Turkish stocks drop after Erdogan's main rival detained

** Turkish stocks drop sharply on Wednesday after authorities detained President Tayyip Erdogan's main political rival

** Istanbul's benchmark BIST 100 XU100 is down 4.37% at 0741 GMT

** The index recoups slightly after falling as much as 6.87% earlier and triggering market-wide circuit breaker and a trading halt that lasted until 0730 GMT

** Main banking index (.XBANK) falls 6.42%