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all people, at all times, have physical and economic access to sufficient, safe and nutritious food to meet their dietary needs and food preferences for an active and healthy life” (United Nations Food and Agriculture Organisation, 1996). Food security can be tackled from many different angles as it incorporates a vast range of subject areas. This review will focus on select themes; pesticides, pathogens and genetic modification of crops. The use of genetically modified organisms (GMOs) in the UK is very limited, but there is scope for GMOs to become more commonplace as food production is put under stress. Populations worldwide are on the rise; cities are expanding and by 2050 70% more food will be needed, leaving agriculture with less area but more demand than ever before for food production (Popp et al., 2013). There are huge inefficiencies in the food supply chain, food is lost to pests and as waste before it can be consumed, this review aims to highlight these inefficiencies and highlight methods that could be used to improve these inefficiencies and therefore food security. The review draws on a combination of scientific evidence and discussion as well as policy documentation for it basis. Specific emphasis is placed on individual papers due to relevance and impact the research could have if taken beyond proof of concept.

Controversies Surrounding Pesticide Use

In agricultural terms, ‘pesticides’ refers to herbicides, insecticides and fungicides. 34% of crops are lost to pests before they are harvested (Oerke, 2006), making them the biggest single drain on world food production. To tackle this agriculture has developed pesticides to eliminate pests and maximise yield, which has led to adverse effects such as reduced biodiversity and interruption of food webs. Popp et al. (2013)’s review ran a cost-benefit analysis of the use of pesticides and whether such use was beneficial long term. The analysis showed that increases in yield to date through pesticide use have generally been attributed to decreases in competition, therefore facilitating crops in to their maximum potential yield. It was also found that very little had been done to increase the maximum potential yield of those crops. Increasing the maximum potential yield may be a crucial development as production limits are reached in coming years (Popp et al., 2013). Single crops are often cultivated on mass scales, usually coupled with limited range of pesticides. This increases the risk of resistance being developed in pest strains due to reduced genetic diversity of the crop and distinct selective pressures on the pest. This increases the likelihood of a favourable mutation arising.

Cost-benefit analysis was used to assign a monetary value for discrete issues separately. Non- specific targeting of pesticides to organisms through methods of application were highlighted as a major cost, it is common that pesticides are applied by spraying of the pesticide so the spray is likely to be carried through the air to nearby areas, thus increasing droplet size was presented as a potential solution to this. Biopestecides could also be a less damaging alternative, being pesticides developed from natural sources, but this does not define them as safe. The uncertainty of value assignment to each point is the main downfall of this method of decision making, a lack of data prevented economic analysis from being performed as monetary values could not be calculated directly for each point. (Popp et al., 2013)   

Table 1 shows Popp et al.’s economic evaluation of pesticide use in the US over a peried of 6 years. It shows that there is a clear advantage for farmers to use pesticides to increase profits which in turn increases food supply, but farmers may not be the sole receiver of the costs of pesticide use, but does not consider cost to 3rd parties.

USD billion

Herbicides 2005

Insecticides 2008

Fungicides 2002

Total 2002-2008

Cost to growers

7.1

1.2

0.9

9.2

Cost increase to growers from no pesticide use

9.7

-

-

9.7

Yield benefit from pesticide use

16.3

22.9

12.8

52.0

Net benefit from pesticide use

26.0

21.7

12.0

59.7

Return ratio: benefit/cost (USD)

3.7

18.1

13.3

6.5

Pathogenic Threat

18% of losses in food production is accounted for by pathogens (Oerke, 2006). The focal point of research currently is into Ug99, a strain of wheat stem rust fungus that has become resistant to all resistance factors in the wheat grown for agriculture worldwide. Ug99 is capable of reducing vast areas of crops to waste within a matter of days, and is the most imminent pathogenic threat to food security currently known. A gene named Sr31 was previously providing resistance to wheat rust for most wheat worldwide, however Ug99 has developed a resistance to this. Two new genes providing protection against wheat rust, Sr33 and Sr35, have recently been isolated from goatgrass, Aegilops tauschii, and wheat, Triticum monococcum, respectively. Sr35 confers near total immunity of the wheat to Ug99 and TRTFF strains of wheat rust, whilst Sr33 provides moderate protection from all strains. Both loci encode nucleotide binding coiled-coil repeats rich in leucine (CNLs) (Ellis et al., 2014; Hahn et al., 2013; Periyannan et al., 2013).

The genes were isolated and screened with a bacterial artificial chromosome library. One Sr33 CNL stock was then mutagenised and screened for mutants that no longer possessed resistance to Ug99. Nine mutants were found and of which five were had mutations in CNLs, showing the CNL was responsible for resistance in each case. The CNL was confirmed to be in the Sr33 locus (Hahn et al., 2013; Periyannan et al., 2013).

The Sr35 sequence was also found to contain CNLs, CNL9 was also mutagenised and proven to be essential for the resistance characteristic. This work in tandem with Sr33 research findings not only proved that presence of CNLs was what was responsible for resistance, but also proved that not all CNLs could provide resistance to wheat rust. The safest option for resistance implementation is undoubtedly a stacking of both Sr33 and Sr35 as single gene resistance provides an easier path for a new resistant wheat rust strain to develop, and neither gene provides total immunity to all known wheat rust strains (Hahn et al., 2013; Periyannan et al., 2013).

Anxieties Relating to Genetic Modification

Genetically modified organisms have been tipped by many to be the solution to providing enough food for the growing population. The power that this technique possesses is undeniable but the application may not be a sound option, especially when it has been said that there is enough food to feed the global population, let alone the U.K.

Potential fears from the use of GMOs are very like those of pesticide use. Non-target application, resistant mutations from weeds, reduced genetic diversity and effects on soil and water are all fears from both. This is because both techniques result in near monocultures being grown as in all agriculture and often GM is used for tolerance of potent pesticides. Very little evidence has been found to say that non-GM and GM crops could provide separate problems, but it is likely that with mass cultivation of GM crops something will arise. It has been argued that the fear of gene flow of genes is flawed as it is unlikely that a single gene passing from one species to another will be enough for a crop to become a weed (Dale et al., 2002). Studies performed on GM salmon discovered that background genetics plays a huge part on the expression of transgenes, and there is a large amount of interplay between species and environment responsible for selection pressures of specific traits (Ahrens and Devlin, 2011).

Gene transfer from transgenic crops is a major fear about the use of GM techniques. It could occur by pollen from a GM crop transferring to a non-GM crop, resulting in the non-GM crop inheriting the GM trait. This can become a huge problem depending on the nature of the trait, especially if the trait is a resistance to herbicides such as glyphosate, resulting in a reduced selection pressure on the weeds that glyphosate is targeting. Various sterilisation approaches have been tested to prevent gene transfer alongside some more novel approaches. No single method has been found to work for all crops yet, but some have had great affect in specific crops; male sterilisation of canola crops prevents direct transfer, but still has the risk of seeds cross pollinating with weeds to develop a resistant and fertile hybrid (Daniell, 2002). Transgenic mitigation is an especially convincing method of safeguarding from gene transfer, the gene of interest is coupled with a mitigation gene that does not affect the target but if the gene is transferred into a different species it causes lack of fitness. This was demonstrated for proof of theory in Brassica napus (rapeseed) transferring genes into relative Brassica rapa weed nearby, it was found that any hybrid species and their offspring had increasingly reduced fitness and worsened reproductive ability. This succeeded in preventing survival of any hybrid crops thus stopping transgenes becoming established in any hybrid species (Al-Ahmad et al., 2006).

Intelligent Use of Genetic Modification

Globally 100% of GM crops are grown for herbicide (Ht) or insect (Bt) resistance as illustrated by figure 1 (Brookes and Barfoot, 2014). Neither of these traits come without controversies or critics, and with such a wide range of uses this seems a narrow-minded application, especially when many countries growing Ht and Bt crops suffer from limited pest pressure. This section will consider genetic engineering experiments that I perceive to be of particular interest due to novel GM use that could provide greater efficiencies of production or beneficial uses, as opposed to pesticide tolerance.

Table 2 compares the benefit of HM crops use across several regions and shows that developing countries could achieve much greater yield increases than countries mass producing GM crops (Qaim and Zilberman, 2003). Small scale farmers would potentially experience a much greater benefit from GM use as they receive the highest pest pressure. Growing Bt cotton in China and U.S. has less than 10% increase in yield, whilst India may benefit from 60% increase in yield on average using Bt cotton compared to the current hybrid crops grown in that region. Bt cotton provides resistance against the American bollworm through a Cry1Ac gene insert, a pest causing major yield loss in many countries, especially India. Field trials in India also showed that insecticide use massively reduced when using Bt cotton, drastically reducing harming environmental side effects (Qaim and Zilberman, 2003).

Since the first GM crops were engineered, photosynthesis and nitrogen fixation have both been key targets. The complexity of both systems has proven difficult to engineer, but progress is at last being made; photosynthesis has recently been improved in a tobacco plant, and nitrogen fixation has been proven to be theoretically possible. Photosynthesis is inherently inefficient with regular damage to photosystem II (PSII) inhibiting photosynthetic ability and requiring valuable energy and materials. The PsbS subunit of PSII was overexpressed along with violaxanthin de- epoxidase (VDE) and zeaxanthin epoxidase (ZPE) through insertion of coding sequences into tobacco plant Nicotiana tabacum. PsbS, VDE and ZPE are involved in non-photochemical quenching, protection of the plant from harsh light conditions. Overexpression increased speed of transition between quenched and relaxed states, especially the relaxation step, this allows the plant to return to optimal rate of photosynthesis when moving from high to low light intensity conditions, thus optimising photosynthetic capacity (Kromdijk et al., 2016). Photosynthesis was increased partially through increased water-use efficiency, which can also be engineered through a reduction in density of the stomata in Arabidopsis. Epidermal patterning factor II (EPF2) was overexpressed and resulted in increased water-use efficiency (Franks et al., 2015). Both techniques are achieved through greater utilisation of resources, without needing any extra input for growth. Figure 2 shows the results of this experiment and prove yield can be increased through this method. Intelligent GM use such as these methods could better food security without additional costs to any parties involved in production.

Nitrogen is provided to plants in different forms of fertilisers, but the use of the nitrogen by plants low. This is called nitrogen use efficiency (NUE) and can be split into uptake (NUpE) and utilisation efficiencies (NUtE). Environmental factors also influence the method of uptake, with plants growing in low pH soil preferring ammonia and amino acid nitrogen sources and higher pH preferring nitrates (Masclaux-Daubresse et al., 2010). The complexity of the system controlling NUE has been a barrier in engineering plants, but genes GS1 and TIP2 are thought to be involved in the system. GS1 encodes glutamine synthase enzyme and TIP2 encodes aquaporins that allow transport of ammonium into the root (Loque et al., 2005). GS1 and TIP2 were isolated and cloned, then inserted into barley strain Hordeum vulgare L. using cisgensis by (Kichey et al., 2009), seemingly an intelligent approach. At the time of writing the paper the transformants were growing in a greenhouse, stating that “They are in process to be tested for the presence and the number of cisgenes”, but follow up work could not be found when searching for literature (Kichey et al., 2009). This suggests the work was unsuccessful.

With vast amounts of work going into increasing NUE, it is likely that sometime soon there will be success, but currently this remains just a theory. The impact of such work would be enormous, cost reduction for producers through more efficient fertiliser use would lead to a food price reduction. Denitrification, runoff, over-application and evaporation all impact NUE. Runoff can be especially damaging as algal blooms can form in nearby water supplies, harming wildlife and creating hostile environments for species native to the original environment. Urea fertilisers are the main source of runoff if applied onto the surface of the soil as they are rarely integrated with the soil on application. In presence of water the fertilisers “run off” the soil and loss can reach up to 40% (Raun and Johnson, 1999). Increased scrutiny when applying such fertilisers may reduce production costs and in turn improve the current state of food security through price decreasing.

Conclusion

Food security is dependent on a complex network of many factors, and improvements are currently predominantly provided by use of pest control. Genetic engineering has the potential to improve food security in much more long term and sustainable means, and emphasis should be placed in research and implementation of these methods. Genetic engineering comes with threat of gene transfer and creating new weeds. However, the chances are slim that a single gene transferred from one crop to another will cause weediness, due to underlying genetic components dictating gene expression. Selection pressures are unlikely to be decreased when a gene is transferred between species, and therefore genes are unlikely to reach fixation if transferred. Current genetic engineering applications focus on allowing crops to reach maximal yield levels, but through the use of different methods it is possible that the total productive capacity of the plant can be increased. Many technologies have already been developed but only to the point of proof of concept, it is the duty of science to push these further and into production as resources become more scarce.  

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