Tesco is leading the food retail sector lower after announcing that chief executive Sir Terry Leahy is to retire next March with Philip Clarke moving up to take his place as CEO at the UK's top supermarket chain.Leahy steps down after 14 years in the top job, a period that has seen Tesco become the dominant force in UK grocery retailing and start to make significant inroads into overseas markets in Asia and more recently the US. He will leave when he reaches 55.Tesco is not the only supermarket undergoing change at the top. Wm Morrison has appointed Waitrose's Richard Hodgson as commercial director. The shares are lower though not as dramatically as Tesco's.An agreed offer from automation technologies giant ABB has sparked a positive reaction in the share price of UK power peripherals supplier Chloride. The board of Chloride has agreed to an all cash offer from ABB that values at it £860m.It leads the electronic & electrical equipment sector - today's best performing sector - higher.Top performing sectors so far todayElectronic & Electrical Equipment 1,842.76 +3.62%Mining 19,608.54 +0.93%Food Producers & Processors 4,865.25 +0.37%Personal Goods 12,519.29 +0.28%Aerospace and Defence 3,158.81 +0.10%Bottom performing sectors so far todayAlternative Energy 5,722.15 -2.83%Oil & Gas Producers 6,871.11 -2.23%Automobiles & Parts 2,782.30 -1.98%Food & Drug Retailers 4,492.72 -1.91%Construction & Materials 3,187.82 -1.87%