Location, Location, Location [Or, Why rice is thrice as nice (maybe…)]

 

Arguably, one of humankind’s greatest achievements is agriculture [“the art and science of growing plants and other crops and the raising of animals for food, other human needs, or economic gain”], which in turn is considered to be a major contributing factor to the development of what we optimistically term civilisation *. However, with only passing acquaintance with the concept one might easily get the impression that it was ‘invented’ in one place – the so-called Fertile Crescent – at one point in time – approx. 12,000 years ago  – with a single category of plants – cereals – as the crop. Further searching of the literature will reveal how wide of the mark that view is. There are numerous examples of different peoples geographically well spread across the globe with multiple independent agriculturalisation events (even within the Fertile Crescent – Simone Riehl et al., Science 341: 65-67, 2013; DOI: 10.1126/science.1236743) who adopted different crops – e.g. maize in Mesoamerica, potatoes in South America, sorghum and millet in Africa (Estelle Levetin and Karen McMahon, Plants & Society, 5e, 2008, McGraw-Hill) and with at least 8 in the Fertile Crescent alone – at different periods (e.g. Michael Balter, Science 316: 1830-1835, 2007; DOI: 10.1126/science.316.5833.1830). In other words, agriculture was not something that arrived fully-formed, all at once; it was more of a gradual development of a phenomenon – an evolution if you will – that was embraced by many groups throughout time.

And there one might be happy to leave it. Because, delving deeper one finds that Man’s relationship with plant foods is even more convoluted than we might have imagined. Take, for example, the history of the domestication [“A plant is said to be domesticated when its native characteristics are altered such that it cannot grow and reproduce without human intervention”] of rice – Oryza sativa. As a staple [“a food that is eaten routinely, and in such quantities that it constitutes a dominant portion of a standard diet in a given people”], more than 3.5 billion people – i.e. over half of the world’s current population!!! – depend on rice for more than 20% of their daily calories. Interest in this member of the grass family (the Poaceae) is not surprisingly high. The question “where does rice come from” (in the sense of where did it originate) is an understandable one. But it doesn’t – yet! – have a straightforward answer.

Although there is a consensus that O. sativa was derived from the wild species O. rufipogon, how the present day varieties of indica and japonica (e.g. Hiroshi Ikehashi, Rice Science 16(1): 1–13, 2009; DOI: 10.1016/S1672-6308(08)60050-5) came to be is contentious. Was there a single domestication event that ultimately gave rise to both (and therefore in one location – in China e.g. Jeanmaire Molina et al., PNAS 108: 8351–8356, 2011; doi:10.1073/pnas.1104686108), or two separate events – and at different sites – leading to japonica in China, and indica in India [e.g. Dorian Fuller, Rice 4: 78–92, 2011; DOI 10.1007/s12284-011-9078-7]? Well, the latest suggestion – by Peter Civáň et al. (Nature Plants 1, Article number: 15164 (2015); doi:10.1038/nplants.2015.164) – is that there were not one, nor two, but in fact three distinct domestication events. Japonica was developed in southern China [so why is it called japonica and not sinensis?] and the Yangtze valley; indica in Indochina and the Brahmaputra valley; and the aus variety (drought-tolerant, early-maturing cultivars within the indica category) in central India or Bangladesh. They also conclude that aromatic rice (such as basmati) is a product of hybridization between japonica and aus **. To add to the ‘cultivation confusion conundrum’, as Dennis Normile points out, the Nature Plants paper used essentially the same data set as was studied by Xuehui Huang et al. but which led that group to conclude that there was a single domestication event (Nature 490: 497–501, 2012; doi:10.1038/nature11532) giving rise to japonica, with indica and aus the products of hybridisation between japonica and local wild rice ***. And muddying the waters still further, Marty McCarthy mischievously muses on the work of Peterson Wambugu et al. (Scientific Reports | 5:13957 | DOI: 10.1038/srep13957) with the notion that Australia could be the ‘home of rice’. All of which makes one extremely cautious in offering any answer to a child’s innocent enquiry, “Mummy/Daddy/Mr Cuttings, where does rice come from?”

Finally, and lest there still be any lingering doubts as to how important rice is, Popular Mechanics magazine has listed 1966’s release of rice type IR8 as one of its 50 inventions from the past half-century that have ‘rocked the world’. In their own words, “The International Rice Research Institute in the Philippines [IRRI] releases a semi-dwarf (e.g. Wolfgang Spielmeyer et al., Proc Natl Acad Sci USA 99: 9043–9048, 2001; doi: 10.1073/pnas.132266399), high-yield indica variety that, in conjunction with high-yield wheat, ushers in the Green Revolution. Indica rice thrives in tropical regions of Asia and South America, raising worldwide production more than 20 percent by 1970”. As is often the way with major breakthroughs, IR8 was not perfect – “Certain pests and diseases attacked IR8 easily. It had a high breakage rate during milling. The grain it produced was actually bold and chalky, so it didn’t look as good to the consumer as highly polished rice. In addition, it had a high amylose content, which meant that it hardened after cooking”, but it’s what it ultimately led to, such as semi-dwarf IR36 rice, that is probably its real legacy.

 

[Ed. – for those who need their fix of molecular studies here’s a trio of rice-related researches that deal with fundamental aspects of yield [“weight of harvested economic product per unit area”]. All three papers explore growth regulating factors (GRFs, plant-specific transcription factors; Mohammad Amin Omidbakhshfard et al., Molecular Plant 8: 998–1010, 2015; doi:10.1016/j.molp.2015.01.013) and their repression by miR396 (a micro RNA that regulates expression of genes) and the impact this has upon rice grain size and/or number: http://nature.com/articles/doi:10.1038/nplants.2015.196; http://nature.com/articles/doi:10.1038/nplants.2015.195; http://nature.com/articles/doi:10.1038/nplants.2015.203. And for those who desire a culinary cornucopia – and more – of rice facts, try Renee Marton’s 2014 publication “Rice: a Global History” in Reaktion Book’s charming ‘The Edible Series’.]

 

* Although we might think of civilization as a ‘good thing’, an alternative view is that agriculture was one of mankind’s biggest ‘mistakes’ (e.g. Clive Dennis; and Jared Diamond). For an interesting ‘debate’ on the pros and cons of agriculture, use the ‘hot link’ provided.

** If you think this is a little dull – dealing as it does with white or, at best, brown, rice – and you’re in the mood for more oryzophytoforensics, Tetsuo Oikawa et al. delve into the history of black rice (The Plant Cell 27: 2401-2414, 2015; doi: http://dx.doi.org/10.1105/tpc.15.00310). Black rice is a much more exotic product; indeed, so much so that for many years it was the preserve of Chinese Emperors. For a good overview of the work and the history of black rice, try Mary Williams’ ASPB Blog item, or Jeremy Cherfas’. And I would have liked to continue to add more colour to this item with good news about golden rice, but, sadly, Guangwen Tang et al’s paper “β-Carotene in Golden Rice is as good as β-carotene in oil at providing vitamin A to children” (Amer. J. Clin. Nutr. 96: 658-664, 2012; doi: 10.3945/ajcn.111.030775) was retracted in 2015 because the study was judged not to have complied with certain ethical guidelines. Although the Golden Rice project as a whole was one of the recipients of the United States’ Patent and Trademark Office (USPTO)’s “Patents for Humanity” Awards 2015.

*** And which is fittingly ironic since Tim Worstall considers Agriculture and the Scientific Method to be the joint number 1 greatest ‘inventions’ of all time.

[Image from: Franz Eugen Köhler, Köhler’s Medizinal-Pflanzen]