Li Na cruises into quarterfinals in Guangzhou

Sept. 29 - 2004 champion Li Na has eased through to the quarterfinals of the WTA Guangzhou International Open after beating compatriot Sun Tiantian in two straight sets: 6-2, 6-1.   Li, Asia's top female tennis player, met with little resistance from national teammate Sun in the mouth-watering Chinese derby and won the match with ease.   Another Chinese player, Chen Yanchong, also burst into the quarterfinals, defeating number-eight seed Anastasiya Yakimova, 6-1, 6-4.   Chen, the 19-year-old wild card, is playing her first WTA Tour quarterfinal.   China's Peng Shuai, however, fell victim to number-one seed Jelena Jankovic, 6-2, 6-3.