Wilson Food Corp., the nation's largest pork processor, reached a tentative contract agreement with striking union meatpackers yesterday, in a package that obliged the union to accept steep salary cuts in order to retain recognition as bargaining agent for the company's employes.

The agreement could end a 20-day strike at seven Wilson plants. Officials of the United Food and Commercial Workers Union said the contract proposal calls for the workers to receive a basic wage considerably less than the $10.69 an hour they were getting before Wilson repudiated its master agreement in April, but more than the $6.50 an hour they have been getting since then.

If accepted by the 6,000 workers this weekend, the accord could end one of the most unusual and controversial labor confrontations in recent years and slow down the sharp erosion of the union's position in the nation's meatpacking industry.

Wilson, formerly a division of LTV Corp., filed for protection under Chapter XI of the bankruptcy laws in April. The company then canceled its contract with the union, and slashed the workers' wages by more than 40 percent.

The union claimed this was an abuse of the bankruptcy law, and on June 4 workers walked off the job at seven slaughtering plants. Then, while the union's attention was focused on Wilson, Greyhound Corp. said it too wanted to escape from the nationwide master contract, and announced plans to close all the unionized plants of its Armour Food subsidiary.

Greyhound said Armour could no longer compete with its non-union rivals. The Armour plants are scheduled to close in September.

Wilson, which is based in Oklahoma City, confirmed that a tentative agreement had been reached, but declined to give details. However, it appeared on the basis of sketchy reports from union officials that Wilson had succeeded in its objective of forcing the union to back down from the master agreement, which itself called for a five-year wage freeze, by offering the workers a choice of jobs at lower pay or no jobs at all.

Wilson Chairman Kenneth J. Griggy said he hoped the agreement would enable Wilson to "clear a major hurdle in the reorganization process" and emerge from Chapter XI with its workers' jobs intact.