* Crosswinds split peloton early in the race * Germany and France trapped behind * Three world champions on podium as Cavendish second and Boonen third (Adds details, quotes) Oct 16 (Reuters) - Peter Sagan became the first rider since 2007 to retain his world championship road race title when he perfectly timed his sprint in Doha on Sunday. The Slovakian, who has won seven Tour de France stages as well as the points classification five times in a row, was on the right side of an early split of the peloton and kept a low profile until the final straight. With only two team mates to help him, while the biggest cycling nations have nine-man teams, Sagan became the first road race rider to retain his rainbow jersey since Italian Paulo Bettini nine years ago. More...