Production of the dihaploid population and expected types. Haploid inducers IVP101 or PL4, both diploids, were used to pollinate tetraploid cultivar Alca Tarma. For simplicity, the potato genome is represented by two chromosome types. The haploid inducer is homozygous for the dominant seed purple spot marker. Normal fertilization and development resulting in hybrids with spotted seed, defined as successful hybridization, results in biparental triploids or tetraploids, depending on the ploidy of the male gamete. Maternal dihaploids are expected among plants germinated from nonspotted seeds. Plants displaying more than eight stomatal chloroplasts (an indication of increased nuclear content) or unusual phenotypes potentially consistent with aneuploidy were discarded (Velásquez et al. 2007; Mihovilovich et al. 2014). Genetic haploid inducers can act through either parthenogenesis (Forster et al. 2007) (development of an unfertilized egg) or genome elimination (Ishii et al. 2016) (rejection of the haploid inducer genome). Addition or introgression of residual haploid inducer DNA indicates the second mode of action.