Diversity in commercial varieties and landraces of black eggplants and implications for broadening the breeders' gene pool

Black-coloured eggplants (Solanum melongena) represent the commercially most important group of eggplants in Europe and North America. Most of the modern varieties of black eggplants correspond to F-1 hybrids, which at the same time constitute an elite gene pool for the development of new varieties. However, there are many black landraces and old varieties, which could be useful as sources of variation for black eggplant breeding programmes as well as for the broadening of the genetic diversity of the breeders' gene pool. We have studied the morphological and molecular [amplified fragment length polymorphism and simple sequence repeat (SSR)] diversity in a collection of 38 black eggplant accessions, including commercial (modern F-1 hybrid and old nonhybrid) varieties and landraces as well as in six nonblack control eggplants, from different origins. The results show that black eggplants contain a considerable morphological and molecular diversity, but commercial varieties, and in particular F-1 hybrids, display a reduced morphological and molecular diversity when compared with landraces. The principal components analysis morphological and principal coordinates analysis molecular analyses show that commercial F-1 hybrids group together, indicating that they share a common and narrow gene pool. Commercial F-1 hybrids present a series of productive advantages, like early production, intense black colour (low L*, a* and b*) values and absence of fruit calyx prickles. However, several of the landraces and old nonhybrid varieties studied present a high yield as well as other traits of interest for eggplant breeding. Furthermore, given the low genetic diversity of F-1 hybrids and the moderate level of SSR heterozygosity found in these materials (0.382), introduction of black landraces and old varieties in the present breeding programmes could contribute to broadening the gene pool used by breeders and this could help increase the heterosis for yield of F-1 hybrids, which is greatly favoured by high heterozygosity levels.