An unusual heteromorphic incompatibility system : 3. On the genetic control of distyly and self-incompatibility in Anchusa officinalis L. (Boraginaceae).

By means of intra- and intermorph crosses it has been shown that the distyly in Anchusa officinalis L. is governed by a single diallelic locus with dominance. Presence of the dominant allele is reflected in the short-styled morph, while homozygous recessives become long-styled. Most of the short-styled plants are heterozygous, but homozygotes have been found among the raised progeny resulting from crossings. Diallel crosses have revealed that at least two incompatibility loci must exist. These and the morphological locus segregate independently. The type of incompatibility system is as yet unknown, though the great frequency of non-reciprocal incompatibility points to a sporophytic system.