THE IMPROVEMENT of the American tomato proceeds inexorably. Last week came the news that scientists have developed a genetically engineered variety that will be bet-ter able to withstand a virus which plagues tomato crops. This week du Pont received a permit to field test a strain of tomatoes capable of surviving the herbicides used to kill surrounding weeds.

Surely today's tomatoes are the most impressive since the dawn of produce: resilient, disease-resistant, travel-hardy, pesticide-proof and vibrantly healthy. If they could talk, they would probably tell us they feel good about themselves, which would be some consolation for the fact that we can't stand them. For in addition to everything else, modern tomatoes are (except during the two months or so when they're in season here) also certifiably inedible. They are pulpy, juiceless and tasteless; sliced, wedged or whole, they're primarily a decorative item to be pushed to the side of the plate or fed to the rabbit.

February, which is as far as one can get from the real tomato season, breeds dark conspiracy theories about this situation. Some claim there are ships full of perfectly good tomatoes sitting off the Jersey coast waiting for the price to hit $8 a pound. Others say research and development on tomatoes is being secretly financed by people who are chiefly interested in their potential use as building materials or machine components.

Our own view is more sanguine. It seems clear to us that the supermarket tomato is simply evolving -- with considerable help from the genetic engineers -- in the way most likely to ensure it a long and happy life span, and that it has finally reached the stage to which all foodstuffs no doubt aspire: it has been improved beyond eating.