Figure 3.—

Diagram illustrating the construction of double S. lycopersicoides introgression lines, and their possible use for increasing recombination frequency in the progeny. The “target” introgression line contains a homeologous segment with a gene of interest, such as a hypothetical disease resistance factor (R). (A) The “driver” line contains a homeologous segment on the opposite arm of the same chromosome. (B) The “bridging” introgression is a line containing a donor segment from L. pennellii. Each double-introgression line is heterozygous for two alien segments, initially in repulsion linkage phase, on the same chromosome. The locations of crossover events, predicted to occur preferentially in homologous stretches, are indicated with an . Representative recombinant chromosomes that are obtainable in the progeny are shown.