Wild Relatives Confer Salt Tolerance

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Biological Strategy

Halophytes

UBC Botanical Garden

Image: Erik-Jan Leusink / Unsplash / Free non-commercial use

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Salt tolerance evolved differently across plant species

Halophytes, or salt-tolerant plants, are found in a number of environments: seashores, mangrove swamps, salt marshes, and saline semi-deserts. As the amount of salt in agricultural soils increases, it’s important to understand how different plants cope with salt, a mechanism known as salt tolerance.

Some plants are much more tolerant of salt than others. Many of the crops we use in agriculture, such as wheat, rice, and corn, have a very low salt tolerance, although their wild relatives (non-domesticated species that are closely-related to food crops) are oftentimes much more tolerant. So, why haven’t food crops evolved to adopt this tolerance?

It is hypothesized that that salt tolerance is an “evolutionary labile” trait, which means that it is less correlated with other traits and therefore doesn’t face the same evolutionary “pressures” that would require it to be expressed in each generation. These traits often vary widely in how they are expressed between individuals and between related groups of organisms. Another way to think of labile traits is that they are not “locked in” within evolutionary lineages. Some examples of evolutionary labile traits are reproductive timing and migration timing. This is in contrast to non-labile traits, which are much more ‘constrained’ by evolution and are less likely to change, for example, leaf size and color.

Preserving wild relatives of food crops allows us to study and understand how salt tolerance has evolved in different species. As sites of both public engagement and plant conservation, botanical gardens are working to educate the public on the value of conserving a variety of different plant species. You can learn more by reading this open-access chapter on Public Education and Outreach Opportunities for Crop Wild Relatives in North America, co-authored by UBC Botanical Garden’s Dr. Tara Moreau.

Adapted from the UBC Botanical Garden “Botany Photo of the Day“

Last Updated February 17, 2020

References

“Despite concerted effort to develop salt-tolerant cereal crops, few commercially viable salt-tolerant crops have been released. This is puzzling, given the number of naturally salt-tolerant grass species. To better understand why salt-tolerance occurs naturally but is difficult to breed into crop species, we take a novel, biodiversity-based approach to its study, examining the evolutionary lability of salt-tolerance across the grass family. We analyse the phylogenetic distribution of naturally salt-tolerant species on a phylogeny of 2684 grasses, and find that salt-tolerance has evolved over 70 times, in a wide range of grass lineages. These results are confirmed by repeating the analysis at genus level on a phylogeny of over 800 grass genera. While salt-tolerance evolves surprisingly often, we find that its evolution does not often give rise to a large clade of salt-tolerant species. These results suggest that salt-tolerance is an evolutionarily labile trait in grasses” (Bennett 2013:1)

Journal article

Repeated evolution of salt-tolerance in grasses

The Royal Society Biology Letters | 23/04/2013 | T. H. Bennett, T. J. Flowers, and L. Bromham

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Reference

Journal article

Delivering on a promise: integrating species traits to transform descriptive community ecology into a predictive science

The University of Chicago Press Journals | 01/06/2013 | W. C. E. P. Verberk, C. G. E. van Noordwijk, and A. G. Hildrew

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Reference

Book section

Public Education and Outreach Opportunities for Crop Wild Relatives in North America

North American Crop Wild Relatives, Volume 1 pp 311-324 | 12/12/2018 | Tara Moreau and Ari Novy

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