Smart breeding for salad rocket

'Salad' rocket is among the most nutritious of leafy vegetables, but concentrations of health beneficial compounds and the taste of leaves is highly variable. Numerous factors are known to influence these attributes in rocket, but very little technical research has been conducted to improve the consistency and perceived 'quality' of leaves. One of the biggest complaints from industrial processors and retailers is this inconsistency throughout the year and between growing regions. A great deal has been learned about what different consumers like or dislike in current rocket varieties. Some people prefer bitter and pungent leaves, whereas others prefer mild and sweet. By utilising this knowledge, and combining it with genetic and chemical information, we are proposing to provide tools for breeding rocket for increased consumer acceptance, increased nutritional density, and increased stability across growing regions. We also aim to produce resources that will allow plant breeders to select varieties with a signature taste and flavour profile that is acceptable to consumers, while maintaining the maximum health benefits associated with the crop.
Previous work at the University of Reading, in collaboration with Elsoms Seeds (a commercial seed merchant and plant breeding company) and Bakkavor (a company composed of international growers, processors and distributors of rocket), has produced a large amount of information relating to the chemical and sensory profiles of rocket. Genomic research into rocket species however, is almost non-existent, and in order to progress the crop significantly these will need to be established. The world's first genomic sequencing of rocket is set to commence before the end of 2015, and conclude Spring 2016. This information will allow us to identify specific 'markers' within the genetic code that can be used to identify rocket plants with specific attributes, such as bitterness, sweetness, or hotness, for example. It will also allow us to identify regions of the genetic code that are heavily associated with health beneficial chemicals, such as glucosinolates. By examining many hundreds of these genetic 'markers' across different growing locations (the UK and Italy), climatic conditions (field and controlled environment), and the whole supply chain, it is possible to create a set of 'markers' for each respective circumstance that will inform us about a plant's propensity to conform to a desired set of attributes. By tracking these 'markers' from one generation of plants to the next it is then possible for the breeder to select plants containing these markers and eventually cross-pollinate them with other promising individuals to develop new varieties.

At specific points in the project (e.g. during field experiments, and industrial processing trials) chemical components will be evaluated. Our primary focus is on glucosinolates; a type of compound that produces health beneficial chemicals called isothiocyanates. Consumption of these has been consistently linked with reduced risk of developing certain types of cancer and reduced incidence of cardiovascular disease. They also produce the distinctive hotness of rocket leaves. We are also interested in looking at sugar and amino acid contents of leaves. Not only do these influence taste, but they are also the building blocks of glucosinolate molecules. Through understanding the genetics of each compound's synthesis, we can highlight specific 'marker' profiles that will give a desired sensory profile. We can also identify markers that are adverse to the desired sensory profile and de-select plants to ensure that they do not persist within future populations.

The genetic resources created at the end of this project will go on to inform selections within the active rocket breeding program at Elsoms Seeds. Ultimately this will create new commercial varieties that have consistent and superior sensory and nutritional qualities compared to existing ones.

The research will provide insight and tools into rocket genetics and biochemistry that can be utilised by plant breeders/salad processors to produce new varieties for commercial sale. This in turn will benefit consumers of rocket as products will have increased nutritional density, and have sensory profiles that cater for differing taste preferences. At the present time, commercial cultivars of rocket lack consistency in nutritional and sensory attributes, and no efforts have been made to produce varieties that take consumer taste preferences into account. To achieve these aims we will utilise a multidisciplinary approach that includes: genotyping, phenotyping, QTL analysis, bioinformatics, genomics, transcriptomics, metabolomics and sensory science. The main aims of our project are to: 1) Provide the tools and knowledge for breeding and producing a salad rocket crop with known and consistent taste, flavour and appearance; and 2) provide improved understanding of the quantitative genetics of rocket phytochemical quality to inform a marker assisted breeding approach to improve these traits.
Our industry partners will provide expertise in plant breeding, propagation, seed production, commercial processing and shelf life. By utilising genomic sequencing data and large volumes of phytochemical data, we can test a predictive model that will produce a desired sensory profile. This can then be used as a 'smart breeding' tool to create new rocket varieties.

The project will underpin the development of improved leafy horticulture crops, demonstrating an integrated approach to breeding that delivers sustainable productivity and consistent, high quality crops that are more resilient to supply chain conditions and which are customised to suit the diversity of consumer preferences. Up to 75% of food waste from salads is caused by loss of quality and the product not meeting consumer expectations. This project will provide tools and agronomic knowledge to develop salad crops which are consistent in quality and which have predictable flavour profiles, thus benefitting consumers who will have the confidence to make a purchase that will meet their expectations. Satisfied consumers are likely to consume more of the leafy vegetables that they buy and this in turn will reduce food wastage.


Plant Breeding companies
Plant breeding companies, including our Project Partner, Elsoms Seeds, will benefit from the project in terms of breeding for improved and consistent flavour, but also for improved shelf life of lettuce. Elsoms Seeds will be able to use the tools developed in this project (sequence, mapping populations) to refine their breeding approach for marker assisted selection of quantitative traits. They will have advanced access to data, giving them competitive advantage over other rocket breeding companies. The unusually collaborative nature of the consortium ensures that the breeder will be working closely with its customer grower base and salad processors, ensuring development of successful products that have a market base and giving them a KPI for these lines.

Downstream industries
The second industrial partner on the project is Bakkavor Holdings Ltd, which owns 36 smaller companies within the group. They have relationships with a number of growers who will be closely involved with the project and the dissemination event will ensure that they know how to use the postharvest data to inform preharvest decision making. Therefore the crop in the field is likely to have known flavour and quality characteristics at the point of harvest, and perform consistently throughout the supply chain. Work to date has demonstrated that Bakkavor should consider developing product lines with different and distinct flavour profiles to suit their range of consumers. The present project will provide the mechanism for this to happen.

Research staff
Research staff on the project will enhance their career prospects by gaining experience of metadata handling and processing, integration of different types of data (genome, transcriptime, metabolome), and of working with industry in the horticultural sector. Luke Bell will be ready for a career as an independent research leader at the end of the project.