Erwinia amylovora, the bacterium that causes the fire blight disease in apple, triggers its infection through the DspA/E effector which interacts with the apple susceptibility protein MdDIPM4. Researchers from Fondazione Edmund Mach used the CRISPR-Cas9 system to produce defective MdDIPM4 which were delivered to susceptible apples using Agrobacterium tumefaciens. The results are published in the Plant Biotechnology Journal.
A total of 57 transgenic lines were generated with an editing efficiency of 75%. Out of the 57, 7 lines exhibited successful mutation leading to loss of function of MdDIPM4. These lines were exposed to fire blight and results showed a highly significant reduction of susceptibility when compared to the control.
The results provide information on the development and application of CRISPR-Cas9 for the production of edited apples with a minimal trace of exogenous DNA.