Nikolai Vavilov

Nikolai Vavilov is born into a Moscow merchant family, elder brother of the physicist Sergey Vavilov.

Vavilov formulates his theory of the geographic 'centres of origin' of cultivated plants, mapped from his worldwide seed-collecting expeditions.

Vavilov's Leningrad institute assembles the largest collection of crop seeds anywhere, conceived as insurance against famine. Published totals differ, from a quarter of a million accessions to some 380,000 samples collected.

The protégé turns on the patron: Vavilov and Lysenko clash openly over genetics, and Vavilov begins to be branded a 'saboteur'.

The purges of 1937-38 consume officials, officers and scientists alike. Gorbunov is arrested on 19 February 1938 and shot on 7 September 1938; Vavilov will be arrested in 1940.

Germany invades Poland. The war will bring the Siege of Leningrad, where Vavilov's colleagues starve guarding his seeds.

Vavilov is arrested by the NKVD on 6 August 1940 while on a seed expedition near Chernivtsi. The military collegium sentences him to death on 9 July 1941; he is not executed and dies in prison in 1943.

The 872-day siege begins. In Vavilov's institute, staff guard a quarter-million seeds and several starve rather than eat them.

Vavilov dies in a Saratov prison, most historians say of starvation, the man who devoted his life to ending famine. He is rehabilitated in 1955.