Genomic mechanisms of climate adaptation in polyploid bioenergy switchgrass.

Long-term climate change and periodic environmental extremes threaten food and fuel security1 and global crop productivity2-4. Although molecular and adaptive breeding strategies can buffer the effects of climatic stress and improve crop resilience5, these approaches require sufficient knowledge of the genes that underlie productivity and adaptation6-knowledge that has been limited to a small number of well-studied model systems. Here we present the assembly and annotation of the large and complex genome of the polyploid bioenergy crop switchgrass (Panicum virgatum). Analysis of biomass and survival among 732 resequenced genotypes, which were grown across 10 common gardens that span 1,800 km of latitude, jointly revealed extensive genomic evidence of climate adaptation. Climate-gene-biomass associations were abundant but varied considerably among deeply diverged gene pools. Furthermore, we found that gene flow accelerated climate adaptation during the postglacial colonization of northern habitats through introgression of alleles from a pre-adapted northern gene pool. The polyploid nature of switchgrass also enhanced adaptive potential through the fractionation of gene function, as there was an increased level of heritable genetic diversity on the nondominant subgenome. In addition to investigating patterns of climate adaptation, the genome resources and gene-trait associations developed here provide breeders with the necessary tools to increase switchgrass yield for the sustainable production of bioenergy.

Analysis of EST sequences suggests recent origin of allotetraploid colonial and creeping bentgrasses.

Advances in plant genomics have permitted the analysis of several members of the grass family, including the major domesticated species, and provided new insights into the evolution of the major crops on earth. Two members, colonial bentgrass (Agrostis capillaris L.) and creeping bentgrass (A. stolonifera L.) have only recently been domesticated and provide an interesting case of polyploidy and comparison to crops that have undergone human selection for thousands of years. As an initial step of characterizing these genomes, we have sampled roughly 10% of their gene content, thereby also serving as a starting point for the construction of their physical and genetic maps. Sampling mRNA from plants subjected to environmental stress showed a remarkable increase in transcription of transposable elements. Both colonial and creeping bentgrass are allotetraploids and are considered to have one genome in common, designated the A2 genome. Analysis of conserved genes present among the ESTs suggests the colonial and creeping bentgrass A2 genomes diverged from a common ancestor approximately 2.2 million years ago (MYA), thereby providing an enhanced evolutionary zoom in respect to the origin of maize, which formed 4.8 MYA, and tetraploid wheat, which formed only 0.5 MYA and is the progenitor of domesticated hexaploid wheat.