Genetic improvement through breeding is one of the key approaches to increasing biomass supply. This paper documents the breeding progress to date for four perennial biomass crops (PBCs) that have high output–input energy ratios: namely Panicum virgatum (switchgrass), species of the genera Miscanthus (miscanthus), Salix (willow) and Populus (poplar). For each crop, we report on the size of germplasm collections, the efforts to date to phenotype and genotype, the diversity available for breeding and on the scale of breeding work as indicated by number of attempted crosses. We also report on the development of faster and more precise breeding using molecular breeding techniques. Poplar is the model tree for genetic studies and is furthest ahead in terms of biological knowledge and genetic resources. Linkage maps, transgenesis and genome editing methods are now being used in commercially focused poplar breeding. These are in development in switchgrass, miscanthus and willow generating large genetic and phenotypic data sets requiring concomitant efforts in informatics to create summaries that can be accessed and used by practical breeders. Cultivars of switchgrass and miscanthus can be seed‐based synthetic populations, semihybrids or clones. Willow and poplar cultivars are commercially deployed as clones. At local and regional level, the most advanced cultivars in each crop are at technology readiness levels which could be scaled to planting rates of thousands of hectares per year in about 5 years with existing commercial developers. Investment in further development of better cultivars is subject to current market failure and the long breeding cycles. We conclude that sustained public investment in breeding plays a key role in delivering future mass‐scale deployment of PBCs.

中文翻译：

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多年生木质纤维素生物质作物柳枝稷、芒草、柳树和杨树的育种进展和大规模部署准备。


通过育种进行遗传改良是增加生物量供应的关键方法之一。本文记录了迄今为止四种具有高产出输入能量比的多年生生物质作物 (PBC) 的育种进展：即柳枝稷、芒属、柳属和杨属。对于每种作物，我们报告了种质收集的规模、迄今为止在表型和基因型方面所做的努力、可用于育种的多样性以及以尝试杂交次数表示的育种工作规模。我们还报告了利用分子育种技术实现更快、更精确育种的进展。杨树是遗传学研究的模型树，在生物知识和遗传资源方面处于领先地位。连锁图谱、转基因和基因组编辑方法目前正用于商业化杨树育种。这些正在柳枝稷、芒草和柳树中开发，产生大量遗传和表型数据集，需要信息学方面的共同努力来创建可供实际育种者访问和使用的摘要。柳枝稷和芒草的栽培品种可以是基于种子的合成群体、半杂种或无性系。柳树和杨树品种以无性系的形式进行商业化部署。在地方和区域层面，每种作物最先进的品种均已达到技术成熟水平，现有商业开发商可以在大约 5 年内将种植面积扩大到每年数千公顷。对进一步开发更好品种的投资受到当前市场失灵和育种周期长的影响。 我们的结论是，对育种的持续公共投资在未来大规模部署 PBC 方面发挥着关键作用。