RT Journal Article SR Electronic T1 The Role of 2n Gametes and Endosperm Balance Number in the Origin and Evolution of Polyploids in the Tuber-Bearing Solanums JF Genetics JO Genetics FD Genetics Society of America SP 287 OP 294 VO 163 IS 1 A1 Carputo, Domenico A1 Frusciante, Luigi A1 Peloquin, Stanley J. YR 2003 UL http://www.genetics.org/content/163/1/287.abstract AB Polyploidization has played a major role in the origin and evolution of polyploid species. In this article we outline the unique characteristics of 2n gametes and implications of their participation in the evolution of polyploid Solanum species. The genetic consequences of 2n gametes indicate that sexual polyploidization results in greater variability, fitness, and heterozygosity than does somatic doubling. Further, the mechanisms of 2n gamete formation and the frequency of 2n gamete-forming genes in present polyploids and their ancestral species provide additional evidence of their involvement. Equally important is the endosperm, via the endosperm balance number (EBN) incompatibility system, in complementing the role of 2n gametes. In fact, the EBN system acts as a screen for either 1n or 2n gametes, depending on the EBN and chromosome numbers of parental species. EBN in combination with 2n gametes maintains the ploidy integrity of diploid ancestral species, while providing the flexibility for either unilateral or bilateral sexual polyploidization.