15 Fine mapping of stigma exsertion QTL se2 . 1 Chen, K . – Y . and Tanksley S . D . Dept . of Plant Breeding, Cornell University, Ithaca, NY 14850 Stigma exsertion was characterized as a quantitative trait resulting in herkogamy that separates anthers and stigma in the space within a tomato flower (Rick and Dempsey, 1969; Scott and George, 1980) . Attempts were raised to use stigma exsertion for hybrid seed production (Scott and George, 1980; Levin et al . , 1994), as well as for the evolutionary studies of the tomato mating system (Rick et al . , 1978; Rick, 1982, Rick, 1995) . se2 . 1 is the major stigma exsertion QTL found in both L . hirsutum and L . peruvianum (Bernacchi and Tanksley, 1997; Fulton et al . , 1997) . In an effort to fine map the se2 . 1 gene, an F2 population of 1535 individuals from the cross L . esculentum cv M82 x IL2 - 5 was used to screen recombinants between molecular marker TG469 and TG167 . 123 recombinants were selected and their corresponding F3 progenies with a homozygous L . pennellii introgression region were screened . 50 RFLP markers (Tanksley et al , 1992; http://soldb . cit . cornell . edu) were used to determine the genotypes of each homozygous recombinant and to ensure that only single crossover events had occurred in the L . pennellii introgression region . The phenotypes of three F4 plants from each homozygous recombinant were analyzed in the summer in the field with a randomized block design .   Analysis revealed that se2 . 1 is located in the chromosomal interval between RFLP markers T1301 and T662 (fig 1) . Since two independent homozygous recombinants showed that the intermediate phenotype was different from the two parental controls, it is very likely that two closely linked genes reside in this chromosomal interval . Moreover, the change of style length is likely a function of the se2 . 1 genes, because there is no significant difference between the stamen length of the recombinants and that of the controls .   Literature cited: Bernacchi D and Tanksley SD (1997) An interspecific backcross of Lycopersicon esculentum X L . hirsutum : Linkage analysis and a QTL study of sexual compatibility factors and floral traits . Genetics 147: 861 - 877 . Fulton TM, Beck - Bunn T, Emmatty D, Eshed Y, Lopez J, Petiard V, Uhlig J, Zamir D, and Tanksley SD (1997) QTL analysis of an advanced backcross of Lycopersicon peruvianum to the cultivated tomato and comparisons with QTLs found in other wild species . Theor Appl Genet 95: 881 - 894 . Levin I, Cahaner A, Rabinowitch HD, and Elkind Y (1994)