Optimising the development of the energy grass Miscanthus through manipulation of flowering time

To combat climate change, it is necessary to use less energy and replace more of the energy we use with renewable sources. Furthermore, there is an over dependence on imported fossil fuels, putting future fuel security at risk. A number of renewable energy sources exist (for example, biomass, wind, solar, marine) and it is widely predicted that in the future no one form will dominate, in other words there will be a mixed energy economy. Biomass from energy crops are an important part of the renewable energy mix because in addition to being able to provide electricity and heat through combustion, biomass can be used to make petroleum replacements such as liquid transport fuels and platform chemicals. Miscanthus is a perennial grass and an ideal energy crop because it combines the fast growth rate of a tropical grass, such as sugarcane, with a tolerance to grow at UK temperatures. Furthermore it is a very 'eco-friendly' crop since it requires herbicide treatment only during initial establishment, produces a high yield of biomass annually with 'compound interest' on previous vegetative growth, and highly effective nutrient recycling at the end of the year reduces cultivation and fertiliser inputs. However as Miscanthus is a new crop, previous basic research has been extremely limited so that little is known about the regulation of growth and development. This proposal seeks to start addressing this deficit by investigating the molecular basis of flowering. To help in this we will exploit technologies developed for, and knowledge of flowering in, model organisms such as Arabidopsis thaliana, rice and maize. Flowering has been chosen because it is the characteristic identified as most likely, when optimised, to maximise yield quickly in Miscanthus. For example it is highly desirable for plants to flower as late as possible to increase the length of the growing season and therefore photosynthesise for longer to produce more biomass. However flowering is also desirable to trigger senescence which is a critical process by which nitrogen and other resources are mobilised to the rhizome, the part of the plant below ground. This can be very important because some plant constituents, principally potassium and chloride are corrosive or form corrosive compounds when combusted and cause damage to energy generation equipment. The commercially grown variety of Miscanthus (Miscanthus x giganteus), is a naturally occurring hybrid between two species, Miscanthus sacchariflorus and Miscanthus sinensis. However flowering appears to be controlled differently in the parent species so that Miscanthus sacchariflorus flowers when the daylength is less than 12 hours but Miscanthus sinensis flowers when sufficient warm days have been experienced. The hybrid only very rarely flowers under UK conditions and is sterile. Therefore in this project we aim to identify the genes most likely to be involved in flowering time in the two parents of Miscanthus x giganteus. Research on model organisms has identified over 40 genes implicated in flowering time and the equivalent genes in Miscanthus will be identified and tested for an equivalent role. This will enable the development of DNA-based molecular markers for flowering which can be used in the UK Miscanthus breeding programme. Use of molecular markers will help with the optimisation and prediction of flowering time in young plants rather than having to wait three years for plants to gain maturity. It will also help in the selection of parent plants for new crosses. The information gained from this project will help to increase biomass yields in Miscanthus more quickly. This will therefore mean that more carbon will be fixed in a smaller area of land, and in addition improve farm economics, decrease pressure on other forms of land use, increase UK fuel security and most importantly reduce global carbon dioxide emissions.

This project aims to deliver information on the coordinate control of growth and development in perennial grasses through the association of flowering time and senescence QTL, with flowering time genes in the C4 energy grass Miscanthus. It is proposed to investigate the molecular basis of flowering in this species by identifying homologues of flowering time genes already identified in the model plants Arabidopsis, rice and maize. There are over 40 flowering time associated genes mapped in rice and approximately half of these have also been mapped in maize. We therefore propose to exploit the dense SSR genetic maps of maize to build genetic maps of Miscanthus regions, focused around these candidate genes, supplementing the maize markers with a smaller number of sugarcane SSRs. Replicate mature plants of two mapping families used to genetically map the candidate flowering time regions will be phenotyped for heading date. This will therefore test the hypotheses that (1) Arabidopsis, rice and maize can be used as genetic models for the control of flowering time in Miscanthus, and (2) Miscanthus cDNAs homologous to rice and Arabidopsis flowering genes can be mapped to Miscanthus flowering time QTL. Mapping homologues of flowering time genes in Miscanthus will also provide comparative genetic information on the extent of synteny that exists between Miscanthus and other grasses. To further test candidate genes from model organisms which co-map to flowering time QTL in Miscanthus, shifts in allele frequency of the Miscanthus orthologous within synthetic populations selected for early and late flowering time will be monitored using SNPs. In other words to test if differences in flowering response exhibited by different Miscanthus species and genotypes are a consequence of allelic variation in orthologues of Arabidopsis and other model species flowering time control genes. Joint with BB/E014682/1