Effective inoculation methods to screen for resistance to Verticillium wilt in olive

- Effective methods to screen massively olive genotypes for Verticillium wilt resistance are needed.
- We tested three different inoculation methods.
- For the best inoculation method, we tested the influence of the environment and the age of the plants.
- Root-dipping inoculation of young olive seedlings and evaluation under growth chamber conditions is an effective method to screen for resistant genotypes.
- This screening method is suitable as a first step in a breeding program for Verticillium wilt resistance in olive.

Effective inoculation methods to screen for Verticillium wilt resistance are essential for the development of olive cultivars resistant to this devastating disease. Three inoculation methods, pot immmersion, bare-root dipping and stem injection using a conidial suspension of a highly virulent Verticillium dahliae isolate (named V117) were tested in olive seedlings. The root-dipping inoculation performed the best, and its effectiveness was further tested in seedlings aged 40, 80 and 120 days in two different environments (greenhouse and growth chamber). The root-dipping inoculation of the 40-day-old olive seedlings discriminated between resistant and susceptible genotypes. This early screening is less costly and requires less time and space than the standard inoculation and evaluation methods conducted with older plants. Therefore, we propose the root-dipping inoculation of 40-day-old olive seedlings as a reliable, fast and effective method to select genotypes at a young age that are potentially resistant to V. dahliae. The application of this method has allowed for the screening of more than 8000 genotypes before their evaluation under field conditions.