Exploiting seed coat properties to improve uniformity and resilience in Brassica seed vigour

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A key current goal in plant breeding is to introduce traits that add resilience to climate change. Growers and seed raisers frequently report to the levy board that they have problems with poor or unpredictable germination, even of expensive seed. Seed vigour is determined by the genetics of the crop, by vigour-enhancing formulations applied during seed processing and crucially, by the temperature during seed production. Our evidence suggests that seed traits are the most temperature sensitive in plants, with temperature changes of 1C during seed set capable of making important changes to seed performance. Large seed companies produce seed at specific locations where environment is suited for maximising vigour, but there is still variation from site to site and stochastic temperature fluctuations that affect quality. Increases in weather and climate variation mean that we need to develop the ability to uncouple seed vigour from temperature influences during seed production. This proposal describes a project for breeding new varieties of Brassica with high seed vigour insensitive to the effects of temperature during seed production. Our work has shown that during seed set temperature is sensed by the mother plant and controls progeny seed germination by varying the development and composition of the seed coat. If we alter seed coat development or metabolism genetically, germination remains high regardless of seed set temperature. These processes are widely conserved among all angiosperms, including Brassicas and other vegetable seeds. Mutagenised populations are important breeding tools in horticulture and have been used historically for novel trait discovery. Here we describe the application of modern state-of-the-art post-genomic technologies to conduct screens of a new mutant B. oleracea population to identify and characterise genes affecting seed coat properties and therefore vigour resilience. We aim to isolate seed coat mutants using simple screens, and using new bioinformatic techniques already available at JIC we can quickly identify causative genes by genome re-sequencing. Using this same population we can also isolate Brassica mutants in specific genes of interest by a process known as TILLING. We know which genes are most important because of extensive work in our lab and others in the closely-related model species Arabidopsis. In this way we can quickly identify Brassica lines in which seed coats and seed vigour resilience are altered compared to laboratory and commercial varieties.Seed companies also enhance seed vigour by applying chemical formulations in coating to the outside of seeds during processing. These formulations can also include pesticides and fungicides. However, seeds are highly discriminating and uptake of applied chemicals can be as low as 5%, leading to widespread contamination of the environment. If the industry is to continue to benefit from the effects of commercial seed formulations is it clear that uptake into seeds must be improved to minimise the environment impacts of the technology. However, currently there are no techniques available for quantitatively monitoring chemical uptake efficiency into seeds without adding fluorescent labels that also change their properties. A side effect of our seed coat engineering approach is that seed coats control both vigour and permeability to chemicals. Therefore the second part of this proposal is to development an exciting new microscopic technique which can follow the uptake of unlabelled chemicals quantitatively, spatially and in real time into plant tissues, and which also can be used to look inside intact whole seeds (Figure 3). In this way we will be able to see what types of chemical are taken up efficiently into seeds and how this can be altered using genetics. The resulting approach can be used to prioritise development of new chemicals and to show whether more seed permeability can be exploited to maximise chemical uptake.