Screening of Lettuce Germplasm for Resistance to Wilt Caused by Verticillium Dahliae
Crop Improvement and Protection Research
2013 Annual Report
1a.Objectives (from AD-416):
Identify source of resistance in lettuce to wilt incited by Verticillium dahliae.
1b.Approach (from AD-416):
Inoculate in pasteurized riverbed sand in the greenhouse. Observe for formation of mycelium, date of occurrence, and date of plant death.
The agreement was established in support of objective 1 of the parent project. This project is screening diverse Lactuca accessions for resistance to race 2 isolates of Verticillium dahliae in greenhouse experiments. This project will not terminate in two months. We have screened over 850 Lactuca sativa and wild Lactuca serriola accessions using race 2 Verticillium dahliae isolate VdLs17 in unreplicated greenhouse experiments. In replicated experiments we have confirmed partial resistance (disease incidence significantly lower than ‘Salinas’) in four Plant Introductions (PI), PIs 169511, 171674, 204707, and 226641. However, all of these PIs had at least a few symptomatic plants, and all but PI 171674 had non-symptomatic plants that are colonized by Verticillium dahliae. It does not appear that these PIs have a sufficient level of resistance to control the disease, and we are pursuing research to determine if intercrossing these four accessions will result in progeny with greater levels of resistance. We are also testing a Lactuca serriola line selected by collaborators at University of California, Davis. The accession was originally collected in Armenia in 2009. The level of resistance expressed by the Lactuca serriola in greenhouse experiments appears to be similar to PIs 169511, 171674, 204707, 226641. Data on 580 accessions have been reported to Western Regional Plant Introduction Station for inclusion in Germplasm Resources Information Network.