The Tata group has announced that Cyrus Mistry will replace Ratan Tata as the head of the Indian business house. Cyrus Mistry would become Chairman of the Tata group's holding company Tata Sons in December 2012 after the retirement of Ratan Tata.

The shares of the group firms opened on a strong note on the domestic stock exchange following the announcement yesterday but lost stream in the weak market. Tata Power, Tata Coffee and Trent remained in the positive, while high value, IT giant TCS shares rose to Rs 1069.75 in the opening trade but fell into the red with a loss of about one per cent to Rs 1050.60.

Other group units like Rallis, Indian Hotels, Tata Chemicals, Tata Elxi, Tata Global Beverages and Tata Investment Corp opened higher but were not able to sustain gains and fell to negative it the weak share market.

Others including Tata Steel, Tata Tele, Voltas, Tata Communications and Tata Sponge opened mostly flat and were trading at a slight lower level during the time of reporting. There are about 30 listed firms in the Tata group, which comprises of close to 100 operating companies.

The benchmark index of the Bombay Stock Exchange, Sensex fell to 15,560.19 points.