Eggplant trees: The ramifications of dividing up the eggplant genepool

By christelle.rabil@croptrust.org
1 February 2022

The diversity tree developed as part of the global conservation strategy for the conservation and use of eggplant genetic resources is now available in Genesys.

A “diversity tree” is a representation of the overall structure of a crop genepool obtained by classifying its diversity in a hierarchical manner, based on information from the literature and expert opinion. The original idea was proposed by Van Treuren et al. (2009). A diversity tree for the eggplant genepool has been prepared as part of the process of developing the global conservation strategy for the conservation and use of eggplant genetic resources, and can be consulted on Genesys.


Using data from Genesys and WIEWS (World Information and Early Warning System on Plant Genetic Resources for Food and Agriculture), Svein Solberg, the first author on the eggplant strategy, and Peter Giovannini, who coordinates the development of crop strategies at the Crop Trust, estimated the number of accessions in each end-group in the eggplant diversity tree, and identified groups that are not well represented.

This analysis highlighted in particular that some crop wild relative species are not well represented in ex situ collections and that a high proportion of accessions in the eggplant genepool have an unknown or undefined “biological type” in Genesys and WIEWS. That means we do not know whether they are landraces, old varieties, or even wild species.

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The primary division into Old World, New World, and Australian species is based on molecular marker research (Weese and Bohs, 2010; Stern et al., 2011; Knapp et al., 2013). But the taxonomy is challenging. The Old World group can be further divided into the Eggplant clade, the Anguivi clade, and “Others”. The Eggplant clade includes brinjal eggplant and its closest wild ancestor, Solanum insanum L. plus nine other wild species (Syfert et al., 2016).  The Anguivi clade includes two other cultivated species -- scarlet eggplant (Solanum aethiopicum) and gboma eggplant (Solanum macrocarpon) -- and more than 30 wild species (Lester and Daunay, 2003; Lester et al., 2011). The third clade includes another 30 wild species, of which 7 are highlighted as eggplant wild relatives. 

In contrast to other important crops, cultivated Solanum melongena lacks molecular studies including a large number of accessions (see for example Tripodi et al., 2021 for peppers). However, there is evidence of distinct occidental (Europe, Africa and America ) and oriental clusters (Asia) (Vilanova et al., 2021, Cericola et al., 2013), and to a lesser extent of morphological and molecular differentiation at the level of the country of origin (Hurtado et al 2012).

Asia is the center of domestication and the primary center of diversity, therefore this region was further divided into subclusters to differentiate countries where high diversity is found, such as India and China. For cultivated Solanum aethiopicum, a differentiation into four cultivar groups is based on fruit and leaf morphology: gilo, kumba, aculeatum, and shum. (Lester and Niakan, 1986; Prohens et al., 2012). Solanum macrocarpon has no recognized cultivar groups.

Yet.

 

This article was provided to Genesys by Svein Solberg, the first author on the eggplant strategy, and Peter Giovannini, who coordinates the development of crop strategies at the Crop Trust, and Luigi Guarino, Director of Science at The Global Crop Diversity Trust.

 

References: 

Cericola, F.,  E. Portis, L. Toppino,  L. Barchi, N. Acciarri, T.  Ciriaci, et al. 2013. The population structure and diversity of eggplant from Asia and the Mediterranean basin. PLoS ONE 8:e73702. doi: 10.1371/journal.pone.0073702

Ebert, A.W., E.B M. Drummond, P. Giovannini, and M. van Zonneveld. 2021. A global conservation strategy for Cucurbitaceae family crops. Global Crop Diversity Trust. Bonn, Germany.

Hurtado, M., S. Vilanova, M.Plazas,  P. Gramazio, H. H. Fonseka, R. Fonseka, et al. 2012. Diversity and relationships of eggplants from three geographically distant secondary centers of diversity. PLoS ONE 7:e41748. doi: 10.1371/journal.pone.0041748

Knapp S., M.S. Vorontsova, and J. Prohens. 2013. Wild Relatives of the Eggplant (Solanum melongena L.: Solanaceae): New Understanding of Species Names in a Complex Group. PLoS ONE 8(2): e57039

Lester, R.N., and L. Niakan. 1986. Origin and domestication of the scarlet eggplant, Solanum aethiopicum, from S. anguivi in Africa. In: D’Arcy, W.G. (ed.) Solanaceae: biology and systematics. Columbia University Press, New York, USA, pp 433–456.

Lester, R.N., and M.C. Daunay. 2003. Diversity of African vegetable Solanum species and its implications for a better understanding of plant domestication. Schriften zu Genetischen Ressourcen 22:137–152.

Lester, R.N., P.M. Jaeger, and  A. Child. 2011. Solanum in Africa. Celia Lester, Birmingham, UK

Prohens, J.,  M. Plazas, M.D. Raigón, J.M. Seguí-Simarro, J.R. Stommel, and S. Vilanova. 2012. Characterization of interspecific hybrids and first backcross generations from crosses between two cultivated eggplants (Solanum melongena and S. aethiopicum Kumba group) and implications for eggplant breeding. Euphytica 186: 517–538.

Stern, S.,M. de F. Agra, and L. Bohs. 2011. Molecular delimitation of clades within New World species of the “spiny solanums” (Solanum subgenus Leptostemonum). Taxon 60: 1429–1441.

Syfert, M.M., Castañeda‐Álvarez, N.P., Khoury, C.K., Särkinen, T., Sosa, C.C., Achicanoy, H.A., Bernau, V., Prohens, J., Daunay, M.C., Knapp, S., 2016. Crop wild relatives of the brinjal eggplant (Solanum melongena): poorly represented in genebanks and many species at risk of extinction. American Journal of Botany 103: 635–651.

Weese, T.L., and L. Bohs. 2010. Eggplant origins: out of Africa, into the Orient. Taxon 59: 49–56.

Tripodi, P., M.T. Rabanus-Wallace, L.Barchi, S. Kale,   S.Esposito, A. Acquadro, R. Schafleitner, M. van Zonneveld, J. Prohens. 2021.Global range expansion history of pepper (Capsicum spp.) revealed by over 10,000 genebank accessions. Proceedings of the National Academy of Sciences 118: e2104315118.

van Treuren, R., Engels, J.M.M., Hoekstra, R., van Hintum, T.J. 2009. Optimization of the composition of crop collections for ex situ conservation. Plant Genetic Resources 7(2): 185–193.

Vilanova, S., J. P. Manzur, and J. Prohens. 2012. Development and characterization of genomic simple sequence repeat markers in eggplant and their application to the study of diversity and relationships in a collection of different cultivar types and origins. Molecular Breeding 30: 647–660. doi: 10.1007/s11032-011-9650-2