Accelerating genetic gain through strategic speed breeding in spring wheat

Spring wheat (Triticum aestivum L.) is a popular bread wheat with high milling and baking requirements. Vernalization is not required for spring wheat, which allows for fast growth under manipulated conditions. This experiment's objective was rapid development of inbred lines of hard red spring wheat throughout the off-season and preserve enough genetic variability to perform selection. A total of 1575 F₂ heads from three distinct populations were randomly harvested in the field-season 2021. To break seed dormancy, seeds were held for 2 days at 0°C. Three breeding cycles were performed through single seed descent under manipulated growth condition during the off-season 2021–2022. We were able to harvest plant materials as quickly as 54 days after planting in comparison to 110 days average field season. We lost a total of 36.4% during the three off-season fast advancement generations and 711 genotypes reached the F_5:6 generation with enough seed to perform a partially replicated small plot yield trial at two locations during the 2022 field-season. Response traits collected included grain yield, grain protein, plant height, days to heading, and bacterial leaf streak (Xanthomonas transluens) disease severity. Heritability of collected traits varied between 0.61 and 0.92. Although we had considerable loss during the speed breeding, we were able to identify superior genotypes compared to the parents.