Refining methods for efficient line development and seed increase in winter wheat: Speed breeding with minibulks and a single‐plant nursery

Abstract

Speed breeding (SB) can accelerate winter wheat ( Triticum aestivum L.) generations, but optimized protocols that integrate rapid early‐generation advancement with efficient field seed increase for multi‐year and multi‐location testing remain limited. Nitrogen (N) and seeding rate management of bulks during SB (“minibulks”) were evaluated to determine whether intergenotypic competition in F ₂ bulk populations could be minimized to reduce natural selection. Additionally, a pipeline combining minibulk advancement with rapid line derivation was designed and studied for feasibility and efficiency. A 4 × 4 × 3 factorial greenhouse experiment evaluated genotype mixtures, N rates (50–300 mg N L ⁻¹ ), and seeding rates (300–7000 seeds m ⁻² ) for their effects on intergenotypic competition, heading date, maturity date, and seed yield. Results indicated that shifts in genotype frequency were minor and could be minimized using a density of 3500 seeds m ⁻² (80 seeds per 232.25 cm ² pot), combined with 150–300 mg N L ⁻¹ , while maintaining seed yield and rapid generation times. Field experiments conducted over 4 years demonstrated that F ₃ seeds from minibulks could be space planted in the field to establish a single‐plant nursery, with single plants producing sufficient seed for 4.76 m ² increase plots, achieving rapid seed amplification. Quadratic relationships between seeding rates and yield were observed in increase plots, illustrating that seed from a single plant is sufficient for seeding an increase plot that produces enough seeds for multi‐environment testing. Overall, this study advances SB methods in winter wheat with a focus on efficiency during line development and seed increase.