One of the biggest potential M&A deals of the year just fell apart

Agricultural products maker Monsanto revealed Wednesday August 26 that it is no longer pursuing a deal for Syngenta, which makes crop protection products.

The transaction would have been worth about $45 billion.

Monsanto first approached Syngenta about a deal in June, and was rebuffed. The company then made a second improved offer on August 18 and offered a whopping $3 billion breakup fee to entice Syngenta into talks.

News of Monsanto's increased bid sent Syngenta shares up more than 7% earlier this week.

Monsanto shares rose about 5% in the immediate wake of reports that the deal had collapsed. Syngenta shares fell for more than 15% in late morning trading Wednesday.

Investors in Syngenta include institutional investors T. Rowe Price and Blackrock, along with hedge funds Raimus LLC and Steve Cohen's Point72.