Resistance Evaluation of Pear Ring Rot on Detached Leaves and Genetic Model Analysis in Four Pear F1 Populations

Pear ring rot, caused by Botryosphaeria kuwatsukai, is a major threat to pear production. The resistance of four pear F1 populations to three B. kuwatsukai isolates was evaluated using detached leaf inoculations, assessed by the Area Under the Disease Progress Curve (AUDPC) and average lesion diameter (ADL). Cluster analysis based on these metrics established a five-level resistance rating scale. All hybrid combinations exhibited clear segregation for resistance, with continuous phenotypic variation and coefficients of variation exceeding 50%, suggesting polygenic inheritance. Broad-sense heritability (H2) of lesion diameter, estimated from replicated inoculations using a linear mixed-model approach, ranged from 0.32 to 0.71 across populations and isolates, indicating that the phenotypic variation was largely under genetic control. Genetic model analysis using the SEA v2.0 package identified a two-major-gene additive-dominant (2MG-AD) model as the best fit for the data across all combinations and isolates, with additive effects predominating. Isolate-specific responses were detected in the ‘Doyenne du Comice’ × ‘Huangguan’ population, and reciprocal differences between ‘Zhongai 1’ × ‘Zaosu’ and its reciprocal cross suggested potential cytoplasmic or maternal effects on resistance expression. Collectively, these findings suggest that pear leaf resistance to B. kuwatsukai is consistent with a two-gene additive-dominant model, supported by moderate-to-high heritability estimates. However, independent validation with additional populations and molecular markers is needed. These results highlight the value of multi-isolate screening, appropriate selection of resistant and susceptible parents, and the use of reciprocal crossing in breeding for broad-spectrum and durable resistance.