Comprehensive Evaluation and Selection on Integrated Resistance to Major Diseases and Desirable Agronomic Traits of 38 Sugar Beet (Beta vulgaris L.) Germplasm in Northeast China

Sugar beet ( Beta vulgaris L.) is the cornerstone of global sugar production, but its yield is still seriously threatened bacterial wilt ( Rhizoctonia solani ), leaf spot ( Cercospora leaf spot , CLS), root rot complex ( Fusarium spp. ) and other diseases. Traditional breeding struggles with yield-disease trade-offs and fragmented trait evaluation. This study establishes a multivariate framework integrating multi-disease resistance and agronomic traits for 38 germplasm accessions in Northeast China. Field trials quantified disease indices (DISB, BSDI, FRRCDI), yield parameters (root yield, sugar production), quality traits (sucrose, K⁺, Na⁺, α-N), and early vigor. Principal component analysis derived two core dimensions: Comprehensive Disease Resistance Value (CDRV, 48.7% variance) dominated by CLS resistance (loading = 0.82), and Comprehensive Agronomic Value (CAV, 31.2% variance) linked to sugar yield (0.89) and sucrose content (0.79). The selection index D = √(CDRV² + CAV²) ranked 780016A/1 (D = 1.71) and 8432/1 (D = 1.70) as elite performers, combining high root yield (54,233 kg·ha⁻¹), optimal sucrose (15.93–17.24%), and moderate multi-disease resistance (e.g., BSDI = 16.5–18.1). A variety of analyses were used to classify 38 germplasm resources into four functional groups, confirming synergistic trait combinations (Group I: elite accessions) and saline-adapted genotypes (Group IV: F85621 with 17.45% sucrose, 1.57 mmol/100g Na⁺). Key correlations included CLS severity-sugar yield anticorrelation (r = − 0.65, p < 0.001) and Na⁺-sucrose trade-off (r = − 0.404, p < 0.05). This framework overcomes single-trait limitations, providing validated germplasm and a data-driven strategy for breeding climate-resilient, high-yielding varieties.