Identification of PCR-based markers flanking the recessive LMV resistance gene mo1 in an intraspecific cross in lettuce

Molecular markers flanking the recessive resistance gene mo1 were identified following analysis of two segregating populations. Generation of a population from a crisphead x crisphead cross of Lactuca sativa that segregated for resistance conferred by the mo1₂ allele, but not morphological traits, was required for accurate mapping of the gene. Resistance was best assessed by symptom development after inoculating F₃ families with the common pathotype II isolate of lettuce mosaic virus (LMV). Bulked segregant analysis for RAPD (random amplified polymorphic DNA) markers using one population, followed by linkage analysis using another, identified markers on either side of the mo1 gene, approximately 8 cM apart. These markers will be useful for more efficient introgression of this resistance gene into additional lettuce cultivars.