Selfing

Marijuana Horticulture

by Jorge Cervantes

Selfing is the process of creating seed by fertilizing a plant with pollen obtained for itself. The result of the self-cross is a population of plants that derive from a single individual. The first generation population is derived from selfing an individual is called the S1 population. If an individual is chosen from the S1, and gain selfed, the resulting population is denoted the S2 generation. Subsequent generations derived in the same manner are denoted S3, S4, etc.

Traits for which the plant is homozygous remain homozygous upon selfing, whereas heterozygous loci segregate, and may demonstrate novel expressions of these characters.

We know homozygous loci remain homozygous in future generations upon selfing, but what about the heterozygous loci? Each selfed generation leads to an increase in homozygosity by 50% for each heterozygous locus, and each subsequent generation, derived from selfing an S1 individual, is 50% more homozygous than the parent from which it was derived. Repeated selfing, or single-seed descent, is the fastest way to achieve homozygosity within a group or family. Again, the more plants grown from a selfed population, the better probability a breeder has of finding selfed progeny that show all of the desired traits.