Pollen development requires both sporophytic and gametophytic gene expression. We are using a map-based cloning technique to isolate sporophytic genes which, when mutant, cause pollen abortion and a male sterile (ms) phenotype in tomato (Lycopersicon esculentum). We have genetically characterized one ms locus (ms14) using RFLP analysis and identified flanking markers. High-resolution genomic physical mapping indicates that the ms14 locus is located in a approximately 300 kb region. We have identified a YAC clone with an insert size of approximately 610 kb that contains the ms14-linked markers, reflects the organization of the physical map and therefore most probably contains the ms14 gene. In addition, we present evidence that the relationship between physical and genetic distance in this chromosomal region changes abruptly from approximately 105-140 kb/cM to less than 24kb/cM, and suggest that the TG393-TG104 region is a hotspot for recombination.