A reciprocal cross repeats a cross with the sexes reversed: if the first cross was plant A (female) × plant B (male), the reciprocal is B (female) × A (male). For ordinary nuclear genes the two should give the same offspring. Differences point to maternal effects, organelle (chloroplast or mitochondrial) inheritance, or sex-linked genes.
In practice
In cannabis, a reciprocal requires a female and a male of each "side", or reversing a female to supply pollen. Breeders sometimes note that a cross made one way round grew differently from the reverse. Organelles are inherited mainly through the seed parent in most flowering plants, and genes on the X and Y chromosomes are inherited differently by sons and daughters, so differences are possible. Claims of large differences in cannabis are mostly anecdotal; few controlled comparisons have been published.
Breeders also say "reversed cross" or "the reverse" when naming. Good records state which parent was the seed parent, because the reciprocal is not automatically the same seed.
Don't confuse with
- Sex reversal: chemically inducing pollen on a female; a different meaning of "reversed".
- Backcross: crossing back to a parent.
