This was my best surprise of the 2017 season.
From a cross of two F2's in 2015, red and orange-red, I selected a very tasty red plum in the F1 2016 to grow forward. I had completely forgotten the lone gf allele from Indian Stripe in one of the original crosses. So imagine my shock when the earliest flower opened with all the characteristics of a black.
Sure enough, the plant ripened a black heart, just 93 days from seed.