A vertical stacking approach to rapid generation cycling for indoor growth of tall annual crops - the case of Vicia faba
Accelerating breeding cycles through rapid generation turnover is a critical strategy to improve genetic gain in crops. This study presents a vertically stacked accelerated single-seed descent (aSSD) protocol for faba bean (Vicia faba L.), aimed at reducing generation time while ensuring robust plant development and seed viability. Alongside photoperiod extension to truncate time to flowering, we present innovations including flurprimidol application to control plant height and enable vertically stacked growth, and optimisation of immature seed desiccation for precocious seed germination. Under controlled environment conditions, the protocol achieved 4.1 to 5.7 generations per year across phenologically diverse germplasm. Plant height was successfully reduced by up to 50% with flurprimidol without compromising flowering or seed yield. The methodology was validated within the University of Adelaide led Australian PBA faba bean breeding program (FBA), advancing 14 recombinant inbred line populations over three years. Beyond faba bean, this scalable, genotype-independent platform offers potential applications for other tall annual species in breeding and vertical farming systems, enabling year-round crop production and genetic improvement. Moreover, the protocols adaptability to closed-environment agriculture presents unique opportunities for plant-based life-support systems in extreme environments, including space missions. This integrated approach to speed breeding and vertical farming represents a significant advancement in agricultural innovation, with implications for food security and space exploration.