A trait-led approach which exploits natural variation in seed vigour to enhance crop establishment.

To grow crops successfully, the farmer has to establish the correct number of seedlings from the seeds they sow. Too many or too few seedlings can have a devastating effect on the profitability of the crops they produce. There is also an environmental consequence, because chemical crop treatments like insecticides, herbicides and fertilisers are not used efficiently. The soil seedbed can be a very harsh environment in which to germinate and therefore seeds with high vigour are required to consistently provide the same number of seedlings following sowing. However, in practice seed vigour is variable. The problem is, that is it not fully understood what makes seeds vigorous and consequently this characteristic is not included in breeding programmes for new crop cultivars. The environment in which seeds are produced can affect seed vigour and seed companies have been addressing this using a range of basic technologies, but despite this seed vigour remains variable. However, we have shown that differences in seed vigour can also have a genetic basis and so there is a further opportunity for improving seed vigour. In this proposal we aim to gain a greater understanding of what underlies these genetic differences. To do this, we will identify the gene or genes which are responsible for arguably the most important aspect of seed vigour, how fast they germinate. During this work we will gain insight and understanding into how these genes regulate processes within the seed that affect germination and this will help companies develop methods to improve seed vigour. Different plant lines can germinate at different rates, and this may be due to only small differences (sequence differences) within the same gene. By looking at the differences in the sequence of our selected gene in a range of lines which are known to germinate at different rates we aim to see how these differences in sequence are linked to differences in germination rate. A further complication is that some crops contain more than one copy of many genes. It is likely that not all copies of the genes will have the same impact on your trait of interest (e.g. germination rate), and so we must also determine which of the gene copies are significantly affecting germination rate. With this type of information it is possible for plant breeders to breed and select for faster germination (enhanced vigour) in the new cultivars they produce. We will carryout the proposed work in the crop species Brassica oleracea which contains familiar vegetables like cabbage, cauliflower and sprouts, but will also work with oil Seed Rape (Brassica napus) which is an increasingly important arable crop. However, in the long term the work has relevance to many other crops and even ornamentals such as bedding plants.

Seed vigour is essential for successful crop establishment and this is the cornerstone of sustainable crop production, but understanding of the genetic basis for seed vigour differences is limited. This project adopts a trait-led approach to identifying key genes underlying seed vigour, to understand their function, and to provide markers for plant breeding. We focus on rate of germination, a seed vigour trait for which we have identified Quantitative Trait Loci (QTL) and have fine mapped the most significant QTL ROG1 in B oleracea. We are constructing a BAC tiling path over ROG1 and aim to identify all candidates from this region. The most likely candidate/s will be selected by determining their function using microarrays, mutant screens and RNAi experiments in Arabidopsis and B oleracea as appropriate. A second aim is to use natural variation to investigate the relationship between allelic differences in the B.oleracea gene/s and phenotypic variation in the rate of germination. We also intend to sequence and map any paralogous copies of the gene/s within B.oleracea, and through co-location with other QTL for this trait confirm if all members of this gene family play a significant role in the regulation of seed vigour. This work will be extended to B.napus to determine if these genes are also important within this crop and to provide information for plant breeding programmes. The continuous involvement of Syngenta will ensure that there is a clear route for exploitation though an industrial pipeline. To facilitate rapid exploitation, markers flanking ROG1 will be given to them at the start of the project to determine the impact of this locus within their elite B.oleracea material. This timely and topical approach also has potential for a significant scientific breakthrough in understanding the basis of variation in seed vigour.