In order to ensure the survival of their offspring, many organisms employ a bet-hedging strategy whereby they produce a large number of progeny having different behavioural characteristics. This approach ensures that a subset of their progeny survive regardless of unexpected fluctuations in their environment. Seed germination in plants also follows this bet-hedging strategy. While seeds are resistant to harsh environmental conditions, seedlings are not, and this makes the correct timing of germination critical for the future survival of plants. Plants have evolved noise-generating mechanisms to create variable behaviour within the individual seeds they produce in order to alter the timing of their germination responses to the environment. In this way at least a fraction of their progeny are ensured survival regardless of future climatic conditions. While this is a powerful adaptive trait for the survival of plants in natural ecological settings, the asynchronous germination of seeds represents an obstacle to agriculture. The vast majority of food production begins with the planting of a seed, and the rapid and uniform establishment of seedlings in the field is key determinant of future yield. Non-uniform germination leaves gaps in the field which increases herbicide use, and asynchronous crop development lowers yield following single-pass mechanical harvesting. Robust and synchronous germination underpins the sale of high quality seed in the £52 billion annual global seed trade. Climate change and variable weather further exacerbates uniformity issues, which continue to persist. This project seeks to uncover the mechanistic basis of variability generation and bet hedging in model and crop seeds, and to leverage this information to synchronise the germination of seed populations. This will be done together with industrial partner Rijk Zwaan through a mutually beneficial interaction. We have previously developed a powerful predictive mathematical model that captures the relationships between hormones in seeds which determine when they germinate. Using this model, the preferential use of alternating temperatures to promote seed germination was accurately predicted (Topham et al. 2017, PNAS). This project will extend the use of this model to identify mechanisms that lead to the creation of variable germination-controlling hormone abundance in individual seeds. By identifying how variability in generated within individual seeds, targeted strategies to mitigate these noise-generating mechanisms will be utilized in order to harmonize the hormone content, and in turn germination, of seed populations. Initial proof of concept studies will be performed in the model species Arabidopsis, and together with Rijk Zwaan this will be extended to the crop species lettuce where agronomically limiting issues in germination synchronization are present. By the conclusion of the project this same germplasm will be modified to have enhanced synchronization in their germination profile. A second aspect to this project involves the development of a vital high throughput germination monitoring system. The expression of genes in individual seeds can be monitored dynamically, and used to predict the future timing of germination following early events. In this way the variability in seed populations can be quantified, and this system can be used to sort seeds having similar germination characteristics. This represents both a powerful scientific tool and agricultural technology to generate populations with synchronized germination behaviour. This project will address a key scientific questions relating to variability and bet hedging which also have a direct and powerful relevance to modern food production systems and industry. Following state of the art modelling and biological approaches and an industrial partnership, the development of strategies and germplasm enhancing the synchronization of crop seed germination will be provided.

This project will take place at Warwick HRI in the University of Warwick (formerly the Horticultural Research International) and is aimed at understanding the molecular mechanisms controlling bolting in lettuce. Over 6,000 ha of lettuce, with a market value of over £80 million, was grown in the UK in 2005 (source DEFRA statistics, 2005). A major problem for lettuce growers is that the crop will sometimes initiate bolting (i.e. flowering) in the field before it is harvested. Whilst plants that are in the early stages of bolting are visibly indistinguishable from non-bolting plants, there are changes in the production of secondary metabolites in the leaves. These compounds may serve to protect the young floral buds from insect attack but give the lettuce plant a bitter and unpleasant taste and render the crop unsaleable. Delayed bolting, or greater holding ability in the field, is a desirable trait in commercial lettuce varieties as it preserves the quality of lettuces sold for consumption, and increases sustainability by reducing crop losses and wastage. This project will exploit the extensive knowledge on molecular mechanisms controlling flowering time gained from the study of model plants such as Arabidopsis. Lettuce genes that are homologous to genes known to control flowering in these model species will be identified. These will be good targets in which to induce variation in order to affect the control of bolting/flowering time. Inactivation of a gene that causes early bolting, for example, may cause later bolting which would mean that that lettuce variety will be less likely to bolt in the field before it is harvested. A greater understanding of the molecular mechanisms controlling flowering in crop species, and the natural variation that has evolved in crops to exert a robust effect on flowering, will also broaden our understanding of the flowering process. This project is a prime example of knowledge transfer from model to crop plants.

Minimal processing adds significant value to fresh produce, however, it also increases its perishability reducing shelf life and leading to waste of the produce and the resources used to grow it. This project is aimed at post harvest discolouration, a significant cause of quality loss in a wide range of fresh produce such as sliced apple, cut cabbage and lettuce. The main issue we are addressing is postharvest discolouration of lettuce in salad packs. UK lettuce production/imports are worth £240m farm gate but the retail value of UK processed salads is £800m. However, Tesco have recently reported that 68% of their salads are thrown away; the situation is similar for other retailers. There is therefore a need to improve postharvest quality to reduce waste and deliver consistently good quality products to consumers. Modified atmosphere packaging can provide control but once the pack is opened oxygen enters resulting in discolouration. Growing conditions also influence postharvest discolouration but are difficult to control in field crops. We are proposing breeding lettuce varieties with reduced propensity to discolour as a way to address the problem. To do this we need to understand the genetics and biochemistry of discolouration. We are building on previous research we have done which identified genetic factors controlling the amount of pinking and/or browning that developed on lettuce leaves in salad packs 3 days after processing. However, we do not know what compounds or which genes are involved and we now intend to find this out by a multidisciplinary project involving three universities; Harper Adams University, Reading and Warwick, a lettuce breeding company, a lettuce grower, a salads processor and the Horticulture Development Company. We have produced a set of experimental lettuce lines which we know show differences in the amount of pink or brown discolouration they produce. We will grow and process these lettuces in a way that mimics commercial production. We will then assess the salad packs for the amount of discolouration developing over 3 days, which is the current best before date for supermarket salads. We can then link this information to the plant's DNA profile to identify genetic factors for discolouration and DNA markers which can be used by plant breeders. The same lettuces will also be analysed for compounds produced by a biochemical pathway called the phenylpropanoid pathway. This is thought to produce the pigments that cause discolouration. We know from other studies in a plant called Arabidopsis the genes which control the phenylpropanoid pathway and we have found the same genes in lettuce. We will see how these genes behave in lettuce plants that produce a lot of discolouration and ones that don't discolour. We will also see how the genes behave under different growing conditions. We can link these gene expression patterns to the amount of pinking and browning to see which genes are the key ones. Once we have done this we can look for naturally occurring versions of the genes which give a reduced discolouration. The compounds produced by the phenylpropanoid pathway influence other things such as pest and disease resistance, taste etc. We do not want to reduce the amount of discolouration by breeding but end up with lettuce susceptible to pests or with poor taste, so we will assess lines which show high discolouration or no discolouration for their resistance to aphids and mildew and for taste to see if there are any differences. There are some compounds produced by the pathway which are colourless but still provide some resistance so by knowing the genetics and biochemistry breeders will be able to carry out smart breeding. We will see if the results for lettuce hold true for other crops by seeing how the key genes behave in apple and cabbage and whether this is related to the amount of browning that develops when they are processed and look for genetic differences in these crops

Turnip yellows virus (TuYV) is a very important pathogen of vegetable brassicas (Latin name Brassica oleracea; cabbage, cauliflower, Brussels sprout, broccoli etc.) and oilseed rape (OSR) in the UK & Europe. Many crops sampled have had very high levels of TuYV infection. Unlike many viruses, TuYV does not cause very obvious symptoms in most brassicas (storage cabbage where it causes tipburn is the exception). This has meant many growers are unaware of the infections. Despite lack of obvious symptoms we showed that TuYV reduces the yield of cabbage by upto 36% and Brussels sprouts by upto 65%. Estimates of OSR yield reductions in the UK alone are upto 30% (losses of GBP 67-180 million/annum). TuYV can move between vegetable brassicas, oilseed rape and weeds, resulting in the high levels of infection of crops seen. A very common greenfly (peach-potato aphid) transmits TuYV; once they acquire the virus they transmit for life. In glasshouse experiments we have identified the best insecticide seed treatments and sprays for controlling TuYV. We have also shown in the field that different cabbage and Brussels sprout cultivars have different susceptibilities to TuYV (all are susceptible, but some less so than others) and that the earlier plants are infected, the greater the yield loss. We have also found a number of sources of extreme resistance to TuYV in Brassica oleracea and have been studying the diversity of TuYV by determining the genetic code of many isolates. Collaborators in the project have a network of suction traps around the UK that trap flying greenfly. They identify the different greenfly species including the peach potato aphid and count them. They are also developing a molecular technique to detect TuYV in the greenfly. All these discoveries provide the opportunity to combine them in to an integrated programme that will give optimal control of TuYV. To develop this integrated control programme we intend to do field experiments in two regions of the UK. At one location we will introduce greenfly carrying TuYV to provide high infection pressure and at the other location we will rely on natural infection. In these experiments we will apply the individual components (partial plant resistance, the best seed treatment and the best sprays) separately, in pairs and in threes in order to quantify the efficacy of individual and combined treatments. This will identify the best combinations and quantify synergy between treatments. The timing of spray treatments will be informed by when peach-potato aphids are flying, this will be known from the suction trap and water trap catches around the experiment. To build on and improve the integrated programme we will identify the best source of extreme resistance to TuYV in our resistant B. oleracea lines. This will be crossed with a susceptible line. The offspring will be tested for resistance/susceptibility by challenging plants with TuYV and testing for TuYV using a quantitative test called ELISA. Some of the next generation of plants will be susceptible to TuYV and some will be resistant. By analysing the genes/chromosomes/RNA/DNA of these plants and comparing this with the susceptibility/resistance status of the plants, it will allow the development of molecular markers. Seed companies will use these to significantly speed up the incorporation of the resistance genes into commercially acceptable varieties. We are collaborating with Syngenta and Dow in the optimal use of seed treatments and sprays and with the seed companies Tozer, Sakata UK, Enza Zaden and Rijk Zwaan UK on the TuYV resistance exploitation. We are also working with Allium and Brassica Agronomy who work with farmers. Through these collaborations the outcomes of the research (integrated programme for TuYV control and new sources of resistance to TuYV) will be exploited by growers in order to reduce residues in vegetables and inputs and increase yields, thereby contributing to food security.