A Widespread Chromosomal Inversion Polymorphism Contributes to a Major Life-History Transition, Local Adaptation, and Reproductive Isolation
Crossing design for production of backcross lines with the LMC (shades of yellow/orange) genetic background. Breeding of plants with SWB (shades of blue) genetic background not shown. Note that the size of introgressed region around the inversion should vary among lines due to different recombination locations during breeding. Different shades are used to indicate that original parental inbred lines have a unique genetic composition. (A) Three pairs of independently derived inbred LMC and SWB lines were crossed to create F1 progeny. (B) F1s backcrossed to parental inbred lines. (C) Marker-assisted selection used for four generations of backcrossing to move the inversion into alternate genetic backgrounds. (D) Heterozygous lines were self-fertilized. (E) Backcross lines that are homozygous with (blue oval) and without (orange oval) the introgressed inversion arrangements were selected for further breeding. (F) Intercrosses conducted among the three independent groups to create outbred backcross lines with and without the introgressed inverted region. (G) Backcrossed lines now ready to be planted into field reciprocal transplant experiment.