Gene for gene hypothesis was given by: (BHU Pre PG 2016)

✅Explanation:
The "gene for gene" hypothesis, which proposes a specific correspondence between resistance genes in the host and virulence genes in the pathogen, was first proposed and studied by H. H. Flor in the 1940s. He primarily worked on the interaction between flax plants and their fungal rust pathogen. His research documented specific matching pairs of genes, where a dominant resistance gene in the host matched a recessive avirulence gene in the pathogen, leading to disease resistance.

• Here's why the other options are not the correct answer:
-(a) A. F. Blakeslee: Blakeslee made significant contributions to plant genetics, but his work primarily focused on polyploidy and sexual reproduction in plants.
-(b) E. C. Stakman: Stakman played a crucial role in understanding the concept of plant disease resistance genes.
-(c) Vander Plank: Vander Plank contributed to the development of quantitative disease resistance models, which differ from the specific gene-for-gene interactions proposed by Flor.