Production and characterization of arboreous and fertile Solanum melongena plus Solanum marginatum somatic hybrid plants

In crop plants the shift from being annuals to perennials may allow future agricultural systems requiring less energy inputs. The practicability of this was tested for Solanum melongena. Leaf protoplasts of S. melongena (2n = 2x = 24) and one of the related arborescent species Solanum marginatum (2n = 2x = 24) were electrofused and fertile somatic hybrids with arborescent habit regenerated. The magnetic cell sorter (MACS) technique was used for the selection of heterokaryons. The hybrid nature of 18 regenerated plants was assessed on the banding patterns generated by inter-simple sequence repeat PCR. When taken to maturity in the greenhouse, hybrids grew more vigorously compared to the parental species. Their morphological traits were intermediate between those of S. melongena and S. marginatum. Hybrids flowered and produced an average of 85% stainable viable pollen and fertile fruits. The somatic hybrids were maintained in the greenhouse for more than 3 years and continued to produce flowers developing into two types of fruits with plentiful seeds. Fruits were either striated green containing non-germinable seeds or yellow with fully germinable seeds. Their S-1 progenies showed common features with S-0 hybrids, including fertility and arborescent habit. Cytologically, somatic hybrids exhibited the expected chromosome number of 2n = 4x = 48, while chromosome pairing during microsporogenesis was associated with a low frequency of intergenomic pairing. It is concluded that an arborescent perennial species has been obtained by somatic hybridization. The usefulness of this species per se or in eggplant breeding will depend not only on the transmission of the arborescent habit to cultivated eggplant varieties, but also on the variability that should be created from backcrossing the S. melongena + S. marginatum hybrids to S. melongena.