Optimized protocol for high-throughput vernalization with speed breeding in winter wheat

Wheat ranks third among cereal crops in terms of global production, and its demand is expected to increase as the human population grows. Plant breeding can increase crop production without burdening natural resources, and one way to accelerate genetic gain is through shortening breeding cycles with speed breeding (SB). Speed breeding protocols for winter wheat have been adapted by adding a vernalization phase to existing spring wheat protocols. Although a protocol for the vernalization phase was previously developed, it was not tested for genotypes grown in the Midwest US, which may have higher vernalization requirements. The transition from vegetative to reproductive stages in winter wheat depends mainly on photoperiod, vernalization temperature, and vernalization length, which determines the time needed to reach flowering. Optimizing vernalization under SB in a greenhouse setting is important for applications in breeding programs. Our objectives were to develop a speed breeding protocol for winter wheat that meets the vernalization requirements of all genotypes and to evaluate the interaction between vernalization temperature and sowing depth.

A significant reduction in the time to flowering via speed breeding was achieved. Compared with normal vernalization, high-throughput vernalization adds on average ten days to the time to harvest. A shallow planting depth results in maturity five days earlier than a deep planting depth.

A combination of speed breeding, shallow planting, and high-throughput vernalization will shorten the breeding cycle by 22 days per generation or 44 days per year compared to normal greenhouse conditions. This system is suitable for genotypes with high vernalization requirements and can be combined with high-throughput systems.