ABSTRACT

RICCARDO AVERSANO, MARIA RAFFAELLA ERCOLANO, IMMACOLATA CARUSO, CARLO FASANO, DANIELE ROSELLINI, and DOMENICO CARPUTO

4.1 POLYPLOIDY IN THE PLANT KINGDOM: OCCURRENCE AND SIGNIFICANCE

The genome sizes of eukaryotes can differ 10,000-fold and part of these differences may be attributed to changes in the ploidy level. Polyploids are organisms having more than two complete sets of chromosomes in their cells. They are common in angiosperms, where at least 70% of the species experienced one or more events of genome doubling during their evolutionary history [1,2]. Many crop species are polyploids (Table 1), and it was stated that “life on earth is predominantly a polyploid phenomenon and civilization depends mainly on use of polyploid tissues-noteworthy is the endosperm of cereals” [3]. Polyploidization is considered a major evolutionary force in plants. It is a definitive cause of sympatric speciation due to the immediate reproductive isolation between newly formed polyploids and their parents [4]. Polyploidization also makes it possible to

overcome hybrid sterility and produce viable offspring following interspecific hybridization. However, there are still several open questions related to polyploidy and polyploidization. For example, Soltis et al. [5] reported that polyploidy frequency in angiosperms is high, even if the number of lineages that really derived from genome-wide duplication (WGD) events is still largely unknown. Similarly, it is not clear if polyploidy causes a change in the interaction with herbivores and pollinators.