Only four matches had finished by the time the courts were flooded by the rains.
Austrian 19th seed Sybille Bammer was the highest ranked player to finish a game but she was easily dismissed by Victoria Azarenka of Belarus 6-1, 6-3.
Home favourite Roberta Vinci gave the sparse crowds something to cheer about as she battled to a 6-4, 4-6, 6-0 victory over Estonia's Kaia Kanepi.
Later in the day both Williams sisters were due to begin their campaigns in the second round.
Venus will play Australia's Samantha Stosur while younger sister Serena will face Ukrainian doubles specialist Alona Bondarenko.
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