Molecular Mapping of the Banded Cucumber Beetle Resistance in Romaine Lettuce Valmaine

Banded cucumber beetle (Diabrotica balteata LeConte) is an economically important insect pest of many vegetable crops in the sub-tropics. The romaine lettuce (Lactuca sativa L.) cultivar Valmaine is known to have resistance to the banded cucumber beetle. A segregating population was developed from a cross between Valmaine and Okeechobee (susceptible) for inheritance analysis and mapping of the resistance. The derived F₁ exhibited banded cucumber beetle resistance. The segregation ratio was 3 resistance : 1 susceptibility in the F₂ and 1homozygous resistance : 2 heterozygosity : 1 homozygous susceptibility among F₃ families, indicating that a single dominant gene is responsible for banded cucumber beetle resistance in Valmaine. The F₂ population is being used for molecular mapping of the resistance with amplified fragment length polymorphism (AFLP) and target region amplification polymorphism (TRAP). Several TRAP markers were found to be associated with the resistance in the bulked segregant analysis (BSA) and are being mapped in the entire F₂ population. Identification of the resistant gene and its associated markers should facilitate the incorporation of the resistance into adapted cultivars to combat damage of the lettuce crop by the banded cucumber beetle.