The one-year reign of Fred McNair IV of Chevy Chase, Md. and Texan Sherwood Stewart as French Open doubles champions came to an abrupt end today as they were beaten in the first round by the obscure Canadian team of Dale power and Greg Halder, 4-6, 6-4, 6-4.

Defending champion Adriano Panatta of Italy led the advance of singles seeds on another warm and sunny afternoon, playing inconsistently but beating Julian Ganzabal, 6-2, 2-6, 6-4, 6-1.

Paul Ramirez had an easier time than expected in dispatching Jeff Borowiak, 6-3, 6-3, 6-2, and Stan Smith looked surprisingly comfortable on the slow red clay of Stade Roland Garros in erasing Jurgen Fassbender, 6-4, 6-3, 7-5.

Wojtek Fibak, winner of last week's Grand Prix event at Dusseldorf, West Germany, concluded a day on which none of the seeds lost by whipping 1975 Australian Open champ Mark Edmondson, 6-2, 6-4, 6-4.

Fibak then drew applause from those in the crowd who waited until nightfall by staying on court and hitting with some of the ballboys.

Renata Tomanova (No. 5) and Nancy Richey (No. 8) were the only seeded women players extended to three sets.

Tomanova, runner-up to Sue Barker here last year in a field similarly depleted by World Team Tennis, defeated Carmen Perea, 6-1, 6-7, 7-5. Richey, champion here in 1968 and still ranked No. 3 in the United States at age 36 even though she played only eight tournaments last year, eutlasted Fiorella Bonicelli, 6-4, 5-7, 6-1.

A little shock wave went through the locker room and players' dining room as news spread that Stewart-McNair, ranked No. 1 in the United States in doubles, had lost to a couple of players many of their colleagues had never heard of. Both Power, 27, and Halder, 21, failed to qualify for the singles here.

"We didn't think we could win, we just wanted to make it as long a match as we could," said Power, who was teaming with his fellow Toronto resident for only the second time. They played one Davis Cup doubles match last fall in Canada's victory over Commonwealth Caribbean.

"We played pretty steady and threw up a lot of lobs," said Power. "I mishit a bunch of overheads and shanked some volleys that went for winners at the right times. Freddie got a little edgy at the thought of losing to a couple of hackers from Canada and started spraying balls all over the place."

Power and Halder had five break points in the first set but couldn't convert any of them. Power lost his serve at 4-5 for the set.

But the Canadians broke Stewart in the fifth game of the second set and the seventh game of the third and served out the match. Stewart blew an overhead from mid-court for the critical break, although the Canadians had keyed on McNair, the more flashy and volatile member of the U.S. Davis Cup pair, at crucial stages.

"They basically weren't ready for a long match. They didn't want to be out there with the likes of us, right?" grinned Power> a former hockey player who went to Oklahoma City College on a tennis scholarship.

"They got a little uptight. I think they were shocked," said Power. "And Greg cracks the ball pretty well. His serve can be a bit intimidating, and he served well today.

"This could be a big lift for us. It could make our future."

Said Halder, a sturdy 6-foot-2, 175 pounder who finished eighth on the WATH satellite circuit this spring, "I had seen them around. I think I talked to Freddie once, but I had never met Sherwood. Usually I have to qualify for tournaments, and i haven't made it in too many, so by the time they get there I'm usually headed to the next one.

"This doesn't beat a big win in singles, but it's better than nothing," Halder said. "At least it's another day I don't have to go scrubbing around for a practice court."