ARS | Publication request: Development of molecular markers for marker-assisted selection in lettuce (Lactuca sativa).

Submitted to: International Society for Horticultural Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 18, 2009
Publication Date: N/A

Technical Abstract: Lettuce dieback disease is widespread in commercially grown romaine and leaf-type lettuces, but not in iceberg-type cultivars. The cause of disease are two closely related tombusviruses -- Tomato bushy stunt virus (TBSV) and Lettuce necrotic stunt virus (LNSV). A single dominant gene on chromosome 2 (Tvr1) was found to be responsible for the resistance observed in modern iceberg lettuces. The population of 192 F8 RILs developed from a cross between the susceptible romaine cultivar Valmaine and the resistant iceberg cultivar Salinas was used to pinpoint the position of the resistance gene with EST-based molecular markers. Nine markers closely linked to the Tvr1 gene were subsequently tested for an association with resistant phenotype in a set of 68 accessions from all horticultural types of lettuce. Sequencing of the marker that showed the exact fit with resistance revealed the presence of three haplotypes; two of them associated with the disease resistance. The High-resolution DNA melting approach that allows for the detection of all three haplotypes in a single analysis was successfully applied to study the marker-trait association in another set of 130 diverse accessions. The results confirmed the usefulness of the marker for marker-assisted selection in all types of cultivated lettuce.