〜となる: become; turn into; end up as (formal)

Noun + となる: "become", like 〜になる, but with a sense of a final result or an official status. Common in writing and news.

雨となる "it turns to rain", 中止となった "it ended up cancelled", 優勝した選手が代表となる "the winner becomes the representative". に can almost always replace と; と sounds more formal and final.