IBL (Inbred Line)

IBL, or inbred line, is a plant line made genetically uniform through repeated self-pollination or sibling crossing over several generations, producing progeny that are highly homozygous and "breed true" for their defining traits (Acquaah 2012; Allard 1999). After ~6–7 generations of selfing, inbreeding coefficient F exceeds 0.98, yielding near-isogenic stock. In cannabis — a dioecious, highly heterozygous, outcrossing species — true IBLs are difficult to produce because inbreeding depression (reduced vigor, fertility) is pronounced (Clarke & Merlin 2013). IBLs are nevertheless the preferred parental stock for producing reliable F1 hybrids, and certified hemp cultivars (Finola, Futura 75, USO-31) more closely approach IBL status than typical drug-type "strains" (Small 2015; Welling et al. 2016). Selfing in cannabis is typically induced chemically — with silver thiosulfate or colloidal silver — on genetic females to produce feminized S1 seed. → See also: Cultivar, F1, BX, Chemotype.