FOOD FOR THE FUTURE

By Dr Charlotte Allender, Genetic Resources Unit, Warwick Crop Centre, School of Life Sciences

Food sustainability and security is a hot topic in the news at the moment, with both famine and GM products being high on the news agenda. The Genetics Resource Unit, part of Warwick Crop Centre in the School of Life Sciences, is a seed bank holding many important species of crop. Here Dr Charlotte Allender, Assistant Manager of the GRU, explains more about the unit and the aims it hopes to achieve. What is the importance of preserving the genetic history of crops?

The chillers in the cold store at Warwick Genetic Resources Unit hum quietly away as they maintain an icy temperature of -20oC. The only light comes from a small viewing window in the heavily insulated door. Switching on the lights reveals metal shelves loaded with boxes of foil pouches all carefully labelled with unique identification numbers. Some of these pouches have been quietly sitting in the cold and dark for over 30 years, awaiting their call into action, some have arrived more recently and others have left the cold, dark world of the store for destinations all over the world.

The pouches collectively represent 14000 individual seed samples which reflect both the history of many UK vegetable crops and a means of developing the varieties of the future, capable of high productivity coupled with reduced requirements for pesticides, fertilizers and water. In short, they are a resource which will contribute to food security for all of us in the face of the twin challenges of environmental change and population growth. The freezing conditions in the cold room provide the best environment for the long term storage of these precious seeds – before being sealed in the foil pouches, seeds are dried to a very low moisture level, and this dryness in combination with the cold temperatures ensures they can survive for decades, if not a century or more. But why is preserving the genetic history of crops so important to our future?

If we step back in time (or even move away from regions where modern mechanised agriculture is currently practised), crops were and are under continual development by farmers. Over many generations, through conscious or unconscious selection, farmers moulded crops to suit their own requirements, be it to thrive on the very particular environment of their farm (including adaptation to soil type, temperature variation, rainfall, local pests and diseases) or to meet local preferences for taste and appearance. Such early versions of crop varieties are given the term ‘landraces’, and these tend to be more variable in terms of both appearance and genetics than modern crop varieties; uniformity was less important than having a stable food supply. We can go back further in time and see the wild populations of plants from which crops were developed, and find them thriving in relatively harsh environments with little in the way of water or nutrients.

Moving towards the present once more, we find that farmers have stopped growing landraces in favour of modern varieties which offer a better economic return – higher yields mean a greater proportion of the crop can be sold rather than eaten, providing an increased income. This switch is happening today in areas of the world where subsistence agriculture is still the norm. Modern varieties tend to be much more broadly adapted as they are developed, marketed and sold over a much wider area than a single farm– think, for example, on a European scale. The variability and hardiness seen in landraces and wild relatives of crops have been much reduced in these modern varieties, where productivity hinges on plants being of the desired size or shape and being ready for harvest at the same time. Yields are high compared to older varieties but the price paid for this is the amount of fertilizers, water and pesticides required to nurture the crop – all of which will be increasingly difficult to supply in the future. The variation inherent in landraces does not sit well with large-scale mechanised agriculture (but we shouldn’t become nostalgic and forget that this sort of agriculture, properly managed, has a major part to play in feeding all of us in the coming decades – there are too many of us on the planet for us to discard it), but it is a potential source of useful attributes such as pest and disease resistance and drought tolerance which can be incorporated into the modern varieties of the future.

...Without intervention, the landrace effectively dies...

The problem lies in the fact that when farmers no longer grow their own landraces, they no longer maintain them, that is to say that they no longer produce and keep seed for them. Without intervention, the landrace effectively dies, and the product of generations of selection, both natural and human, disappears and is not available to call on for the future. The same fate potentially awaits older commercial varieties when they are no longer competitive as market requirements and agricultural technology advances. Moving back into the freezing temperatures of the cold stores, the foil packs are in some cases the last refuge of horticultural and agricultural history. Some of the seed in the store exists nowhere else in the world. Seeds collected from farmers during the last few decades rest quietly, their metabolism slowed by the cold. The cold store offers an efficient way to preserve the diversity in many crops, and indeed there are similar facilities all over the world which conserve the many products of agricultural history in a similar fashion, each dedicated to a particular crop or a particular type of agriculture.

Far from being a museum or a kind of sealed time capsule, the seed collections in Warwick Genetic Resources Unit are in constant use. Around one thousand sub-samples are retrieved from the cold room and sent out every year. The foil packs which leave the arctic environment of the cold store do so at the request of a variety of people and organisations. Seed is conserved and managed for research, plant breeding, education and development. It can therefore arrive in the laboratory of a researcher interested in the network of genes that control aspects of plant growth and development, or to the field station of a plant breeder wishing to add new variation to their breeding programme. Seed can also find use in exhibits at public attractions such as The Eden Project or in small scale crop improvement programmes carried out by groups of farmers in countries as diverse as France and India.

The way in which the collections are being used is evolving too. Technological advances in DNA sequencing mean that potentially hundreds of genomes can be analysed in a shorter time and at a fraction of the price than when the human genome was sequenced. Comparing genetic differences between plants with contrasting appearance, maturity time or disease resistance (or indeed any interesting trait) allows researchers to understand and identify the genes responsible, and through doing this channel them into new crop varieties more quickly than traditional plant breeding would allow. However, once the genetic analyses have been completed, and DNA sequences are safely stored, the seed itself will still be required to transfer the genetic diversity forward into the new varieties ultimately destined to end up on our plates.

Seed collections such as that housed in the Warwick Genetic Resources Unit are a vital resource in the quest to produce more food in a less environmentally damaging manner. Entering the cold room and breathing in the frigid air, it is easy to sense the history sealed in each of the foil pouches, and to pause and contemplate the potential of the diversity held in a cold-induced sleep. But not for too long – it is, after all, very cold in there.

The Genetic Resources Unit is supported by funding from Defra.

Dr Charlotte Allender is the Assistant Manager of the Genetic Resources Unit, a seed bank which maintains several globally significant collections of vegetable crops and related wild species. Dr Allender is particularly interested in the patterns and nature of the distrubition of genetic diversity among crop species and their wild relatives. Dr Allender lead a three year Defra funded project (IF0189) aimed at understanding the genetic diversity present in UK Brussels sprout varieties and how to maintain F1 hybrids within plant genetic resources collections. Finally, Dr Allender is in the process of designing and producing a standard carrot Diversity Set (Defra project IF0158), which will enable researchers and breeders from different institutions and countries to carry out trait and marker screening on a common set of lines.