Introgression of the sunflower HaHB4 gene in modern wheat: An advancement in resilience to deal with climate change

Breeding for improved tolerance to water deficit is critical to mitigate climate change impact on wheat yield. In 2020, Argentina approved the first wheat transformed with the sunflower HaHB4 gene (INDØØ412-7), which increased yield by 16% compared to the non-transformed parental Cadenza under drought conditions. Previous studies may have overestimated HaHB4 benefits, as Cadenza is a long cycle for the Pampas region. Quantifying the yield advantage of HaHB4 in modern, well-adapted cultivars and elucidating the physiological processes involved, is crucial for identifying optimal environments for this technology. In a broad network of experiments (one greenhouse and 29 field environments), an HaHB4 -introgressed line of Algarrobo was compared with the conventional cultivar. Under water deficit during the reproductive phase, the yield advantage of HaHB4 was 15% in the greenhouse and 13% in the field. HaHB4 improved the relative yield by 0.06 to 0.08 % per mm of water deficit. The enhanced water use and water use efficiency conferred by HaHB4 , allowed maintaining growth and yield under water deficit. HaHB4 showed the highest benefit with moderate heat stress (∑Tmax > 30 °C ∼40-60 °Cd). In areas prone to drought combined with heat stress, HaHB4 would enhance yield stability by improving water-limited yield.