An exciting and illuminating battle of the sexes may occur in the Wood Memorial Stakes at Aqueduct Saturday.

Genuine Risk, the country's bect 3-year-old filly, has been entered against Plugged Nickle, the colt who is the early favorite for the Kentucky Derby. If Genuine Risk wins, she would almost certainly become the first filly to run in the Derby since 1959.

But that probably won't happen. If the confrontation does materialize (and Genuine Rish's trainer, Leroy Jolley, is still deliberating whether to run), Plugged Nickle figures to win it decisively. Such a result would, of course, confrim the opinion of the majority of American racetrackers, who believe that fillies are the natural inferiors of colts.

In fact, there is plenty of evidence to the contrary. European fillies do compete on even terms with colts.In the last eight runnings of the Prix de l' Arc de Triomphe, the continent's most important race, fillies have won four and finished second four times. By contrast, no filly has won America's most famous race since Regret captured the 1915 Derby.

What's wrong with American fillies?

The answer, obviously, does not lie in the nature of the fillies on the two continents. Many of the most successful European fillies have been American-bred imports.

The difference is the way they are trained and campaigned. In Europe, where there are few races limited to females, fillies have no choice but to run against colts. They are forced to be equal. In America, fillies can spend their whole career running exclusively against members of their own sex. Being sheltered from the toughest competition, they don't develop as much.

The careers of Plugged Nickle and Genuine Risk provide a classic contrast.

When Plugged Nickle won two stakes races at the end of last fall, trainer Tommy Kelly immediately started thinking of him as a Derby horse and planned the colt's campaign with that objective in mind. Plugged Nickle ran against the best colts in Florida this winter, and established himself as the leader of his generation with a seven-length triumph in the Florida Derby.

He runs in the 1 1/8-mile Wood Saturday because Kelly considers it the best possible final prep for his assignment at Churchill Downs two weeks later.

Genuine Risk, too, showed signs of ability last fall, winning all four of her races, including one against a top-class stakes field. Students of speed handicappiing would said that her "figures" were about equal to Plugged Nickle's. At the same stage of their careers, they showed comparable ability.

But just as relatively few bright little girls grow up to be doctors or lawyers because nobody expects them to, talented young fillies don't grow up to be Derby winners. Trainer Leroy Jolley probably never even considered mapping out a Derby-oriented campaign for Genuine Risk as Kelly did for Plugged Nickle.

Instead, he ran her once in an allowance race for fillies at Gulfstream, and then in a weak handicap against filles at Aqueduct, making her career record six-for-six. Having been shielded from demanding competition, her development has lagged far behind that of Plugged Nickle.

Now Jolley is wavering about whether to throw Genuine Risk into competition against males for the first time. "This situation has me rolling and tossing," he said. "I'm exicted but I'm scared, too."

If Jolley does take the plunge, Genuine Rick will be placed at a great disadvantage. Horses don't win races like the Wood without proper seasoning. dThey don't win the Derby. Genuine Rish will probably be beaten, and then will return to competition against females, where she should acheve the most that American fillies ever achieve: the distinction of being "the best of her sex."