(Reuters) - Shares of Rivian Automotive Inc opened almost 37% higher on the Nasdaq on Wednesday, giving the Amazon-backed electric vehicle maker a market valuation of nearly $93 billion and making it the second most valuable U.S. automaker. Reporting by Noor Zainab Hussain in Bangalore and additional reporting by Niket Nishant; Editing by Arun Koyyur and Anil D’Silva