TOKYO (Reuters) -Japan's ruling party picked conservative nationalist Sanae Takaichi as its head on Saturday, putting her on course to become the country's first female prime minister in a move set to jolt investors and neighbours. The Liberal Democratic Party, which has ruled Japan for almost all of the postwar era, elected Takaichi, 64, to regain trust from a public angered by rising prices and drawn to opposition groups promising stimulus and clampdowns on migrants. A vote in parliament to choose a replacement for outgoing Shigeru Ishiba is expected to be held on October 15.