Merkel said she had "liked it very much".
However, the mass-circulation daily Bild alleged in its online edition that the German leader, a long-time regular in Bayreuth with her husband Joachim Sauer, had suffered a dizzy spell and fainted briefly during the first of the evening's two intervals.
But the report was subsequently denied by government spokesman Georg Streiter.
The German news agency DPA suggested a chair on which Merkel had been sitting may have been broken, causing her to slip.
That version of events was subsequently taken up by Bild.
Otherwise, the glittering opening night appeared to have been a hit with the its audience, made up of Germany's political and social elite.
Katharina Wagner, who runs the month-long summer music fest, was greeted with cheers and applause when she took her curtain call.
By contrast, boos were heard for conductor Christian Thielemann and German soprano Evelyn Herlitzius, who had taken on the demanding role of Isolde at very short notice.
- Dark interpretation -
The new production sets the action in a maze of staircases in the first act where the two lovers can never come together.
The second act depicts the jealous King Mark, to whom Isolde is betrothed, as an evil and manipulative figure who imprisons the two lovers in his own personal torture chamber, where Tristan is eventually stabbed to death.
The third and final act shows the delirium of the dying Tristan.
US tenor Stephen Gould was rapturously applauded for his intense portrayal of Tristan.
Herlitzius gave a scorching performance as Isolde, making up in sheer stage presence for what she might have lacked in tonal beauty.
German mezzo Christa Mayer and Scottish baritone Iain Paterson were also outstanding in the roles of Brangaene and the servant Kurwenal.
Tickets for Bayreuth are still among the hardest to come by in the world of opera and classical music, with the waiting list stretching to as long as 13 or 14 years for some productions, according to the festival's commercial chief Heinz-Dieter Sense.
Of the 60,000 tickets on sale this year, around 45,000 were available to the general public, half of them online. The other 15,000 were reserved for the Society of Friends of the festival, one of the main donors, and festival employees.
It is only the second time that Katharina has directed in Bayreuth's Festspielhaus -- the opera house built to her great-grandfather's own designs -- after her "Mastersingers of Nuremberg" a few years ago was heavily panned by audiences and critics alike.
Classical music aficionados suggest Bayreuth, more generally, could be losing some of its veneer. And Katharina's critics lay the blame squarely at her door.
Under her leadership, the festival's aesthetic preferences have veered towards confrontational directors, such as the self-styled "enfant terrible" of German theatre, Frank Castorf, whose current production of the sprawling four-opera "Ring" cycle has met with deafening waves of boos and whistles since it premiered in 2013.
Dyed-in-the-wool Wagnerians tend to be deeply conservative in their operatic tastes, and seasoned Bayreuthers say they are feeling increasingly alienated by the provocative, in-your-face productions.
- Backstage rivalries -
In the run-up to the festival, media reports -- vigorously dismissed -- had claimed that Katharina Wagner and conductor Christian Thielemann, recently named the festival's music director, had colluded to have her half-sister and fellow director Eva Wagner-Pasquier barred from the festival complex on Bayreuth's Green Hill once rehearsals for "Tristan" had started.
There has also been speculation of bitter rivalry between Russian conductor Kirill Petrenko, who is conducting the four-opera "Ring" cycle this year, and Thielemann after Petrenko was named chief conductor of the Berlin Philharmonic.
Thielemann was seen to have coveted the prize position for years.
Ever since the festival's beginnings in 1876, the composer's descendants have torn each other apart in bitter feuds for control of Bayreuth, whose guests traditionally include royalty and the political and social elite of the day.
Adolf Hitler was a fervent Wagnerian and regularly attended the festival.
The Bayreuth Festival runs until August 28 with 30 performances of seven different operas -- "Tristan and Isolde", "Lohengrin", "The Flying Dutchman" and the "Ring" comprising "Rhinegold", "The Valkyrie", "Siegfried" and "Twilight of the Gods".
----------------------------------------------------------------------------------------------------------------
However, the mass-circulation daily Bild alleged in its online edition that the German leader, a long-time regular in Bayreuth with her husband Joachim Sauer, had suffered a dizzy spell and fainted briefly during the first of the evening's two intervals.
But the report was subsequently denied by government spokesman Georg Streiter.
The German news agency DPA suggested a chair on which Merkel had been sitting may have been broken, causing her to slip.
That version of events was subsequently taken up by Bild.
Otherwise, the glittering opening night appeared to have been a hit with the its audience, made up of Germany's political and social elite.
Katharina Wagner, who runs the month-long summer music fest, was greeted with cheers and applause when she took her curtain call.
By contrast, boos were heard for conductor Christian Thielemann and German soprano Evelyn Herlitzius, who had taken on the demanding role of Isolde at very short notice.
- Dark interpretation -
The new production sets the action in a maze of staircases in the first act where the two lovers can never come together.
The second act depicts the jealous King Mark, to whom Isolde is betrothed, as an evil and manipulative figure who imprisons the two lovers in his own personal torture chamber, where Tristan is eventually stabbed to death.
The third and final act shows the delirium of the dying Tristan.
US tenor Stephen Gould was rapturously applauded for his intense portrayal of Tristan.
Herlitzius gave a scorching performance as Isolde, making up in sheer stage presence for what she might have lacked in tonal beauty.
German mezzo Christa Mayer and Scottish baritone Iain Paterson were also outstanding in the roles of Brangaene and the servant Kurwenal.
Tickets for Bayreuth are still among the hardest to come by in the world of opera and classical music, with the waiting list stretching to as long as 13 or 14 years for some productions, according to the festival's commercial chief Heinz-Dieter Sense.
Of the 60,000 tickets on sale this year, around 45,000 were available to the general public, half of them online. The other 15,000 were reserved for the Society of Friends of the festival, one of the main donors, and festival employees.
It is only the second time that Katharina has directed in Bayreuth's Festspielhaus -- the opera house built to her great-grandfather's own designs -- after her "Mastersingers of Nuremberg" a few years ago was heavily panned by audiences and critics alike.
Classical music aficionados suggest Bayreuth, more generally, could be losing some of its veneer. And Katharina's critics lay the blame squarely at her door.
Under her leadership, the festival's aesthetic preferences have veered towards confrontational directors, such as the self-styled "enfant terrible" of German theatre, Frank Castorf, whose current production of the sprawling four-opera "Ring" cycle has met with deafening waves of boos and whistles since it premiered in 2013.
Dyed-in-the-wool Wagnerians tend to be deeply conservative in their operatic tastes, and seasoned Bayreuthers say they are feeling increasingly alienated by the provocative, in-your-face productions.
- Backstage rivalries -
In the run-up to the festival, media reports -- vigorously dismissed -- had claimed that Katharina Wagner and conductor Christian Thielemann, recently named the festival's music director, had colluded to have her half-sister and fellow director Eva Wagner-Pasquier barred from the festival complex on Bayreuth's Green Hill once rehearsals for "Tristan" had started.
There has also been speculation of bitter rivalry between Russian conductor Kirill Petrenko, who is conducting the four-opera "Ring" cycle this year, and Thielemann after Petrenko was named chief conductor of the Berlin Philharmonic.
Thielemann was seen to have coveted the prize position for years.
Ever since the festival's beginnings in 1876, the composer's descendants have torn each other apart in bitter feuds for control of Bayreuth, whose guests traditionally include royalty and the political and social elite of the day.
Adolf Hitler was a fervent Wagnerian and regularly attended the festival.
The Bayreuth Festival runs until August 28 with 30 performances of seven different operas -- "Tristan and Isolde", "Lohengrin", "The Flying Dutchman" and the "Ring" comprising "Rhinegold", "The Valkyrie", "Siegfried" and "Twilight of the Gods".
----------------------------------------------------------------------------------------------------------------