Market Center sells to the South, in the South

''A bite out of the Big Apple'' was the headline - perhaps rather gleefully written - on Page 1 of the Aug. 15 Atlanta Constitution. The article reported that the electrical fire temporarily blacking out most of New York City's garment district last month had proved an unexpected bonanza for Atlanta's Apparel Mart. The fire struck just two days before a major clothing exhibition was to open at the mart in Atlanta. So department store buyers from California to Massachusetts changed their airline reservations and headed for the Big Peach. The Atlanta fair's attendance was up 23 percent over last year, a third of the increase coming from buyers diverted from Manhattan.

That a regional market center could take up the slack from once all-powerful New York illustrates the decentralization, or regionalization, of the United States. ''New York and Chicago's dominance as a national trade center has been totally diminished,'' claims Sam Williams, manager of the Atlanta Market Center, of which the Apparel Mart is part. Medium-size department store chains and the smaller shops tend to send their buyers to Atlanta or to Dallas, San Francisco, or Los Angeles, he maintains.

Some 10,000 manufacturers are represented in the Atlanta Market Center, which includes showrooms for furniture, carpet, and gifts, as well as clothing. It draws 250,000 people annually, one-quarter of Atlanta's convention business, and generates $8 billion in sales.

The center is also a sort of Southern declaration of marketing independence. Says Mr. Williams, ''What we're doing is completing the vertical integration of the manufacturing, marketing, and distribution of the product. It's made in the South, it's marketed in the South, and it's consumed in the South. We're no longer going through the pipeline of New York and Chicago for the marketing of Southern consumer products.''