In vitro-assisted compression of breeding cycles

The compression of breeding cycles to quickly progress segregating material to homozygosity has attracted substantial international research interest for some decades. Modified pedigree breeding methods such as single seed descent (SSD) have enabled faster generation turnover and commercialization of new crop cultivars. Since the latter part of the last century, doubled haploid technology has revolutionized the progression to genome fixation in responsive species. In unresponsive but economically important families, biotechnological tools are being developed to accelerate traditional SSD - either by completing the full plant life cycle in vitro or by coupling controlled environmental conditions in the soil to elicit rapid floral onset with germination of immature seed in vitro to truncate seed filling. Both techniques have resulted in step-change efficiencies in generation turnover with up to fourfold improvements in species such as grain legumes. Such enhanced SSD systems are also valuable for breeding complex traits across a range of species. In this chapter, we explore the recent advances in in vitro-assisted breeding cycle compression in crops, opportunities to combine rapid phenotyping for key traits and the benefits of in vitro life cycle completion when researching under restrictive regulatory frameworks and working with enfeebled or rare material.