Additional mechanisms to reduce foliar symptoms in iceberg lettuce
Complete resistance to race 1 of the pathogen is known, but adequate levels of resistance are not available against race 2. Additional mechanisms or traits that reduce foliar symptoms (FS) are needed to lessen economic losses from this disease.
Since the disease affects leaves, the harvested product, identification of iceberg cultivars that delay the onset of FS past peak MM could reduce yield loss from the disease. The goal of a new study was to identify iceberg lettuce germplasm with delayed onset of FS. Diverse iceberg cultivars were evaluated in replicated field experiments for MM, FS severity, and adaptation.
A few winter-adapted cultivars showed fewer FS past MM and seem to be promising candidates for breeding. These cultivars are not adapted to the California Central Coast where the disease currently predominates.
Further studies will determine the usefulness of this trait for breeding improved cultivars for use in V. dahliae–infested fields. Developing new cultivars that combine currently available sources of partial resistance against race 2 with delayed onset of FS could lead to reduced crop losses should race 2 of V. dahliae become widespread.
Access the full study at HortScience.