If you think about a traditional Christmas dinner, there’s turkey with pigs in blankets, or maybe you prefer a nut roast. But the rest is vegetables. A large proportion of our plate should be covered in vegetables, and the standard winter varieties, like carrots and sprouts, are grown very successfully in the UK.
But will this always be the case? Climate change is bringing with it new challenges as well as making known pests and diseases more difficult to tackle. Scientists at Warwick's Crop Centre, are working to understand the pests and diseases of the some of the UK’s major crops and developing, using traditional plant breeding and genetic expertise, new resistant varieties.
SOS, Save Our Sprouts
Whether you love them or hate them, sprouts will definitely make an appearance on most Christmas plates. You’ll probably eat at least one – just for tradition. But did you know that there is a silent battle happening between sprout plants and various enemies - including viruses - that makes it difficult for farmers to guarantee top quality sprouts for the Christmas dinner table year after year?
Professor John Walsh, plant pathologist at Warwick’s Crop Centre, explains: “Two of the biggest threats to the sprout crop every year are Turnip mosaic virus and Turnip yellows virus. Both pathogens are common, transmitted by greenfly, and can reduce the yields of Brussels sprout crops - in severe cases making them completely unmarketable.
“We have discovered natural plant genes that will make sprouts resistant to these two pathogens and these are now being exploited by commercial seed companies.”
Turnip mosaic virus causes particularly severe symptoms, including black spots on the sprout buttons and leaves. Turnip yellows virus stunts the growth of sprouts, and can significantly reduce the size of buttons and overall yield. Known as ‘the unseen virus’ it often gives little or no symptoms, so growers are unaware that it is present. In some years, when there are large numbers of greenfly around, 100% of plants are infected by Turnip yellows virus in some brassica crops. Even in years when there are few greenfly around, more than half of plants can be infected.
Sprouts are part of the brassica family and related to broccoli, cabbage, mustard and oilseed rape and of course - turnips. It is one of the most diverse food plant families, with many brassica types affected by the same two viruses. This has a massive commercial impact on the brassica crop every year. Professor Walsh’s research is aimed at developing a comprehensive, integrated approach to controlling the virus and the greenfly vectors in the field – protecting not only sprouts, but other brassica plants too.
Professor Walsh continues: “Growing virus-resistant plants will improve food security and reduce the need for pesticides and other inputs. Unlike many plant disease resistance genes – which can be rapidly overcome by new strains of pathogens - the enhanced resistance we are developing at Warwick looks like it will be durable, and an effective defence against a broad-spectrum of virus strains.
“Developing crops with long-term durable disease resistance is a long-winded process but is the most sustainable approach to disease control.”
Savour a better sprout flavour
As well work on pest and pathogen resistance, researchers at the Crop Centre continue to work on crop quality and yield.
Dr Guy Barker, a plant geneticist in Warwick’s School of Life Sciences, explains: “Quality and yield in all our vegetables is an ongoing concern and at Warwick we are engaged through the DEFRA funded VeGIN program to provide prebreeding improvements in Brassica crops, including Broccoli and Brussels sprouts. We can identify the gene for flavour in sprouts or colour in root vegetables and select the breeding lines that express the particular traits growers are searching for.
“This collaboration between academia and the breeding industry speeds up the selection process and means improvements are delivered to the actual vegetable product as quickly as possible. So consumers can see the better improved vegetables – whether it be a whiter parsnip or a sweeter sprout – in their supermarket much more quickly.”
Caring for our carrots
Carrots are a favourite vegetable in many households and will feature on many Christmas dinner plates. Over 700,000 tonnes of carrots are grown in the UK every year and as they are harvested nearly all year round, they have to cope with many environmental challenges to reach us in good condition. But with the UK experiencing more challenging weather conditions in recent years – and with worse likely to come – growers are going to need new options for carrot crops.
Dr Charlotte Allender, lead researcher at Warwick’s UK Vegetable Gene Bank, explains: “UK carrot growers will need a range of new varieties better able to withstand a changing climate as periods of flooding, drought and hot or cold spells become more and more commonplace. Crop losses from plant diseases will also likely increase, due to a combination of changing weather patterns and a reduction in the number of chemical treatments available for use.
“At Warwick Crop Centre, we are studying how genetic variation across the whole of the carrot genepool can be used to introduce useful traits into carrots.
“One particular issue is a disease called cavity spot; this causes sunken black lesions on the surface of carrot roots, making them unmarketable. There are very limited options for control of this disease so understanding the infection process and being able to test for resistance in the wider gene pool is key to developing resistant varieties.
“Work is under way to test different types of carrot from around the world for natural resistance to cavity spot. With better varieties, growers will be able to sell more of their crop, which will have a major impact on food waste as well and ensuring consumers continue to enjoy a ready supply of carrots all year round – not just for Christmas.”
Don’t forget the onions
You may not fancy a roasted onion on your Christmas plate, but they are the main ingredient in the stuffing, the flavouring in gravy and vital in the Boxing day curry. Onions are the unsung vegetable hero which we take for granted. You would miss onions if they went.
That is why, Dr John Clarkson, a Reader at the Crop Centre, is working on a hugely damaging fungal pathogen – Fusarium oxysporum.
He explains: “Fusarium oxysporum is a soilborne fungus which has many different forms which are uniquely adapted to infect different host plants and cause some of the most devastating diseases in horticulture. The different types of the fungus can be detrimental to a wide variety of crops including onion, lettuce, tomato, cucumbers, strawberry and watermelon to name but a few. It causes root and stem rots which result in wilted plants and subsequent death.
“However, there are also some non-pathogenic types which are actually beneficial members of the soil’s ecosystem. As all the different types of the fungus are so closely related – it is very difficult to identify and distinguish between the different pathogenic and non-pathogenic types without longwinded and expensive testing on plants. We have therefore developed specific DNA-based tests to identify more quickly the forms that damage particular crops.
“One particular target we are looking at Wellesbourne is Fusarium oxysporum f.sp. cepae (FOC) which causes basal rot in onion bulbs and causes losses estimated at a minimum £11 million a year in the UK alone. In some cases, entire crops can be lost either in field or in store and the losses for growers are getting worse year on year.
“FOC produces long-lived spores which makes it difficult to control. In the past we relied on techniques like soil sterilisation or pasteurisation and fungicidal drenches or seed treatments. However, these approaches may not be effective, and can have negative impacts on the environment. Legislation surrounding chemical treatment of crops and seeds is also changing and so some products farmers rely on may not be permitted in future.
“We have developed a specific and rapid DNA-based test for FOC which we hope will be useful for growers in assessing disease risk through its use as a pre-planting soil test. We have also identified plant resistance to basal rot in onion, and have begun to work to understand the genetic basis for this important trait. This will provide information to help produce varieties of onion with resistance to FOC and reduce the need for fungicide treatments.”
Bringing back the old genes
While new varieties are developed, others researchers are working hard to preserve the old varieties in the hope that the heritage crops, or even the wild plants that they originally came from, have kept important characters and qualities which modern crops may have lost. These traits could offer solutions to vegetable production in a changing environment, combining resilience to unfavourable weather conditions with a reduction in the need for inputs like fertilizers, pesticides and water.
The UK Vegetable Genebank at Wellesbourne Campus holds a seed collection of approximately 14,000 samples of different vegetable crops such a Brussels sprouts, onion, parsnip and carrots. These seed resources are used not just by researchers at Warwick Crop Centre, but are sent out to plant breeders and scientists across the UK, Europe and the world.
“Having access to these seeds – and their genetic diversity – will ensure that we continue to have delicious and healthy vegetables on our plates for the Christmases of the future,” concludes Dr Allender.
16 December 2019
Warwick Crop Centre, part of the School of Life Sciences at the University of Warwick, is an internationally recognised centre for translational research in sustainable agriculture, horticulture and food security.
Read more like this:
Terms for republishing
The text in this article is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).