Plant Genome III Conference

QTL ANALYSIS OF THE PRODUCTION OF ACYLSUGARS RESPONSIBLE FOR PEST RESISTANCE IN THE WILD TOMATO, LYCOPERSICON PENNELLII.

Lycopersicon pennellii, a wild relative of the tomato, L esculentum, is resistant to a number of important pests of cultivated tomato due to the presence of acylsugars, which constitute 90% of L. pennellii LA716 type IV trichome exudate. Acylsugars of L pennellii LA716 are a complex of 2,3,4-tri-O-acylated glucose esters possessing C4 to C12 fatty acids. Cultivated tomato does not produce detectable levels of acylsugars, and the interspecific Fl created by crossing L esculentum x L pennellii LA 716 produces a mixture of acylglucoses and acylsucroses. The purpose of this work was to determine the genomic regions associated with the ability to synthesize acylsugars, the type of sugar incorporated into the acylsugar, and the levels of acylsugars produced. An F2 population was derived from the cross of L esculentum cv New Yorkerlp4 x L pennellii LA716, in which the L esculentum parent was derived from the L escutentum line New Yorker but contains L pennellii cytoplasm, Two hundred and thirty four F2 plants were surveyed at 16 weeks of age for acylsugar production. The traits examined included levels of acylglucoses, acylsucroses, and total acylsugars, and glucose as a percentage of total acylsugars. Since a number of plants were killed in a greenhouse failure, the mapping was done on a random subset of 144 plants using 150 genomic mapping clones of known chromosomal locations (supplied by Dr. S. D. Tanksley). Data was analyzed using MAPMAKER with and without log 10 transformation. Thresholds used for determination of significant LOCI scores were 2.4 (default value for MAPMAKER ) and levels calculated according to the method of Doerge and Churchill (1994). Genomic regions were identified that affected acylglucose levels, acylsucrose levels, total acylsugar levels or acylglucose as percentage of total acylsugars. Two regions on chromosome 2 and one region on chromosome 11 were identified by all analytical methods as affecting some aspect of acylsugar production. Additional regions on chromosomes 3 and 4 were identified using the less conservative LOCI 2.4 threshold. Comparison of these results to the regions transferred by a breeding program based on selection for acylsugar production and to the mapping results published in the genus Solanum am discussed.