The Role of 2n Gametes and Endosperm Balance Number in the Origin and Evolution of Polyploids in the Tuber-Bearing Solanums

The Role of 2n Gametes and Endosperm Balance Number in the Origin and Evolution of Polyploids in the Tuber-Bearing Solanums

Domenico Carputo^a, Luigi Frusciante^b, and Stanley J. Peloquin^c
^a Department of Soil, Plant, and Environmental Sciences, Faculty of Biotechnological Sciences, University of Naples "Federico II," 80055 Portici, Italy,
^b Department of Soil, Plant, and Environmental Sciences, Faculty of Agricultural Sciences, University of Naples "Federico II," 80055 Portici, Italy
^c Department of Horticulture, University of Wisconsin, Madison, Wisconsin 53706-1590

Corresponding author: Domenico Carputo, Plant, and Environmental Sciences, Via Università 100, 80055 Portici, Italy., carputo{at}unina.it (E-mail)

Communicating editor: Z-B. ZENG

Polyploidization has played a major role in the origin and evolutionof polyploid species. In this article we outline the uniquecharacteristics of 2n gametes and implications of their participationin the evolution of polyploid Solanum species. The genetic consequencesof 2n gametes indicate that sexual polyploidization resultsin greater variability, fitness, and heterozygosity than doessomatic doubling. Further, the mechanisms of 2n gamete formationand the frequency of 2n gamete-forming genes in present polyploidsand their ancestral species provide additional evidence of theirinvolvement. Equally important is the endosperm, via the endospermbalance number (EBN) incompatibility system, in complementingthe role of 2n gametes. In fact, the EBN system acts as a screenfor either 1n or 2n gametes, depending on the EBN and chromosomenumbers of parental species. EBN in combination with 2n gametesmaintains the ploidy integrity of diploid ancestral species,while providing the flexibility for either unilateral or bilateralsexual polyploidization.

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