The apple is the most common and culturally important fruit crop of temperate areas. The elucidation of its origin and domestication history is therefore of great interest. The wild Central Asian species Malus sieversii has previously been identified as the main contributor to the genome of the cultivated apple (Malus domestica), on the basis of morphological, molecular, and historical evidence. The possible contribution of other wild species present along the Silk Route running from Asia to Western Europe remains a matter of debate, particularly with respect to the contribution of the European wild apple. We used microsatellite markers and an unprecedented large sampling of five Malus species throughout Eurasia (839 accessions from China to Spain) to show that multiple species have contributed to the genetic makeup of domesticated apples. The wild European crabapple M. sylvestris, in particular, was a major secondary contributor. Bidirectional gene flow between the domesticated apple and the European crabapple resulted in the current M. domestica being genetically more closely related to this species than to its Central Asian progenitor, M. sieversii. We found no evidence of a domestication bottleneck or clonal population structure in apples, despite the use of vegetative propagation by grafting. We show that the evolution of domesticated apples occurred over a long time period and involved more than one wild species. Our results support the view that self-incompatibility, a long lifespan, and cultural practices such as selection from open-pollinated seeds have facilitated introgression from wild relatives and the maintenance of genetic variation during domestication. This combination of processes may account for the diversification of several long-lived perennial crops, yielding domestication patterns different from those observed for annual species. The apple, one of the most ubiquitous and culturally important temperate fruit crops, provides us with a unique opportunity to study the process of domestication in trees. The number and identity of the progenitors of the domesticated apple and the erosion of genetic diversity associated with the domestication process remain debated. The Central Asian wild apple has been identified as the main progenitor, but other closely related species along the Silk Route running from Asia to Western Europe may have contributed to the genome of the domesticated crop. Using rapidly evolving genetic markers to make inferences about the recent evolutionary history of the domesticated apple, we found that the European crabapple has made an unexpectedly large contribution to the genome of the domesticated apple. Bidirectional gene flow between the domesticated apple and the European crabapple resulted in the domesticated apple being currently more similar genetically to this secondary genepool than to the ancestral progenitor, the Central Asian wild apple. We found that domesticated apples have evolved over long time scales, with contributions from at least two wild species in different geographic areas, with no significant erosion of genetic diversity. This process of domestication and diversification may be common to other fruit trees and contrasts with the models documented for annual crops.

This paper describes the complete findings of the EU-funded research project OPTIMISC, which investigated methods to optimize the production and use of miscanthus biomass. Miscanthus bioenergy and bioproduct chains were investigated by trialing fifteen diverse germplasm types in a range of climatic and soil environments across central Europe, Ukraine, Russia and China. The abiotic stress tolerances of a wider panel of 100 germplasm types to drought, salinity and low temperatures were measured in the laboratory and a field trial in Belgium. A small selection of germplasm types was evaluated for performance in grasslands on marginal sites in Germany and the UK. The growth traits underlying biomass yield and quality were measured to improve regional estimates of feedstock availability. Several potential high-value bioproducts were identified. The combined results provide recommendations to policymakers, growers and industry. The major technical advances in miscanthus production achieved by OPTIMISC include: 1) demonstration that novel hybrids can out-yield the standard commercially grown genotype Miscanthus x giganteus; 2) characterisation of the interactions of physiological growth responses with environmental variation within and between sites; 3) quantification of biomass-quality-relevant traits; 4) abiotic stress tolerances of miscanthus genotypes; 5) selections suitable for production on marginal land; 6) field establishment methods for seeds using plugs; 7) evaluation of harvesting methods; and 8) quantification of energy used in densification (pellet) technologies with a range of hybrids with differences in stem wall properties. End-user needs were addressed by demonstrating the potential of optimizing miscanthus biomass composition for the production of ethanol and biogas as well as for combustion. The costs and life-cycle assessment of seven miscanthus-based value chains, including small- and large-scale heat and power, ethanol, biogas and insulation material production, revealed GHG-emission- and fossil-energy-saving potentials of up to 30.6 t CO2eq C ha-1y-1 and 429 GJ ha-1y-1 , respectively. Transport distance was identified as an important cost factor. Negative carbon mitigation costs of -78 € t-1 CO2eq C were recorded for local biomass use. The OPTIMISC results demonstrate the potential of miscanthus as a crop for marginal sites and provide information and technologies for the commercial implementation of miscanthus-based value chains.