Support of the endosperm balance number hypothesis utilizing some tuber-bearing Solanum species

The normal development of the endosperm appears to depend on a ratio of two female genomes to one male genome in most angiosperms. However, successful crosses between some tuber-bearing Solarium species do not conform to this ratio. An endosperm balance number (EBN) hypothesis has been proposed to reconcile the two female genomes: one male genome ratio proposal and the anomalous crossing behavior of some species. Crosses performed to test the EBN hypothesis are reported in this paper. The results support the hypothesis and demonstrate its usefulness in predicting the success or failure of a cross and the ploidy of the offspring. A format for conducting and reporting crossing experiments is proposed that facilitates the comparison of results of different experiments.