JOHANNESBURG ( Reuters) - South Africa's rand weakened against the dollar on Wednesday after Finance Minister Pravin Gordhan cut economic growth forecast and predicted wider budget deficits in his medium-term budget statement. At 1539 GMT, the rand traded at 13.9100 per dollar, 1.09 percent weaker from its New York close on Tuesday. "Gordhan's budget plans rely on an economic acceleration that we believe is unlikely to materialise," Capital Economics Africa economist John Ashbourne said in a note. "If growth stays weak, South Africa will over-shoot its deficit and debt targets." The minister said the economy would grow by 0.5 percent in 2016, down from an estimate of 0.9 percent in February and forecast wider budget deficits for the next three fiscal years. On the bourse, stocks ended lower, with petrochemical giant Sasol topping the decliners' list as worries over oil oversupply weighed crude prices. [O/R] Sasol, which makes fuel from coal and gas but sells it at the same price as companies that import and refine crude oil, dropped 2.3 percent to 387.61 rand. The JSE benchmark Top-40 index was off 0.42 percent at 45,011 and the All-share index ended 0.38 percent lower at 51,552. Trading volumes were low with around 172 million shares changing hands, well below last year's daily average of 296 million shares. Government bonds weakened alongside the currency, with the yield for the benchmark instrument due in 2026 adding 9 basis points to 8.88 percent. (Reporting by Tiisetso Motsoeneng and Olivia Kumwenda-Mtambo; Editing by Joe Brock)