‘Fengyuan No. 1’: A High-Protein, Stress-Tolerant Forage Mulberry Variety from Northern China

The shortage of high-quality forage and the need for alternative protein sources are critical challenges for livestock production in northern China, where cold winters and saline–alkaline soils limit crop options. Mulberry (Morusalba L.) is a promising high-protein forage, yet few varieties have been bred for these conditions. Here, we report the breeding of ‘Fengyuan No. 1’, developed through systematic evaluation of 31 mulberry accessions for five forage traits, followed by a 4 × 3 factorial crossing design using four female parents (‘8036’, ‘Dahongpao’, ‘Jinqiang 63’, ‘Hongguo 2’) and three male parents (‘Nongsang 14’, ‘Yu 2’, ‘Yiyuan Huanglu’) selected based on comprehensive evaluation and complementary agronomic traits. Among the nine hybrid families with sufficient seed, family X01 (‘8036’ × ‘Nongsang 14’) ranked first in a three-year (2011–2013) comprehensive evaluation of growth traits using membership function analysis and was subsequently named ‘Fengyuan No. 1’. Multi-location (Shandong, Anhui, Shaanxi) field trials (2018–2021) with ‘Fengchi’ as the control showed that ‘Fengyuan No. 1’ achieved an average annual leaf yield of 12,596.48 kg DM·ha−1 (+14.20%) and total branch–leaf biomass of 25,341.95 kg DM·ha−1 (+13.36%). Leaf crude protein reached 30.87% on a dry matter basis (+25.64% vs. control). Silage prepared from this variety exhibited excellent fermentation quality (pH 4.10) and a relative feed value of 272.46, exceeding alfalfa silage standards. The variety maintained 100% survival at 0.4% NaCl and a 13.74% biomass advantage over the control on saline–alkaline field soils, with winter-desiccated shoot tips reduced by 53%. These results establish ‘Fengyuan No. 1’ as an elite forage mulberry for the Yellow River Basin and similar ecoregions.