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

Lead Research Organisation: Rothamsted Research
Department Name: Agro-Ecology


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 transport fuels, chemicals and building materials. 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 requires little to no fertiliser or herbicide inputs and produces a high yield of biomass every year. However as Miscanthus is a new crop, previous basic research has been extremely limited so that little is know 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. 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 parental 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.

Technical Summary

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 thaliana, 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 and Miscanthus RAPDs to align to an existing map. Replicate mature plants of two mapping families used to 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 this will 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/E014933/1


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Description Significant advance in our understanding of flowering time control in Miscanthus, including the identification of species specific differences and the modelling of flowering time to geographic origin. This information is now being used by plant breeders to improve the efficiency of collection, making new hybrids and also for phenotyping plants in field trials across Europe (including in the Renewable Materials LINK project GIANT and a new Framework 7 project, OPTIMISC).

Generation of the first high density genetic map of Miscanthus in collaboration with Ceres Inc. using the flowering time mapping population. Additional markers have also been identified for association mapping in 142 replicated field grown Miscanthus plants which were phenotyped over 5 years in this project.

Comparative genomics. Demonstration that M. sacchariflorus is a quantitative short-day plant like Sorghum, and at least one QTL for flowering in M. sinensis aligns through synteny to the same region in Sorghum.
Exploitation Route Directly - the genes can be selected for in breeding programmes.
Sectors Agriculture, Food and Drink,Energy,Environment

Description Flowering time was characterised in 244 genotypes from 3 species of Miscanthus in the field and this was related to the flowering response in other species (paper published in GCB Bioenergy). During the lifetime of the grant the Sorghum genome was sequenced and a high quality genome assembly produced. Sorghum, like Miscanthus, is a C4 grass and has been the subject of detailed flowering time analyses. We therefore used Sorghum as the closest model for our studies, which links through to rice and Arabidopsis. A study under controlled environment to replicate tropical photoperiods and temperatures has demonstrated the similarity of the flowering time response in Miscanthus to Sorghum.
First Year Of Impact 2013
Sector Agriculture, Food and Drink,Energy,Environment
Impact Types Societal,Economic