-6 6-3 6-4 victory.
The 23-year-old, ranked 49th, twice came back from a set down and recovered from 2-0 behind in the final set to win in a minute short of four hours.
Edmund's best previous victory at a Grand Slam tournament, in terms of rankings, had been his win over 15th seed Richard Gasquet at the 2016 US Open.
He had lost his only previous encounter with Anderson over five sets at last year's French Open, and was in no mood to suffer a similar defeat by the South African.
Asked if it ranked as his best win to date, Edmund told BBC Radio 5 live: "I think so."
Image source, Getty ImagesHow about this...
Ukraine's Marta Kostyuk has just become the youngest player to reach the third round of a Grand Slam since Mirjana Lucic-Baroni at the US Open in 1997.
The 15-year-old beat Australia's Olivia Rogowska 6-3 7-5 on Margaret Court Arena.
Lucic-Baroni, now 35, is in action herself later today, when she features in the doubles alongside Andrea Petkovic.
BBC Radio 5 live sports extra
BBC Radio 5 live sports extra is on air right now to bring you all the build up to Kyle Edmund's second round meeting with Denis Istomin.
Click the link at the top of this page to listen in.
Piers Newbery
BBC Sport at Melbourne Park
Image source, BBC SportDay two ended, in British terms, out on court 13 with Heather Watson's disappointing defeat by Yulia Putintseva, and day three begins at the same location for Kyle Edmund v Denis Istomin.
Grigor Dimitrov is among the big names to have come a cropper there in recent years, and there is already quite an atmosphere building this morning after an Aussie doubles team kicked off the schedule.
Edmund should not lack support once he gets going - yesterday we saw a large contingent of British fans make the journey out to the edge of Melbourne Park, and there were already plenty in evidence this morning. Let's hope they packed sunblock, water and headgear.
Image source, ReutersAnd then there were two...
Heather Watson's first-round exit on Tuesday means that by day three of the Australian Open only Kyle Edmund and Johanna Konta are left to fight the British corner.
Edmund, the only British male to make the main singles draw, has already showed he is battle hardened enough to trouble the seeds in Melbourne.
The 23-year-old is ready for another tricky test this morning, with Uzbekistan's Denis Istomin standing between him and a place in the last 32.