Feasibility analysis of expanding winter rapeseed northwards in China

• Ultra-winter-hardy varieties of Brassica rapa L. exhibit exceptional adaptability to extreme cold conditions. • The potential cultivation area for winter rapeseed in Northern China could increase significantly. • The promotion of cold-resistant rapeseed varieties is strategically important for enhancing agricultural resilience. With high elevations, complex topographies, cold winter, diverse ecosystems, and a long history of oilseed Brassica rapa cultivation, Northwest China is rich in winter-hardy B. rapa germplasms. Using these germplasms, a number of ultra-winter-hardy rapeseed cultivars were developed in past three decades, leading to a large-scale northward expansion of winter rapeseed production in China. Based on 19 years of field trial data, this study was to assess the feasibility of growing winter rapeseed in the areas of northern China where conventionally no winter rapeseed had grown prior to availability of the ultra-winter-hardy B. rapa cultivars. The impacts of the major climate factors on overwintering rates and yields were analyzed. Using the boundary line analysis, the suitable growing regions for different cultivars were defined. The ultra winter-hardy cultivars displayed exceptional adaptability in frigid environments, with overwintering rates exceeding 70 % under conditions of extreme winter temperatures as low as -42.35 °C. Suitability analyses indicate that up to 534,000 km² of farmland in northern China are suitable for expanding winter rapeseed cultivation, potentially yielding between 5.61 and 12.34 million tons of winter rapeseed. This expansion could result in an approximately 30 % increase in the total domestic oilseed processing volume, significantly enhancing China's self-sufficiency in vegetable oil production. Our data suggest that these new ultra-winter-hardy rapeseed cultivars have made winter rapeseed production feasible, profitable, environmentally beneficial, and economically important in northern China.