Linkage Disequilibrium

Linkage disequilibrium (LD) refers to the non-random association of alleles at different loci in a population's genome. In cannabis breeding, LD describes how certain genetic markers or traits remain physically linked on chromosomes and are inherited together more often than would occur by chance. Understanding LD patterns helps breeders predict trait co-inheritance, identify genomic blocks under selection, and avoid unintended linkage drag—where an undesirable allele near a target gene gets inherited along with desired traits. Cannabis exhibits variable LD decay across its genome, influenced by breeding history, population bottlenecks, and reproductive system. Mapping LD structure is foundational for genomic selection and marker-assisted breeding programs seeking precision trait stacking.

Breeders leverage LD mapping to design efficient crosses and avoid linkage drag that can compromise trait expression. Knowledge of LD blocks guides decisions about recombination-based breeding strategies versus direct marker selection to break unfavorable allele associations.