A portrait of Pablo Picasso’s “golden muse” and secret lover has sold for $139.4m (£114m) at auction in New York, making it the second most valuable work by the 20th-century artist. Femme à la montre, painted in 1932, was described by Sotheby’s as the “prized jewel” of about 120 artworks owned by Emily Fisher Landau, one of the greatest art collectors of the 20th century, that were sold on Wednesday evening. The portrait comfortably exceeded Sotheby’s estimate of at least $120m but fell short of the record for a Picasso at auction, held by Les femmes d’Alger, which sold for $179.4m in 2015. Four other works by Picasso have sold for more than $100m in the past 20 years. Picasso painted Femme à la montre during his explosive “year of wonders” as he prepared for his first large-scale retrospective in Paris at the age of 50. By 1932, his clandestine affair with Marie-Thérèse Walter had been under way for several years. The relationship began when the artist, then 45, spotted the 17-year-old through the window of Galeries Lafayette in Paris. She inspired paintings, drawings and sculptures, some of which are considered the greatest works of Picasso’s eight-decade career. The portrait was bought in 1968 by Fisher Landau, one of the greatest art collectors of the 20th century. She hung it above the mantelpiece in the living room of her New York apartment. By the time she died, aged 102, earlier this year, her art collection could have filled several museums. Fisher Landau began collecting art in earnest after a burglar made off with diamonds, emeralds, rubies and sapphires that had been gifts from her husband. Instead of replacing the jewellery, Fisher Landau decided to use the substantial insurance payout to buy paintings and sculptures. She acquired works by Mark Rothko, Franz Kline, Henri Matisse, Georgia O’Keeffe, Piet Mondrian, Paul Klee and others. Andy Warhol painted her portrait. The Fisher Landau sale on Wednesday kicked off the autumn auction season, which is expected to include more than £2bn of art sold by the big three auction houses Sotheby’s, Christie’s and Phillips. On Thursday, Christie’s will sell a large Claude Monet water lily painting that has been largely unseen by the public, having been owned by the same family for more than 50 years.