Lysenko rejected Mendelian genetics in favor of the doctrine of acquired characteristics, a form of Lamarckism. (According to the earlier doctrine of Lamarck, evolution occurs because organisms can inherit traits acquired by their ancestors. Giraffes can only survive by eating leaves high up on trees so they stretch their necks to reach the leaves and this stretching of the neck is passed on to later generations.)
Lysenko was president (1938-56, 1961-62) of the Lenin Academy of Agricultural Science and directed (1940-65) the Institute of Genetics of the Soviet Academy of Sciences. His ideas were accepted as gospel until after the death of Joseph Stalin. They are now rejected.