Population Bottleneck

A population bottleneck in cannabis genetics occurs when a breeding line descends from a small number of parent plants, drastically reducing genetic diversity. This restriction can happen intentionally—when breeders select heavily for specific traits—or unintentionally, through seed loss, culling, or limited germination. Bottlenecks concentrate both desirable alleles and recessive genetic load, sometimes producing phenotypic uniformity but at the cost of vigor, disease resistance, and adaptability. Historical examples include early Northern Hemisphere imports that were bred repeatedly from minimal stock, establishing narrow genetic pools. Understanding bottleneck effects is critical for long-term breeding programs seeking to maintain outcross vigor and genetic stability.

Breeders deliberately create mild bottlenecks to fix desired traits, but must carefully manage them to avoid inbreeding depression and loss of heterozygosity. Recovery strategies include intentional outcrossing, landrace reintroduction, or genomic analysis to identify and purge hidden recessives.