LITTLE ROCK—Wal-Mart stores in Arizona now stock Grand Canyon sweet onions while aisles in New York display state-grown eggplant, as the world’s largest retailer says it’s become the nation’s largest buyer of locally grown fruits and vegetables.

Wal-Mart Stores Inc. said it will purchase and sell $400 million worth of produce grown by local farmers within its state stores this year, an effort the company says will only grow. Academic studies show buying local cuts down on transportation mileage, while also assuring customers of a product’s providence amid mass recalls.

“Wal-Mart would not be the first” to buy local, said Rich Pirog, associate director of the Leopold Center for Sustainable Agriculture at Iowa State University. “But they’re obviously, without question, the largest retailer to go down this route.”

Among retailers, Whole Foods Markets of Austin, Texas, is perhaps best known for buying and selling locally grown produce, Pirog said. Others, like New Seasons Market stores around Portland, Ore., and Hen House Market stores in Kansas City, cater to customers looking for fresh produce.

For Wal-Mart, which leverages bulk purchases to keep prices down, buying from local farms might not appear to fit the company’s strategy. However, the Bentonville-based company has focused on buying fruits and vegetables from farms nearest to their distribution centers, making shipping easier while cutting down on trucking in produce from outside of the area, said spokeswoman Deisha Galberth.

For example, the retail giant once only bought peaches from a few suppliers. Now, Wal-Mart buys 12 million pounds of peaches from farms in 18 different states, distributing them closer to their customers, she said.

Wal-Mart made the announcement during an event in Georgia, highlighting that state’s cantaloupes, onions and watermelons. The move comes as the company continues a marketing campaign highlighting its environmentally focused practices.