Breeding and Sustainability of Shrub Willow for Marginal Lands in the Northeast US

Shrub willow is among the best suited perennial crops for bioenergy feedstock production in the Northeast US due to its high yields, ease of conversion, and overall sustainability. Breeding efforts are aimed at improving yields on typical ag land, strengthening pest and disease resistance, and developing cultivars that can produce viable yields on highly disturbed sites, such as reclaimed mine land. We have developed and characterized association and linkage mapping populations of Salix purpurea with the aim of identifying QTL and tightly-linked SNPs for marker-assisted selection.  We have adopted genotyping-by-sequencing as a high-density marker system and have mapped putative candidate genes for a number of traits related to yield, pest and disease resistance, and sustainability using the genome sequence and annotation developed by the DOE Joint Genome Institute.  We have also initiated a survey of the soil microbiomes associated with willow roots across a range of yield trial sites using high-throughput sequencing of soil DNA samples. We have measured and modeled carbon dioxide and nitrous oxide exchange from land planted with shrub willow, as well as modeled potential yield. Further yield increases, improvements in nutrient use efficiency, and adaptation to increasingly marginal sites facilitated by genomics-assisted breeding will broaden adoption of this highly sustainable alternative to fossil fuels.