Unravelling the effect of winter warming on flowering time, flower fertility and crop yield

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Climate change is predicted to warm winters in western Europe between 2C and 8C above pre-industrial temperatures this century. It is well known that warm winters negatively affect the yield of perennial crops where incomplete chilling of flower buds in winter leads to weak bud break and fewer open flowers: indeed the requirement for winter chill generally determines the climate zones favourable for cultivation of temperate perennial crops. In Europe high yielding major arable crops are grown as winter annuals, that is they are sown in late summer or autumn and have a requirement for winter chilling to promote the transition to flowering in spring, a process known as vernalisation. However, we have recently shown that for the winter oilseed rape crop this vernalisation process actually happens in mid-autumn, followed quickly by the floral transition and formation of a flower bud in late autumn. We also showed that the stage of flower bud development corresponds to a period in the field where warm winter temperatures have a substantial negative affect on the UK yields the following summer. This raises the question of whether like perennials, winter annual crops have a requirement for chilling of flower buds to maximise crop performance in the following spring, and whether climate change is reducing yields in climate zones where winter chilling is not guaranteed. The preliminary data provided here provides compelling support for this hypothesis. Most specifically, we show that chilling of flower buds promotes earlier bud break in spring, and that winter warming of flower buds leads to production flowers in spring with obvious abnormalities and poor fertility.This proposal uses a combination of physiology, molecular genetics, breeding and genomic approaches to understand the mechanism by which warm winters negatively impacts winter oilseed rape yields, especially in climate zones prone to warm spells during early winter when inflorescence development is taking place, such as the United Kingdom and China. Then we will use genomic approaches to breeding to clone genes in oilseed rape that may confer more resilient yields in growing seasons with warm winters, exploiting our previous discovery of one variety that we show has no significant yield response to temperature variation during inflorescence development. By introgressing these traits into elite germplasm we can determine whether climate change resilient genetics can be combined with modern high yielding lines to generate lines suitable for modern breeding programmes.