Gene for Gene Hypothesis in Plant Breeding
The concept of gene for gene hypothesis was first developed by Flor in 1956 based on his studies of host pathogen interaction in flax, for rust caused by Malampsora lini. The gene for gene hypothesis states that for each gene controlling resistance in the host, there is corresponding gene controlling pathogenicity in the pathogen. The resistance of host is governed by dominant genes and virulence of pathogen by recessive genes. The genotype of host and pathogen determine the disease reaction. When genes in host and pathogen match for all loci, then only the host will show susceptible reaction. If some gene loci remain unmatched, the host will show resistant reaction. Now gene – for –gene relationship has been reported in several other crops like potato, sorghum, wheat, etc. The gene for gene hypothesis is also known as “Flor Hypothesis.”
At molecular level, it is considered that gene for gene resistance usually involves production of toxins antibiotic proteins by a resistance gene. The production of toxins is related to gene dosage. The resistance controlled by domain gene is the most desirable. Gene for gene relationship are rare or unknown for disease caused by viruses, bacteria, Fusarium, and other organisms that cause rot.