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Information - The FFC Bulletin - 2014 V1 January

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The end of cockies cocaine?  Biological nitrogen fixation for any crop without genetic engineering

By Charles Merfield

Synthetic nitrogen fertilisers, such as urea, have been the keystone of the transformation of agriculture over the last century.  Without them there would have been no ‘Green Revolution’ in the developing world nor the dramatic increase in yields in the west.  However, synthetic nitrogen fertilisers have proven to be a double edged sword: while they have clearly boosted agricultural productivity, they have also caused multiple problems, including eutrophication of waterways and contributed to climate change through both the large amount of energy needed for their manufacture, which comes from fossil fuels, and the increased production of nitrous oxide (N2O) from soil.  The effects of synthetic nitrogen are so large and far reaching, the Stockholm Resilience Centre rates modification of the nitrogen cycle as one of only two, of the nine planetary safety boundaries that humanity has crossed.  However, the world’s agriculture is now pretty addicted to bag nitrogen, as alluded to by that pointed rural kiwi idiom ‘cockies cocaine’.  There is therefore an urgent need to wean society off this addiction.  

One very long standing idea for reducing the worlds addiction to synthetic N has been to make all crops fix their own nitrogen, as the legumes do through their symbiosis with rhizobia bacteria.  This idea has existed since the late 1800’s when N fixation by legumes was first understood.  In more recent times transgenics (genetic engineering) has been put forward as the best way to achieve this.  However, as the lack of any results from over a century of trying indicates just how hard this is to achieve.  This lack of progress means that the results achieved by Professor Edward Cocking, Director of The University of Nottingham’s Centre for Crop Nitrogen Fixation, of putting nitrogen-fixing bacteria into the cells of a wide range of major crop plants and get them to fix N under real-world field conditions is even more astonishing and a potentially world changing technology of a Nobel Prize level, and something that could be of huge value to farmers and growers.  

Professor Cocking discovered that a strain of the endophytic nitrogen fixing bacteria Gluconacetobacter diazotrophicus, originally found on sugar cane in Brazil, could be made to intracellularly colonise a wide range of crop plants, including maize, rice, wheat, oil seed rape, tomato and white clover, form a symbiosis and fix nitrogen.  Picking this apart, it is multiply astonishing:  That this one species of bacteria can colonise and form a symbiosis with such a wide range of plant species is stunning - most symbioses are highly specific, i.e., the two species forming the symbiosis (e.g. legume and bacteria) cannot make a symbiosis even with other closely related species, which is why different legumes need different inoculants.  That G. diazotrophicus also continues to fix nitrogen while hosted by this highly diverse range of plant species, including both monocots and dicots, is even more impressive as many different components need to work, for example, the plant must not attack the bacteria but instead protect it and allow it to feed on the sugars the plant has made; the bacteria has to fix nitrogen, which requires the oxygen level to be kept low enough to avoid ‘poisoning’ the N fixing process while still allowing the bacteria to live and for a decent proportion of the reactive nitrogen to then be passed back to the plant for it to use.  On top of all of that, Prof. Cocking and his team have worked out how to deliver G. diazotrophicus as a seed dressing.  Many laboratory ‘proof of concepts’ done under sterile conditions often fail when faced with the microbiologically competitive real world of farming.  However, in pretty short order, this technique has undergone field trials proving that it is a practically viable technology.  

However, the technology is not yet a complete panacea or replacement for nitrogen fertilisers.  The first field trials, while showing that the crops were successfully colonised (which is very impressive) and that they fixed nitrogen which the plant was able to access (even more impressive), they ‘only’ supplied nitrogen at between a quarter and half the recommended N application rates.  While that achievement should not be downplayed, the gold standard would be the supply of all the nitrogen that the crop needs for optimal growth.  Having said that, even a ¼ or a ½ reduction in the amount of bag N applied, at both a farm and global level, would be a significant benefit.  Plus these are very early days: there is considerable scope for breeding both crops and G. diazotrophicus to considerably improve the level of N fixation and bring it closer to the total needed by the crop for optimum growth.  

The University of Nottingham also clearly thinks that there is potential in the technology, as it has spun-off a commercialisation company, Azotic Technologies  (named after ‘azote’ coined by French chemist, biologist and ‘Father of Modern Chemistry’ Antoine Lavoisier (1743 – 1794), who saw it as the part of air that cannot sustain life, and which also forms part of the taxonomic name of G. diazotrophicus and the name diazotrophs given to microbes that fix nitrogen).  

To conclude, considering that science has been trying to introduce biological nitrogen fixation into non-legume crop plants for over a century, it is truly stunning that, Prof. Cocking and his team have achieved so much in such a short space of time.  While, it is not yet a full replacement for synthetic nitrogen fertilisers, this may be possible with further improvements, and any reduction in the amount of bag N used is a significant benefit.  At the same time, if this is truly going to be a world changing technology, it is unlikely to achieve that goal if the intellectual property is locked down, it needs to be made freely and widely available and modifiable , much like open source software.  With that kind of freedom this really does have a chance of being world changing, no hyperbole.  

Further information

University of Nottingham press release http://www.nottingham.ac.uk/news/pressreleases/2013/july/world-changing-technology-enables-crops-to-take-nitrogen-from-the-air-.aspx

Prof. Edward Cocking http://www.nottingham.ac.uk/biosciences/people/edward.cocking

Azotic Technologies website http://www.azotictechnologies.com/

Journal papers

Symbiosome-like intracellular colonization of cereals and other crop plants by nitrogen-fixing bacteria for reduced inputs of synthetic nitrogen fertilizers http://link.springer.com/article/10.1007/BF03187127

Intracellular colonization of roots of Arabidopsis and crop plants by Gluconacetobacter diazotrophicus http://link.springer.com/article/10.1079%2FIVP2005716