South African retailer Woolworths reported a 20.5 percent jump in pretax profit on Thursday, defying feeble growth in Africa's most advanced economy. The nation's retailers are battling to boost sales as consumers rein in spending in the face of high unemployment and rising fuel and transport prices, but Woolworths is faring better than rivals thanks to the appeal of its upmarket food and clothing to high-income customers.Sales increased by 55 percent to 61.97 billion rand in the first six months of the year, though headline earnings per share - the most widely watched profit measure in South Africa - were up only 7 percent, diluted by stock issued to fund last year's acquisition of department store chain David Jones.Shares in Woolworths have gained about 30 percent since the start of the year, outperforming a 3 percent decline for the Johannesburg bourse's all-share index...