Melbourne: Ricky Ponting's Australia are now just one defeat away from losing their world number one crown after South Africa crushed them by nine wickets in the second Test to register their first ever series victory Down Under.

Having taken an unassailable 2-0 lead in the series, South Africa will topple Australia from their top ranking if Graeme Smith's men can win the third and final Test in Sydney.

Resuming on 30 for no loss, South Africa needed 42 overs to score the remaining 153 runs for a memorable win and the moment came soon after lunch when Hashim Amla flicked Michael Clarke behind square leg for two runs.

In a match where Smith struck two fifties, JP Duminy scored his maiden hundred and Ponting scored 101 and 99, Dale Steyn was adjudged Man of the Match for his match haul of 10 for 154 besides the crucial 76 he scored in the first innings.

Graeme Smith's cool 75 (94b, 10x4) set up South Africa's first series win in Australia as they eased to a nine-wicket victory that destroyed the hosts' world-beating reputation. Rain was the home side's only chance on the fifth day and while there was some in the morning, play began on time, Smith quickly attacked the wilting bowling attack, and the success was sealed after lunch when Hashim Amla flicked Michael Clarke for two behind square leg.

Ponting, meanwhile, became the first Australian captain in 16 years to suffer a series defeat on home soil. Last time Australia lost a series at home was against the West Indies in 1992-93. If they succumb again in Sydney from Saturday it will be Smith's team that is officially No. 1. While Ponting's men cling to the top rating, the best they can hope for in the unofficial rankings is third following their performances over the past three months.

Smith came to Australia with a calm confidence and his strength and drive have been immense. In the first Test his 108 put South Africa on track for an incredible chase of 414 and in Melbourne his half-century ensured there would be no costly slips.

The Australian injury epidemic - Andrew Symonds has a knee problem and Shane Watson will be out for up to six months with back stress fractures - will ensure a new-look team will walk out in Sydney. Australia are learning how the rest of the world lived over the past decade.

Reports by session

1st Session: Runs 102, Wkt 1, Ovr 27
2nd Session: Runs 51, Wkt 0, Ovr 15
3rd Session: Not required

Brief Score: South Africa 459 & 183/1 (Smith 75, McKenzie 59*) beat Australia 394 & 247 by 9 wickets.
Full Scoreboard

South Africa beat Australia in home series. SA team to beat them their own backyard since 1992-93. Here are the last five instances when the Aussies lost a series at home.