Marker-Trait Association Study in New RIL Population from a Cross Between Two Iceberg Lettuce Cultivar

Tipburn is a highly unpredictable, problematic physiological disorder of lettuce (Lactuca sativa) in which leaf margins and meristematic regions become necrotic.  All lettuce types are susceptible to tipburn but susceptibility varies considerably among cultivars and its incidence is highly influenced by developmental and environmental factors.  We developed a new RIL population specifically to study the genetic basis of tipburn. The pedigree of this RIL population is cv. Salinas by cv. Calicel, which are two iceberg type lettuce cultivars developed for coastal production in California. Salinas and Calicel differ in their susceptibility to tipburn incidence but are very similar genetically and phenotypically. In the summer of 2015, the RIL population of 382 families was planted in Salinas, CA in an alpha-lattice design with two replications. The population was phenotyped for tipburn incidence, plant fresh weight, and head firmness. The phenotypic data reveals transgressive segregation for tipburn incidence and plant fresh weight. The population is being genotyped by genotype-by-sequencing and QTL analysis is currently underway.