Short answers, pulled from the story.
Nikolai Vavilov was a Russian botanist and geneticist born on the 25th of November 1887 in Moscow. He identified the geographic centers of origin of cultivated plants, built the world's largest seedbank at his Leningrad institute, and documented over 148,000 plant specimens by 1933. His work on crop genetic diversity underpins much of modern plant breeding.
Vavilov was arrested in August 1940 by the NKVD while collecting seeds in Ukraine. He was accused of spying for the British and of sabotaging Soviet agriculture. His opposition to Trofim Lysenko, whose anti-genetics views had Stalin's backing, was the underlying cause. He made a false confession after interrogation and was sentenced to death in 1941.
Vavilov died in prison in Saratov on the 26th of January 1943. His death sentence had been commuted to twenty years' imprisonment in 1942. Prison medical records list pneumonia, dystrophy, and edema as his diagnoses; some authors assert the actual cause was starvation. His sentence was posthumously voided in 1955.
The seedbank held approximately 250,000 samples of seeds, roots, and fruits at the start of the siege. Scientists at the Vavilov Institute boxed up a cross section of the collection, moved it to the basement, and guarded it in shifts throughout the twenty-eight-month siege. None of the guards ate the seeds; by the end of the siege in spring 1944, several had died of starvation.
Vavilovian mimicry is the process by which weeds evolve to resemble the crop they grow among. Vavilov observed that when farmers or winnowing machines removed weed seeds, only seeds most similar in appearance to the crop survived, gradually producing a weed that looked like the crop. He cited cereal rye as a crop that originated through this process. The biologist Georges Pasteur formally named the phenomenon in 1982.
The N.I. Vavilov Institute of Plant Industry in St. Petersburg was renamed after him in 1968. The USSR Academy of Sciences established the Vavilov Award in 1965 and the Vavilov Medal in 1968. A monument to Vavilov was unveiled in Saratov in 1997, and the minor planet 2862 Vavilov, discovered in 1977 by Soviet astronomer Nikolai Stepanovich Chernykh, bears his name along with a crater on the far side of the Moon.