Summary: Bioenergy from plants, particularly from perennial grasses and trees, could make a substantial contribution to alleviation of global problems in climate change and energy security if high yields can be sustained. Here, yield traits in a range of key bioenergy crops are reviewed, from which several targets for future improvement can be identified. Some are already the focus of genetically modified (GM) and non‐GM approaches. However, the efficient growth strategies of perennial bioenergy crops rely on newly assimilated and recycled carbon and remobilized nitrogen in a continually shifting balance between sources and sinks. This balance is affected by biotic (e.g. pest, disease) and abiotic (e.g. drought) stresses. Future research should focus on three main challenges: changing (photo)thermal time sensitivity to lengthen the growing season without risking frost damage or limiting remobilization of nutritional elements following senescence; increasing aboveground biomass without depleting belowground reserves required for next year's growth and thus without increasing the requirement for nutrient applications; and increasing aboveground biomass without increasing water use. Contents Summary 1 I. Introduction 1 II. Bioenergy, biomass and biofuel crops 2 III. Bioenergy yield traits 2 IV. Bioenergy composition traits 8 V. Sustainable bioenergy production from crops 9 VI. Increasing bioenergy yields in a sustainable way 10 VII. Conclusions and perspectives 12 Acknowledgements 13 References 13

A variety of different molecular techniques can be used for the study of botanical diversity. Restriction fragment length polymorphism (RFLP), arbitr