Neglected tropical crops?

PUBLISHED: 1 DECEMBER 2015 | ARTICLE NUMBER: 15204 | DOI: 10.1038/NPLANTS.2015.204 editorial Neglected tropical crops? Medical science has acknowledged that research resources are not always directed where they will be most effective. Is it time that we paid similar attention to blind spots within the plant sciences? Published research articles 2013–2015 (logarithmic scale) Over the past decade or so, there has been correlation between the number of research as pigeon peas, millet, plantain, cassava, an increased awareness of what are known as articles and cultivated area for common cashew nuts and sorghum. These are all neglected tropical diseases (NTDs). These are crop species (Fig. 1). Wheat, rice and maize largely cultivated in the same tropical and a diverse group of communicable diseases dominate the crop research field, but the subtropical regions where they constitute that, despite affecting a vast number of the roughly linear correlation can be used to a major part of the local diet: for example, world’s population and causing substantial identify crops for which the amount of sorghum in West Africa, millet in West economic costs for the countries where they research is not proportional to the area of Africa and Southeast Asia, and cassava are endemic, attract little money for research land used for their cultivation. throughout Africa and Southeast Asia — or treatment. In 2012 the World the same areas where NTDs are Health Organization published most prevalent. a roadmap for the eradication or However, it cannot be said Wheat Rice control of 17 NTDs by the end that there is a complete lack of Maize Soybean of this decade. Their list includes high-quality research on these dengue, leprosy, guinea worm, crops. Sorghum has had its Tobacco Tomato leishmaniasis, schistosomiasis, genome sequenced and published Orange Apple Grape yaws and other micro- and (Nature 457, 551–556; 2009), Barley Tea macroparasitic conditions. with three further sequences NTDs occur predominantly in appearing a couple of years Sorghum Coffee tropical and subtropical countries. later (Genome Biol. 12, R114; Cucumber They are associated with poor 2011). A reference genome for Mango Cassava sanitation and lifestyles that foxtail millet (Setaria italica) Millet bring peoples into close contact has also been published Plum with infectious vectors such as (Nature Biotechnol. 30, 555–561; domestic animals and livestock. 2012), and last year so were draft Put simply, they are diseases of genomes of domesticated and Cashew nut Asparagus poverty — one substantial aspect wild cassava (Nature Commun. Plantain of which is a meagre and insecure 5, 5110; 2014). Such detailed food supply. Why, then, are crops genetic analyses should provide Pigeon pea that form a substantial part of a framework on which more the global diet not the subject translational studies can build. Global cultivated area (logarithmic scale) of equally substantial research The diseases that reduce the and development? harvests of these crops are also a Figure 1 | Number of research articles against global cultivated area for The Food and Agriculture common crop species. Red indicates substantially under-researched species, focus of research. For example, a Organization of the United study was published earlier this with point size indicating the relative extent of the research short-fall. Nations (FAO) collects annual year about receptors involved statistics on global crop in triggering germination in production (http://faostat3.fao.org/home/). The most dramatic deviations are in Striga hermonthica (Science 349, 864–868; The most recently available data is for 2013; a positive direction: plants that are the 2015), a destructive parasitic plant that it shows that wheat, maize and rice are the subject of far more research than their crop preys on sorghum and other grain crops most widely grown crops, having global production would suggest. This may be across Africa and beyond. There has also cultivated areas of 219, 185 and 165 million because their use in research is unrelated to been a recent project by Queen’s University hectares, respectively. The yields from their status as a crop. Tobacco and tomato, Belfast (funded by the Bill & Melinda Gates each crop vary, so that maize produces the for example, are the subject of considerable Foundation) to develop safe and effective largest harvest weight of the three at just research — they are the fifth and sixth most treatments against nematode species over 1 billion tonnes for the year — but the researched crop plants, respectively — affecting sub-Saharan crops such as plantain. impressive yields obtained from sugarcane because they are commonly used models, It is a cruel, if unsurprising, irony that make it the largest crop of all by harvest particularly for disease resistance and the communities that suffer most from weight (1.9 billion tonnes), despite being development. Fruit is also disproportionately NTDs are sustained by crops that are only the tenth by cultivated area. researched considering the relatively small themselves relatively neglected by science. Assessing research investment is a harder size of their harvest, as are crops that could Poverty is a global problem, but its solutions task. No precise statistics exist, but a fair be considered luxuries, such as tea, coffee, are overwhelmingly local — whether it be proxy would be numbers of published cocoa and asparagus — ‘cash crops’, rather the provision of clean water and sanitation, research papers. The exact numbers depend than staples. or providing communities with highon the source (PubMed, Google Scholar, However, there are also substantially yielding resilient crops suited to their ISI, Scopus, and so on), but there is a clear under-researched or neglected crops, such local environment.  ❐ NATURE PLANTS | VOL 1 | DECEMBER 2015 | www.nature.com/natureplants © 2015 Macmillan Publishers Limited. All rights reserved 1  (...truncated)