BREEDING SUSTAINABILITY IN PLANTS

An interview with Dr Rosemary Collier and Dr Graham Teakle, School of Life Sciences

Growing vegetables and grain in the 21st century has a number of significant challenges to contend with. There’s climate change, the need to feed an ever increasing world population, and food security moving up the political agenda. Here, Dr Rosemary Collier and Dr Graham Teakle, School of Life Sciences, explain how changes in EU and UK legislation about chemicals used in growing are complicating matters even more.

The situation for growing vegetables and grain is further complicated by changes in EU and UK legislation which means that the chemical armoury that growers have relied upon is decreasing due to concerns over their safety. The goal now is to increase plant yield and quality whilst using less energy, water, fertilisers and pesticides.

Dr Rosemary Collier and Dr Graham Teakle in the University of Warwick’s School of Life Sciences are at the foreground of these challenges. In association with other colleagues at Warwick they are researching various ways to increase the sustainability of crop production. Techniques include developing improved pest control strategies, using conventional breeding approaches that will lead to new varieties resistant to various diseases, and increasing the productivity per unit area of land.

Pests of edible crops are a specialism of Dr Rosemary Collier who is examining a range of alternative approaches to control them. Strategies include developing ways of using insecticides more efficiently by applying them in the right place at the right time, or determining when their use can be safely avoided. A practical outcome of this work was the development of a computer-based pest forecasting system that is used to predict potential insect outbreaks and which is now run in collaboration with a company called Syngenta. Other approaches under evaluation are the use of companion planting, where non-host plants disrupt the fixed sequence of events that plant-feeding insects used to find a host, and the biological control of pests using predators or insect diseases.

Understanding what is required to breed improved crops is a speciality of Dr Graham Teakle. He is interested in a number of traits, including the efficiency with which plants use nitrogen and other minerals, disease resistance, flowering time and the developmental control of plant structure, known as morphology. He is currently working towards identifying the plant genes controlling these processes.

Diseases are a significant constraint to crop productivity. For most crops, breeding for disease resistance is a major goal, with the added benefit of also reducing farmer dependenence on chemical controls. “Resistance can be one single gene that can give strong control to your disease pathogen, but after a year it can be overcome by the pathogen. Then it’s back to the start” explains Dr Teakle. Another strategy breeders use is to find sources of resistance that are referred to as ‘quantitative traits’. “This means that the resistance is conferred by a number of genes and, although they may not provide absolute control of the disease, they are more difficult for the pathogens to overcome and so provide a more durable form of disease control.”

Breeders race continually to find new sources of resistance with which to combat the often rapid changes in pathogen populations. When sources of resistance in normal crops have been exhausted they look to wild species and relatives forced to survive without careful nurturing by farmers. These are a potentially good source for disease-resistant genes and also other traits for sustainable farming.

Resistance can be one single gene that can give strong control to your disease pathogen

Breeding a new disease resistance trait into a crop typically takes eight years or more using traditional breeding selection techniques. The process is to cross pollinate a crop plant with a resistant plant, select an offspring that is resistant, cross it again to another crop plant and keep doing this until sufficient desirable characters have been combined that can be marketed as a new variety. This process is even more difficult for quantitative traits. However, if researchers can identify the genes that confer these traits then they can use genetic markers to follow the genes during the crossing and speed up the breeding process. Marker assisted breeding is becoming widely adopted for the traits for which the genes are known. Tracking down the genes for the many other traits is a major target for crop scientists.

Maximising yield from existing farmland is a key component of sustainable farming. The UK is notable for its high crop yields compared with most other countries. There is, however, a conundrum when it comes to crop productivity issues. In order to market a new variety it has to meet a number of criteria which are evaluated in standardised trials and each year the yield for the latest varieties increases. For most cereal crops the national yield is significantly less than this. For example the best oilseed rape varieties yield field tonnes per hectare in trials, whereas the national average is less than three and a half tonnes. Why? This is a topic of much debate for which there are probably a number of underlying causes. Some of these are likely to be new and researchers are actively trying to identify them.

Agriculture accounts for nine per cent of the UK’s total greenhouse gas emissions and the majority of this is from the manufacture and application of nitrogen-based fertilisers. In fact, over one per cent of the world’s total energy supply is used in making fertilisers. Sufficient fertiliser is necessary for high yields and it takes 200 kgs of nitrogen per hectare to grow oilseed rape per year. Dr's Teakle and Collier are working to make crops more sustainable in terms of their carbon footprint by using less nitrogen or producing greater yield with the same amount of nitrogen.

Global warming and climate change are affecting the range of pests and diseases affecting crops. Researchers expect a changing demographic within the UK, and new arrivals are likely from Europe, and are preparing for them. Climate change is also increasing the need for water use efficiency. Breeders have to take a long term view when developing new varieties and therefore also take these factors into account. While plant farmers will be under increased pressure as the 21st century continues, science continues to seek new ways to meet the coming challenges.

Dr Rosemary Collier, in the School of Life Sciences, is a research entomologist. Her main interests are modelling interactions between insects and the environment, the host-plant finding behaviour of phytophagous insects and the development of Integrated Pest Management systems for the pests of field vegetable and bulb crops.

She is a former convenor of the International Organisation for Biological Control Working Group on Integrated Protection of Field Vegetables. She talks regularly to grower groups and writes topical articles for HDC News and similar publications.

Dr Graham Teakle is a Research Scientist also in the School of Life Sciences. He joined the University of Warwick in 1998. His research includes the genetic control of nitrogen use efficiency in oilseed rape; and brassica developmental genetics with a focus on meristem identity genes associated with the floral transition.

By Penelope Jenkins