The famous “Gene-for-gene” is first established in 1946 in—

The "Gene-for-gene" hypothesis, a fundamental concept in plant pathology, was first proposed by H.H. Flor in 1946 based on his studies of the interaction between flax (Linum usitatissimum) and the flax rust fungus (Melampsora lini). This hypothesis states that for each gene controlling resistance in the host, there is a corresponding gene controlling avirulence in the pathogen. This interaction determines whether the pathogen can successfully infect the host.

📌Other Options Explanations:
-Option B: Phytophthora infestans: This oomycete is responsible for the devastating late blight disease in potatoes and tomatoes. While it's a significant plant pathogen, it was not the organism used to establish the gene-for-gene concept.
-Option C: Botrytis cinerea: This fungus is a necrotrophic pathogen that causes gray mold on various plants. Although it is a widely studied pathogen, its interaction with hosts doesn't exemplify the classic gene-for-gene relationship.
-Option D: Alternaria solani: This fungus causes early blight in tomatoes and potatoes. It's another important pathogen but not directly associated with the establishment of the gene-for-gene hypothesis.