Vavilov would, I hope, have been happy to learn that the wild apple forests of Kazahkstan have helped to answer an outstanding scientific mystery. Why do the leaves of some trees turn red in autumn? As I wrote elsewhere:
Yellow leaves are easy to explain; the breakdown of chlorophyll exposes yellow carotenoids that were there all along but masked. Red, however, is the result of anthocyanins, which the plant manufactures specifically. That imposes a cost, so evolutionary biologists have long looked for the corresponding benefit.
And the benefit seems to be that it keeps aphids — and the diseases they carry — away. Apples, aphids and evolution gives the full story.
