Gains of about 1% each in tech heavyweights Microsoft MSFT.O and Apple AAPL.O also helped support the S&P 500. By Lewis Krauskopf, Devik Jain and Sruthi Shankar June 23 (Reuters) - Wall Street's main indexes were mixed in choppy trading on Thursday, as gains in defensive shares countered declines for economically sensitive groups amid growing worries about a recession. In his second day of testifying before Congress, U.S. central bank chief Jerome Powell said the Fed's commitment to reining in 40-year-high inflation is "unconditional" but also comes with the risk of higher unemployment.