5 Pulses that are Packed with Goodness

Each year on February 10, the United Nations commemorates what probably sounds to many like a strange occasion: World Pulses Day.¹⁾World Pulses Day, United Nations

But, as a researcher focused on forgotten and underutilized legumes,²⁾Dr Nadia Radzman, University of Cambridge I think the initiative is an important step towards food security. Getting people to eat more pulses can ultimately help achieve UN Sustainable Development Goal 2: Zero Hunger.³⁾Goal 2: Zero Hunger. United Nations

First, for clarification, “legumes” and “pulses” have different meanings. “Legumes” are all plants belong to the family Leguminosae or Fabaceae, while “pulses” are the dried seeds of legume plants. Pulses include beans, lentils and chickpeas.

One reason that legume plants offer such promise in ending hunger is that they don’t need good soil or nitrogen fertilizers. Plants need nitrogen to build important molecules such as protein and DNA. Most legumes can thrive in poor soil by fixing nitrogen gas from the air for their own use. This happens through symbiotic interaction with friendly bacteria known as rhizobia. The rhizobia are housed inside structures called nodules on the plant’s roots.

Thanks to their nitrogen-fixing ability, pulses are nutritional powerhouses: high in protein and fiber, and low in fat.

But that’s not the only interesting thing about legumes and pulses. In honor of World Pulses Day, I would like to highlight five pulses that have unique properties and stories.

1. The African yam bean: high protein beans and underground tubers

The African yam bean (Sphenostylis stenocarpa) offers two servings of food: beans and underground tubers. The tubers have higher protein content than any non-legume tuber crops like potato and cassava, and the beans are also high in protein. Their nutritional value was proved during the Nigerian Civil War (1967-1970) when the beans were cooked with amaranthus, telfaria or cassava leaves to feed the malnourished in war-affected areas.⁴⁾Nwokolo, E. (1996). African yam bean (Sphenostylis stenocarpa (Hoechst ex. A. Rich.) Harms.). In: Nwokolo, E., Smartt, J. (eds) Food and Feed from Legumes and Oilseeds. Springer, Boston, MA. https://doi.org/10.1007/978-1-4613-0433-3_18

This crop is native to Africa and was once grown across the African continent.⁵⁾Potter, D. Economic Botany ofSphenostylis (Leguminosae). Econ Bot 46, 262–275 (1992). https://doi.org/10.1007/BF02866625 Researchers have proposed that it may have been domesticated multiple times in west and central Africa.⁶⁾Potter, D., Doyle, J.J. Origins of the African Yam bean (Sphenostylis stenocarpa, leguminosae): evidence from morphology, isozymes, chloroplast DNA, and linguistics. Econ Bot 46, 276–292 (1992). https://doi.org/10.1007/BF02866626 Today, it is mostly grown as security or subsistence crop, rather than commercially. But its high protein content and drought tolerance are attracting increasing interest.⁷⁾Toyosi T. George, Anthony O. Obilana, Samson A. Oyeyinka, The prospects of African yam bean: past and future importance, Heliyon, Volume 6, Issue 11, 2020, https://doi.org/10.1016/j.heliyon.2020.e05458

2. Common bean: diversity and environmental versatility

The common bean (Phaseolus vulgaris) comes in many varieties around the world. Examples are black beans, red kidney beans and pinto beans – they look different but they are the same species. What’s special about them is that they can pair with a larger number of rhizobial species⁸⁾Martínez-Romero, E. Diversity of Rhizobium-Phaseolus vulgaris symbiosis: overview and perspectives. Plant and Soil 252, 11–23 (2003). https://doi.org/10.1023/A:1024199013926 than other legumes can.⁹⁾Lira MA Jr., Nascimento LRS and Fracetto GGM (2015) Legume-rhizobia signal exchange: promiscuity and environmental effects. Front. Microbiol. 6:945. doi: 10.3389/fmicb.2015.00945 This may have helped the common bean to thrive outside its native land and diversify in various habitats around the world. It’s able to fix nitrogen in different environments, making it a resilient legume species.

3. Pea: a role in early understanding of genetics

The pea (Pisum sativum) is among the oldest domesticated crops in the world. It contributed to the understanding of genetics, thanks to Gregor Mendel’s famous experiment with pea plants.¹⁰⁾Miko, I. (2008) Gregor Mendel and the principles of inheritance. Nature Education 1(1):134 Mendel observed the way that different physical properties of the pea plants were inherited: pod shape, seed shape, seed colour, unripe pod colour, flower colour, stem length, and flower placement. He crossed two pea plants that had different properties and observed the seven traits in the subsequent generations for two years. From this experiment, he established Mendel’s Rules of Inheritance – still applicable in modern day genetic study.

The rich genetic diversity of the pea is also a valuable resource for important crop traits that can withstand various weather conditions due to climate change.¹¹⁾Smýkal P, Aubert G, Burstin J, Coyne CJ, Ellis NTH, Flavell AJ, Ford R, Hýbl M, Macas J, Neumann P, et al. Pea (Pisum sativum L.) in the Genomic Era. Agronomy. 2012; 2(2):74-115. https://doi.org/10.3390/agronomy2020074

4. Chickpea: built for drought

Many pulses are drought tolerant and use less water for production than animal-sourced proteins, especially beef. Chickpea (Cicer arietinum) is known to be highly drought tolerant.¹²⁾Rani A. et.al. Developing Climate-Resilient Chickpea Involving Physiological and Molecular Approaches With a Focus on Temperature and Drought Stresses. https://doi.org/10.3389/fpls.2019.01759 Most of this crop is grown under rainfed conditions in arid and semi-arid areas. This special ability to grow where water is scarce is more prominent in wild species of chickpea. Wild chickpeas can also tolerate temperatures up to 40°C – another valuable genetic resource for better drought tolerance in modern chickpeas.¹³⁾Toker, C., Canci, H. & Yildirim, T. Evaluation of perennial wild Cicer species for drought resistance. Genet Resour Crop Evol 54, 1781–1786 (2007). https://doi.org/10.1007/s10722-006-9197-y

Still, chickpea yield is highly compromised when there is lack of water. Therefore, scientists are looking for beneficial traits that can reduce the yield loss in chickpeas during drought. This may contribute to a more secure food source in the midst of climate change.¹⁴⁾Varshney, R.K., Thudi, M., Roorkiwal, M. et al. Resequencing of 429 chickpea accessions from 45 countries provides insights into genome diversity, domestication and agronomic traits. Nat Genet 51, 857–864 (2019). https://doi.org/10.1038/s41588-019-0401-3

5. Lupins: special cluster roots to seek nutrients

White lupins (Lupinus albus), yellow lupins (Lupinus luteus) and pearl lupins (Lupinus mutabilis) can form special roots to get more nutrients without the need for additional fertilisers.¹⁵⁾Hocking, P., Jeffery, S. Cluster-root production and organic anion exudation in a group of old-world lupins and a new-world lupin. Plant and Soil 258, 135–150 (2004). https://doi.org/10.1023/B:PLSO.0000016544.18563.86 Plants need not only nitrogen but phosphorus. Usually it’s given to plants in fertiliser to increase crop yield. Phosphate fertiliser is made from phosphate rock –- a non-renewable resource which is rapidly depleting through agricultural use.¹⁶⁾Understanding phosphorus fertilizers. University of Minnesota Extension The white, yellow, and pearl lupins have unique root modifications called cluster roots that can liberate phosphorus from soil particles when the nutrient is low. These roots look like bottlebrush and are formed only when the level of phosphorus in the soil is low.¹⁷⁾Shane, M.W., Lambers, H. Cluster Roots: A Curiosity in Context. Plant Soil 274, 101–125 (2005). https://doi.org/10.1007/s11104-004-2725-7 These cluster roots exude negatively charged compound called carboxylate that can liberate phosphorus from the soil and make it available for the plant to use.¹⁸⁾Hans Lambers, John G. Bishop, Stephen D. Hopper, Etienne Laliberté, Alejandra Zúñiga-Feest, Phosphorus-mobilization ecosystem engineering: the roles of cluster roots and carboxylate exudation in young P-limited ecosystems, Annals of Botany, Volume 110, Issue 2, 1 July 2012, Pages 329–348, https://doi.org/10.1093/aob/mcs130 So lupins do not have to rely on phosphate fertilisers and can even help neighbouring plants by increasing the phosphorus level in the soil.

Food security

Pulses deserve our attention not just on February 10 but every day. The five pulses I’ve presented here can serve as sustainable protein sources and make food systems more diverse. They can greatly contribute to better food security in the future.

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This article is republished from The Conversation under a Creative Commons license. Read the original article.

nadiaradzman

Nadia is a Research Associate in Plant Biology at the University of Cambridge. She is doing a research project about improving the tuber production of African Yam Beans.