Genetics of wheat grain color was studied by:

Explanation

Nilsson-Ehle studied the genetics of wheat grain color and demonstrated that it is a polygenic trait. He crossed a dark red grain plant with a white grain plant, resulting in F1 grains with an intermediate light red color, initially suggesting incomplete dominance. However, the F2 generation exhibited a range of seven shades in a specific ratio, illustrating polygenic inheritance. Darwin is associated with the theory of evolution, Mendel with the fundamental laws of inheritance, and Correns with incomplete dominance, making them incorrect choices for this question.