Limes are apparent hybrids of citron and papedas (Scora 1975) or trihybrid cross
of citron pummelo and Microcitrus (Barrett and Rhodes 1976).
Mendel actually did a trihybrid cross
in which two of the three genes were on the same chromosome.
A dihybrid cross involves inheritance patterns for two traits considered simultaneously, a trihybrid cross
involves three simultaneous traits, and so on.
Although I describe our specific class example in which we use this method with the F2 data from a dihybrid Drosophila cross, this method could easily be adjusted for analysis of a Drosophila trihybrid cross
as well, mapping each pair of genes individually (Brooker, 2005).