Despite the rating downgrades of UPL Corporation by Fitch and S&P after the announcement of its plans to acquire Florida-based agrochemicals player Arysta LifeScience for USD 4.2 billion in a leveraged buyout, the parent UPL's stock rallied 15 per cent today. While Fitch today revised the rating outlook on the Mauritius-based firm to negative from stable, S&P downgraded the same to stable from positive over the weekend. But Fitch has affirmed its long-term foreign-currency issuer default rating at BBB-.