Inheritance and Molecular Mapping of Serpentine Leafminer (Liriomyza trifolii Burgess) Resistance in Romaine lettuce (Lactuca sativa L.) Valmaine

Serpentine leafminer (Liriomyza trifolii Burgess) is an economically important pest of lettuce in the United States. Farmers have relied on pesticides to control L. trifolii for decades. However, L. trifolii can develop resistance to frequently applied insecticides within a few years. Nonchemical methods of controlling the pest are desirable. Host plant resistance has been long-sought in plant breeding. Identification of genes controlling L. trifolii resistance is being conducted in a population comprised of 125 F2 plants derived from a cross between Valmaine (resistant) and Okeechobee (susceptible). Progeny testing on F2 individuals showed 22 homozygous dominant, 64 heterozygous, and 39 homozygous recessive, fitting the ratio 1:2:1 (r =4.696, P=0.0956). In addition, 64 segregating individuals produced 573 resistant and 212 susceptible plants, fitting the ratio 3:1 (r = 1.685, P=0.1942). These results support the hypothesis of a single dominant allele controlling the L. trifolii resistance in romaine lettuce Valmaine. Amplified fragment length polymorphisms (AFLPs) marker system is being used to map the resistance gene. Identification of closely linked markers will facilitate the transfer of the L. trifolii resistance gene to elite lettuce cultivars through marker-assisted selection.