Amazon.com Inc. and Whole Foods Market Inc. said Thursday they will lower prices on a range of groceries on Monday to mark the close of Amazon’s $13.7 billion acquisition of the organic grocer.

The price of items including avocados, bananas, organic baby kale and salmon will come down, the companies said in a joint statement. The goal is to “make organic food more affordable for everyone.”

The companies AMZN, +2.70% US:WFM will also start to integrate Amazon Prime into Whole Foods’ point-of-sale system.

“[W]e will make Amazon Prime the customer rewards program at Whole Foods Market and continuously lower prices as we invent together,” said Jeff Wilke, CEO of Amazon worldwide consumer.

The companies are planning to invest in logistics and merchandising as a way to lower Whole Foods’ costs.

The news sent stocks of rival grocers sharply lower in afternoon trade. Kroger Co. stock KR, +0.80% tumbled 6%, Costco Wholesale Corp. COST, +0.42% fell 3.8%, Sprouts Farmers Markets Inc. SFM, -0.04% was down 3.6% and Wal-Mart Stores Inc. WMT, +0.16% fell 2%. Supervalu Inc. shares US:SVU slid 6.4%.

Whole Foods said private label products like 365 Everyday Value and Whole Paws will be available through Amazon, AmazonFresh, Prime Pantry and Prime Now. And Amazon lockers will be available at select Whole Foods stores. Shopper will be able to have products shipped from Amazon to Whole Foods for pick up, or send returns to Amazon while visiting a Whole Foods store.

The companies say they will hire additional staff as new stores open, and Whole Foods will continue to operate as that brand. John Mackey will stay on as chief executive and the Whole Foods headquarters will remain in Austin, TX.

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Also:Amazon ‘will be a top 5 grocer in the U.S.’ with Whole Foods acquisition

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Amazon shares were flat Thursday, but are up nearly 27% for the year so far. Whole Foods shares were up 0.7% for a 36.5% gain in 2017.

The SPDR S&P Retail Exchange-traded fund XRT, +1.05% has fallen 12% in the year so far, while the S&P 500 SPX, +0.07% has gained 9%.

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