Interspecific Hybridization between Eggplant and Wild Relatives from Different Genepools

Abstract

<jats:p>Wild relatives represent a source of variation for many traits of interest for eggplant (<jats:italic>Solanum melongena</jats:italic>) breeding, as well as for broadening the genetic base of this crop. However, interspecific hybridization with wild relatives has been barely used in eggplant breeding programs. As initiation of an introgression breeding program we performed 1424 interspecific hybridizations between six accessions of eggplant from the Occidental and Oriental groups and 19 accessions of 12 wild species from the primary (<jats:italic>Solanum incanum</jats:italic> and <jats:italic>Solanum insanum</jats:italic>), secondary (<jats:italic>Solanum anguivi</jats:italic>, <jats:italic>Solanum dasyphyllum</jats:italic>, <jats:italic>Solanum lichtensteinii</jats:italic>, <jats:italic>Solanum linnaeanum</jats:italic>, <jats:italic>Solanum pyracanthos</jats:italic>, <jats:italic>Solanum tomentosum</jats:italic>, and <jats:italic>Solanum violaceum</jats:italic>), and tertiary (<jats:italic>Solanum elaeagnifolium</jats:italic>, <jats:italic>Solanum sisymbriifolium</jats:italic>, and <jats:italic>Solanum torvum</jats:italic>) genepools. Fruit set, hybrid seed, and seed germination were obtained between <jats:italic>Solanum melongena</jats:italic> and all wild species of the primary and secondary genepools. The highest fruit set percentage and quantity of seeds per fruit were obtained with the two primary genepool species <jats:italic>S. incanum</jats:italic> and <jats:italic>S. insanum</jats:italic> as well as with some secondary genepool species, like <jats:italic>S. anguivi</jats:italic>, <jats:italic>S. dasyphyllum</jats:italic>, or <jats:italic>S. lichtensteinii</jats:italic>, although some differences among species were observed depending on the direction of the hybridization. For small-fruited wild species, the number of seeds per fruit was lower when using them as maternal parent. Regarding tertiary genepool species, fruit set was obtained only in interspecific hybridizations of eggplant with <jats:italic>S. sisymbriifolium</jats:italic> and <jats:italic>S. torvum</jats:italic>, although the fruit of the former were parthenocarpic. However, it was possible to rescue viable interspecific hybrids with <jats:italic>S. torvum</jats:italic>. In total we obtained 58 interspecific hybrid combinations (excluding reciprocals) between eggplant and wild relatives. Some differences were observed among <jats:italic>S. melongena</jats:italic> accessions in the degree of success of interspecific hybridization, so that the number of hybrid combinations obtained for each accession ranged between 7 (MEL2) and 16 (MEL1). Hybridity of putative interspecific hybrid plantlets was confirmed with a morphological trait (leaf prickliness) and 12 single nucleotide polymorphism markers. The results show that eggplant is amenable to interspecific hybridization with a large number of wild species, including tertiary genepool materials. These hybrid materials are the starting point for introgression breeding in eggplant and in some cases might also be useful as rootstocks for eggplant grafting.</jats:p>

Line × Tester Analysis for Morphological and Fruit Biochemical Traits in Eggplant (Solanum melongena L.) Using Wild Relatives as Testers

“…The popular variety is based on local preferences [37]. The secondary genepool species are the reserve of useful genes for the improvement of present-day varieties, but because of breeding barriers, they are not exploited to their full potential [4,42,43]. Therefore, most of the time, the local germplasm is used extensively which might have resulted in the lower genomic diversity of eggplant, which has further resulted in the yield stagnation and susceptibility to diseases [44].…”

“…Eggplant (Solanum melongena L.; Solanaceae) is a highly diverse vegetable with a large array of phenotypically variable local varieties. Several studies show that eggplant can be hybridized with many wild related species, opening the way for introgression breeding by using wild relatives as donors of variation [3,4]. Although the center of origin of eggplant is the Indo-Chinese region [5], the greatest diversity in its wild relatives is found in Africa [6].…”

Crop wild relatives of the brinjal eggplant (Solanum melongena): Poorly represented in genebanks and many species at risk of extinction

“…Defining genepools in large genera such as Solanum is challenging and we have approached this with a compromise solution that takes into account phylogenetic relationships and crossability (Vorontsova et al, 2013; Plazas et al, 2016). The concept presented here uses primarily phylogenetic relationships to define GP2, and GP3 includes less closely related but useful species which have previously been used in eggplant breeding but that thus far cannot be easily crossed with S. melongena (Plazas et al, 2016). Our newly suggested genepool concept for eggplant includes one wild species (the wild progenitor of the eggplant, S. insanum ) in GP1, 48 species in GP2, and three more widespread weedy species with native distributions in the New World in GP3 (see Table 2).…”

“…They separated S. insanum into three major genetic groups and suggested that geographic isolation and limited gene flow have structured the genetics of this species in the study area. This high genetic divergence among populations suggests that further population level sampling across the range of S. insanum will uncover genetic novelty worth conserving in genebanks, especially given the lack of reproductive barriers between S. insanum and S. melongena (Davidar et al, 2015; Plazas et al, 2016).…”

“…Because crossability relationships have not been established for numerous crops and their associated wild species, surrogate categories have been created based on taxonomic hierarchy (Maxted et al, 2006), and a combination of evolutionary relationships, ploidy level, and reproductive biology (Wiersema et al, 2012). For eggplant, or other crops that are members of large genera such as Solanum , the delimitation of biologically meaningful genepools is challenging due to limited crossability data that are systematically reported (Plazas et al, 2016) as well as the extremely large number of potential genepool members. Here we adopt a combined approach to delimit a meaningful genepool concept for the cultivated eggplant taking into account both relatedness as measured by phylogenetic analyses (Vorontsova et al, 2013; Aubriot et al, in press) and, where available, crossability data (Plazas et al, 2016), as outlined in Genepool concept definition in Results.…”