Chimeric apple

Jim Arbury, fruit superintendent at RHS Garden Wisley in Surrey, said it was probably the 'result of a random genetic mutation'. 'This is known as a chimera where one of the first two cells has developed differently giving rise to one half of the apple being different,' he said.

'It is unlikely to be a stable mutation but it is worth checking next year to see if it recurs. There are instances of some striped apples and pears where the mutation remains stable including one striped pear in the collection at Wisley called Pysanka.'

Via J-Walk.