Wild relatives represent a source of variation for many traits of interest for eggplant (Solanum melongena) 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 (Solanum incanum and Solanum insanum), secondary (Solanum anguivi, Solanum dasyphyllum, Solanum lichtensteinii, Solanum linnaeanum, Solanum pyracanthos, Solanum tomentosum, and Solanum violaceum), and tertiary (Solanum elaeagnifolium, Solanum sisymbriifolium, and Solanum torvum) genepools. Fruit set, hybrid seed, and seed germination were obtained between Solanum melongena 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 S. incanum and S. insanum as well as with some secondary genepool species, like S. anguivi, S. dasyphyllum, or S. lichtensteinii, 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 S. sisymbriifolium and S. torvum, although the fruit of the former were parthenocarpic. However, it was possible to rescue viable interspecific hybrids with S. torvum. In total we obtained 58 interspecific hybrid combinations (excluding reciprocals) between eggplant and wild relatives. Some differences were observed among S. melongena 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.

Introgression breeding can contribute to broadening the genetic background of eggplant (Solanum melongena). We used six eggplant varieties and 44 interspecific hybrids between these eggplant accessions and 10 accessions of wild relatives from the primary genepool species S. insanum and secondary genepool species S. anguivi, S. dasyphyllum, S. incanum, S. lichtensteinii, and S. tomentosum to obtain first backcross generations to S. melongena. Pollen viability in cultivated and wild parents and interspecific hybrids with S. insanum was high, while for interspecific hybrids with secondary genepool species it was variable. First backcross generations to S. melongena were obtained with interspecific hybrids of all the wild species, with the best results being obtained in crosses with hybrids between S. melongena and S. insanum. However, ample differences were observed among eggplant varieties in the success of the crosses. Additionally, the six eggplant varieties were crossed with secondary genepool species S. campylacanthum, S. lidii and S. vespertilio and with tertiary genepool species S. bonariense, S. elaeagnifolium and S. sisymbriifolium with the aim of obtaining new interspecific hybrids. Successful interspecific hybridization was achieved with the three new secondary genepool species tested and, using embryo rescue, with the tertiary genepool species S. elaeagnifolium. The new backcross generations and interspecific hybrids obtained will contribute to broadening the genetic background of the eggplant and to the genetic enhancement of this crop.

Crop wild relatives (CWRs) have barely been used in eggplant (Solanum melongena) breeding. However, introgression breeding may help in coping with the challenges posed by climate change. During the rainy and dry seasons, we evaluated nine accessions of eggplant, nine accessions of seven related species (of which six are CWRs and one is a cultivated relative), and 12 interspecific hybrids. Drought tolerance scores, calculated as ratios of growing rates and ratios of mean values during the rainy and dry seasons, were obtained for vegetative growth and yield‐related traits. Considering the vegetative growth and yield‐related traits evaluated, the F1 hybrid progenies of eggplant with S. insanum MEL1 × INS2 and MEL4 × INS3, S. anguivi MEL6 × ANG1, and S. dasyphyllum MEL6 × DAS1, plus the S. sysimbriifolium accession SIS1, displayed drought tolerance. Small to large gaps were observed between phenotypic and genotypic CVs of drought tolerance scores, reflecting variable influence of environmental factors on drought tolerance of the traits evaluated. In addition, the narrow‐sense heritability was generally moderate, indicating that genes with dominance and/or epistasis effects may be involved in the expression of drought tolerance. High genotypic correlations for drought tolerance scores between pairs of traits such as branching index and leaf length, leaf petiole diameter and plant height, number of stamens per flower, and fruit pedicel length suggest that drought tolerance of these traits is controlled by genes that are in linkage disequilibrium and/or have pleiotropic effects. The results are relevant for the development of drought‐tolerant cultivars of eggplant.

Abstract:The Solanum aethiopicum Gilo group, described as homogeneous, shows a high diversity, at least at the morphological level. In Côte d'Ivoire, farmers distinguish three subgroups, named "N'Drowa", "Klogbo" and "Gnangnan", within this group. Data were obtained from 10 quantitative and 14 qualitative morpho-agronomic traits measured in 326 accessions of Gilo eggplants, at flowering and fruiting stages. Univariate and multivariate analyses allowed clearly clustering the studied accessions into the three subgroups. Fruit taste, leaf blade width, fruit diameter, leaf blade length, fruit weight, fruit color at commercial ripeness, petiole length, germination time, plant breadth, fruit position on the plant, fruit length and flowering time were, in decreasing order, the twelve most discriminating traits. Compared to the "Gnangnan" subgroup, the "N'Drowa" subgroup has smaller plant breadth and larger leaves. The fruits of this subgroup were mainly white at commercial ripeness, larger and sweeter. Most of the traits of the "Klogbo" subgroup were intermediate between those of the "N'Drowa" and "Gnangnan" subgroups. Our results could contribute to a better understanding of S. aethiopicum diversity and to the development of a core collection for African eggplant breeding. OPEN ACCESSAgriculture 2014, 4 261

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